Tropical Storm EARL

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TROPICAL STORM EARL DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
1100 PM EDT FRI SEP 03 2010
 
EARL HAS CONTINUED TO SLOWLY WEAKEN THIS EVENING.  WHILE THE
CENTRAL PRESSURE REMAINS 958 MB...AIRCRAFT DATA SUGGEST THAT EARL
IS NOW BELOW HURRICANE STRENGTH.  THE INITIAL INTENSITY OF 60 KT IS
BASED ON A BLEND OF PEAK SFMR VALUES OF AROUND 55 KT AND A 700-MB
FLIGHT LEVEL WIND MAXIMUM OF 67 KT JUST PRIOR TO 0000 UTC.  THE
DEEP CONVECTION WITH EARL IS INCREASINGLY LIMITED TO THE NORTHERN
SEMICIRCLE OF THE CIRCULATION...DUE TO SOUTHERLY WIND SHEAR OF
15-20 KT AND DRY AIR ADVECTION SOUTH OF THE CENTER.  EARL WILL BE
CROSSING THE NORTHERN WALL OF THE GULF STREAM SOON...AND COLD WATER
AND INCREASING SHEAR SHOULD RESULT IN CONTINUED WEAKENING UNTIL
EXTRATROPICAL TRANSITION BEGINS.  GLOBAL MODEL FIELDS AND PHASE
SPACE DIAGRAMS SUGGEST THAT EARL WILL BE UNDERGOING EXTRATROPICAL
TRANSITION BY 24 HOURS...WITH THE TRANSITION COMPLETE IN 36 HOURS.
 
THE INITIAL MOTION ESTIMATE IS TOWARD THE NORTHEAST...OR 035 DEGREES
AT 22 KNOTS.  EARL SHOULD CONTINUE TO ACCELERATE AHEAD OF A LARGE
MID- TO UPPER-LEVEL TROUGH MOVING EASTWARD FROM THE GREAT LAKES
INTO SOUTHEASTERN CANADA OVER THE NEXT COUPLE OF DAYS.  BEYOND THAT
TIME...MUCH OF THE GLOBAL MODEL GUIDANCE NOW SUGGESTS THAT EARL WILL
TURN NORTHWARD AND THEN NORTHWESTWARD AS A DISTINCT CYCLONE THROUGH
72 HOURS BEFORE DISSIPATING OR BEING ABSORBED.  THE EXTRATROPICAL
PORTION OF THE TRACK IS BASED ON COORDINATION WITH THE OCEAN
PREDICTION CENTER.
 
EARL REMAINS A LARGE TROPICAL CYCLONE...AND WILL BRING HIGH WINDS
AND RAINFALL TO MUCH OF COASTAL NEW ENGLAND AND THE CANADIAN
MARITIMES OVERNIGHT TONIGHT AND SATURDAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/0300Z 40.0N  69.7W    60 KT
 12HR VT     04/1200Z 43.1N  66.6W    55 KT
 24HR VT     05/0000Z 48.2N  61.6W    45 KT...POST-TROPICAL
 36HR VT     05/1200Z 52.5N  56.5W    45 KT...POST-TROP/EXTRATROP
 48HR VT     06/0000Z 55.5N  54.0W    40 KT...POST-TROP/EXTRATROP
 72HR VT     07/0000Z 57.0N  57.0W    40 KT...POST-TROP/EXTRATROP
 96HR VT     08/0000Z...DISSIPATED
 
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FORECASTER BRENNAN
 
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