Hurricane EARL

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HURRICANE EARL DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
500 AM EDT WED SEP 01 2010
 
THE EYE OF EARL HAS BECOME LESS DISTINCT IN SATELLITE IMAGERY DURING
THE PAST FEW HOURS...AND THE EYEWALL CLOUD TOPS HAVE WARMED A
LITTLE.  AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED A
CENTRAL PRESSURE OF 941 MB...WHICH IS LITTLE CHANGED FROM EARLIER. 
HOWEVER...THE MAXIMUM FLIGHT-LEVEL WINDS WERE 116 KT...WHICH WAS
LOWER THAN THE PREVIOUS MISSION...AND SURFACE WIND ESTIMATES FROM
THE SFMR WERE UNDER 100 KT.  THE INITIAL INTENSITY IS DECREASED TO
110 KT...AND THIS COULD BE A LITTLE GENEROUS.

EARL IS MOVING 310-315 DEGREES AT ABOUT 14 KT.  FOR THE NEXT 36 OR
SO...THE HURRICANE SHOULD CONTINUE TO MOVE GENERALLY NORTHWESTWARD
ON THE SOUTHWESTERN SIDE OF A LOW/MID-LEVEL RIDGE OVER THE CENTRAL
ATLANTIC.  AFTER THAT...EARL IS EXPECTED TO TURN NORTHWARD AND THEN
NORTH-NORTHEASTWARD AS IT ROUNDS THE END OF THE RIDGE AND ENTERS
THE WESTERLIES ASSOCIATED WITH A DEEP-LAYER TROUGH MOVING INTO THE
NORTHEASTERN UNITED STATES.  THE TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH THIS SCENARIO.  HOWEVER...THERE ARE SOME SMALL
DIFFERENCE IN THE MODEL GUIDANCE THAT COULD HAVE LARGE IMPLICATIONS
IN TERMS OF IMPACTS.  THE GFDN...NOGAPS...AND UKMET FORECAST THE
CENTER TO PASS NEAR OR OVER THE NORTH CAROLINA COAST AND NEW
ENGLAND.  THE OTHER MODELS ARE FARTHER TO THE EAST...KEEPING THE
CENTER OFFSHORE.  THROUGH 48 HR...THE NEW FORECAST TRACK IS SIMILAR
TO THE PREVIOUS TRACK...KEEPS THE CENTER OFF THE NORTH CAROLINA
COAST...AND LIES JUST WEST OF THE CENTER OF THE GUIDANCE ENVELOPE. 
AFTER 48 HR...THE GUIDANCE ENVELOPE HAS SHIFTED A LITTLE TO THE
WEST...AND THE NEW FORECAST TRACK DOES LIKEWISE TO BE IN THE CENTER
OF THE ENVELOPE.  THIS PART OF THE TRACK IS CLOSER TO THE NEW
ENGLAND STATES THAN THE PREVIOUS FORECAST.

THE INTENSITY FORECAST IS A CONUNDRUM.  ON THE FAVORABLE SIDE...THE
HURRICANE IS OVER VERY WARM SEA SURFACE TEMPERATURES...HAS GOOD
CIRRUS OUTFLOW IN ALL DIRECTIONS EXCEPT TO THE SOUTH...AND HAS A
GOOD CONVECTIVE STRUCTURE.  ON THE NEGATIVE SIDE...EARL IS
EXPERIENCING 15-20 KT OF SOUTHWESTERLY VERTICAL WIND SHEAR...AND
WATER VAPOR IMAGERY SHOWS A TONGUE OF MID/UPPER-LEVEL DRY AIR
WRAPPED MORE THAN HALFWAY AROUND THE CYCLONE.  SOME SHEAR IS LIKELY
TO CONTINUE FOR THE NEXT 36-48 HR...AND NONE OF THE INTENSITY
GUIDANCE CALLS FOR MUCH STRENGTHENING AT THIS TIME.  BASED ON
THIS...THE NHC INTENSITY FORECAST CALLS FOR LITTLE CHANGE IN
STRENGTH FOR 36 HR...FOLLOWED BY WEAKENING AS EARL ENCOUNTERS
COOLER SEA SURFACE TEMPERATURES AND INCREASING SHEAR.  EARL IS
EXPECTED TO BECOME EXTRATROPICAL BY 96 HR.  
 
HURRICANE WARNINGS WILL LIKELY BE REQUIRED FOR PORTIONS OF THE NORTH
CAROLINA COAST LATER THIS MORNING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0900Z 24.0N  71.2W   110 KT
 12HR VT     01/1800Z 25.8N  72.9W   110 KT
 24HR VT     02/0600Z 28.5N  74.6W   110 KT
 36HR VT     02/1800Z 31.3N  75.2W   110 KT
 48HR VT     03/0600Z 34.6N  74.4W   105 KT
 72HR VT     04/0600Z 42.0N  68.0W    85 KT
 96HR VT     05/0600Z 50.0N  61.5W    60 KT...POST-TROP/EXTRATROP
120HR VT     06/0600Z 57.0N  58.0W    45 KT...POST-TROP/EXTRATROP
 
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FORECASTER BEVEN
 
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