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.

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