Tropical Storm JOSEPHINE

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TROPICAL STORM JOSEPHINE DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL102008
1100 AM EDT TUE SEP 02 2008
 
VISIBLE IMAGERY REVEALS AN INCREASE IN THE CYCLONE'S
ORGANIZATION...WITH VERY WELL-DEFINED CONVECTIVE BANDS AND EVEN A
DECEPTIVE CENTRAL FEATURE DISGUISED AS AN EYE.  THE CONVECTIVE TOPS
ARE NOT EXCEPTIONALLY COLD IN THE INFRARED...BUT DVORAK INTENSITY
ESTIMATES ARE A CONSENSUS 35 KT...SO THE DEPRESSION IS UPGRADED TO
A TROPICAL STORM...THE TENTH OF THE 2008 ATLANTIC SEASON. 
JOSEPHINE IS CURRENTLY OVER SEA-SURFACE TEMPERATURES OF ABOUT 28
CELSIUS...AND THE WATERS ALONG THE FORECAST TRACK WILL REMAIN AT
LEAST THAT WARM FOR ABOUT THE NEXT 24 HOURS.  WIND SHEAR IS
ESSENTIALLY NON-EXISTENT OVER THE CYCLONE...SO STEADY STRENGTHENING
SEEMS LIKELY IN THE SHORT TERM...AND COULD BE RAPID GIVEN THE
INCREASED ORGANIZATION AND THAT THE SHIPS-BASED RI INDEX GIVES A
50% CHANCE OF AN INTENSITY INCREASE OF 30 KT OR MORE IN THE NEXT 24
HOURS.  BEYOND 24 HOURS...JOSEPHINE WILL TRAVERSE SLIGHTLY COOLER
WATERS...AND DUE TO AN UPPER-LEVEL LOW FORECAST BY THE MODELS TO
MOVE IN TANDEM WITH THE TROPICAL CYCLONE...WIND SHEAR WILL PROBABLY
INCREASE IN A COUPLE OF DAYS.  EVEN THOUGH ALL OF THE OBJECTIVE
GUIDANCE CALLS FOR A WEAKENING TREND TO START BY 72 HOURS...TO
MAINTAIN SOME CONTINUITY THE NEW OFFICIAL INTENSITY FORECAST SIMPLY
SHOWS AN INTENSITY PLATEAU AT 60 KT IN THE LONGER TERM.

THE INITIAL MOTION REMAINS BRISK ALONG A HEADING JUST NORTH OF DUE
WEST...OR 280/13...BUT THE INITIAL POSITION HAS BEEN ADJUSTED
SLIGHTLY NORTH OF THE PREVIOUS TRACK BASED ON VISIBLE IMAGERY AND
AN EARLIER QUIKSCAT PASS.  A MID-LEVEL HIGH CENTERED OVER THE
EAST-CENTRAL SUBTROPICAL ATLANTIC IS CURRENTLY THE PRIMARY STEERING
MECHANISM...BUT THIS FEATURE IS FORECAST BY THE MODELS TO PROCEED
WESTWARD AND SHIFT TO THE WESTERN ATLANTIC IN A FEW DAYS. 
MEANWHILE...THE DEEP-LAYER LOW JUST OFF THE NORTHEASTERN UNITED
STATES WILL PROPAGATE EASTWARD AND ERODE THE RIDGE NORTH OF
JOSEPHINE...WHICH WILL PROBABLY JUST CAUSE A SLIGHT BEND TO THE
RIGHT AND A SLOWER FORWARD MOTION AT DAYS 3-5.  MODELS ARE IN VERY
GOOD AGREEMENT THROUGH 48 HOURS BUT THEN DIVERGE MARKEDLY...WITH
THE GFS TURNING THE CYCLONE WESTWARD AND THE GFDL AND HWRF TAKING
IT NORTHWESTWARD.  THE OFFICIAL TRACK FORECAST SPLITS THE
DIFFERENCE AND FOLLOWS THE CONSENSUS...WHICH IS JUST A LITTLE NORTH
OF THE PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/1500Z 13.2N  25.3W    35 KT
 12HR VT     03/0000Z 13.6N  27.4W    45 KT
 24HR VT     03/1200Z 14.3N  29.9W    55 KT
 36HR VT     04/0000Z 15.2N  32.4W    60 KT
 48HR VT     04/1200Z 16.1N  34.9W    60 KT
 72HR VT     05/1200Z 18.5N  39.5W    60 KT
 96HR VT     06/1200Z 20.0N  43.5W    60 KT
120HR VT     07/1200Z 21.0N  47.0W    60 KT
 
$$
FORECASTER KNABB
 
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