Hurricane Irene: Major Northeast Threats

Updated: August 25, 2011 6:30 am ET

Our projected path map below continues to paint an ominous picture by pointing Hurricane Irene right in the direction of the East Coast this weekend. The latest computer model guidance confirms this threat and the first hurricane watches have been issued for the United States.

The potential is real for the strongest hurricane hit on the Northeast in at least a couple decades this weekend!

Northeast threat from Hurricane Irene | See latest on Irene

Let's lay out all the potential threats and timing involved with Hurricane Irene.


High winds

The 5 a.m. EDT forecast discussion Tuesday from Stacy Stewart, Sr. Hurricane Specialist at the National Hurricane Center mentioned Hurricane Irene is "forecast to become a larger than average hurricane."

This means its wind field, both of tropical storm-force and hurricane-force winds, will cover a large swath of real estate. Reason again not to focus solely on the path of the center of circulation, although it is around and especially east of the eye where the strongest winds will be.

Our graphic below highlights the general area of wind threat from Hurricane Irene. As you can see, a large swath of the Northeast may see power outages and downed trees. The severity will be dictated by Irene's exact path and intensity, which remain uncertain at this time.

The Bottom Line: Wind threat

• Timing: Conditions deteriorate Saturday night. Strongest winds Sunday. Lingering strong winds possible Sunday night into early Monday in New England.
  
• Possible impacts: Widespread trees downed, power outages, particularly near the coast. Potential for some structural damage in strongest gusts near center of Irene.

Northeast high wind impact threat area

Heavy rain/flood threat

It's already been a wet August in the Northeast.

Philadelphia will likely have its wettest single month on record, breaking a record from Sep. 1999, which included heavy rain from Hurricane Floyd passing to the east.

New York City may also break their previous wettest month record dating back to 1882!

Heavy rain threat from Hurricane Irene (dark green shading) & tornado threat (red shading)

But first...a cold front will bring scattered severe thunderstorms with locally heavy rainfall into the Northeast Thursday. Some areas may seen between 1-3" of rainfall from these Thursday storms, further soaking already wet ground.

Then, depending on the path of Hurricane Irene (latest forecast), a strip of heavy rainfall is expected, especially along and just to the west of the path of the center of circulation from eastern North Carolina to New England.

The wet soil from this soggy August will also heighten the concern for downed trees from strong winds.

The Bottom Line: Heavy rain/flood threat

• Timing: Heavy rain may arrive ahead of Irene's center Saturday morning along the Delmarva Peninsula, later Saturday in New Jersey and Long Island, and early Sunday morning in New England. Heavy rain may continue through Sunday afternoon in Long Island and NYC metro, and through Sunday night or early Monday morning in parts of New England.
  
• Potential impacts: Not simply urban flash flooding, but more widespread flash flooding with rapid rises on small creeks and streams. Minor to moderate flooding of some mainstem rivers and tributaries.

Read article: Don't underestimate inland flood threat


Storm surge/coastal flood threat

Before the 2010 hurricane season, TWC Hurricane Expert, Dr. Rick Knabb (Follow on Twitter | Become a Facebook fan) published a list of the 5 most hurricane vulnerable and overdue cities.

Among those cities: New York City and Atlantic City

According to Knabb, many parts of the Northeast are very vulnerable to storm surge, including New York Harbor and Buzzard's Bay.

Relative surge vulnerability of the East Coast and Gulf Coast

If Hurricane Irene's center tracks close or even a little inland of the Jersey Shore into southern New England, that places New York City and southern New England on the eastern semicircle of the circulation, meaning significant storm surge flooding possible in these vulnerable locations! Coastal flooding would also begin well ahead of the arrival of the center of Irene, in this scenario.

You can see that on the computer model image below. Note: the image below is not an official forecast, and the forecast is subject to change.

If Irene tracks near the coast or slightly inland, surge flooding will result Image: WSI

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The Bottom Line: Storm surge threat timing

• Late Saturday: Delmarva Peninsula
  
• Saturday night/Sunday: N.J. shore, NYC/Long Island
• Sunday/Sunday night: Coastal New England

How rare are Northeast hurricanes?

Going back to 1851, there have been only 5 hurricanes whose centers of circulation have passed within 75 miles of New York City. The last hurricane within that distance from New York City was Hurricane Gloria 26 years ago.

Read article: NYC's hurricane history

Similarly, only 10 hurricanes since 1851 have passed within 75 miles of Boston. The most recent was almost exactly 20 years ago: Hurricane Bob.

Hurricane center tracks within 75 miles of New York City (left) and Boston (right) Image credit: NOAA

A typical tropical cyclone flirting with the Northeast will have weakened to a Category 1 hurricane or a strong-end tropical storm by the time it reaches the Northeast.

The danger with Hurricane Irene is that it could still be at least a Category 2 hurricane on the Saffir-Simpson wind scale, if not a rare Category 3 near the Northeast seaboard!

See what people are saying about the weather: New York | Boston

So, are you truly "hurricane ready?"

Now is the time to prepare your hurricane plan, not when a hurricane is bearing down.

WeatherREADY: Preparedness tips | Watch Video

Watch The Weather Channel and check back with us at weather.com for the latest on this major Northeast threat.

Follow on Twitter: @TWCjerdman

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