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Tropical Storm HANNA


ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM HANNA DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082008
1100 AM EDT TUE SEP 02 2008
 
HANNA HAS FINALLY SUCCUMBED TO THE STRONG VERTICAL SHEAR WITH
VISIBLE SATELLITE IMAGERY SHOWING A PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION AND A SHRINKING CDO FEATURE.  THE INITIAL INTENSITY IS
SET AT 60 KT...BUT GIVEN THE CURRENT SATELLITE PRESENTATION...THIS
MIGHT BE A BIT GENEROUS.  AN AIR FORCE RECONNAISSANCE AIRCRAFT WILL
INVESTIGATE HANNA THIS AFTERNOON AND PROVIDE A BETTER INTENSITY
ESTIMATE.  WATER VAPOR IMAGERY SHOWS A SHARP EDGE OR DEFORMATION
AXIS ON THE NORTH SIDE OF THE CIRRUS CANOPY SUGGESTING THAT THE
SHEAR WILL PERSIST IN THE SHORT-TERM...AND SOME ADDITIONAL
WEAKENING IS POSSIBLE TODAY AND TONIGHT.  IN ABOUT 24
HOURS...GLOBAL MODELS SHOW THE SHEAR WEAKENING AND THIS COULD ALLOW
HANNA TO RESTRENGTHEN.  HOWEVER...GIVEN THE PRESENT LACK OF
ORGANIZATION...IT IS DIFFICULT TO KNOW HOW MUCH STRENGTHENING IS
POSSIBLE.  THE NEW OFFICIAL FORECAST IS LOWER THAN THE PREVIOUS
ADVISORY BUT SHOWS HANNA BECOMING A CATEGORY ONE HURRICANE IN ABOUT
36 HOURS.  IT SHOULD BE NOTED THAT THIS IS A LOW CONFIDENCE
FORECAST.  IN FACT...IF ONE CONSULTS THE WIND SPEED PROBABILITY
PRODUCT INCLUDED IN THIS PACKAGE...IT CAN BE SEEN THAT THERE IS
NEARLY AN EQUAL PROBABILITY OF HANNA BEING A TROPICAL STORM OR
HURRICANE AT DAY 3. 

HANNA CONTINUES TO MEANDER BUT THE BEST ESTIMATE OF AN INITIAL
MOTION IS 250/05. SLOW AND ERRATIC MOTION IS EXPECTED TODAY BUT
HANNA SHOULD START MOVING NORTHWESTWARD TONIGHT OR TOMORROW AS A
LARGE MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC LIFTS NORTHWARD
AND THE SUBTROPICAL RIDGE BUILDS BACK IN. HANNA SHOULD ACCELERATE
NORTHWESTWARD AT DAYS 2 TO 3 AS THE RIDGE STRENGTHENS. DYNAMICAL
TRACK MODELS HAVE SHIFTED A LITTLE TO THE WEST AND THE NEW OFFICIAL
FORECAST FOLLOWS SUIT. ON THE FORECAST TRACK...HANNA IS EXPECTED TO
APPROACH THE EAST COAST OF FLORIDA... GEORGIA...OR SOUTH CAROLINA
IN 2 TO 3 DAYS. IT SHOULD BE STRESSED THAT THE EXPECTED ANGLE OF
APPROACH AND TRACK UNCERTAINTY MAKE IT IMPOSSIBLE TO NARROW DOWN
THE POTENTIAL IMPACT AREA. INTERESTS IN THE NORTHWESTERN BAHAMAS
AND ALONG THE ENTIRE SOUTHEASTERN UNITED STATES COAST SHOULD
CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/1500Z 21.0N  73.5W    60 KT
 12HR VT     03/0000Z 21.4N  73.7W    55 KT
 24HR VT     03/1200Z 22.3N  74.2W    60 KT
 36HR VT     04/0000Z 23.6N  75.3W    65 KT
 48HR VT     04/1200Z 25.1N  76.8W    70 KT
 72HR VT     05/1200Z 29.5N  80.5W    75 KT
 96HR VT     06/1200Z 36.5N  80.0W    35 KT...INLAND
120HR VT     07/1200Z 45.5N  70.0W    25 KT...INLAND REMNANT LOW
 
$$
FORECASTER RHOME/KNABB
 
NNNN


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Page last modified: Tuesday, 21-Apr-2009 12:09:17 UTC