Tropical Storm HANNA

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TROPICAL STORM HANNA DISCUSSION NUMBER  36
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082008
500 PM EDT FRI SEP 05 2008
 
REPORTS FROM AN AIR FORCE RESERVE HURRICANE HURRICANE HUNTER
AIRCRAFT INDICATE THAT HANNA IS JUST BELOW HURRICANE STRENGTH.  THE
STEPPED FREQUENCY MICROWAVE REPORTED TWO AREAS OF WIND OF ABOUT 65
KT.  HOWEVER...DROPSONDE DATA SUGGESTS THAT THE SFMR ESTIMATES WERE
A LITTLE TOO HIGH.  THE MAXIMUM 850 MB FLIGHT-LEVEL WINDS WERE 75
KT ABOUT 75 N MI EAST OF THE CENTER.  THE LAST REPORTED CENTRAL
PRESSURE WAS 984 MB...UP A LITTLE FROM THIS MORNING.  BASED ON ALL
THIS...THE INITIAL INTENSITY IS SET AT 60 KT.  IT SHOULD BE NOTED
THAT THERE IS NOT MUCH DIFFERENCE METEOROLOGICALLY BETWEEN A 60-KT
TROPICAL STORM AND A 65-KT HURRICANE.

THE MOTION IS A SOMEWHAT WOBBLY 360/17...WITH A RE-ANALYSIS OF
AIRCRAFT DATA SUGGESTING THIS MOTION BEGAN JUST AFTER THE 11Z
AIRCRAFT FIX.  HANNA IS MOVING AROUND THE WESTERN END OF THE
SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC AND SHOULD ENTER THE
WESTERLIES IN 24-36 HR.  THIS SHOULD RESULT IN RECURVATURE TO THE
NORTHEAST AND ACCELERATION.  ALL GUIDANCE AGREES WITH THIS
SCENARIO...AND THERE ARE NO SIGNIFICANT OUTLIERS AMONGST THE
DYNAMICAL MODELS.  THE NEW FORECAST TRACK IS ADJUSTED A LITTLE TO
THE RIGHT OF THE PREVIOUS TRACK AND LIES DOWN THE MIDDLE OF THE
GUIDANCE ENVELOPE.

VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT ARE STILL ISSUES FOR
HANNA...AND SIGNIFICANT STRENGTHENING APPEARS UNLIKELY BEFORE
LANDFALL.  HOWEVER...THERE IS A POSSIBILITY THAT A CONVECTIVE BURST
COULD CAUSE THE STORM TO REACH HURRICANE STRENGTH.  THE CYCLONE
SHOULD WEAKEN AFTER LANDFALL AND BECOME EXTRATROPICAL IN ABOUT 36
HR.  THE GFS AND UKMET CONTINUE TO SUGGEST THE POSSIBILITY OF
DEEPENING AS AN EXTRATROPICAL SYSTEM LATE IN THE FORECAST
PERIOD...AND THIS IS REFLECTED IN THE 96 AND 120 HR FORECASTS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2100Z 30.8N  78.7W    60 KT
 12HR VT     06/0600Z 33.2N  78.5W    60 KT
 24HR VT     06/1800Z 36.7N  76.8W    50 KT...INLAND
 36HR VT     07/0600Z 40.7N  72.4W    45 KT...EXTRATROPICAL
 48HR VT     07/1800Z 44.5N  65.6W    40 KT...INLAND EXTRATROPICAL
 72HR VT     08/1800Z 50.0N  47.5W    40 KT...EXTRATROPICAL
 96HR VT     09/1800Z 51.0N  30.0W    45 KT...EXTRATROPICAL
120HR VT     10/1800Z 52.5N  14.0W    45 KT...EXTRATROPICAL
 
$$
FORECASTER BEVEN
 
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