Thursday, August 25, 2011

Irene, New Depression & Blistering Heat

Hurricane Irene headlines the weather discussion for today and will continue to do so for days to come. As of 10 a.m. on Thursday, Irene is still a major Category 3 hurricane, with maximum sustained winds estimated to be around 115 mph. The storm has been barreling through much of the Bahamas for the better part of 24 hours and should finally lift north of the island-nation later today. The latest visible satellite image shows Irene passing over Abaco Island in the northwestern Bahamas.

The small bit of good news since late Wednesday is that Irene's intensity has leveled off for now.  Much of that seems to be related to an apparent 'eyewall replacement cycle'. In an eyewall replacement, an outer eyewall forms around the main eye, eventually causing it to collapse.  That process typically results in the storm intensity leveling off or even dropping off a bit.  However, the new eyewall often contracts with time and results in restrengthening of the storm if conditions allow.  Additionally, these eyewall replacement cycles often cause the wind field to expand and it appears that has been the case with Irene.

The latest run of computer models continue to paint a disturbing picture from the Mid-Atlantic into the Northeast.  The models are showing remarkable consistency and agreement in having Irene rake the coast from the Outer Banks of North Carolina to New England. In the image below, the 4 eastern-most tracks are among our less reliable models, so it's easy to see the threat that exists for much of the East Coast.

The official forecast calls for Irene to approach the Outer Banks as a major hurricane before weakening some as it tracks farther north and encounters cooler waters and some wind shear.  However, most of our guidance still shows a formidable hurricane impacting the Northeast.

If current trends continue, Irene could be a storm for the history books.  A number of major metropolitan areas -- including D.C., Baltimore, Philadelphia, New York City, and Boston -- could see significant impacts from the storm.  We would be talking about millions without power over the weekend.  Additionally, heavy rain and storm surge will be big threats.  It's not something we often think of, but even places like Long Island and Lower Manhattan are susceptible to storm surge with the right storm track.

And while our attention is rightfully focused on Irene, the season's 10th tropical depression quietly formed overnight in the far eastern Atlantic.  T.D. #10 could become Tropical Storm Jose in the next day or two, but for right now, the system appears destined to stay over the open Atlantic.

Chief Meteorologist Jay Grymes did some digging and found that if T.D. #10 does become Jose in the next day or so, we will be only slightly behind the pace of 2 of our most active seasons on record in terms of named storms -- 1995 (19 total named storms) and 2005 (28 total named storms).

And finally...can we do something to break this heat?  Unfortunately, there's no significant relief in sight.  Today looks to be our 24th straight day with a high temp of 95° or above in Baton Rouge.  We're now just adding on to a record for consecutive 95°+ days, having surpassed the previous mark of 21 days set in 1960.    We're also adding on to a record for the number of 95°+ days in a given summer.  Today will make 58 in the summer of 2011 for Baton Rouge, easily surpassing the previous record of 46 days in 1990.  Ouch!

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