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.

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