Wednesday, August 31, 2011

Aug 31, 2011: Nice Pattern Continues

As the clean up from Hurricane Irene continues, a high pressure over the region brought yet another mostly sunny and seasonable day, with high temperatures in the lower 80s inland, mid to upper 80s in the immediate NYC area, and in the lower to mid 80s in Long Island/S CT. The set up bringing these seasonable temperatures will continue through Saturday, when an approaching cold front will bring scattered thunderstorms for the weekend through Monday.


Tomorrow's Outlook:

The high pressure over the region will stay in its place tomorrow as a cut off low develops in the western Atlantic, blocking a building heat surge in the Great Lakes from reaching the region, keeping seasonable temperatures in place. Partly sunny skies are expected tomorrow, with high temperatures reaching the upper 70s to lower 80s inland, lower to mid 80s in the immediate NYC area, and the mid 70s to 80 degrees in Long Island and southern Connecticut.


Friday And Weekend: Dry Conditions Turn Wet

The cut off low previously mentioned will remain stationary through Friday, which will help suppress the heat surge in the Midwest, which will bring temperatures into the upper 90s as far north as Michigan. With a SE wind, tomorrow will bring slightly colder temperatures, reaching the mid to upper 70s inland, upper 70s to lower 80s in the immediate NYC area, and the mid to upper 70s in Long Island and S CT.

As the cut off low pressure moves away on Saturday, what's left of the heat surge will reach the Northeast, with 850 mb temperatures reaching nearly 20 degrees celsius in the area. The warm temperatures aloft will not reflect the conditions in the surface, however, as cloud cover and precipitation will help keep temperatures lower than what they would typically be with 850 mb temperatures near 20c, peaking in the lower to mid 80s inland, mid 80s in the immediate NYC area, and the upper 70s to lower 80s in most of Long Island/S CT due to a SW/SSW wind. Scattered thunderstorms are possible, however widespread heavy rain is not a risk with these storms.

The front approaching the region is driven by a storm well to the north of the region, and as a result, the front will be weak when reaching the region, and another low pressure will move through southern Canada on Sunday and Monday, pushing the front through the Northeast US. This low pressure will bring more widespread thunderstorms for Sunday and potentially Monday as well, with temperatures similar to, if not slightly cooler than those of Saturday.


Next Week: Chilly Or Wet?

Uncertainty returns into the forecast for next week once the front moves to the east of the area. This cold front is expected to keep Katia east of the region, only posing a risk to places such as Bermuda and Newfoundland. Attention then turns into the Gulf of Mexico, however, as tropical invest 93L, currently in the southeastern Gulf of Mexico, is expected to become a tropical storm this weekend, which would be named Lee. There is uncertainty with what this storm does, though at this time, the majority of the models keep 93L stuck in the Gulf of Mexico while bringing a strong cool down into the area, with highs only in the lower to mid 70s in NYC. The GFS model, however, shows a different scenario where 93L moves up the East Coast, bringing another heavy rain risk. At this time, the GFS is by itself with this solution, but this possibility will be watched. Stay tuned for more information for next week with tomorrow's update.

Tuesday, August 30, 2011

Aug 30, 2011: Seasonable Pattern Develops

Note: The 5-Day Forecast page will be updated tomorrow morning.

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After Hurricane Irene affected the area with extreme rainfall and strong winds, a colder air mass moved in behind, bringing much nicer weather for the area over the last two days, with mostly sunny skies and slightly below average temperatures. A quiet weather pattern is expected to continue through the rest of this week with seasonable temperatures and dry conditions, and will last until this weekend, when an approaching cold front will bring a risk of thunderstorms.


Tomorrow's Outlook:

Tomorrow will be another nice day across the area. With a high pressure sticking over the region, mostly sunny skies are expected once again along with light winds. The air mass is expected to only slightly warm up, resulting in temperatures similar to, if not slightly warmer than those of today, peaking in the lower to mid 80s inland, mid 80s in the immediate NYC area, and in the lower 80s across most of Long Island/S CT except for the immediate coast, where temperatures should stay in the upper 70s.


Thursday - Friday: Seasonable Weather Continues

A heat wave is expected to build into the Ohio Valley and Great Lakes, with temperatures getting as high as the upper 90s in Illinois. Fortunately, the area will be spared from this surge of heat. A cut-off low pressure will begin to develop tomorrow in the western Atlantic Ocean, east of the Mid Atlantic, and with a high pressure sticking over the area, a SE wind is expected to develop, which will keep a cooler air mass over the region while the building heat wave will be blocked from reaching the Northeast. As a result, temperatures on Thursday will slightly cool down into the upper 70s to mid 80s from NYC and further west and the mid to upper 70s in Long Island/S CT, and Friday will bring colder temperatures, in the mid 70s to 80 degrees from NYC and further west, and in the mid 70s in Long Island/S CT.


Saturday And Beyond: Cold Front, Then Colder Air Mass

The low pressure driving the heat surge towards the Great Lakes will be in southern Canada on Friday, and is expected to move northeast through Canada. This will put the storm well north of the region on Saturday, and due to the storm being so far north, the cold front will be very weak when reaching the region, and will slowly move towards the area on Saturday, potentially stalling somewhere near the area.

With the cut off low pressure drifting away from the western Atlantic Ocean by Saturday, the leftovers of the heat surge will reach the area, with a warmer air mass and a southwest wind. As a result, warmer temperatures are expected, reaching the lower to mid 80s from NYC and further west and the upper 70s to lower 80s in Long Island/S CT. Due to the cold front, there is a risk of scattered thunderstorms in the late afternoon and evening, but at this time, any severe weather risk appears to stay low due to a lack of bulk shear and decent LI/CAPE values.

As previously mentioned, the cold front could stall somewhere near the northern Mid Atlantic or southern Northeast on Sunday. This would keep a risk of showers and/or thunderstorms in place across the area with temperatures in the mid 70s to lower 80s across the area. On Sunday night, another wave of low pressure could develop in the Great Lakes and move towards southern Canada on Monday, which would push the cold front through and bring a stronger chilly air mass into the region. Should this scenario verify, as the GFS model is currently showing, the timing is still uncertain, but should the potential storm slow down so that the front moves through in the evening hours, the potential is there that the area may see another round of thunderstorms on Monday. Stay tuned for more information on the potential Sunday-Monday storm.


Longer Range Outlook: Behind the cold front, a much colder air mass could move into the region, potentially bringing high temperatures in NYC as low as the lower to mid 70s for the middle of next week, which is below average. Such a cool down will be able to keep Tropical Storm, soon to be hurricane Katia, well east of the region, only affecting Bermuda and Newfoundland. This is the expected scenario at this time, but it is possible that the forecast could change, which could potentially bring Katia closer to the Unisted States. Stay tuned for more information on the longer range.

Sunday, August 28, 2011

Hurricane Irene Summary


October 2012: This post is for hurricane Irene from 2011. For the latest information about the upcoming Hurricane Sandy, please refer to the 10/26/12 Hurricane Sandy discussion.

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Tropical cyclones affecting the NYC tri-state is a relatively common occurence. Tropical storms occasionally move up the East Coast, either in the process of transitioning into extratropical cyclones or in the form of remnants, bringing rain into the NYC tri-state area. The last tropical cyclone to directly affect the area was Tropical storm Hanna in 2008, bringing moderate rain across the area as it made landfall in central Long Island.

Major tropical cyclones are more uncommon, however, as the last tropical cyclone to bring a significant impact in the tri-state area was Hurricane Floyd in 1999. Irene's intensity was not an unusual event, as it made landfall as a strong tropical storm as Floyd did, but what made Irene unusual was its track as it made landfall right over New York City, a very uncommon event with tropical cyclones affecting the area. Irene produced very heavy rainfall in the area as well as strong wind gusts, which resulted in widespread power outages and major flooding in the area, making Irene the most damaging tropical cyclone to affect the area since Floyd.


Irene History:

Irene formed from a tropical wave in the eastern Caribbean on Saturday, August 20. At that time, Irene was expected to move over the major Caribbean islands and staying as a tropical storm. Despite the original forecast, Irene moved WNW and steadily intensified, making landfall on Sunday in eastern Puerto Rico and intensifying into a hurricane shortly afterwards. Irene intensified into a category 2 hurricane on Monday is it stayed just north of Hispaniola.

Irene slightly weakened on Tuesday to a category 1 hurricane, but quickly intensified into a category 3 hurricane as it moved through the Bahamas on Wednesday and Thursday. During that time, Irene's pressure dropped but the wind speed stayed the same, and as a result, it began to grow into a very large hurricane. As Irene turned to the north early on Friday, it unexpectedly weakened into a category 2 hurricane as dry air and higher shear began to affect the system. Due to its large size, it was very slow to weaken despite these unfavorable conditions, and made landfall on Saturday afternoon as a strong category 1 hurricane in eastern North Carolina. Irene slightly weakened as it moved up the Mid Atlantic coast, making landfall in NYC on Sunday morning as a 65 mph tropical storm.


Irene's Impact In East Coast/NYC


*Irene at 5 PM, when starting to affect the area*
Irene's outer bands began to reach the Carolinas by Friday afternoon, when Irene was east of Florida and moving north. These bands became stronger and more widespread as Irene moved up the coast, making landfall in eastern North Carolina on Saturday afternoon. Due to Irene's very large size, its outer rain bands already reached parts of the NYC area by Saturday morning, when it was still south of North Carolina. Irene's steady rain slowly moved up through New Jersey during the afternoon hours of Saturday, and steady rain developed in the area by 4-5 PM. In Long Island and southern Connecticut, the rain varied in intensity until the overnight hours; most places experienced cloudy skies while scattered yet heavy thunderstorms developed offshore and moved into those areas. From NYC and further west, however, a steady moderate to heavy rain developed, and intensified through the late evening and early overnight hours.


*Irene at 12 AM, when the peak of the storm began in the area*

The worst of Irene took place from 12 AM Sunday until Irene's center made landfall in NYC. A steady wind-driven heavy rain fell across most of the area, especially from NYC and further west, and a band of tornado warned storms previously over central NJ moved into the area. After the storm, two EF-0 tornadoes were confirmed in the tri-state area. Winds steadily increased, with gusts peaking in the 40-65 mph range across most of the area. The highest gusts ended up in NYC and Long Island, where gusts were in the 60-70 mph range in some places, and a 91 mph wind gust was even observed in Sayville, NY.

Rainfall from Irene ended between 7-11 AM, when Irene made landfall in NYC. Cloudy skies continued throughout the day, but winds picked up once again for a few hours in the afternoon hours as Irene's center moved north of the area, with gusts returning into the 40-60 mph range in parts of the area before calming down in the evening.


Irene's Rain, Wind And Tornado Impact


Rain Amounts: Major flooding resluted from Irene in parts of the area, as very heavy rain fell in a short period of time. Using the National Weather Service rain reports in parts of the region, I made an estimated rainfall map for the Mid Atlantic region which was posted to the left. In general, 6 to 11 inches of rain fell in northern NJ and SE NY and 4 to 7 inches fell in NYC. Long Island and S CT saw more variable amounts; as little as 1-2 inches fell in eastern Long Island/SE CT, with as much as 5-7 inches in western Long Island/SW CT.

Wind: Irene also produced strong wind gusts in the area. Most places saw wind gusts in the 40-60 mph range, with parts of NYC and Long Island seeing gusts in the 60-70 mph range. A peak gust of 91 mph was observed in Sayville, NY (Long Island).

Tornadoes: Tropical cyclones often tend to produce tornadoes, and Irene was no exception. Several tornadoes were confirmed from the Carolinas up the Mid Atlantic coast, and two tornadoes were confirmed in the NYC area as well. An EF-0 tornado was confirmed in Queens, and another EF-0 tornado was confirmed near West Islip, NY.


Record Wet August: August was already a very wet month prior to Hurricane Irene, with monthly rain totals as high as 11-12 inches in JFK and Central Park. Hurricane Irene brought heavy rain across most of the area, nearly double the August rainfall prior to Irene in some places. As a result, rain records were broken across the area, with parts of the area ending up in the 15 to 20 inch range for rain totals this month, making this August not only the wettest August on record, but the wettest month in record as well in New York City. Below are a few selected rain totals this month in the area.

18.95" - Central Park
17.24" - JFK
16.11" - Teterboro, NJ
14.30" - Sussex, NJ


Forecasting Irene's Track And Impact

*GFS model run from Wednesday, 8/24, showing Irene east of NYC*

Irene was a difficult storm to forecast, and uncertainty with Irene's impact in the area continued up until the worst of the storm began. When Irene first formed, the majority of the models took Irene over the Caribbean islands, such as Hispaniola and Cuba, and into the Gulf of Mexico. By Irene's 2nd day as a tropical cyclone, however, some of the model guidance, such as the GFS model, shifted east towards Irene moving up the East Coast. Not all models caught on as quickly, and the UKMET and the GFDL models took another few days to adjust from a Gulf of Mexico track to an East Coast track.

Once it became apparent that Irene would move up the East Coast, the new question was how far east/west Irene would end up. The models split at that point; the ECMWF model took a western track, taking the storm right over New Jersey and Pennsylvania consistently for a few days, the GFS model took the middle solution with a track ranging from Long Island to Cape Cod, and the GGEM model was the eastern solution, mostly showing the storm staying east of NYC. At one point, the model consensus kept Irene east of Long Island; an image of a GFS run on 8/24 from the NCEP Model Analyses and Guidance link, which I posted above, shows Irene staying east of NYC and affecting central/eastern Long Island with the heaviest rain.


*NAM model run from Friday, 8/26, showing Irene over NYC*

On 8/25, the model consensus dramatically shifted to the west; in fact, by the evening model runs, the model consensus took Irene west of New York City, led by the ECMWF model which was consistent with such a solution for a while. There were still models that took Irene over Long Island, such as the GFS and NAM, and by the morning of the 26th, a day before Irene began affecting the area, the models finally reached a consensus showing Irene moving over western Long Island/NYC.

In addition to the track, there was also some uncertainty on Irene's intensity and timing. Originally, Irene was expected to intensify into a category 4 hurricane, but an eyewall replacement cycle prevented Irene from doing so. Once it completed this cycle, its pressure quickly dropped, but its wind speed did not increase, and instead, the pressure drop resulted in Irene growing to a much larger size. Some models showed Irene intensifying once moving north of North Carolina and reaching NYC, including the NAM model posted above; this solution was unlikely, however, considering that Irene was being affected by dry air, higher wind shear and land interaction while moving into an area of colder sea surface temperatures. The timing was also an issue with forecasting Irene, as the models trended faster with Irene's impact in the area as Irene came closer. At first, Irene's rain was expected to continue in NYC until Sunday evening, when in reality, the rain already ended before noon.


Forecast Verification for Irene:




Rain Verification: I posted a comparison image above; to the left is my rain forecast for Irene from my August 26 Irene discussion, and to the right is the estimated rain total map I made using the storm reports from the National Weather Service, filled in to show the Mid Atlantic. To the west of Irene's center, the heavier rain ended up slightly west of my forecast, but otherwise, the rain totals were close to the forecast. To the east of Irene's center, including Long Island and eastern New England, however, my forecast was too high, as totals ended up below the forecast. I expected Long Island to see 4-8 inches of rain, when in reality, totals ended up as low as 1-3 inches in the east to as much as 4-7 inches further west. In New England, totals were slightly lower than expected in some areas, as 3-8 inches of rain fell across most of New England (CT, RI, MA and NH) with locally higher/lower amounts, when my forecast map showed these areas receiving at least 4-9 inches of rain. The rain forecast for Vermont did verify, as 4 to 8 inches of rain fell in most of the state, which is the same as my forecast map showed.


Track Verification: In each of my updates from August 22 to August 26, I provided a forecast map for Irene with each updates. While Irene did end up in the cone of uncertainty with each update, the forecast track did not fall exactly in line with Irene's actual track. The August 22 forecast had Irene too far west, making landfall close to South Carolina. The August 23 forecast went too far east, showing Irene staying just east of Long Island. By the August 24 update, I went with a further west solution, taking Irene over central Long Island, and went close to Irene's actual landfall, showing a western Long Island/NYC landfall for the August 25/26 updates. From each evening update, my August 25 update had the closest verification rate, while from the intermediate updates posted each morning in the Tropics page, the August 25 morning forecast track had the best overall verification, with the forecast track almost identical to Irene's actual track.


Summary: Even though Irene was not as strong as originially thought when it made landfall in NYC, Irene caused widespread damage along the East Coast from the Carolinas to New England. Wind damage uprooted trees and left millions without power. Excessive rains from Irene combined with what was already a record wet August in some places caused widespread flooding in the NYC area and in New England as well. While Irene was not the most damaging tropical cyclone to ever affect the East Coast, it will be remembered for its widespread flooding and wind damage, and is another addition to what has been a year of extremes in the NYC area.

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Irene Poll: A few days before Irene reached the area, I opened a poll regarding Irene's impact in NYC for the viewers to vote. Below are the results of this poll:

What will NYC see from Hurricane Irene? (78 votes)

4 votes - Nothing, Irene will stay to the east
1 vote - Light rain, up to 1/2 inch
19 votes - Moderate rain, 1-5", some wind
54 votes - Very heavy rain, 5-12", strong winds (Correct answer)

Saturday, August 27, 2011

Aug 27-28 Hurricane Irene Updates

Frequent updates will be posted on Hurricane Irene as it approaches the NYC tri-state area, including updates on any changes in the forecast. Should I lose power during the middle of the storm, my coverage on Hurricane Irene will end early.

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8/28 - 7:00 PM: Due to issues with power and internet connection, an update will not be posted tonight. An update is likely to be posted sometime tomorrow, and the Hurricane Irene summary will be posted sometime on the first week of September.

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8/28 - 10:50 AM: Irene Ending Earlier Than Expected

A steady heavy wind-driven rain continued to fall across the area last night as Irene continued to move to the NNE along the coast, and made landfall a few hours ago over New York City as a 65 mph tropical storm. The storm is ending earlier than expected, however, as Irene made landfall a few hours earlier than expected, and the rain bands have already cleared Long Island, NYC and northern New Jersey. Some isolated showers may be possible later today, but otherwise, Irene's rain has ended. Winds will also steadily decrease throughout the day as Irene's center moves to the north of the area.

A more detailed storm summary, including forecast verification, will be posted this evening, but from the latest reports, Irene did bring moderate to significant impacts across the area mainly in the form of flooding, downed trees and wind damage. Fortunately, due to Irene being weaker and faster than expected, dry air affecting Irene, and the surface winds staying weaker than expected, the damage across the area was less than what could've happened had Irene hit the area as a slower, strong category 1 hurricane with no dry air issues and strong winds aloft reaching the surface. Very heavy rains still fell across the area resulting in widespread flooding, however, with as much as 8-10 inches of rain across portions of northern New Jersey. These rain totals brought most of the area to a record wet August, and the year to date rain totals are as high as 40-50 inches in parts of the area, almost the average rainfall amounts for the entire year from January to December!

Unless anything unexpected happens this afternoon, this is the last storm update for Irene. Another post will be made this evening summarizing Irene's forecasts, impact on the area, and the forecast verification, as well as a brief update on the forecast for this coming week.


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12:00 AM: Tornadic Activity To Increase

NHC's 11 PM advisory ended up keeping Irene as a minimial category 1 hurricane with 80 mph sustained winds, but Irene's pressure slightly went up, to 954 mb instead of 951 mb. Irene is still expected to continue moving NNE, making landfall near NYC as a 70 mph tropical storm.

Additional heavy rain will continue across most of the area through at least 3 AM, and some of these storms could produce tornado warnings with isolated tornadoes. Later tonight, a brief break in the rain intensity is expected, but rain should continue through the morning hours as Irene moves right up the NJ coast, making landfall over NYC late tomorrow morning. The storm will then calm down after 2 PM, with clearing skies expected by the late evening.

This is the last update for tonight. The rain and wind outlooks have not changed. If my power does not go out tonight, my next update will be at 6-7 AM tomorrow morning.


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11:00 PM: Conditions Deteriorating

NHC's 11 PM update was not out yet at the time when this post was created, however very slight weakening of Irene is expected at the 11 PM advisory, and I continue to expect that Irene should be downgraded to a tropical storm just east of New Jersey. Even if Irene makes landfall as a 70 mph tropical storm instead of a 75 mph hurricane, the main difference between these is the name used to describe the storm, as the impacts will be almost the same.

A long band of heavy rain along with some thunder is currently moving into NE New Jersey, NYC, and western Long Island, moving towards the WNW. Behind this band, however, there is a large band of heavy rain coming onshore into central New Jersey, and as Irene is moving to the NNE, this band of rain is shifting to the north as well, and will begin to affect the area around 12 AM, around the time when steadier rain should begin to move into Long Island. These storms, currently shown in the radar image to the left as the long line of storms east of central NJ, are currently producing several tornado warnings, and these storms will be capable of producing isolated tornadoes in the NYC area starting at 12-1 AM.


Forecast Update: I added very minor changes to the rain outlook, but for the main part, it is close to the last two outlooks. From NYC to eastern Pennsylvania, a general 5 to 9 inches of rain are expected, with the heaviest rain ending up near the NJ/PA border, especially over western New Jersey, where up to 7-12 inches of rain are expected. Further east, 2-4 inches are expected in eastern Long Island/S CT to as much as 3 to 6-7 inches in central/western Long Island and Connecticut. The wind outlook still has not changed from earlier this evening, and can be found in the 6 PM update earlier in this post.

The next and final update for tonight will be posted at 12 AM. If I do not lose power tonight, additional updates will be posted tomorrow starting at 6-7 AM.


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9:40 PM: Heavy Rain Continues, Tornado Threat Increases

As of 9 PM, the latest NHC update has kept Irene's intensity the same as the previous update, with 80 mph sustained winds and a minimum pressure of 951 mb. Heavy rain is now covering all of NYC, northern NJ and SE NY, and with additional bands of heavy rain offshore intensifying and becoming more widespread as they move towards the area, heavy rain will continue over the next several hours. East of NYC, the rain continues to vary in intensity for Long Island/S CT, with occasional heavy thunderstorms popping up in that area with otherwise cloudy skies or light rain. As the bands of heavy rain offshore continue to slowly shift to the north, steadier rain is expected to develop in Long Island/S CT by 12 AM.

Isolated tornadoes are also a risk from Irene. With some of the heavier rain bands moving into New Jersey and the area, some rotation of the storms is possible, and the NWS has issued a Tornado Watch across most of the tri-state area. The next update will be posted at 11 PM, and will discuss the latest scenario for Irene as well as any potential forecast change.


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8:35 PM: Update On Irene Forecast

As of 8 PM, the latest NHC update shows that Irene has maintained sustained winds at 80 mph, but its pressure slightly went up by 1 millibar, to 951 mb. Irene is currently offshore, just east of extreme SE Virginia which is on track with the forecast, and is moving to the NNE. The latest radar images show that Irene has what appears to be an eye structure, but it is not completely organized and is not filled in to the SE of the center.


Forecast Update: Over the last hour, Irene's appearance on the radar has slightly dried up, but seems to have gotten a little wetter in the last 1/4 hour. Due to Irene's faster movement, less rain is expected in the area than in North Carolina/Virginia, where radar estimates show 10-15 inches of rain, but heavy rain is still expected in the area. Looking at the latest water vapor loop, however, dry air is increasing to the west of Irene's center, and there is much more dry air entering Irene's eastern side. As a result, I slightly lowered my rain forecast; From NYC to eastern Pennsylvania, a general 5 to 8 inches of rain are expected, with the heaviest rain ending up near the NJ/PA border, especially over western New Jersey, where up to 7-10 inches of rain are expected. Further east, 2-3 inches are expected in eastern Long Island/S CT to as much as 3-6 inches in central/western Long Island and Connecticut. The wind outlook has not changed for now; it is possible, however, that depending on the observations for Irene later tonight that the wind forecast could be slightly lowered by about 5 mph. Stay tuned for the next update at 9:30 PM.


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7:10 PM: Heavier Rain Starting

The steady moderate to heavy rain from Hurricane Irene is now starting to move into the area, as an expanding band of heavy rain is entering New York City, and with additional rain building behind this band, heavy rain will start to fall across most of the area within the next hour and will continue with little variation in intensity through most of the overnight hours. It will take time for the heavier rain to become steady in eastern and central Long Island/Connecticut, where the rain is expected to vary in intensity from light to moderate/heavy until later tonight, but steady heavy rain is expected to develop in these areas as well later tonight, after at least 12 AM.

The next update will be posted between 8 and 8:30 PM, discussing the dry air impact on Irene, the latest NHC update, and any potential change in the forecast for Irene's intensity.


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6:00 PM: Rain Starting To Move In

As of NHC's latest update, Irene is still a category 1 hurricane with 80 mph sustained winds and a minimum pressure of 950 mb. Irene's center is currently over NE North Carolina, and is moving to the NNE at 13 mph. Hurricane Irene's outer bands have started to affect the area as a band of light to moderate rain has moved into Long Island and northern New Jersey. The main bands are still mostly to the south of the area, however, and mostly light to occasionally moderate/heavy rain will fall across the area until 8 PM.


Updated Forecast: Looking at the latest radar and taking Irene's track into consideration, however, Irene's heaviest rain is expected to stay to the west of NYC. The heaviest rain bands are currently centered over eastern/central Virginia, which is to the west of Irene's center and west of last night's forecast. Considering that Irene will move NNE from this point and move over New York City tomorrow, Irene's heavier rain is expected to end up from Irene is expected to end up from eastern New Jersey to eastern/central Pennsylvania, where a general 5 to 10 inches of rain are expected, with the heaviest rain ending up near the NJ/PA border, especially over western New Jersey, where up to 8-12 inches of rain are expected. Further east, 2-3 inches are expected in eastern Long Island/S CT to as much as 4-7 inches in western Long Island/SW CT/NYC.

Irene has slightly weakened this afternoon, but due to its very large size and unusually low pressure for a category 1 hurricane, slow weakening is expected, and Irene is expected to make landfall in NYC as a 70 mph tropical storm. The wind forecast was only slightly changed from last night; I am currently expecting sustained winds between 35 and 50 mph in western New Jersey and Orange county in NY, with gusts up to 50-60 mph possible. In the immediate NYC area, sustained winds between 50 and 65 mph are expected, with gusts up to 65-80 mph, especially in NYC. Long Island and southern CT should see windy conditions as well, with sustained winds between 50 and 70 mph. Gusts between 60-80 mph are expected. Near the location where Irene makes landfall, wind gusts up to 85 mph may be possible.

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5:00 PM: Frequent updates will now be posted on Hurricane Irene, and will continue through tomorrow afternoon when the storm ends. The updates will end early should I lose power during the middle of the storm.


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9:15 AM: Irene Weakening More Than Expected

As of last night's update, Irene was struggling to maintain its core as it was moving NNE towards North Carolina. As of this morning, Irene has failed to redevelop an organized eye and core as it made landfall in eastern North Carolina. Its weakening trend continued as Irene weakened more than expected once again, and is currently a category 1 hurricane with 85 mph sustained winds and a minimum pressure of 952 mb. As of yesterday morning/afternoon, Irene was still expected to be a category 2 hurricane when making landfall in North Carolina.

The weakening trend does bring a very slight improvement to the wind forecast for the area, though it does not mean that Irene will fail to have any significant impact in the area. Regardless of Irene's intensity, it is still expected to produce very heavy rain in the area, and the rain forecast has not changed since last night's discussion. Irene's intensity, however, appears to be slightly weaker than yesterday, and especially due to land interaction and colder sea surface temperatures, additional slight weakening is expected throughout today, and Irene could weaken into a 70 mph tropical storm as early as tonight or tomorrow morning, while just east of Delaware/southern New Jersey, making landfall near western Long Island/NYC potentially as a 65 mph tropical storm. If this scenario verifies, winds will be slightly lower than expected with yesterday's update by at least 5 mph.

There is still some uncertainty regarding Irene's intensity when it reaches the area, and it is possible that it could end up between 60 and 70 mph when making landfall in the area. Regardless of these winds, Irene's wind field will continue to grow in size, spreading tropical storm force sustained winds (40+ mph) across the entire area. The next update will be posted between 4-5 PM today, and frequent updates will be posted from then until the overnight hours.

Friday, August 26, 2011

Aug 26, 2011: Final Hurricane Irene Forecast

Notes:

- Even though the 5-Day Forecast was not changed, the forecast is still valid and was used for this update. The forecast for each part of the area was described in more details below.

- The poll for Irene's impact in NYC is still open. This poll will close on Saturday afternoon.

- Frequent updates will be posted in this page as well as the tropics page throughout the day tomorrow and on Sunday, which will include any potential changes to the forecast.

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Hurricane Irene has been a very difficult storm to forecast up to this point. Constant changes in the model guidance resulted in uncertainty with Irene's track, and Irene's unexpected weakening today could result in a slightly better scenario for the East Coast than previously thought. Regardless of these issues with Irene and its forecast, Irene is a very large hurricane with its impacts being felt far away from the center of the storm, and will be the most significant tropical cyclone to affect the area since Hurricane Floyd in 1999.


Latest Information/Forecast For Hurricane Irene


As of NHC's 8 PM update, Irene is located south of North Carolina with 100 mph sustained winds and a minimum pressure of 950 millibars. Irene is moving to the NNE at 14 mph. Irene's outer rain bands are currently affecting the eastern half of North Carolina with heavy rain along with isolated tornadoes, and Irene's center is starting to appear in the North Carolina radar.


Irene's Intensity: Since yesterday, Irene has failed to improve in organization. This morning, Irene unexpectedly weakened into a category 2 hurricane while east of Florida; Irene was expected to maintain category 3 intensity until reaching North Carolina. This trend continued throughout the afternoon hours as Irene's core became disorganized and an eye was no longer evident. Dry air and shear affected Irene, and it weakened at 2 PM to a weak category 2 hurricane with 100 mph sustained winds while east of South Carolina; Irene was not expected to reach this intensity until reaching Delaware's latitude. As of this evening, Irene is attempting to reorganize its structure, and its pressure dropped by 1 millibar, but Irene has failed to reorganize its core and form a well defined eye. Due to Irene's large size, any minimal drop in pressure is unlikely to result in any large increase in wind speed, and as a result of the above and Irene running out of time over water, Irene is expected to maintain its intensity, if not slightly weaken to a strong category 1 hurricane with 90 mph sustained winds, by the time that it makes landfall in North Carolina early on Saturday afternoon.

After making landfall in North Carolina, Irene will encounter colder sea surface temperatures, and is expected to begin weakening. At the same time, Irene will be interacting with a trough and will begin to become extra-tropical. Due to Irene's very large size, only slow weakening is expected, and Irene is expected to maintain category 1 intensity throughout Saturday. There is some uncertainty on Irene's intensity when making landfall near the NYC area, which will depend on how close to the Mid Atlantic coast Irene tracks as well as its intensity during the day tomorrow. At this time, Irene is expected to make landfall in western Long Island or NYC as a strong tropical storm, with sustained winds around 70 mph, but it is possible that Irene could be slightly weaker or stronger, with sustained winds between 65 and 75 mph possible when Irene makes landfall.


Irene's Track: Irene's track has been uncertain over the last couple of days, but a much clearer model consenus has finally emerged today, which allows for a higher confidence forecast for Irene's impact in the region and the area. From Irene's current location, a NNE movement is expected, which will take Irene into eastern North Carolina early on Saturday afternoon. From there, Irene is expected to move NNE right up the coast, making landfall in western Long Island. Some models are still showing an eastern Long Island landfall scenario or a storm moving through western New Jersey, but there is a much clearer model consensus taking Irene through western Long Island, with a decreasing number of models showing other scenarios. Even though the models agree on a specific track, these are only computer models, and it is possible that Irene may slightly move to the west or east of the expectation, but regardless, no significant change in the forecast track is expected.


Timing Of Irene's Impact In NYC Area


At this time, Irene's track has been nailed down for the most part, moving up eastern New Jersey before moving over NYC or western Long Island. There is no doubt that Irene will cause heavy rainfall over 6 inches, which will cause major flooding and lead to record breaking rainfall in the area, and that Irene will cause windy conditions in the area. The main uncertainty at this time is Irene's intensity when it reaches the area, which will determine how strong the winds will be across the area, and the exact spot where Irene makes landfall, which will determine which place has the strongest winds.


Saturday: Mostly cloudy skies are currently covering the area. These clouds are already a part of Irene, whose center is still south of North Carolina, showing how large the hurricane is. Irene's outer rain bands are expected to begin affecting the area on Saturday afternoon as scattered showers and thunderstorms begin to reach the area. These storms will mainly be scattered, but will be capable of causing heavy rainfall. These bands will be moving in from the ESE, or from the Atlantic Ocean, moving WNW and then west, as they rotate around the center of Irene. The wind will not be much of an issue tomorrow with a light SE/ESE wind expected, though breezy conditions should begin to develop by the late afternoon and evening hours. Rainfall amounts between 1/4 and 1/2 inch are expected across parts of the area by tomorrow evening, with locally higher amounts in places that get affected by these storms.


Saturday Night - Sunday: Deteriorating conditions are expected by Saturday evening after 8 PM, with increasing ESE/east wind. Moderate to heavy rain bands ahead of Irene will begin to move into the area after at least 10 PM-12 AM, and will steadily increase through the rest of the overnight hours, with the heaviest rain focusing from NYC and further west. By the early morning hours, a steady heavy wind-driven rain is expected across the area.

The worst of Irene will take place during Sunday morning into at least 2-4 PM. During this time, winds will continue to increase coming out of the east/NE. The rain is expected to continue intensifying from NYC and further west, and in Long Island/S CT, which should be east of Irene's center, the rain should still be heavy but not as heavy as in places west of NYC. Irene's center will make landfall in western Long Island or NYC around the early-mid afternoon hours, and once it does so, the rain should begin to weaken from north to south across the area. By the evening hours, with Irene's center already in New England, the rain should end across the area with diminishing winds.


Irene's Rain/Wind Impact


Irene's Rain Outlook: The rain from Irene will be a major concern, as parts of the area have already seen a foot of rain this month, and an additional foot of rain from Irene alone could fall in the same areas, bringing rain totals this month over 20 inches, a very unusual event for NYC. Looking at Irene's rain totals, most of the area should see over at least 4-6 inches of rain, with the lightest amounts in the easternmost and westernmost parts of the area. At least 3 to 7 inches of rain should fall in NW NJ and Orange county in NY, 6 to 12 inches in the immediate NYC area, and 5 to 10 inches of rain in Long Island and southern Connecticut. These rain totals will produce major flooding, especially near rivers and in the coastal areas, where Irene's storm surge will also result in coastal flooding.

Wind Outlook: Irene's wind forecast is more uncertain, and depends on Irene's uncertainty when it makes landfall in the area. Given the current expectation of a 70 mph landfall in western Long Island or NYC, I am expecting sustained winds between 35 and 50 mph in western New Jersey and Orange county in NY, with gusts up to 55-65 mph possible. In the immediate NYC area, sustained winds between 50 and 65 mph are expected, with gusts up to 65-80 mph, especially in NYC. Long Island and southern CT should see windy conditions as well, with sustained winds between 50 and 70 mph. Gusts between 65-85 mph are expected. Near the location where Irene makes landfall, wind gusts up to 90 mph may be possible. This wind outlook has a slightly lower confidence level than the rain outlook, and it is possible that the wind forecast may have to be adjusted tomorrow to show more or less wind depending on Irene's intensity.


Irene is a very large and dangerous storm, and should not be taken lightly. Impacts will be felt in the area, ranging from large waves to extreme rainfall amounts to strong wind gusts, with results being significant damage in the area including downed trees and widespread power outages. Stay tuned for frequent updates on Irene in the main page and in the Tropics page throughout the day tomorrow and on Sunday, which will include any potential changes to the forecast.

Thursday, August 25, 2011

Aug 25, 2011: Latest On Hurricane Irene

Brief Thunderstorm Update: Behind today's line of storms, which dumped a general 1/4 to 3/4 inch of rain from NYC and further west and less than 1/4 of an inch in Long Island and southern Connecticut, conditions have dried up. The actual cold front is approaching the area, but will only bring isolated thunderstorms to the western parts of the area before drying out. The immediate NYC area and Long Island/S CT are expected to stay dry through tonight.


Hurricane Irene: Western Long Island Landfall Possible


Over the last day, uncertainty continued with Hurricane Irene's track in the area as the computer models showed solutions ranging from Irene staying east of Long Island to a scenario where its remnants move through central Pennsylvania. These uncertainties will continue through at least tomorrow afternoon/evening, when a much clearer image should emerge on Irene's path, but at this time, there is already a better idea on where Irene could make landfall, and at this time, it appears that this could be in western Long Island or potentially over NYC itself.


Irene's Intensity: After last night's eyewall replacement cycle, Irene improved in organization throughout the day. Irene has developed a more organized eye this afternoon and evening, and since the last update, its minimum pressure dropped to as low as 946 mb, its lowest pressure so far, and the equivalent of approximately a weak category 4 hurricane. Despite the pressure drop, sustained winds have failed to increase, and actually are below 115 mph in most of the hurricane. We have seen a scenario like this happen with Hurricane Ike in 2008, where the pressure dropped but the winds failed to increase, and as a result, Ike increased in size. The same may happen with Irene, and Irene will remain a very large hurricane as it begins to move up the East Coast.

There is an area of higher wind shear to the north of Irene, however there are warm sea surface temperatures as well, in the mid 80s. With signs of Irene already starting to intensify, additional intensification is expected, and Irene will peak with sustained winds between 120-125 mph during the day tomorrow. As Irene reaches North Carolina where there will be colder sea surface temperatures, Irene will begin to weaken, but especially due to its large size, only slow weakening of Irene is expected, and it will weaken to a category 2 hurricane on Saturday as it makes landfall in eastern North Carolina. From there, Irene will gradually weaken as it moves up the coast, and is expected to be a weak category 1 hurricane with 75-85 mph sustained winds as it makes landfall somewhere from eastern Long Island to NYC.


Irene's Track: As with the last few days, the most difficult part of forecasting Irene is its track. While the range in model solutions has slightly decreased since yesterday, the models continued to shift back and forth, going from an eastern Long Island track yesterday to a western New Jersey track this afternoon and back to a NYC track this evening. The ECMWF and GFDL models were the main models yesterday to show a far inland track through Pennsylvania, but the other models have not shifted towards showing such a track, and the main model consensus takes Irene over western Long Island or NYC. There are still another 72 hours until Irene makes landfall in the area, and some changes in the track are still possible, but model differences will only decrease from this point and on, and a better model consensus is expected to develop starting at least tomorrow afternoon/evening, when Irene will be two days away from making landfall.

For the short term, Irene will continue to move towards the NNW, and will switch to a north direction tonight or by tomorrow morning. From there, Irene will begin to turn more towards the NNE as it makes landfall in eastern North Carolina. From there, the question is what direction Irene takes, as it could go north/NNE and hug the coast, making landfall in NYC, or Irene could take more of a NNE/NE direction, making landfall in central or potentially eastern Long Island. A few models continue to portray a scenario where Irene moves due north and enters eastern Pennsylvania, however this solution is becoming much less likely, especially as the model which showed this solution with the majority of its runs, the ECMWF model, has shifted to the east. The latest models continue to shift back east; in fact, the latest 00z NAM run shows Irene making landfall in eastern Long Island, sparing NYC from the worst of the hurricane.

For tonight's update, my forecast track shows little change from yesterday's forecast, showing Irene moving NNE from North Carolina, just east of the New Jersey coast, before making landfall in central Long Island. This track is not final yet, however, and it is possible that Irene could shift west towards a NYC landfall, or Irene could shift even more east once again, with landfall in eastern Long Island, and the scenario where Irene's center stays east of Long Island still cannot be ruled out, although it is a less likely scenario. It is a possibility that should the models continue to trend east with increasing support for such a solution, I may shift my forecast track towards an eastern Long Island landfall, but otherwise I am sticking with a central Long Island landfall at this time. Stay tuned for more information on Irene's track with updates in the Tropics page tomorrow, the first one at 11 AM.


Irene's US/NYC Impact: Irene will be a large hurricane when it reaches the area, and even if it stays east of NYC, its impacts will still be felt all the way to western NJ and eastern Pennsylvania. As previously mentioned, there is still uncertainty with Irene's track, and it is possible that Irene could shift further west or east. Shifting Irene further east would take the worst of Irene's rain and wind further east, but due to its large size, heavy rain and strong wind gusts will still be felt all the way to the immediate NYC area. With Irene still a category 1 hurricane when making landfall in Long Island, sustained winds of up to 75 mph are possible in Long Island during landfall, with destructive wind gusts gusts up to 90 mph possible. A track near NYC will bring 80+ mph gusts into parts of the city itself as well as the immediate NYC area, while an eastern Long Island track will shift these gusts into Long Island, with wind gusts up to at least 60-70 mph in NYC.


Forecast For NYC Area: Irene's outer bands are expected to arrive by Saturday afternoon, with cloudy skies and scattered thunderstorms which could produce heavy rainfall. Saturday afternoon and evening will still be relatively calm, but winds will begin to increase overnight into the late morning as steady rain and thunder begins to move in from the south.

The worst of Irene will take place during the day on Sunday. Based on my latest forecast, Irene's heaviest rains will be in western Long Island into NYC, where anywhere from 6 to as much as 10-12 inches of rain could fall. Irene's strongest winds would cover Long Island and southern Connecticut, with sustained winds up to 60-70 mph possible with wind gusts potentially between 70-90 mph. In the immediate NYC area, the rain will be the biggest issue, with 5 to 8-10 inches of rain expected. Gusts will be less than those in Long Island, with sustained winds between 50-60 mph possible along with gusts potentially between 60-75 mph. Should Irene track closer to NYC than currently expected, these gusts will be higher. In the western parts of the area, moderate to heavy rain is expected with a total of 2 to 6 inches possible. Winds will be lighter, with gusts between 40 and 50 mph expected.

Rain and wind will gradually increase in the morning, with the worst of Irene in the mid afternoon hours as its center makes landfall in Long Island. After at least 8-10 PM, conditions across the area will begin to calm down, with decreasing winds and rain tapering off. Clearing skies are expected for the late overnight hours, with mostly sunny skies returning for Monday.


Other Potential Scenarios: The scenario mentioned above is based on the track I am currently expecting, which would take Irene through central Long Island. This is only one of several possible tracks, which the model consensus could shift towards as there is still time left for the models to change. The second likely scenario would be where Irene tracks through eastern Long Island, which would result in the heaviest rains from Irene affecting central and western Long Island, along with all of southern Connecticut, with the strongest winds in central/eastern Long Island. NYC would see less of an impact but still a significant one; 3 to 7 inches of rain would fall in the immediate NYC area, with sustained winds between 40-50 mph with gusts up to 50-60 mph.

Another potential scenario is where Irene makes landfall over western Long Island or NYC, which would bring the worst of Irene in the immediate NYC area; in this scenario, 7 to 12 inches of rain would fall, along with sustained winds between 60-70 mph and gusts between 70 to as much as 90 mph. Long Island and Connecticut would see less rain but strong winds, with 3 to 8 inches of rain along with sustained winds between 50 and 70 mph and gusts up to 80-90 mph possible. The two scenarios previously mentioned are the two other possibilities should the current forecast track for Irene change, and are just as possible as the current scenario.


While the exact impacts from Irene in the area are still uncertain, and depend on Irene's intensity and location when making landfall, Irene will be a large and intense system when reaching the region, and could produce significant damage along the East Coast from the Carolinas to the NYC area and New England. With increasing confidence in the forecast expected by tomorrow night, tomorrow night's update will include a more detailed section on Irene's potential impact in the NYC area, including potential rain and wind maps, as well as the different scenarios described in more details. Stay tuned for more information on Irene throughout the day tomorrow, with the next update to be posted in the Tropics page at 11 AM.

Aug 25, 2011 Storm Updates

10 AM Hurricane Irene Brief Update: An update on Irene will be posted in the Tropics page at 11 AM and again at 6 PM, but from the latest model projections, Irene could make landfall somewhere near or over New York City as a weak category 1 hurricane. The update will also briefly discuss the potential that Irene trends even more west and moves through western New Jersey, which would spare most of the area of any significant impact.

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10:20 AM: While today's thunderstorms were expected to start affecting the area in the late afternoon, a squall line has formed much earlier than anticipated, and is already in NW NJ and is moving slowly to the ENE. This squall line will be capable of producing gusty winds, as well as heavy downpours which could dump 1/2 to 1 inch of rain in a short period of time. The squall line is expected to reach NYC around 11:30-12:00 PM, then moving into Long Island and southern CT between 12-3 PM.

Behind these storms, some breaks in the cloud cover are expected. While there is some uncertainty regarding this afternoon, it is possible that another round of scattered strong to potentially severe thunderstorms could develop in Pennsylvania this afternoon and move towards the area this evening. More updates on today's storms will be posted later this afternoon.

Wednesday, August 24, 2011

Aug 24, 2011: Update On Hurricane Irene

Reminder: The poll for Hurricane Irene's impact in NYC is still open. Please vote your thoughts in the poll, which will close on Saturday afternoon.

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Tomorrow's Outlook: Severe Weather Expected

A cold front will move through the region tomorrow, bringing a risk of strong to severe thunderstorms. Temperatures will warm up early in the day with partly to mostly cloudy skies and a SSW wind, reaching the mid to upper 80s from NYC and further west. With decent severe weather parameters and high precipitable water values, a squall line will form ahead of the front covering the Northeast down to Virginia, and is expected to move through the area between 5 and 10 PM tomorrow. This squall line will be capable of producing gusty winds as well as heavy rain, with up to 1-2 inches of rain possible in a short period of time. The storms will end by 12 AM across most of the area with clearing skies afterwards. Stay tuned for storm updates tomorrow afternoon and evening starting at 4 PM covering these storms.


Hurricane Irene: Hurricane Landfall Close To NYC?


Hurricane Irene is a difficult storm to forecast, mainly due to the model spread that developed once Irene reached North Carolina, with a wide range of model solutions up to this morning either keeping Irene offshore, bringing Irene into the eastern half of the area, or bringing Irene's center straight into NYC. With today's models, however, there were signs that a consensus is starting to form, and while there is still time for the models to shift around, unfortunately this consensus is placing Irene closer to NYC than previously thought.


Irene's Intensity: Irene has rapidly intensified since last night, and is now a major Category 3 hurricane. Irene continues to grow in size while maintaining a small eye, and slow intensification is expected. Irene could go through an eyewall replacement cycle tonight into tomorrow, which should temporarily weaken Irene into a strong category 2 hurricane, but once this replacement cycle is completed, Irene could intensify into a category 4 hurricane by at least Thursday evening. Irene will slightly weaken into a moderate category 3 hurricane on Friday, maintaining its intensity until reaching eastern North Carolina. From there, Irene wil enter colder SSTs and will weaken into a category 2 hurricane. Irene is expected to make landfall somewhere between western Long Island and Rhode Island with maximum sustained winds of 85 to 100 mph, making it either a strong category 1 hurricane or a weak category 2 hurricane.


Irene's Track: Over the last day, Irene has maintained a NW movement, and is expected to begin turning NNW tonight with a more northward movement by tomorrow afternoon. This will put Irene's westernmost extent south of approximately North Carolina's central coast, which is further west than expected yesterday. Irene will begin to turn NNE by Friday as it moves towards north Carolina, and while there is still some uncertainty regarding whether Irene makes landfall in Cape Hatteras or not, especially due to the west shift in the forecast track for tomorrow and Friday, I shifted Irene's track slightly west to make landfall in eastern NC.

There is still uncertainty for Irene on Saturday and Sunday, but the latest model guidance is starting to lock in on a specific track area for Irene. While there is still a relatively large spread, the spread has decreased since yesterday with the consensus shifting to the west. The latest 00z model guidance shows Irene making landfall in central or eastern Long Island, with less models showing a Cape Cod landfall. Where Irene ends up depends on the approaching trough's speed and intensity, putting the range of Irene's potential landfall from western Long Island to Rhode Island.

A landfall near western/central Long Island will put the immediate NYC area under the worst of Irene, while a landfall in eastern Long Island/Rhode Island will put Long Island/Connecticut under the worst of Irene, with NYC on the western edge of the heaviest rain and strong wind areas. With the increasing model consensus, I shifted my track west of the previous forecast and went for a middle solution, where Irene makes landfall near central/eastern Long Island. This track would put western Long Island in the path for Irene's heaviest rainfall. Once again, there is still uncertainty with Irene's track and landfall for Saturday and Sunday, and the scenario I am currently expecting could change around over the next few days. Stay tuned for more information on Irene's forecast.


Irene's US/NYC Impact: Irene will be a large and intense hurricane when reaching the area, and is still expected to be a category 1 or 2 hurricane when making landfall near Long Island or Rhode Island, making Irene a very dangerous storm for the east coast from the Carolinas to New England. The heaviest rain will be in areas to the west of Irene's center, where anywhere from 6 to as much as 12-14 inches of rain could be possible. These areas will also experience strong winds, with gusts up to 50-80 mph possible. To the east of Irene's center, less rainfall is expected, but the strongest winds will be in the eastern side of Irene, where winds could gust up to or even potentially above 80 mph. The wind speeds and gusts associated with Irene will depend on its intensity when it makes landfall.


Currently Expected Scenario: At this time, based on the scenario I am using for tonight's forecast, clouds from Irene will spread into the area on Saturday with mainly cloudy skies during the day. Some showers and thunderstorms ahead of Irene will spread into the area by the afternoon and evening hours, but the heavy rain from Irene will arrive into the area at least after 12-2 AM. From that point and on, steady heavy rain will fall from the early morning hours through Sunday evening before tapering off by at least 10 PM-12 AM. Winds will steadily increase throughout Sunday morning, peaking during the afternoon and evening hours before calming down after 12 AM.

The worst of Irene is expected to take place in Long Island and southern Connecticut, where rainfall amounts between 5 to as much as 12-14 inches of rain are possible. With Irene making landfall near central/eastern Long Island as a category 1/2 hurricane on Sunday afternoon, wind gusts have the potential to reach or even potentially exceed 80 mph in parts of LI/S CT. Further west in the immediate NYC area, slightly less rain and wind are expected, with approximately 4 to as much as 8-10 inches of rain possible. Wind gusts will be lower, possibly ending up from 50 to as much as 70 mph. Should Irene track closer to NYC, these gusts will be higher. The western parts of the area will see less of an impact, with moderate to heavy rain bringing at least 2 to 6 inches of rain. Gusts will not be as intense as well, potentially up to 40-50 mph.

The scenario mentioned above is still preliminary and is subject to change. It is possible that Irene trends further west, which would shift the impacts in Long Island over to the immediate NYC area, or it is possible that Irene trends east, which would shift each impact zone one step to the east, with moderate-heavy rain in NYC and heavy rain/strong winds in Long Island/S CT. Regardless of where Irene ends up, it will be a large, intense and dangerous storm, and could result in significant damage up the East Coast from the Carolinas to the NYC area and into New England. Stay tuned for additional updates throughout the day tomorrow on Irene in the Tropics page, and storm updates will be posted late tomorrow afternoon as well regarding the severe thunderstorms for tomorrow afternoon/evening.


Tuesday, August 23, 2011

Aug 23, 2011: Hurricane Irene Discussion

Note: A poll has been opened for Irene's impact in NYC. Please vote your thoughts in the poll, which will close on Saturday afternoon.

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With a chilly air mass sticking over the region, today was another mostly sunny day across the area with below average temperatures, peaking in the upper 70s inland, upper 70s to lower 80s in the immediate NYC area, and in the mid to upper 70s in Long Island and southern Connecticut. Temperatures will slowly warm up tomorrow and again on Thursday as a cold front moves through the area, potentially bringing a squall line late in the day containing heavy rain. This is just a taste of what will come in the weekend, as Hurricane Irene threatens to bring over 8 inches of rain and strong winds to parts of the area, especially in Long Island and Connecticut, on Sunday.


Wednesday - Friday Outlook:

Tomorrow will be another nice day but with slightly warmer temperatures due to a SSW wind, reaching the upper 70s to mid 80s from NYC and further west and the mid 70s to lower 80s in Long Island/S CT. On Thursday, a cold front will move through the region, which combined with high precipitable water values and decent severe weather parameters, could result in a squall line moving through the area in the late afternoon/evening hours, producing heavy rain locally up to 1-2 inches and gusty winds. More information on Thursday's storms, including a forecast map, will be posted with tomorrow's update. Friday will bring drier and colder conditions, with temperatures and cloud cover similar to those of today.


Hurricane Irene Update: Long Island/New England Targeted

Since yesterday, the forecast models have continued to change Irene's track in the region, and a more solid consensus is growing for Irene to stay near or just east of Cape Hatteras, moving NNE from there and ending up just east of Long Island. Such a scenario would bring the worst of Irene into Long Island and New England. Despite this, there is still some uncertainty, and it is still possible that Irene could either shift east, sparing most of the region, or shift west, putting NYC directly in Irene's heaviest rain area.


Intensity Forecast: Irene has unexpectedly weakened over the last few hours, and is now a Category 1 hurricane. Despite this, Irene's pressure has been consistently dropping and is now down to 969 mb, the equivalent of approximately a strong Category 2 hurricane, and Irene has reorganized itself with a more visible eye. As a result, I am expecting Irene to re-intensify into a Category 2 hurricane tonight, perhaps as soon NHC's 11 PM update. Irene will continue to intensify and is expected to reach Category 3 intensity later tomorrow or on Thursday at the latest, and while less likely, a weak Category 4 hurricane cannot be ruled out. Should Irene's current intensification continue, it is not out of the possibilities that Irene becomes a Category 3 hurricane as soon as 11 AM tomorrow. As Irene reaches the cooler waters north of Cape Hatteras and starts to become extra-tropical, Irene will weaken around Saturday to a Category 2 hurricane, then a category 1 hurricane overnight.


Track Forecast: As with yesterday's update, Irene's forecast track remains the biggest challenge in the forecast, and any small shift could either keep the worst of Irene offshore or could hit New Jersey, NYC and the rest of the tri-state area with very heavy rain and strong winds. For the short term, Irene will continue to move WNW tonight, changing more towards a NW direction tomorrow. By the time that Irene reaches northern Florida's latitude, approximately where it should begin to turn more north and slightly NNE, Irene is expected to be south of eastern North Carolina, and will begin to move NNE from that point. There is some uncertainty regarding whether Irene makes landfall near Cape Hatteras or stays just offshore, and at this time, there is an equal chance of both happening. For tonight's map, I put Irene just east of Cape Hatteras, but it is possible that Irene shifts slightly west and makes landfall there.

From North Carolina and further north, uncertainty increases on the track. A trough is expected to approach the Northeast from Canada on Saturday/Sunday, with Irene catching up to that trough and accelerating to the NNE/NE while becoming extra-tropical. There is some uncertainty with Irene's interaction with the trough, and as a result, there are two main scenarios at this time. In the first case scenario, Irene will continue to move NNE from Cape Hatteras, making landfall near central Long Island. This scenario would bring very heavy rain and strong winds to New Jersey, NYC and SE NY, with slightly less rain but much stronger winds in Long Island and southern Connecticut. The second scenario is where Irene recurves more to the NE, which would take it just east of Long Island with landfall near Rhode Island or Cape Cod. At this time, the model consensus is pointing towards the second scenario, but the first scenario cannot be ruled out as well, and it is possible that I may shift my forecast track slightly west with tomorrow's update if the model consensus shifts further west and becomes more concentrated with a smaller spread. Stay tuned for more information on Irene with the next update in the Tropics page at 11 AM Wednesday.


Irene's US/NYC Impact: With the two scenarios previously mentioned, there is still uncertainty with Irene's exact impact, but at this time, Long Island and southern Connecticut are the most likely places to see the worst of Irene out of the tri-state area. Irene will start to affect the area on Saturday night with developing rain and increasing winds, and the worst of Irene will take place throughout the day on Sunday before calming down overnight. The places that will see the worst of Irene, currently in the Likely Impact Zone but could be further east or west, could end up with 5 to as much as 12 inches of rain resulting in significant flooding, especially when combined with the rain so far this month and Thursday's storms, along with potentially near hurricane force wind gusts (74 mph). Places further west will see lighter rain, up to 5 inches, with lighter wind gusts, in the tropical storm force range (40-74 mph). There is still uncertainty with Irene's impact, but Irene has the potential to be a dangerous storm which could result in significant damage across the East Coast. Stay tuned for more information on Irene over the next several days.


Monday, August 22, 2011

Aug 22, 2011: Stormy Pattern Continues

Notes: Today's update includes an updated 5-Day Forecast and Tropics pages. Throughout the day tomorrow, the Tropics page will be updated, and storm summaries for last weekend's storm and the Friday-Sunday severe weather events will be posted tomorrow and on Wednesday, respectively.


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With a trough moving into the region behind yesterday's cold front, today brought much drier conditions into the area along with colder temperatures, peaking only in the mid to upper 70s inland, upper 70s to lower 80s in the immediate NYC area, and in the upper 70s across most of Long Island and southern CT, making today feel more like an early September day.

The area so far has seen an unusually wet August, with Central Park and JFK having seen 11.59" and 11.94" of rain this month, respectively. Dry conditions will continue through Wednesday, but the break from the rain will be short lived as yet another cold front brings another heavy rain risk on Thursday. Skies will clear on Friday, but trouble may be on its way as Hurricane Irene could move up the East Coast and directly affect the area, potentially shattering August rain records across the area.


Tomorrow's Outlook:

With the trough still over the region, tomorrow will be another nice and comfortable day. With a WNW/NW wind and mostly sunny skies expected once again, high temperatures will reach the mid to upper 70s inland, upper 70s to mid 80s in the immediate NYC area, and the upper 70s to lower 80s in Long Island and southern Connecticut.


Wednesday - Friday: Storms Return Once Again

The cold air mass will slowly pull out of the region on Wednesday, bringing more of a SSW wind and warming temperatures. High temperatures will reach the upper 70s to lower 80s inland, lower to mid 80s in the immediate NYC area, and due to the south wind, Long Island and S CT will reach the mid 70s to lower 80s. Mostly sunny skies are expected as well.

By Thursday, however, the dry conditions will come to an end. Another cold front will move through the area in the afternoon and evening hours, bringing a risk of thunderstorms across the Northeast, including the area. Severe weather parameters are moderately supportive, including 30-45 knots of bulk shear and lift index down to -5. The biggest risk with these storms will once again be heavy rain, however, as precipitable water values are expected to end up near 2 inches, meaning that storms will have the potential to produce heavy rain. In addition to the heavy rain, gusty winds are also a risk with Thursday's storms. Stay tuned for more information on these storms.

By Friday, with the cold front east of the area and another weak trough moving in, cooler conditions will return. In contrast to Thursday, when a SSW wind will bring temperatures into the mid to upper 80s from NYC and further west and upper 70s to lower 80s in Long Island/S CT, mostly sunny skies and a NNW wind will return, bringing temperatures down into the upper 70s to lower 80s across most of the area.


Saturday - Monday: Hurricane Irene Threatens East Coast

Saturday is expected to be another mostly nice day across the area, with high temperatures once again reaching the upper 70s to lower 80s across most of the area. Increasing cloud cover by the evening, however, will signal that trouble is on the way as Hurricane Irene will move up the Southeast coast and towards the Mid Atlanticc and Northeast. Yesterday's brief post mentioned that Irene may affect the area, and the model consensus today is for the hurricane to move up the coast, directly affecting the area with heavy rain and wind.


Intensity Forecast: Since the last update, Irene has continued to move on a WNW path, and is currently just north of the Dominican Republic. As Irene will stay north of Hispaniola, no significant weakening is expected. Irene has intensified into a Category 2 hurricane earlier than expected, and with a mostly favorable environment ahead of it with high SSTs and low wind shear, additional intensification is expected, and Irene will likely become a Category 3 hurricane by at least Tuesday morning, if not the afternoon. With a mostly favorable environment persisting and the potential for Irene to rapidly intensify, I updated the forecast to show Irene strengthening into a lower to middle end Category 4 hurricane, peaking with 140-150 mph sustained winds.


Track Forecast: Irene's track is mostly certain for the next day, moving on a WNW track and staying just north of Hispaniola. By Wednesday and Thursday, however, there is increasing uncertainty with Irene's track. Looking at the latest models, the UKMET, NAM and GFDL are the western solutions, with Irene moving through Florida, likely moving up the coast in the form of remnants. The ECMWF and GFS are in the middle, with Irene moving right up the coast, affecting the coast from the Carolinas to NYC and New England with heavy rain and strong winds. The GGEM is further east with the storm staying mostly offshore, but is an outlier with how it handles the storm, especially due to the timing being off by at least a full 24 hours compared to the other models.

Looking at the latest trends, the models have shifted slightly east, shifting from a consensus for the storm to track just east of Florida as of this morning to a South/North Carolina landfall as of this evening's runs. Last night's westernmost solutions, showing a track in the Gulf of Mexico, have shifted east as well. There is still uncertainty for this time period, but at this time, I expect Irene to start recurving earlier than the western models show, keeping Irene mostly east of Florida with a landfall somewhere from the northern coast of South Carolina to east central North Carolina. Irene would then follow a path not too far off the coast as it moves towards the NNE/NE and becomes extra-tropical, staying just east of Long Island and over Cape Cod. Such a solution would affect the area with rain and wind, but keep the worst of Irene to the east of NYC. Confidence on this solution is not very high, and Irene could end up anywhere from a track just west of NYC, to a track just east of NYC, to a track mostly offshore with minimal impact in NYC. Stay tuned for more information on Irene over the next few days.


Impact On East Coast/NYC: As previously mentioned, there is still uncertainty with Irene's exact location, but Irene will affect the area, whether directly or indirectly. Should Irene take the track I previously mentioned, the area would be affected by a strong Tropical Storm Irene on Sunday through Sunday night. NYC would see rain and wind, but the heaviest rain would stay in Connecticut and Long Island. This is a more eastern scenario, and should Irene take the middle path as suggested by the GFS and ECMWF, which is a reasonable solution that cannot be ruled out, the area could experience heavy rain, potentially well over 4 inches, and up to near hurricane force wind gusts. It is also a possibility that Irene tracks just west of NYC in the form of remnants, which would bring moderate to heavy rain into the area but with lighter winds.

There is still a lot of uncertainty with Irene, and the forecast could change towards more or less impact, but Irene is expected to affect the area, whether it's directly or indirectly. Stay tuned for more updates on Irene in the Tropics page, where updates will be posted 2-3 times a day, and with the daily evening discussions, which will discuss Irene's impact on the area in more details.

Aug 22, 2011 Morning Update

11:30 AM: I am currently working on several updates for this blog, which will be posted throughout the day today and tomorrow. In addition to updated 5-Day Forecast and Storm Summary pages later today, stay tuned for updates in the Tropics page as updates on Hurricane Irene will be posted this morning, afternoon and evening. Tonight's update will include a more detailed discussion on Irene's potential impcact on the East Coast, including the NYC area, for Saturday-Monday.

Sunday, August 21, 2011

Aug 21, 2011 Storm Updates

***NOTE:***

Some storm updates will be posted this afternoon regarding the severe weather currently affecting the area. Several updates will be posted tomorrow and on Tuesday regarding the following information:

- Summary and forecast verification of last weekend's heavy rain and flooding
- Summary of Friday's and today's severe weather outbreaks
- Updated longer range forecast, including a discussion on the possibility that Tropical Storm Irene might affect the East Coast, including the area, in the form of a hurricane early-mid next week

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6:30 PM: Heavy Storms Entering NYC

An area of moderate to locally heavy rain associated with strong thunderstorms near the NJ/PA border is moving ENE, and is currently just near NYC. Moderate rain is currently affecting northern NJ and interior SE NY, and is about to enter NYC. Moderate to heavy rain will continue to affect N NJ/NYC through at least 9-10 PM before starting to end, with rain lasting until at least 10 PM-12 AM in the eastern parts of the area.

Sunday, August 14, 2011

Aug 14, 2011 Storm Updates


NOTE: Another update may be posted later this morning. If there are no significant changes, however, this will be the last update until Monday, August 22.

In addition to this update, the last update to the 5-Day Forecast until August 22 will be posted by 11 AM.

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12:55 PM: Plenty Of Rain Approaching NYC

Since this morning, additional rain continued to fall across the area, and rain totals so far include 3.54" in JFK, 4.10" in Central Park, 5.09" in La Guardia airport, and as much as 6.80" in JFK airport. There is plenty of rain to come, however, and it is possible that the amounts listed above could be doubled, if not more, by the time that the storm ends on Tuesday.

As the latest radar shows to the left, there is widespread moderate to heavy rain developing in southeastern Pennsylvania and moving slowly towards the area. While there is a brief break in the heavy rain in the immediate NYC area at this time, heavy rain will return within the next 1-2 hours and continue through the rest of the afternoon hours, bringing an additional 1 to as much as 3-4 inches of rain through this evening.

Forecast Update: After the late afternoon, the heavy rain should become less widespread as the peak of the storm should be during the day today. Occasional heavy rain will continue in the central and eastern parts of the area, however, and will continue through Monday afternoon/night before becoming more isolated and lighter. As a result, I slightly increased the forecast rain totals to 3 to 7 inches in northern NJ, 2 to 5 inches in SE NY, 5 to 10 inches in NYC/western Long Island, and 2 to 6 inches in eastern Long Island/S CT. Amounts could be locally lower or higher, and it is possible that a few parts of NYC could see as much as a foot of rain by the time that the storm ends.


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10:30 AM: Heavy Rain Continues


While heavy rain was expected for last night and today, there was much more rain than expected last night as a heavy rain band stalled over the immediate NYC area through the overnight hours. The latest radar estimates show that over 1.5 inch of rain fell so far from central Long Island into NYC and northern NJ, with amounts as high as 4-5 inches of rain just during the overnight hours in Staten Island and parts of Queens, Brooklyn, and Nassau county. SE NY and southern CT saw anywhere from 1/3 inch to 1 inch.

Looking at the latest radar, moderate to heavy rain is still affecting the immediate NYC area including Long Island and southern Connecticut. The rain is slow moving and does not seem to be weakening, though a break in the rain is possible for NE NJ/NYC in about an hour as a dry spot on the radar in central NJ moves towards these areas. Occasional moderate to heavy rain is expected to continue today, with the models and short range models in agreement of additional heavy rain amounts through this evening, and an additional 1 to 3 inches of rain are expected in the immediate NYC area, Long Island and southern Connecticut today with locally higher amounts up to 4 inches possible. The western parts of the area (NW NJ/Orange county) should see lighter rain today, but locally heavy rain is still possible.


Updated Forecast: Additional rain is expected to continue through tonight and Monday, but lighter amounts are expected as the coastal low pressure develops, which will keep the heavier rain from NYC and further north/east. Occasional moderate rain will continue through Monday night with lighter rain into Tuesday. By the time that the storm ends, at least 3 to 6 inches of rain are possible in northern NJ, 2 to 4 inches in SE NY, 4 to 8 inches in NYC/western Long Island, and 2 to 5 inches in eastern Long Island and southern Connecticut. The heavier rainfall will not cover the entire area, and locally lower or higher amounts are possible. If the forecast additional rain amounts verify, amounts could end up as high as 8-10 inches locally.