Sunday, October 31, 2010

Oct 31, 2010: Tracking Strong Storm Potential

Notes:

- The 5-Day Forecast was updated for most of the area tonight. In addition, NYC Area Weather has a Freeze Warning in effect for most of the area tonight.

- Reminder: The polls for the potential winter temperatures and snowfall (top right, below the radar loop) will remain open until November 27. At this time, there are 5 votes, which favor average temperatures and snowfall.

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Today was a partly cloudy day across the area, with high temperatures in the lower 50s inland, and in the upper 50s to lower 60s for the rest of the area. The cold front that moved through earlier today also brought widespread snow showers for the Northeast, with moderate snow accumulating up to 1-2" in central Maine. As the strong trough moves into the region, temperatures will significantly cool down, with below freezing temperatures expected for a good part of the area tonight and tomorrow night.

Tonight/Tomorrow's Outlook:

Tonight will be the coldest night so far for a lot of places, with widespread frost expected. Low temperatures will be in the mid to upper 20s inland, upper 20s to mid 30s north and west of NYC and in southern Connecticut, lower to mid 30s in Long Island, and mid to upper 30s in NYC. A freeze warning is in effect for most of the area tonight.

Tomorrow will be a mostly sunny and chilly day. High temperatures will only be in the mid to upper 40s inland, and the upper 40s to lower 50s for the rest of the area. A NNW wind is expected during the day.

Tuesday And Wednesday: Staying Cold, Dry

Monday night will likely be the coldest night of this cold spell, with low temperatures in the mid 20s inland, mid 20s to lower 30s north and west of NYC and in S CT, upper 20s to lower 30s in Long Island, and in the mid to upper 30s for NYC. Tuesday will be slightly warmer than Monday, with Wednesday slightly warmer. Tuesday night will still be cold but with temperatures slightly warmer.

Late Week Storm: Update On The Potential Scenarios

Yesterday, I mentioned how there were large differences with the models, especially with the GFS, ECMWF, and the GGEM. I mentioned in my 5-Day Forecast that rain is likely for Thursday, but with not much detail on which solution. After looking at the latest models today, the trends, and the expected pattern, however, I am leaning towards an inland storm track that was suggested by the GGEM yesterday.

The GFS model has not been consistent with this time frame from the start, for example the trough expected to drop into the Midwest was at first shown to be so far east that it would barely even affect Maine. With each run, the storm kept trending more and more west, and it is also trending slower as well, with the last few runs taking large steps towards the GGEM and ECMWF. The GGEM and ECM have some differences, such as how far the storm ends up inland, but both show the main idea that the storm is likely to track slightly inland of the coast, and bring heavy rainfall and mild temperatures to the Mid Atlantic and New England, with several inches of rain possible.

There are still a lot of differences including phasing of the storm, and the forecast could change over the next few days, but it is becoming more likely that this storm could take an inland track, bringing high temperatures into the upper 50s and 60s for parts of the area, with potential impacts ranging from several inches of rain and strong winds in the eastern side of the storm to potential snowfall on the western side of the storm, which could be anywhere from the Northeast to the Ohio Valley/Great Lakes.

The GFS model is trending towards the ECM/GGEM but is not quite there yet, quickly taking the storm out by Friday, but given its progressive bias, and the fact that it is trending slower, I am leaning towards something closer to the ECM/GGEM. This solution, however, is not final yet, and is based on the latest trends and potential trends over the next few days. Stay tuned for more details on this storm over the next few days.


Hurricane Tomas: Soon-To-Be Tropical Storm


As expected, Tomas strengthened to a Category 2 hurricane last night, and encountered stronger shear today. This shear, however, had a stronger effect on Tomas than expected, and it is now barely a Category 1 hurricane, likely to be downgraded to a tropical storm later tonight. Tomas has lost a lot of its convection and is much more disorganized due to this shear, which is expected to continue affecting Tomas for the short term.

By Tuesday/Wednesday, however, shear is expected to weaken while the steering currents collapse, with Tomas starting to drift north likely towards Hispaniola, and Tomas will likely strengthen again, potentially rapidly if the environment is favorable enough, and may return to Category 2 intensity before making landfall in the Caribbean islands, likely somewhere between Jamaica and the Dominican Republic. Tomas has the potential of being a dangerous hurricane, and the Caribbean islands from Cuba to Puerto Rico, especially Haiti, should closely follow Tomas.

Saturday, October 30, 2010

Oct 30, 2010: Storm Potential Late Next Week

Today was another chilly and windy day for the area, with high temperatures in the mid to upper 50s across most of the area. Low temperatures were in the lower to mid 30s inland, mid 30s to lower 40s north and west of NYC and in the lower 40s in NYC, which was slightly warmer than expected due to more cloud cover.

The next few days will be cold and dry, with widespread frost expected on Sunday/Monday night being why I issued a Freeze Watch for most of the area, however uncertainty returns to the forecast for the late week, when there is the potential for a storm to affect the region.



Tomorrow's Outlook:

Tomorrow will be a partly to mostly sunny day with a WNW wind. High temperatures will be in the lower 50s inland, mid 50s in the immediate NYC area, and mid to upper 50s in Long Island/S CT as a cold front moves through in the morning.

Overnight temperatures will be cold, in the mid to upper 20s inland, upper 20s to mid 30s for the areas north and west of NYC, and in the upper 30s for NYC. Widespread frost is possible, being why a freeze watch is in effect for most of the area.

This cold front will be related to a weak storm moving out of the region, which should produce accumulating snow in central Maine tonight through tomorrow morning, with a general 1 to 3 inches of snow. Widespread rain/snow showers will be observed in the Northeast tomorrow, but the NYC area will stay dry.

Monday And Tuesday: Dry, Cold
Mainly sunny weather will persist for Monday and Tuesday, with mostly sunny skies expected. High temperatures on Monday will be in the mid 40s inland, upper 40s to lower 50s for Long Island/S CT, and in the mid 40s to lower 50s in the immediate NYC area. Low temperatures on Monday night should be slightly colder than those of Sunday night, with Tuesday night's lows also cold. Tuesday's highs should be slightly warmer than those of Monday.

Longer Range: Storm Potential, Then Cold Again

For the longer range, it is nearly certain that a storm will develop and potentially affect the region, but how it develops, where and when is still a question. Up to Wednesday, the models are in good agreement with a low pressure in the Gulf of Mexico and a high pressure near the area. Afterwards, however, there are significant differences with the models, even the ensemble means, with solutions ranging from the GGEM showing an intense storm covering all of the East Coast with heavy rain, to the ECMWF which develops the southern low pressure and has it going inland into the Great Lakes, or the GFS that barely develops the storm but instead develops another one around November 6-7.

The main uncertainty with the models seems to be with which low pressure to develop, one near the North Carolina coast which would lead to a scenario like the one I mentioned yesterday, or the southern one in the Gulf of Mexico, which would lead to a solution closer to the ECMWF or GGEM, which are much further inland. It is possible that the first storm fails to become anything significant and a potential second storm that the GFS and DGEX are showing is the main storm.

At this time, in my 5-Day Forecast, I mentioned a chance of rain on Thursday afternoon, but this is just a general forecast which doesn't exactly follow these potential storm tracks. The ensemble means still show a coastal storm, but have trended much further west than yesterday. As uncertainty decreases on the models, I will discuss the scenario in more details. Stay tuned for more details on this storm.

After the storm, however, one thing that is likely again is that a strong cold air mass could affect the area. There is uncertainty on how strong this cold air mass is, or whether a second storm like the GFS/DGEX show has any effect on it, but if the latest models verify, temperatures could be even colder than those of Monday/Tuesday.


Tropics: Tomas Now A Hurricane

Last night, Tomas continued to quickly strengthen, and is now a 90 mph Category 1 hurricane, which passed through the southern Lesser Antilles earlier today causing damage. Tomas has an eye that formed not too long ago, though the eye is not well organized yet. Tomas will likely continue strengthening tonight, reaching Category 2 intensity by tomorrow.

Afterwards, due to increasing shear that the models are forecasting, Tomas may slightly weaken, but the shear is then expected to relax, and with a very favorable environment, Tomas may rapidly intensify. The peak intensity is uncertain, however at this time I put the potential for Tomas to reach Category 4 intensity in my forecast map, posted above.

Tomas' Track: For the short range, there is agreement with the models, showing a general WNW movement for the next 2 days. Afterwards, however, it appears that the steering currents should collapse, with Tomas significantly slowing down, then starting to move more north. There is uncertainty on where Tomas could so do, and at this time, while the latest models show landfall near Hispaniola/Haiti, there is a large range of potential landfall areas, ranging from Puerto Rico to Jamaica/Cuba. Regardless of the track, Tomas will likely be a dangerous hurricane, and people from Puerto Rico to Cuba should pay close attention to Tomas over the next few days.

Friday, October 29, 2010

Oct 29, 2010: Cold Week, Then Major Nor'easter Possible

The 5-Day Forecast tonight was updated for the immedate NYC area only. An update tomorrow morning will add the rest of the area.

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The last few days were extremely active for most of the United States, with an unusually intense storm in the north central US bringing widespread high winds to that region, 72 tornadoes from the Ohio Valley to the Mid Atlantic and Southeast, nearly 500 strong wind reports, and a blizzard to the west of the storm center with over 6 inches of snow.

This storm, however, failed to bring anything to the area more than a few showers, despite the expectation of a strong cold front bringing a widespread 1/2 to 1.5 inches of rain. With the first storm on Tuesday, the heaviest rain was supposed to be over the area, but from the start it set up further north/west of NYC than expected, leading to the heaviest rain over central NY with only a few showers in the area. The cold front on Wednesday did bring the heavy rain it was capable of bringing as expected, producing rainfall amounts locally up to 1-2" in some places, but the heavy rain failed to affect the area. The rain bands that were supposed to affect the area were at first too far west, then too far south/east, leaving a large dry area from NYC to Boston where less than 1/4 inch fell.

Yesterday was another mild day, however today was much cooler than yesterday, with highs back into the 50s. Things, however, are about to get much colder, as a colder pattern settles in for the region.

Tomorrow's Outlook:

Tonight will be a very chilly night, with lows ranging from the upper 20s inland to the lower-mid 30s north and west of NYC, to the upper 30s to lower 40s in NYC. Frost is expected north and west of NYC.

Tomorrow will be another chilly day, but slightly warmer than today, with highs in the mid to upper 50s across the area. A SW wind is expected.

Sunday - Tuesday: Strong Trough, Very Cold

At first, it was thought that a strong warm up could take place around this time frame. Since then, however, it appeared that a 1030+ mb high pressure would move into the Northeast, with a strong trough moving into the region. Temperatures are expected to be at their coldest points yet, with lows in the mid 20s inland, upper 20s to mid 30s north and west of NYC, and in the upper 30s for NYC. High temperatures will be at their coldest on Monday, from the mid 40s to lower 50s across most of the area.

Longer Range: Storm Potential In The Late Week

Over the last few days, I mentioned a potential for a storm to affect the region during this time frame. While details have changed, especially the expected timing, the general idea remains that a storm is expected around this time frame. For the last 2 days, the models were all over the place with this storm, and still are, ranging from an intense low pressure moving through the Ohio Valley to a weak clipper moving through, redeveloping offshore and intensifying near Nova Scotia. Instead of trying to follow the models, I decided to look at the overall pattern, which shows a ridge in the west, a trough in the East, with an intensifying low pressure offshore.

There is uncertainty on some details such as the exact track of the low pressure, but with the details mentioned above, at this time I am expecting a coastal low to potentially intensify quickly off the coast on Thursday while interacting with a potential clipper to its northwest, ending up near or over the Northeast on Friday, where the most significant impact from the storm could be, with snow possible in the interior NE. The storm would then exit on Saturday, with a strong trough dropping into the region potentially bringing temperatures similar to those of the early week, if not slightly colder.

There is still some uncertainty at this time on the solution mentioned above, but as of now this is my understanding on the potential set up for the late week. Stay tuned for more details on this storm and how it may affect the area.


Tropics: Activity Quickly Picking Up, Season Approaching Historic Levels

When making my hurricane season outlook, I was mainly expecting the activity to focus through mid September, which it did, but I was not expecting a record active September like we had, where the 8 named storms tied the record for the most named storms in September. In addition, I did not think that the high activity would continue for this long, with this many hurricanes.

Last night, Tropical Storm Shary formed in the central Atlantic, and around this afternoon, just as Shary quickly strengthened and was nearly a hurricane aiming straight at Bermuda, attention quickly turned to the SE Caribbean, where Tropical Storm Tomas formed, being the 19th named storm this season and only the 3rd storm to have a name start with a "T".

Tomas' formation area is quite unusual for this time of the year, but it is well organied, and despite only forming several hours ago, it is already quickly intensifying and may be just below hurricane strength at this time. With clear waters, very warm SSTs and a very favorable environment, significant strengthening may be possible. If nothing disrupts Tomas' intensification, it may become one of the strongest, if not the strongest storms this season, with a major hurricane a good possibility and Category 4 or even 5 not out of the question.

Regarding Tomas' track, there is uncertainty on the longer range as it is expected to recurve north somewhere near the central Caribbean, but a recurve is expected, and Tomas will affect land directly while close to its peak strength, with landfall possibilities ranging from Cuba to Puerto Rico. Stay tuned for more details on Tomas.

Wednesday, October 27, 2010

**No Update Posted October 27th**

No update will be posted today. Updates over the next 2 days, if any, will likely be brief, but I will try and get a storm summary done for the Midwest storm over the next few days, which brought widespread tornadoes from the Ohio Valley to the southern Mid Atlantic, and officially became the 2nd strongest non-tropical low pressure to affect the interior United States.

I opened two polls for this coming winter, one for the potential temperature departures from average, and the other for potential snow amounts. The polls will remain open for the next month, until November 27.

Tuesday, October 26, 2010

Oct 26, 2010: Extreme Midwest Storm Approaches

Note: No full update will be posted tonight. The next full update, including a discussion on the longer range and a potential cold spell for Sunday-Tuesday followed by a storm for November 2-4.


8:35 PM: The storm in the Midwest that has been forecasted for the last 9 days is reality, and is even more extreme than the models early on suggested it would be. The low pressure earlier today dropped to nearly 954 mb in northern Minnesota, making it the 2nd, if not the strongest non-tropical low pressure in the United States. In comparison, the nor'easter we had early in the month only reached 985 mb, and Hurricane Karl, a devastating Category 3 hurricane this season that caused billions of dollars in damage in Mexico, had a low pressure of 955 mb, which is even weaker than this storm!

The storm brought a wide range of extreme weather to the central United States, including blizzard warnings in the north central US, wind advisories covering over 1/3 of the United States at one point, widespread high wind warnings covering almost all of the north central US, a high risk of severe weather in the Ohio Valley with over 250 reports of wind damage and 21 tornado reports so far, and a very large size with the storm extending from the Gulf of Mexico to Canada.

How will the storm affect the area? Like I expected for the last few days, the strong cold front will approach the area tonight, moving through tomorrow, and the cold front will bring locally heavy rainfall and strong to potentially severe thunderstorms. While the best chance of severe weather will be to the south and west of the area, as the cold front will slightly weaken once it reaches the area and the best parameters will remain to the south, thunderstorms are still expected, which could be strong with gusty winds being the main concern. As the cold front also significantly slows down while over the region, with precipitable water values over 2 inches, locally heavy rainfall is also expected with these storms.

Brief 7-Day Outlook: The storms will start late tonight, and should end by tomorrow evening. For the several days afterwards, expect a much colder air mass to move in for Thursday night, with Friday's highs in the lower to upper 50s across the area. Friday night will be cold, with lows from the upper 20s-lower 30s inland to the lower-upper 30s in the N/W suburbs of NYC and southern CT, and the lower-mid 40s in NYC. Saturday will have similar temperatures to Friday, and while there is uncertainty on the longer range, it is possible that a strong trough moves into the region, bringing the coldest temperatures of the fall yet for Sunday night and Monday.

Monday, October 25, 2010

Preliminary Winter 2010-2011 Outlook

Preliminary Winter 2010-2011 Outlook
NYC Weather

With October coming to an end and only a little more than one month left until meteorological winter begins, I decided to work on my preliminary winter outlook. I consider it to be preliminary because there is still uncertainty on the month by month pattern and the smaller details such as the NAO and AO, details that I discuss in more details with my final outlook which will be posted around early-mid November. In this outlook, I will discuss the current scenario we are seeing with the La Niña, the patterns that are expected to make up this winter, and a general outlook for the Mid Atlantic and the rest of the United States.


Part 1: Factors for my winter forecast


La Niña:

Last winter, we were dealing with a strong El Niño. During the spring, the El Niño rapidly collapsed, with a La Niña starting to form. The models, however, did not handle this rapid drop well, most of them expecting the La Niña to stay in the weak territory, however the La Niña intensified more than expected and is unofficially a strong La Niña. In order to officially become a strong La Niña, it would need to have departures greater than -1.5o C for 3 months. I expect the La Niña to peak in intensity within the next month, then slightly weaken and remain steady in the moderate territory.





When the La Niña developed in the summer, it was generally east based, meaning that the coldest departures were found in ENSO regions 1+2 and 3, or the eastern regions, with smaller negative departures in the western ENSO regions, 3.4 and 4. Since then, however, the La Niña became less east based and more basin wide, occasionally fluctuating to slightly east based. At this time, I am expecting ENSO regions 1+2 to remain steady with regions 3.4 and 4 slightly cooling down, leading to a basin wide, occasionally slightly west based La Niña for the winter. In general, a west based La Niña means widespread warmer than normal temperatures in the East and below normal temperatures in the west with a stronger SE ridge, and an east based La Niña has colder departures further east, into the Northeast and northern Mid Atlantic with a weaker SE ridge.


NAO:

The North Atlantic Oscillation (NAO) is an important factor in addition to the La Niña. When the NAO is negative, it typically results in a colder East coast, and when it is positive, warmer temperatures generally take place in the East. Currently, we are in a negative NAO which lasted through most of the year, making it one of the longest lasting –NAO in the last few decades. The negative NAO has been weakening, though it is still negative as of now. While the NAO is more predictable in the shorter range, and I will discuss the NAO/AO/PNA in more details with my final outlook, I currently expect a slightly negative NAO for December, with a neutral to occasionally positive NAO for January and February.


PNA:

The Pacific/North American Pattern (PNA) is also an important factor in the general pattern across the US. When the PNA is positive, that means there is a ridge in the western US resulting in above average temperatures, and can sometimes mean a trough in the eastern US resulting in below average temperatures. When the PNA is negative, a trough is likely for the western US with below average temperatures, which can mean a ridge in the eastern US bringing above average temperatures. As with the NAO, it is more difficult to predict the PNA in the longer range, though at this time, I expect a slightly positive PNA for December, with a neutral to negative PNA for January and February.

Other Factors:

It has been observed that sometimes, colder than average Octobers result in colder than average winters for Central Park, NY and Philadelphia, PA. 2009’s October was slightly colder than average and resulted in an average winter. 2007’s October had record warmth and the following winter was unusually warm. October 2010 brought below average temperatures, and the following winter brought near-slightly below average temperatures to the Mid Atlantic. This October is expected to end up with slightly above average temperatures, which could support a slightly warmer than average winter.

The SE ridge, typically associated with a +NAO pattern, is something that is usually seen with La Niñas, especially strong La Niñas. The SE ridge is a high pressure off the East Coast, which tends to bring above average temperatures to the SE US, or if it’s strong enough, to all of the eastern US. This winter, I expect a neutral to occasionally positive NAO to develop for January and February, which is when I think the SE Ridge will become more frequent, but especially with the La Niña being central based, I do not think it will extend as far inland as it did in some La Niña years, but there could be some times where it briefly extends further inland. There will also likely be some times where we see a –NAO/–AO and a strong cold spell can briefly push into the Mid Atlantic and/or parts of the SE, but such strong cold spells likely won’t be too common, with most of the intense cold spells focused in the north central US.


Part 2: Forecast For The Mid Atlantic (Including NYC Area) And Northeast


This winter will be the complete opposite of last winter. Unlike last winter, when suppression took place with frequent snowstorms for the Mid Atlantic with below normal temperatures, and drier and warmer than normal conditions for New England, the storm track this year will be further north, though there will be a few times where we could see coastal storms, but nothing like those of last year.

With a negative NAO/AO expected, winter will likely start with near/below average temperatures, with opportunities for snow as well as mixed precipitation in the Mid Atlantic. By January, however, I am thinking that the NAO/AO could become more neutral, occasionally becoming positive, and with a SE ridge developing, should bring drier and warmer than normal conditions for the southern Mid Atlantic, slightly above normal temperatures and average precipitation for the northern Mid Atlantic, and near to potentially slightly above average temperatures in most of the Northeast. The storm track will frequently run through the Northeast, occasionally into the Great Lakes, leading to heavy rain events for the northern Mid Atlantic and southern Northeast, with wintry precipitation in the central/northern Northeast.

The ridge could persist into parts of February, however it is likely to then start weakening, which would lead to colder temperatures returning to the Northeast and potentially the northern Mid Atlantic. With above average precipitation likely, heavy snowfall is possible in the Northeast, with snow chances returning to the northern Mid Atlantic. There could also be occasional brief yet strong cold spells that drop into the Mid Atlantic.

Summary: Overall, winter is likely to bring above average temperatures for most of the Mid Atlantic and potentially parts of SNE, with slightly below average temperatures for northern New England and the western Northeast. Precipitation will be below average in the southern Mid Atlantic, near normal in the central and parts of the northern Mid Atlantic, and above average from the northern Mid Atlantic into the Northeast. Most of the snow in the central/northern Mid Atlantic will come from overrunning events which will also bring mixed precipitation, weak Alberta Clippers that bring light to moderate snowfall amounts, and potentially a few coastal storms.


Part 2A: Forecast For Parts Of The United States


Western US: As the storm track moves through the NW US, expect above average precipitation in the Pacific Northwest, with a wetter winter than last year. With colder than average temperatures also likely, expect above average snowfall.

California will see a much drier winter compared to last year, and while some rainstorms are still possible, most of the storms as well as the storm track will be focused to the north, with near average temperatures and below average precipitation likely.

Midwest: (Minnesota, N/S Dakota, Montana): Expect below average temperatures this winter, as strong cold air masses dropping from Canada will focus on this region. Precipitation is expected to be near average, with snowfall also near, potentially slightly above average.

Great Lakes: As the storm track will occasionally move through the Great Lakes, or in the Northeast, this will likely be an active region this winter. Above average precipitation is expected for most of the Great Lakes, and as the storm track is expected to be close to the region with colder air to the west, below average temperatures are also likely, but not as cold as those in the Midwest. While there could be a few times where the SE ridge could be strong enough that the storm track is near the Great Lakes and some places see rain/mix, there will likely be a lot of snow in this region, with above average snow likely.

Southeast: December will likely start out as an average month, but as the SE ridge develops, warmer than normal temperatures and drier than average conditions are likely to develop and persist for a good part of the winter. There will be a few times when strong yet brief cold spells could make it down to the SE, but this will likely not be too frequent.


Uncertainty:

This is only a winter forecast, and with it still being my preliminary outlook (my final outlook will be posted in early-mid November), there is still some uncertainty with parts of the forecast. Some uncertainties include the southern/western ends of the above average snow area, the extent of below/above average temperatures in the west, and how far north the above average temperatures extend in the Mid Atlantic.



Experimental forecast snow totals by city:

New York City: Average: 26. Forecast: 19-31
Philadelphia: Average: 19. Forecast: 15-24
Washington DC: Average: 16. Forecast: 9-16
Richmond: Average: 13. Forecast: 3-7


Part 3: Forecast Maps For The United States









Sunday, October 24, 2010

Oct 24, 2010: Above Average Temps Until Wednesday

Note: I finished working on my preliminary Winter 2010-2011 outlook, it will likely be posted tomorrow in the late afternoon or evening hours.

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Today was a mostly cloudy day for most of the area, with warmer temperatures as a warm front moved through the region, bringing in a much warmer air mass with 850 mb temperatures rising over 10c for the first time in the last few weeks. Widespread light rain showers fell across most of the area during at least one part of the day, with heavier precipitation further north into central/northern New York, where snow also fell in the higher elevations.

The warm front will continue to push northeast, eliminating any significant cold air from the region, leaving most of the United States with a mild pattern, but a storm current in the NW US will change all of that in the middle of the week, bringing thunderstorms on Wednesday followed by a cold front which will end the week on a cold note.

Tomorrow's Outlook:

Tomorrow is expected to bring mostly cloudy skies to the area with warmer temperatures. High temperatures will be in the lower 70s inland, lower to mid 70s in the immediate NYC area, and in the mid to upper 60s for Long Island/S CT. A SW wind is expected.

Tomorrow night, a widespread area of rain and thunderstorms will move through the region. While the rain and thunderstorms will generally be light to moderate, with rainfall amounts between 1/4 and 1/2 inch, locally heavier thunderstorms are expected, which could bring up to 1 inch of rain to parts of the area. That potential will be mentioned in more details with tomorrow's update.

Tuesday - Wednesday: Much Warmer, Thunderstorms For Weds

There are no changes with the expected set up for this storm, which has been discussed in more details in yesterday's post, and with it being in the short range, no significant changes are likely to the expected scenario. The low pressure will rapidly strengthen on Monday night, peaking on Tuesday night in northern Minnesota near 955 mb, the intensity of a Category 3 hurricane, leading to strong wind gusts in parts of the Midwest as well as heavy rainfall.

The area will see dry conditions on Tuesday and Tuesday night, but with unusually mild temperatures, with Tuesday's highs in the mid to upper 70s in NYC, and overnight lows in the lower to mid 60s across most of the area.

On Wednesday, the cold front will move through the region, bringing rain and thunderstorms, locally heavy, and a few storms may be strong with gusty winds. High temperatures will be in the mid to potentially upper 70s in the immediate NYC area, and in the lower to mid 70s inland.

Thursday - Friday: Brief Cold Spell

On Thursday, the cold front will be east of the area, but mild temperatures will briefly persist, with highs in the upper 60s to lower 70s in the immediate NYC area and in the mid 60s inland. On Thursday night, however, the trough will start to move into the area, and despite the cold air mass having moderated to the point where 850 mb temperatures are barely below 0c, colder temperatures are still likely, with low temperatures on Thursday night dropping into the 40s for most of the area and 30s inland, including parts of the N/W suburbs of NYC.

Friday will be a colder day, with 850 mb temperatures near -1c, and comparing the air mass to the one we had on Friday the 22nd, when 850 mb temperatures were near -4c, this would mean that high temperatures will be slightly warmer than those of the 22nd, potentially in the lower 50s inland and in the mid 50s for the immediate NYC area. Friday night would then be the coldest night, with lows potentially in the lower 30s inland and in the mid 30s for the N/W suburbs of NYC and in Long Island/S CT. Note that these forecast temperatures are still subject to change as there is still some uncertainty with the intensity of the trough and the timing.

Saturday And Beyond: Warmer, Then Another Storm Possible

By Saturday, however, it is likely that the cold air mass exits the region. A weak low pressure in the north central US will be moving east, and is likely to stay to the north of the area, meaning that it will help to draw in a mild air mass while pushing the trough out of the region, like what today's low pressure in the north central US was doing in some ways. The storm could bring some light rain for Halloween, otherwise partly to mostly cloudy skies are likely with warmer temperatures than Saturday, potentially in the upper 50s to lower 60s.

Attention then turns to the central US, where like this week's pattern in some ways, it is possible that a storm could form in the first 1-2 days of November and move NE, well NW of the area, bringing in a colder air mass into the United States again which would move towards the area. Stay tuned for more details on this time frame.

Saturday, October 23, 2010

Oct 23, 2010: Monday Night, Wednesday Thunderstorms

This morning was the coldest of the year so far, with lows ranging from the upper 2 s inland to the lower-mid 30s for most places north and west of NYC, with lows in NYC in the lower to mid 40s. The colder spots in eastern Long Island also reached the lower 30s this morning. Temperatures warmed up quickly in the afternoon, and the highs were slightly warmer than expected, peaking in the mid 60s across most of the area.

During the next few days, a much more active pattern will unfold, including the potential for severe weather on Wednesday with thunderstorms and heavy rain.

Sunday/Monday Forecast:
Tomorrow's outlook hasn't changed much, please refer to yesterday's discussion for today's expected temperatures. Monday is expected to be mostly cloudy with highs warming up, reaching the mid 70s in the immediate NYC area. A weak low pressure is going to bring widespread rain and thunderstorms on Monday night, however rainfall amounts for the main part will be light, ranging from 1/4 to 1/2 inch. Locally heavier rainfall amounts are still possible, potentially up to 3/4 inch.

Tuesday And Wednesday: Major Storm Expected


As I previously mentioned with the expected set up for this time frame, a low pressure entering Canada tomorrow will be in southern Canada on Monday, merging overnight with a rapidly developing low pressure to its south to form an intense storm in Minnesota on Tuesday.

This storm is expected to peak near 960 mb, the equivalent of a Category 2 hurricane, which will lead to strong winds in the Midwest along with heavy rainfall, as well as some snow at the end of the storm as colder air gets drawn into the NW side of the storm. Meanwhile, the storm will draw in much warmer air into the Eastern US, which will lead to widespread thunderstorms south of the storm, potentially strong.

The area will see mostly cloudy skies on Tuesday with highs in the lower to mid 70s, and as the warmest air mass moves through overnight, with 850 mb temperatures near 18c, low temperatures will be unusually mild, even warmer than the average high temperatures, reaching the mid to upper 60s in the immediate NYC area.



Wednesday: The storm is expected to peak in intensity on Tuesday night between 960 and 965 mb, and will remain stationary while starting to weaken and drifting ENE. The rain, however, will expand, with a strong cold front leading to a long line of heavy rain and thunderstorms moving through the Ohio Valley, with strong wind gusts being a threat with these storms.

On Wednesday, the cold front will move through the area. As the expected scenario has not changed, I am using yesterday's scenario map for this section. The strong cold front, with a much colder air mass behind it, will run into the very warm air mass in the region, with 850 mb temperatures between 15-18c, which will lead to thunderstorms. With precipitable water values near 2 inches, these storms could produce locally heavy rainfall. CAPE is expected to be up to 750-1000, LI between -2 and -4, and bulk shear will be near 50 knots, which will lead to the potential of strong to severe storms, with strong wind gusts being a risk. As with yesterday's update, I am mentioning the potential of heavy rain/gusty winds for Wednesday in the 5-Day Forecast.



Longer Range: Colder, Then Warming Up For Halloween

For the longer range, it now appears that the pattern will be too progressive to allow a storm to form and move up the coast. Thursday will bring slightly cooler temperatures but with drier conditions, though as the trough enters on Thursday night, temperatures will start to cool down, with low temperatures returning into the 40s, and even potentially 30s for the interior. Friday will then bring colder temperatures with highs in the mid 50s to lower 60s possible.

The trough will already be in the area on Friday, however it will have significantly moderated from when it comes into the United States in the middle of the week, which means that the cool down won't be as strong as the current one, but still strong enough to cause a large change in temperatures from the early-mid week. Friday night could be the coldest night, though there is some uncertainty with the trough's intensity and how far south it gets.

Looking at the general pattern, however, a storm should enter the NW US on Thursday, and start to move east, and if it's far north enough as currently expected, it will quickly push out the cold air mass by Saturday night, leaving most of the United States with a mild air mass again, and leading to chilly but not as cold conditions for Halloween. If this verifies, this could leave us with a set up quite similar to the one we will be dealing with this week, as the GFS model is already hinting of a storm that may form in the central US on November 1st, affecting the region between November 2-3. Stay tuned for more details on this time frame.

Friday, October 22, 2010

Oct 22, 2010: Warmth To Return, Storm On Wednesday

Note: Two alerts are currently in effect for the area, a Frost Alert for most of the area other than NYC, and a Freeze Warning inland. In addition, I am currently working on my preliminary Winter 2010-2011 outlook, which will probably be posted sometime next week.

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Today was the coldest day of the year so far for many places, with high temperatures ranging from the upper 40s in the interior areas to the lower-mid 50s in the immediate NYC area. Due to more cloud cover than expected, the low temperatures this morning were slightly warmer than expected. This was associated with widespread showers in the Northeast, which combined with cold temperatures led to many places seeing their first snow showers in the Northeast this morning.

With clear skies, tonight will see very cold lows, as low as the upper 20s in Sussex/Orange counties, being why a freeze warning is in place for those areas, with frost alerts for the rest of the area except for NYC. Starting tomorrow, however, temperatures will steadily warm up, and a much warmer air mass will replace the current trough, leading to well above normal temperatures for early to mid next week, which will end with thunderstorms on Wednesday.

Tomorrow's Outlook:

Tomorrow will be warmer than today but still chilly as the cold air mass lifts out of the region. High temperatures are expected to range from the upper 50s inland to the mid 60s in the immediate NYC area. A west wind is expected.

Sunday - Monday: Warming Up, Mainly Cloudy

A warm front will move through on Saturday night, bringing in a much warmer air mass, with 850 mb temperatures rising above 10c, which hasn't happened in a while. Showers will fall in the central and northern Northeast, associated with a low pressure near the Midwest. While the northern Northeast will stay cold, the Mid Atlantic will significantly warm up, with high temperatures in the area ranging from the upper 60s to lower 70s, and upper 70s for southern Virginia.

On Sunday night, the warm front as well as the storm will continue to push northeast, bringing in even warmer 850 mb temperatures, while completely eliminating cold air from the United States, leaving a widespread mild pattern. What we need to pay attention to then is a strong storm entering the NW US on Sunday, which will influence the pattern for the rest of the week.

Monday will be a warmer day with mostly cloudy skies, with high temperatures from the upper 60s to mid 70s across the area, but it will only continue to get warmer from this point.

Tuesday - Wednesday: Strong Cold Front To End Warmth

Storm Set Up: As I previously mentioned, we need to pay attention to the storm entering the NW US on Sunday, which will drive the pattern for most of the week. Not much details have changed since I first discussed the set up of this storm several days ago, other than some minor timing differences. A low pressure related to the storm will form in SW Canada and move ESE, being just north of Montana on Monday afternoon. On Monday night, a low pressure will start to rapidly develop near Iowa, moving NNE, then merging with the storm further north to form an intense sub-970 mb low in Minnesota on Tuesday.

This storm, meanwhile, will start to pull down colder air into the north central US, while drawing in an even warmer air mass into the East, including the Mid Atlantic. As it reaches its peak intensity, the storm will be nearly stationary on Tuesday night, then start to move ENE while weakening. On Tuesday, the heaviest precipitation will be located near the Great Lakes, but on Tuesday night, will start to move eastward in the form of a line of potentially strong thunderstorms along a strong cold front, which will later affect the NYC area on Wednesday afternoon.

Storm Forecast: Some light to moderate rain is expected for the area on Monday night, but that will be from a different system. Tuesday will bring even warmer temperatures for the area, with highs in the lower to mid 70s, with Tuesday night being unusually mild for this time of the year, with lows in the upper 50s inland and lower to mid 60s for the immediate NYC area.

On Wednesday, the strong cold front will move through the area, bringing a round of rain and thunderstorms, potentially strong, and with precipitable water values nearing 2 inches, locally heavy rain is also possible with these storms. Wednesday is when the high temperatures will be at their warmest, potentially near the upper 70s in NYC, with mid 80s for southern Virginia.

Note that there are still several days left until this event, and there is still some uncertainty on the forecast, so it may change a little over the next few days. Stay tuned for more details on this storm.

Longer Range: Modified Cold Spell?

At this time, the models are suggesting that the pattern will be too progressive to allow for a low pressure to move inland through the eastern US as yesterday's models suggested, with the trough simply moving into the region on Friday with a coastal low on Thursday night mainly staying offshore but potentially affecting the area. By then, however, the cold air mass will have moderated, and will bring temperatures similar to those of today, if not a little warmer. This is still in the longer range though, and there is uncertainty on this time frame, so it may still change over the next few days.

Thursday, October 21, 2010

No Update Oct. 21

No full update will be posted tonight. The next update will be posted tomorrow evening.

The 5-Day Forecast was updated today, and the forecast is the same as yesterday's other than some minor changes, being making the longer range a little warmer, with Monday's highs in the mid 60s to lower 70s and Tuesday's highs in the upper 60s to mid 70s across the area. For the longer range, rain and thunderstorms are likely on Tuesday night, with another storm bringing rain to the area on Thursday to Friday followed by colder temperatures.

Tomorrow's update will discuss the longer range in more details, as well as an update on Tropical Storm Richard, which could strike the southern Yucatan Peninsula as a Category 2 or even Category 3 hurricane on Sunday.

Wednesday, October 20, 2010

Oct 20, 2010: Very Active Pattern To End October

Today was a mostly cloudy day due to a storm passing to the south of the area, bringing heavy rain to a narrow area from central VA into the Delmarva Peninsula and southern New Jersey. Low temperatures this morning were quite chilly, in the lower 30s inland and in the upper 30s to mid 40s in the immediate NYC area. High temperatures were in the upper 50s to lower 60s across most of the area.

Up to today, the pattern in October has generally been average, with no extremes as we have seen in previous October, such as lows well into the 30s and 20s, accumulating snow in the interior parts of the area as we've seen last year and in 2008, or high temperatures into the 80s or even 90s. The cold spell expected for Friday and Saturday will bring below average temperatures, but nothing unusual for this time of the year. Next week, however, a much more active pattern will set up, with two large storms and a potential cold spell to end October.

Tomorrow's Outlook:


The area will see cloudy skies tomorrow morning and afternoon with some clearing in the late afternoon and evening hours, with a WSW turning WNW wind. High temperatures will be in the mid to upper 50s inland, lower to mid 60s for the immediate NYC area, and lower to mid 60s for Long Island/S CT.

The cold front moving through will bring scattered showers to the area, but thunderstorms may also be possible, potentially strong. There is expected to be a LI around -2, but bulk shear will be around 50 knots, which could lead to thunderstorms from NYC into Long Island and southern New England during the afternoon as the cold front moves through, with the main threat being small hail and gusty winds.

Tomorrow Night:


The trough will begin to move into the region tomorrow night, bringing much colder temperatures. Low temperatures will drop near or below the freezing mark in many places in the interior, which combined with scattered precipitation, could lead to widespread snow flurries mixing with the rain showers for a lot of places in the Northeast. Even accumulating snow may be possible in southern New York if some models verify.

Low temperatures will be chilly in the area, ranging from the mid 30s inland to the mid to upper 30s north and west of NYC and in S CT, upper 30s to lower 40s in Long Island, and lower to mid 40s in NYC.

Friday's Outlook:

Friday will be the coldest day of this cold spell, with high temperatures ranging from the lower 50s inland to the lower to mid 50s in the immediate NYC area. That is when the air mass will be at its coldest, with 850 mb temperatures near -4 degrees celsius.

On Friday night, the trough will start to exit, but that is when the coldest temperatures will happen. The models have trended slower with the timing, which is more reasonable as they were too fast yesterday. Low temperatures are expected to be in the lower 30s inland, lower to upper 30s for the N/W suburbs of NYC, lower to mid 30s for S CT, mid to upper 30s for Long Island, and lower 40s for NYC. Even upper 20s may be possible for the interior in the colder case scenario. Accordingly, I issued frost alerts for most of the area, with a freeze watch for the interior.

Weekend Outlook: Warming Up

As the trough exits for Saturday, temperatures will be warmer but still chilly. High temperatures will reach the upper 50s inland and in the lower 60s for the immediate NYC area. Overnight lows will also be warmer, ranging from the lower to mid 40s inland to the mid 40s to lower 50s in the immediate NYC area, though cloud cover will increase ahead of a low pressure.

Sunday will bring mainly cloudy conditions and scatterd showers, mainly to the north of New York City, as a low pressure from the west approaches the region. This will also help to draw in a warmer air mass, with high temperatures in the lower 60s inland and in the mid 60s in the immediate NYC area.

Early To Mid Week Outlook: Active Pattern Begins

On Monday, as the low pressure continues to push northeast, the area will see scattered showers but even warmer temperatures, reaching the mid 60s inland, and the upper 60s in the immediate NYC area, where lower 70s may even be possible if the area is dry. The attention then turns to the Midwest, where a developing storm will set the pattern for the rest of the week.

A low pressure will enter the NW US/SW Canada between Saturday and Sunday, with the low pressure then moving into Canada, being in southern Canada by Monday. Between Monday night and Tuesday, the storm will merge with a rapidly developing area of low pressure to its south, forming an intense storm by Tuesday afternoon, which there is uncertainty on the location but it could be located near the NW Great Lakes. This storm will then expand, bringing heavy rain from the Great Lakes into the Ohio Valley, and while the timing is uncertain, the storm could bring rain and thunderstorms to the area between Tuesday afternoon and Wednesday afternoon.

This storm will draw in a warm air mass into the region while pulling down a trough into the north central US, and high temperatures could reach the lower 70s across parts of the area on Tuesday. This will leave a colder air mass in the area, but if the latest models verify, the trough may not move into the Mid Atlantic just yet.

Mid To Late Week: Potential Storm, Cold Spell

The models are now hinting of a low pressure forming in the Southeast and moving NE up the East Coast, affecting the area around Thursday. There is more uncertainty on this time frame, and this solution could change with the next few runs, but if the current solution was to verify, the storm could bring rain to the area on Thursday, and after it exits, the strong trough in the central US and Canada would drop into the region, bringing a cold end to the month and starting November on a cold note.

As I previously mentioned, this is still in the longer range, and can still change. Stay tuned for more details on this time frame.

Brief Tropics Update:

Invest 99L in the western Caribbean has gotten itself much more organized, and will become Tropical Depression 19 at 11 PM. If it is named, it will be named Richard, only the 3rd storm to have a name start with "R" since naming tropical cyclones started in 1950, and would be the 17th named storm of the season. There is uncertainty on where TD19 tracks, but it will likely affect the Gulf of Mexico. More updates will be posted on TD19 in the next few days if needed.

Tuesday, October 19, 2010

Oct 19, 2010: Cold Friday, But Warmer Weather To Follow

Today started out mainly cloudy, with showers in parts of the area due to a wave of low pressure that brought up to 1 inch of rain in south-central PA and NJ, though skies cleared by the afternoon, with high temperatures rising into the upper 50s across most of the area other than a few lower 60s in the immediate NYC area.

Tomorrow's Outlook:



Partly sunny skies are expected for the area tomorrow, with a SW wind. The air mass will remain similar to today, but slightly warmer, leading to slightly warmer temperatures. High temperatures will rise into the lower 60s inland, lower to mid 60s for the immediate NYC area, and lower 60s for Long Island/S CT.

Another wave of low pressure is expected to be active tomorrow morning, however it will be further south than today's wave, with the low pressure expected to be off the Carolinas, producing locally moderate to heavy rain from Virginia into the Delmarva, where amounts locally up to 1 inch or slightly higher are expected. The rain will stay to the south of the NYC area.

Thursday - Saturday: Cold Spell, Widespread Frost Possible



On Thursday, a low pressure well to the north of the area will bring down a strong trough into the Mid Atlantic and Northeast, which will bring scattered showers to the area with highs in the mid to upper 50s inland and upper 50s to lower 60s in the immediate NYC area.

This air mass will be cold enough that it will be able to produce snow showers on Thursday night for a large part of New York State, and some flurries may even reach the interior parts of the area if it gets cold enough and there is precipitation. Low temperatures are expected to be in the lower to mid 30s inland, mid to upper 30s for S CT and the north/west suburbs of NYC, upper 30s to lower 40s for Long Island, and mid 40s for NYC.

Friday will be the coldest day of this cold spell. With the coldest 850 mb temperatures during Friday afternoon near -4c, this will lead to the coldest high temperatures yet for most of the area under dry conditions, with highs currently expected to be in the lower 50s inland and the mid 50s for the immediate NYC area as well as Long Island/S CT.

Friday night will have similar low temperatures to Thursday night, though the trough will start to exit around this time as another low pressure approaching the Great Lakes will push this trough quickly to the east while another trough develops behind the second low pressure. The second trough, however, won't dig as far south as this one.

Saturday will bring a return of warmer temperatures as the trough exits the area and a low pressure is well to the north of the area. Partly sunny skies are expected with highs in the upper 50s to mid 60s across the area, but increasing clouds are expected on Saturday night, marking the start of a wet time frame from Sunday to Wednesday.

Sunday - Monday: Warmer, But Wetter

On Sunday, as the second trough settles in the Northeast, bringing dry conditions and cold temperatures for northern New England, the area will be south of the trough, with a low pressure near the Ohio Valley approaching the area. This will lead to occasional showers throughout the day, but with the warmer air mass, high temperatures will warm into the lower to mid 60s for most of the area.

On Monday, the trough will start to exit the Northeast as the low pressure pushes northeast, and the area will still see occasional showers but with warmer temperatures, near the upper 60s for the immediate NYC area.

Tuesday And Beyond: Storm Potential

For the middle of next week, the pattern will be dominated by an intense storm in the north central United States. Looking at the overall scenario, a low pressure entering the NW US on Saturday will be in south central Canada on Monday, and will likely merge with a rapidly developing low pressure to its south on Tuesday to form an intense low pressure located in the north central US. With a large ridge in the eastern US, a strong trough will start to drop into the Dakotas and Minnesota, which would interact with the storm. This will set the stage for Wednesday's pattern.

Drier conditions are possible for the area on Tuesday, but a much warmer air mass will enter, with 850 mb temperatures above 10c, leading to highs potentially reaching the lower 70s if dry conditions take place. On Wednesday, as the low pressure reaches its peak intensity, a strong cold front approaching the area will push the ridge offshore, with a strong trough moving into the United States, which would later bring colder temperatures to the area. While there is uncertainty with the smaller details, given that this is a week away, the strong cold front would be able to produce heavy rain and thunderstorms for the area, and even severe weather cannot be ruled out.

This is my current understanding on the potential scenario for this time frame, and as this is in the longer range, could still change. Stay tuned for more details on this storm and how it may affect the area.

Monday, October 18, 2010

Oct 18, 2010 : Cool Conditions To End This Weekend

Note: I apologize for not being able to fully update the blog lately, including the 5-Day Graphics and the Long Island/S CT forecasts, as I have been busy lately. Once I have enough time, I will update these parts of the website, including adding more graphics to the daily discussion.

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Today was a partly to mostly cloudy and dry day, with high temperatures ranging from the upper 50s inland to the lower 60s in the immediate NYC area. A few showers are expected for tonight into tomorrow morning, as well as Thursday, but anything more than light rain will wait until next week, when a warmer pattern is expected to dominate most of the United States.

Tomorrow's Outlook:

Tomorrow will be mainly cloudy due to a weak low pressure riding along a stalled frontal boundary to the south of the area, but most of the rain will stay to the south. High temperatures will be in the upper 50s to lower 60s across the area.

Wednesday's Outlook:

As another wave of low pressure stays to the south of the area, mostly cloudy skies are expected, with slightly warmer highs, in the lower 60s inland and lower to mid 60s in the immediate NYC area.

Thursday - Friday: Scaled Down Cold Spell?

A low pressure near the Great Lakes on Wednesday will move east and drop a strong trough into the region on Thursday afternoon. Thursday night will bring colder temperatures with low temperatures ranging from the mid 30s inland, to upper 30s-lower 40s in the N/W suburbs of NYC, to the upper 40s in NYC.

Afterwards, however, a slight change took place in the forecast. The whole pattern is now modeled to go faster than previously expected, with the trough moving in on Thursday night, not Friday. Looking at the pattern in the West Coast, a low pressure in southern Canada is modeled to be further south than previously expected, which prevents the trough in the East from digging as far south as it could have been. With the low pressure in Canada also moving faster than expected, it is expected to quickly push out the trough in the region, with the 0c line already moving out by Saturday morning when it was supposed to be at its southernmost extent.

While I think that the models could be a little too fast, this reduces the probability of seeing frost in the immediate NYC area and freeze inland. If the faster solutions do verify, no freeze will be observed inland, and the first freeze of the fall may end up coming later than the average. For now, I am going for a solution close to the NAM/GFS but a little slower, expecting Saturday's highs in the mid 50s to lower 60s across the area, which is slightly below average, and lows in the mid-upper 30s inland and upper 30s to mid 40s in the immediate NYC area, which is close to the average lows. Note that these forecast temperatures are still subject to change over the next 2 days.

Saturday And Longer Range: Warmer, Rain Returns

What is likely is that on Saturday, warmer temperatures return to the area. The low pressure in southern Canada that I previously mentioned will be near the Great Lakes, which will bring another trough behind it. While there is uncertainty on how far south it drops, at this time I think that it will mainly stay in the Northeast, with the southern end potentially clipping the area. It is possible that the trough could be a little further south, but at this time it's only a possibility. An area of rain is likely to set up near the southern end of this trough, which would bring several waves of weak low pressures to those areas producing light to moderate rain for Sunday and Monday. At this time, this is shown to be over the area, but could end up being slightly further north or south. Stay tuned for more details.

Afterwards, the pattern of a positive PNA and negative NAO is expected to collapse, with the trough and high pressure in the NE exiting and a storm potentially active in the north central US. This would bring a ridge into the area with warmer temperatures, with a rain storm possible for the 26-28th of October as the storm moves further east. This potential is still in the longer range, but it will be kept an eye on.

Sunday, October 17, 2010

Oct 17, 2010: Chilly Start, Cold End To Week

Today was a mainly sunny yet rather mild day, with high temperatures ranging from the upper 60s inland and in Long Island/S CT to the lower 70s in the immediate NYC area. While this is warmer than the average, we have seen 80s in this time frame before, most notably in 2007, also when 90s were observed in early October. This week, however, will bring much cooler temperatures, as well as several snow potentials in the higher elevations of the Northeast.

Tomorrow's Outlook:

Tomorrow will bring colder temperatures as a trough moves into the Northeast, though the models yesterday overestimated the intensity of the trough, a bias that they usually have. A WNW wind is expected during the day. I went slightly warmer than yesterday's forecast, expecting upper 50s to lower 60s inland and lower to mid 60s in the immdiate NYC area. Long Island/S CT will have highs in the lower 60s.

Tuesday And Wednesday: Cloudy, Chilly, And Rainy

The cold front related with the trough will stall in the central/southern Mid Atlantic tomorrow night. A weak wave of low pressure will ride along the stalled front, moving through the central Mid Atlantic. The heaviest rain will fall in southern Pennsylvania into central New Jersey, where at least 1/2 inch of rain is expected. The area will see around 1/4 inch, with high temperatures in the lower to upper 50s. It may be cold enough that some snow could fall in NE PA and in the Catskills, but the question is if enough precipitation can reach these areas and if it will be cold enough for that to happen.

Tuesday night will bring drier conditions but mainly cloudy skies, while another storm starts to form along the stalled front. This storm will be further south than the first one, and will bring moderate rain to the central/southern Mid Atlantic on Wednesday. While the area is expected to be dry, an isolated shower south of NYC cannot be ruled out. High temperatures will be slightly warmer than those of Tuesdady.

Thursday - Saturday: Cold Spell Potential

On Thursday, an area of low pressure near the Great Lakes will bring through a cold front, with widespread showers for the area in the afternoon, which will end by the evening. A strong trough behind this cold front will drop into the region, with 850 mb temperatures potentially below zero degrees celsius. If this solution is to verify, some snow flakes would fall in the interior NE on Thursday evening/night, with lows dropping into the 30s for a lot of places. Friday would bring much colder temperatures with highs in the lower to mid 50s for most of the area, and on Friday night, just as the trough is about to exit, low temperatures have the potential of reaching the upper 20s to lower 30s inland according to the GFS model.

While there is still some uncertainty on what happens, for example the GGEM doesn't show a trough as strong as the GFS and has it further north, but a strong trough is generally expected around this time frame, which could bring cold temperatures to the area. Stay tuned for more details on this time frame.

Longer Range: Warm Up, October 26-28 Storm?

After the trough exits, warm air will spread into the region, and unless a trough shown to be in southern Canada on the models doesn't drop south, then according to the latest models, a much warmer pattern will take place for the central/eastern United States, with high temperatures potentially back into the 70s. The models are likely to change though, so there is still uncertainty.

The GFS model has been consistent in showing a storm around the 27th, tracking well to the north/west of the area and bringing potentially heavy rain. This potential will be tracked over the next few days, and will be discussed in more details if it remains on the models over the next few days.

Saturday, October 16, 2010

Oct 16, 2010: Cold Spell Potential Next Friday

Today was a partly sunny and windy day, with highs ranging from the upper 50s inland to the lower 60s in the immediate NYC area. The winds are calming down, and some frost is possible tonight in the interior with lows in the mid 30. From now until next weekend, however, cold temperatures will be the main issue.

Tomorrow's Outlook:

As the trough exits and another one approaches, the area will see slightly warmer 850 mb temperatures, leading to warmer temperatures. High temperatures will be in the lower to mid 60s inland, mid to upper 60s in the immediate NYC area, and the mid 60s for Long Island/S CT.

Monday - Wednesday Outlook:

A trough will move into the Northeast on Monday, and while it will not dig very far south, it will be quite strong, bringing highs into the 40s for the interior Northeast. The area will be in the southern end of the trough, with 850 mb temperatures near zero, which in comparison today also had 850 mb temperatures near 0 degrees celsius. This will lead to high temperatures in the mid 50s to lower 60s across the area on Monday.

The cold front will stall to the south of the area, in West Virginia and Virginia, and a wave of low pressure is expected to form along this stalled front and move towards Virginia and Washington DC. This will bring a wide area of moderate rain in Virginia, New Jersey and southern New England. As this will be a cold storm, some snow is possible on Tuesday morning for the Catskills and NE PA, and if the colder case scenario verifies, some flakes may even be possible for the higher elevations of Sussex county in NJ and Orange County in NY. There is uncertainty on where the storm ends up, as it could be suppressed, but at least 1/2 inch of rain could be possible out of this storm, with high temperatures in the mid 40s to lower 50s due to the cloud cover and rain. Stay tuned for more details.

Wednesday will be drier as the storm moves offshore with an isolated shower possible. High temperatures will be warmer than those of Tuesday, in the upper 50s to lower 60s.

Thursday - Saturday: Significant Cold Spell?

Yesterday, I mentioned the potential of a significant cold spell moving into the Northeast. A low pressure near the Great Lakes will bring a cold front into the Northeast on Thursday, and from there, the cold front may dig south into the Mid Atlantic, bringing a much colder air mass for Friday and Saturday. There is uncertainty if this does end up being the case as this is in the longer range and the models can still change, but a negative NAO/AO and a positive PNA hint that we could in fact see a trough move into the Northeast, and if the current models verify, high temperatures in the upper 40s to mid 50s and lows in the upper 20s to upper 30s could be possible, with widespread frost and freeze. Stay tuned for more details on this time frame and what it could bring.

Beyond Saturday, there is still a lot of uncertainty, however it is possible that a warm up could take place by the late weekend to early week.

Friday, October 15, 2010

Oct 15, 2010: Colder Pattern In Control This Week

The storm's rain ended in the overnight hours, with at least 1-2 inches of rain for parts of the area, but the storm's wind only started during the afternoon hours, with gusts occasionally reaching 40 mph in the central and eastern parts of the area. Windy conditions will continue through tomorrow, with a less windy and warmer Sunday, but from Monday and on, a cooler, much more fall-like pattern will set up across the Northeast and stay for the week.

Weekend Outlook:
Tomorrow will be a mostly cloudy and windy day, with winds from the northwest. High temperatures will be in the upper 50s inland, lower 60s for the immediate NYC area, and in the upper 50s to lower 60s for Long Island/S CT. Chilly temperatures are expected for tomorrow night, in the mid 30s inland and upper 30s to lower 40s for the N/W suburbs of NYC.

Sunday will briefly warm up as the trough exits the area, with high temperatures reaching the mid to upper 60s inland, upper 60s for the immediate NYC area, and mid 60s for Long Island/S CT, with a WSW wind expected, however this warm up will be short lived as a trough moves into the Northeast for Monday.

Monday - Wednesday Outloook:


As a trough moves into the Northeast on Monday, high temperatures will drop into the mid 50s to lower 60s, however things will only get colder from there. A cold front will stall to the south of the area, around Maryland/Virginia, with a wave of low pressure moving along the front. A cold air mass will be to the north, with a warm air mass bringing high temperatures in the upper 70s to the south of the cold front, in Virginia.

This wave of low pressure will be close enough to the cold air mass to bring a cold rain to the northern Mid Atlantic and southern Northeast. There is uncertainty on how cold the high temperatures will be, the current models show highs in the lower to mid 40s. For now I went warmer than the models, expecting highs in the upper 40s to mid 50s, but this is still subject to change. Light to moderate rain will fall during the day, and it may be cold enough that a little snow falls in the Catskills, however this potential is still uncertain.

On Wednesday, some showers are still possible with slightly warmer temperatures, but meanwhile a low pressure may start to move into the Great Lakes, bringing a strong trough along with it that could affect the area on Friday and Saturday. There is still a lot of uncertainty on this time period, though a negative NAO/AO suggest that a trough could in fact move into the Northeast. Stay tuned for more details on this time frame.

Thursday, October 14, 2010

Oct 14, 2010: Final Storm Forecast

Note: The graphics and information for most of this post were created around 5-6 PM, but I was unable to post it over the last 2 hours, so some information here is not up to the latest radar observations.

***Due to a computer error, no second update will be posted tonight. An update on the longer range will be posted tomorrow, with details about the wind lasting through Saturday, a storm for Monday-Tuesday, and a cold, much more fall-like pattern that may set up afterwards.***

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8:26 PM: Moderate rain has been falling over most of the area for the last several hours, with heavy rain now moving into Long Island. This storm will start to end over western New Jersey over the next 1/2 to 1 hour, with the end of the rain moving from SW to NE.

Rainfall amounts so far are generally between 1/2 to 1 inch from central New Jersey and further east, with at least another 1/4 to 1/2 inch of rain possible before the rain ends for central NJ. Further east, a round of heavy rain will move in for tonight, with more on that below.



Tonight's Forecast:


As the low pressure deepens off the coast, it will continue to become negatively tilted, meaning that the precipitation will run from ESE to WNW, instead of south to north as we've seen earlier today. The low pressure is currently near 1004 mb and is off the coast of Delaware, moving northeast. As it is expected to move NE, then NNE late tonight, it will continue to quickly intensify, reaching 995 mb after midnight, with the rain becoming more widespread and heavier. The models did in fact end up trending east from yesterday's solutions, and this is the direction I followed for this forecast.

By that time, however, most of the rain will have already passed the area, with generally light rain remaining for places outside of Long Island/Connecticut. As the rain map in the bottom of this post shows, the storm will have its greatest impact on New England in terms of rain. Heavy rain, however, will continue to affect Long Island and Connecticut through most of the overnight hours, and a few thunderstorms are also possible.


Tomorrow's Forecast:

The storm is expected to have peaked in intensity by the early afternoon hours, near 975 mb. It will become vertically stacked around then, meaning it can no longer intensify, and will stall until the evening hours, when it will start to slowly move to the NE. Precipitation will be the heaviest and most widespread around the early afternoon, with heavy rain affecting most of New England and Maine. As a colder air mass will also enter New England, wet snow will fall in the higher elevations. Throughout the evening hours, precipitation will weaken throughout the Northeast.

The rain will be northeast of the area, with a cloudy and windy day expected due to the low pressure northeast of the area. Winds will be sustained between 25 and 35 mph, with gusts up to 50 mph possible in the immediate NYC area and Long Island/S CT, being why I have a Wind Alert in effect, which was issued 2 days ago. The central/southern Mid Atlantic will see some light rain due to a weak disturbance moving into these areas, south of the main storm. High temperatures will be in the mid 50s to lower 60s across the area.

Friday Night - Saturday: Chilly, And Windy

As the storm moves out on Friday night, lows will be in the lower 40s inland, lower to mid 40s north/west of NYC, and in the upper 40s for NYC and closer to the coast, with Saturday's highs in the mid 50s to lower 60s across the area. The windy conditions will continue until Saturday afternoon, then start to calm down.


Overall Storm Forecast:

By the time that the storm ends, totals will be similar to where they are now in the interior, slightly higher in the immediate NYC area, and between 1 and 2 inches for Long Island/S CT. To the left, I posted my rain map for the storm from 2 PM today, and I also included a snow map for the interior Northeast, as snow will begin to fall in the higher elevations tomorrow afternoon and last through Saturday, bringing the first flakes of the season to many places.


As this is a high elevation snow event, some places will see less snow than the map shows, with the higher elevations potentially seeing more snow than the forecast shows. Snow totals will generally be in the 1 to 3 inch range in places where snow does accumulate, and it will be wet snow.

Wednesday, October 13, 2010

Oct 13, 2010: Rain/Wind To Start Tomorrow

Today was a mainly sunny day across the area, and temperatures were slightly cooler than those of yesterday. Starting tomorrow, however, clouds will return to the area, and a rapidly developing nor'easter will produce a round of heavy rain followed by windy conditions for the area, and will even produce several inches of snow for the higher elevations of the Northeast.


Thursday - Saturday: Storm, Wind Expected


Thursday: Tomorrow will start out partly cloudy, but cloud cover will increase in the morning due to an approaching storm, and the afternoon will bring cloudy skies with a SE wind expected. High temperatures will be in the mid to upper 50s inland, lower to mid 60s for the immediate NYC area, and lower 60s for Long Island/S CT.

The storm, meanwhile, will approach from the west, with a weak low pressure starting to develop in eastern Virginia, producing heavy rain in central/northern Virginia and Maryland. There is still some slight uncertainty with the development of the storm, and at this time, I am considering the latest GFS runs to be potential outliers, as they seem to be developing a low pressure well off the coast instead of the one in eastern Virginia, leading to a much more progressive and weaker storm that barely brings 1/4 inch of rain to the area. For this forecast, I am leaning towards the NAM/GGEM/ECMWF models, which the NAM and ECM have been more consistent.


Thursday Night: As the low pressure moves offshore and the trough becomes negatively tilted, the storm is expected to begin to rapidly intensify while moving northeast, producing a developing area of heavy rain to the west of the storm, which will make its closest approach to the area between 11 PM and 4 AM when the low pressure is just near the eastern end of Long Island with minimum pressure close to 990 mb.

The question is how far west the heavy rain extends, with some models focusing the heavy rain in Long Island and the others on northern New Jersey. More on this will come with tomorrow's final forecast for the storm, when it will be possible to compare the latest data to the storm and make more accurate short term forecasts, but for now I am thinking the heaviest rain falls near NYC and western Long Island, with 1.5 to 2 inches of rain falling overnight.


Friday: The storm will peak in intensity during Friday afternoon, when a sub-980 mb low is expected over eastern Massachusetts. The storm will then have become vertically stacked, and will no longer be able to intensify, meaning that from Friday afternoon and on, the storm will begin to weaken along with the precipitation. A few showers are possible during the day on Friday, but with the storm to the northeast, Friday will mainly be a cloudy and chilly day, with highs in the lower to upper 50s. Windy conditions will also develop, with a WNW/NW wind gusting to 40-50 mph for the central/eastern parts of the area.

For the Northeast, however, while the storm is at its peak intensity, cold air will enter the storm from the northwest, leading to temperatures reaching the mid 30s in the higher elevations of the Northeast, including the Adirondacks and the Catskills. This will be enough to support snow falling over these areas, with as much as several inches of wet snow possible. Widespread heavy rain will affect central/northern New England, which will begin to weaken by the evening hours.


Storm Summary:

By the time that the storm is over, at least 1 to 2.5 inches of rain are expected for the area, with the highest amounts towards east central NY further east into central New England. It is possible that the GFS ends up being correct in its eastern solution, and while at this time I am leaning towards the western solutions, it is possible that tomorrow's update could be different, especially as details become clearer. More details will be posted with tomorrow's update, as well as rain and snow maps.

Longer Range: Chilly, Then Cold?

Tomorrow's update will also cover more on the longer range, including a potential cold spell that may affect the area starting on October 20. Stay tuned for more details on this time frame.

Tuesday, October 12, 2010

Oct 12, 2010: Nor'easter To Bring Heavy Rain, Wind

Note: While today's update is only a brief one, the 5-Day Forecast page and the Weather Alerts page were updated. A more detailed discussion will be posted tomorrow.

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For Wednesday/Thursday, the forecast remains the same as it was yesterday, though Wednesday is expected to be slightly warmer than yesterday's forecast.

Rain will start falling on Thursday afternoon, and will increase in intensity during the overnight hours, becoming lighter by Friday in the late morning. At least 1 to 2 inches of rain are expected with locally higher amounts possible. Windy conditions will also develop and persist until Saturday night.

The forecast temperatures remain the same as yesterday's update, with Saturday night being the coldest night.

Monday, October 11, 2010

Oct 11, 2010: Heavy Rain, Wind Possible For Friday

Severe thunderstorms moved through the area this evening, bringing wind and hail damage to places near New York City. Before the storms, it was a mainly sunny, mild day with highs in the 70s. Today, however, was the last mild day for a while. Tomorrow will bring light rain and chilly temperatures to the area, and a trough will then affect the area through Thursday. On Friday, a strong nor'easter may affect the area, potentially bringing heavy rain, windy conditions, and even accumulating wet snow to the higher elevations of the Northeast.

Tomorrow's Outlook:

Tomorrow will be a mainly cloudy day with light rain expected mainly before noon. High temperatures will be in the mid to upper 60s inland, upper 60s in the immediate NYC area, and mid 60s in Long Island/S CT. A north wind is expected.

Wednesday - Thursday: Chilly, Dry

A trough will move into the area on Wednesday, and while it will not be very strong, it will be enough to cool temperatures even more, into the upper 50s to lower 60s inland and in Long Island/S CT, with lower to mid 60s in the immediate NYC area. Thursday is expected to be slightly warmer in Long Island/S CT, similar temperatures in NYC, and colder temperatures inland, with increasing cloud cover.

Thursday Night - Saturday: Strong Nor'easter Potential


Over the last few days, I mentioned in my discussion that with the pattern setting up, a -PNA leading to a west coast ridge and a trough dropping into the central United States, that a coastal storm could form along the coast of the Mid Atlantic. The models have now trended towards this solution, and while there is uncertainty on where the storm develops, it is likely that the storm goes through rapid intensification on Thursday night, stalls near New England on Friday, then starts to slowly head northeast again on Saturday.

This storm will react with the trough to its northwest, which would lead to cold air entering the storm. As a result, if this solution verifies, the area would see a cold, heavy wind-driven rain, with high temperatures in the mid 40s to lower 50s, and 1-3 inches of rain are possible with the heaviest rain on Thursday night. The storm could draw in enough cold air to produce accumulating wet snow in the higher elevations of the western Northeast. Behind the storm, a cold air mass would then enter the Mid Atlantic, leading to high temperatures in the 50s/60s and lows in the 30s/40s on Saturday, with a warmer air mass returning for Sunday.

There is still uncertainty with this storm as it only recently showed up on the models, and while some trending is expected, it is likely that an intense storm will be present during this time frame, potentially having a significant impact on the area. Stay tuned for more details on this storm and how it may affect the area.

Oct 11, 2010 Severe Thunderstorms

***NYC Area Weather has issued a Severe Thunderstorm Watch for the interior and the immediate NYC Area. Even though storm updates will be posted, please refer to the National Weather Service for the latest alerts and warnings.***

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**Note: Click on the short term outlook maps to the right of each storm update to view them in a larger size.**

9:10 PM: The severe thunderstorms are currently in southwestern Long Island, focusing near JFK, and moving ESE and out to sea. Light to moderate rain and thunder will affect central/eastern Long Island, with locally heavy storms also expected.

The storm coverage has ended for today. Stay tuned for tonight's update, which will be posted by 10 PM.


8:20 PM: The storm has changed directions. It is now moving more SE than ESE, now putting all of Hudson (NJ), Brooklyn, and parts of Queens and southern Manhattan in the path of this storm. Again, this is a very dangerous storm. Take cover if you are in the path of this storm.

Another severe thunderstorm has formed in northern Somerset county, NJ, moving ESE. This storm will affect Linden, NJ and parts of Staten Island, producing strong wind gusts, small hail, and heavy rain.


8:05 PM: WARNING: A severe thunderstorm currently in eastern Morris county is moving ESE, and will affect eastern Passaic, southern Bergen (including Fort Lee), Brooklyn, Manhattan, Hudson, and Queens over the next 1/2 to 1 hour. Expect damaging wind gusts, moderate to potentially severe hail, and very heavy rainfall with this storm. An isolated tornado also cannot be ruled out.

This is a very dangerous storm. Take cover if you are in this storm's path.


6:59 PM: The storms are currently moving east, and have weakened quickly. Most of the storms are no longer severe, though most of them are still producing thunder and moderate to light rain, locally heavy.







5:50 PM: An area of severe thunderstorms is currently located in northeastern Pennsylvania, and is moving to the ESE/SE. This storm is capable of producing strong wind gusts, small to moderate hail, and rainfall amounts up to 3/4 inch in a short period of time. While no tornado is currently expected, the storm did briefly show a tornado vortex signature earlier this hour.


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3:28 PM: An unexpected change took place in the forecast, and the storm currently approaching the area is producing severe thunderstorms ahead of it, currently in central Pennsylvania moving ESE towards New Jersey. While the severe storms are not likely to affect the entire area, they are likely to affect at least parts of the area, mainly the western and southern parts.

There is enough instability to support these storms maintaining strong to severe intensity while moving into New Jersey, but the storms are travelling in an ESE motion, indicating that they are going to mainly affect eastern Pennsylvania and central/northern New Jersey. The main risk with these storms is strong to damaging wind gusts and small hail. An isolated tornado cannot be ruled out.

Impact: Expect these storms to arrive around 5-6 PM, and affect New Jersey and New York City. Even though the storms will likely have the greatest impact on central/central western New Jersey, New York City could still see thunderstorms. Long Island and southern Connecticut will see less of an impact, with eastern Connecticut being the least likely place to be affected by these severe thunderstorms.

Storm updates will be posted if needed later this afternoon.


Evening Update: Potential Nor'easter?

Yesterday, I did not focus on the forecast specifics for this coming week as the update focused on the storm review, though for the last few days, I mentioned the potential of a coastal storm to affect the area between Thursday and Friday. Stay tuned for a full update later tonight, focusing on a strong nor'easter that may affect the area on Friday, potentially bringing heavy rain and windy conditions along with chilly temperatures to the area. Details will also be included on a tropical cyclone expected to form shortly in the Caribbean, which will be named Tropical Storm Paula.