Thursday, August 25, 2011

Hurricane Irene Poised to Strengthen Before Making Run at East Coast...

I chose to lead-off this post with an infrared (measures the cloud temperature) satellite image of Irene instead of the usual visible image, because its easier to see the eye that way at the moment.  The visible ("naked eye") and watervapor (measures the water content of the atmosphere) are shown below:

You can see that the water vapor image also shows the eye quite well, in addition to the classic symmetrical bands flowing counter-clockwise around the center of Irene.

As alluded to in the headline of this post, Irene is poised to further intensify tonight and Friday, for a couple of reasons:  (1).  she is moving through a region with the warmest water temperatures and highest moisture content that she's seen so far, and (2). middle and upper-level wind profiles are favorable for intensification.

As of the 5pm EDT National Hurricane Center (NHC) Advisory, the center of Hurricane Irene was located about 575 miles South of Cape Hatteras, North Carolina. Maximum sustained winds were 115 mph, and the minimum central pressure was 28.05 inches of mercury (950 millibars).

During the afternoon, Irene has slowly begun to make the critical (to the forecast) Northward turn that I mentioned in a post earlier this morning.  Instead of moving directly toward the Northwest, she is now moving toward the North/Northwest at 15 mph.  This general motion is forecast to continue this evening, with a gradual turn more directly toward the North expected overnight.

The above trends are also captured by the latest computer model forecast composite, shown on the image below:

...and the NHC is currently staying right down the middle of the consensus forecast track, as shown on the 3 and 5 day official forecast track maps below:

The latest watches and warnings are also shown on the above NHC track forecast maps.  As of the 5pm EDT advisory, the following watches and warnings are now in effect for the U.S. East coast:

Tropical Storm Warning:
Coast of South Carolina from Edisto Beach to Little River Inlet

Hurricane Warning:
Coast of North Carolina from Little River Inlet to the Virginia border
This includes the Albemarle, Pamlico and Currituck Sounds

Tropical Storm Watch:
For the Chesapeake Bay from Smith Point Northward, including the Tidal Potomac

Hurricane Watch:
From the Virginia/North Carolina border, North to Sandy Hook, New Jersey
This includes Delaware Bay and the Chesapeake Bay South of Smith Point

By this point in time, those in the warning areas should be rushing preparedness activities to completion by tomorrow.  Those in the watch areas should be well underway with their preparedness plans, and be ready for completion of those activities by early Saturday.

Some evacuation orders have already been issued along portions of the East Coast, and trust me, many more are to come.  Hundreds of flights are also being cancelled all along the Eastern seaboard, so be sure to call ahead before going to the airport if you have flight plans for tonight through Monday.

Some of the the outer bands of Irene have been moving across Florida during the afternoon.  You can also see the eye of the storm on the far right side of the Melbourne, FL radar image below:

Showers and occasional thunderstorms along with gusty Northeast winds can be expected across Florida overnight, along with battering waves and higher than normal surf along the East coast of the state.

As I mentioned earlier, Irene is gradually making the expected Northward turn, and is now moving toward the North/Northwest at about 15 mph.  If she continues to move as forecast, she'll be on an almost directly Northward heading by tomorrow morning.  The latest GFS computer forecast model is calling for the eye to pass over the Outer Banks of North Carolina on Saturday afternoon.  The image from that forecast model valid 5pm EDT Saturday is shown below:

As I've been saying for days now, please don't concentrate on the forecast track of the center (eye) of the storm only!  The above computer model image is forecasting damaging, hurricane force winds in excess of 80 mph as far West as the Raleigh-Durham area on Saturday afternoon and evening.  This is unchanged from yesterday's forecast, and was mentioned in my post last night.

If the above computer model forecast verifies (which certainly seems possible based on current observations) then winds of up to 100 mph will be a strong possibility as far West as I-95 in North Carolina on Saturday afternoon and evening.  The potential for tree damage across this region will be huge.  Heavy rains across the region recently have the ground and the trees full of water, making it that much easier for them to be downed by these strong winds.  This, of course, will also increase the already staggering likelihood of widespread power outages across the region.

The same model then forecasts Irene to track North/Northeastward along the coast, hammering the Baltimore/Washington areas on Saturday night (GFS computer model forecast valid 2am EDT Sunday morning is shown below):

...and the New York City area by Noon on Sunday (GFS computer model forecast valid 11am EDT on Sunday shown below):

By 5pm EDT on Sunday, Irene will be hammering the Boston area and New England.  The GFS computer model forecast valid at that time is shown on the image below:

Strong, damaging winds in excess of 80 mph and potentially destructive (or even deadly) storm surges are forecast in each of the above mentioned areas during the time frames indicated.

If you live in the above described areas, please take this situation very seriously.  With each passing hour it appears that Irene will be at least as strong as the "Long Island Express" hurricane of 1938.  Regardless of how the individual details pan out, this will be the most significant even across the Eastern seaboard in many, many years.

Please review hurricane preparedness tips here, and make sure that you have a severe weather safety kit ready to go if you live in these areas.  

I will be making additional posts specific to particular regions along the forecast path of Irene later this evening and on Friday.  I intend to go into greater detail about the potential for wind, storm surge and flooding impacts for each of these areas.  Please check back for updates.

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