25 August 2011

Irene heading for US coast, TD10 forms

Major Hurricane Irene is wrapping up its destructive tour of the Bahamas, and has its eye on the eastern US coast now.  At 15Z today, the center of the storm was located very near Abaco Island in the Bahamas, and about 650 miles south of Cape Hatteras NC.  The intensity is 100kts (Cat 3, 951mb) and the heading is NNW at 11kts.  The structure got a little jumbled overnight, but appears to be reorganizing and intensifying now.  This is a very large storm, with tropical storm force winds extending an average of 170 miles from the center, and hurricane force winds extending an average of 49 miles from the center.  These will only increase with time.

The forecast track is becoming more and more certain thanks to large-scale troughs and ridges that are governing its motion in a very straightforward manner.  Select model tracks are plotted on Jonathan Vigh's website: http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2011/al092011/track_late/aal09_2011082506_track_late.png
The official NHC forecast has a first landfall near Morehead City NC on Saturday morning as a Cat 3, then skimming along the coast, passing over the big northeast cities on Sunday morning-afternoon as a Cat 2 hurricane.  Hurricane watches are already posted for much of NC, evacuation of the Outer Banks is underway, and a state of emergency has already been declared for coastal NC.

On this track, and at this intensity, and with its large size, Irene has the potential to cause a lot of trouble from NC to ME.  "Trouble" refers to flooding rains, destructive winds, tornadoes, coastal erosion, and very large inundating storm surges.  Some prior hurricanes with similar tracks hitting Long Island are quite infamous: Carol (1954), Donna (1960), Belle (1976), and Gloria (1985).  The storm surge threat is very real with this storm, especially in big cities where many people are affected... Washington DC, Philadelphia, New York City, Boston, etc.  In addition, very heavy rain can be expected all along the track; this map to the right shows the 5-day forecast accumulation totals.  Given the enormous population and low elevation, New York City is a huge concern with a storm like this.  Finally, if you live anywhere along the east coast from NC on up to ME, pay close attention to the local news, make preparations well ahead of time, and evacuate if told to so.

Of much less significance now, TD10 formed this morning from the easterly wave I mentioned yesterday.  It is located at about 32W and is forecast track northwest and perhaps reach tropical storm intensity.  This does not look like it will be a storm of any concern to anyone, but the next name on the list is Jose.

Please visit my tropical Atlantic headquarters.

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