[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 050250
TCDAT1

TROPICAL STORM FLORENCE DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062012
1100 PM AST SAT AUG 04 2012

FLORENCE IS BECOMING BETTER ORGANIZED.  BANDING FEATURES ASSOCIATED
WITH THE CYCLONE HAVE RECENTLY DISSIPATED IN FAVOR OF A CENTRAL
DENSE OVERCAST.  EARLIER TRMM AND WINDSAT OVERPASSES REVEAL A WELL-
DEFINED LOW-LEVEL STRUCTURE UNDERNEATH THIS NEW CONVECTIVE MASS...
WITH A NEARLY CLOSED RING OF CONVECTION NOW PRESENT.  A DVORAK
INTENSITY ESTIMATE OF 3.5/55 KT FROM TAFB AT 0000 UTC AND THREE-
HOURLY AVERAGED ADT VALUES OF AROUND 3.3 ARE THE BASIS FOR
INCREASING THE INITIAL INTENSITY TO 50 KT FOR THIS ADVISORY.

THE INTENSITY FORECAST IS TRICKY.  DESPITE BEING IN A LOW-SHEAR
ENVIRONMENT...FLORENCE IS FORECAST TO MOVE THROUGH A TONGUE OF
MARGINALLY WARM WATERS OVER THE NEXT COUPLE OF DAYS.  IN ADDITION...
EUMETSAT RGB SATELLITE IMAGERY INDICATES THAT THE CYCLONE IS
SURROUNDED BY A RATHER DRY AIR MASS...AND THIS AIR MASS SHOULD
ACCOMPANY FLORENCE ON ITS WESTWARD TREK. THESE NEGATIVE FACTORS
SUGGEST THAT ANY STRENGTHENING IN THE SHORT TERM WOULD NOT LIKELY
BE SIGNIFICANT.  BEYOND 72 HOURS...GLOBAL MODELS SHOW FLORENCE
ENCOUNTERING INCREASING SOUTHWESTERLY SHEAR ASSOCIATED WITH AN
UPPER-LEVEL TROUGH OVER THE CENTRAL ATLANTIC.  EVEN THOUGH THE
STORM WILL BE MOVING OVER WARMER WATERS BY THIS TIME...THE SHEAR
SHOULD BE STRONG ENOUGH TO INDUCE WEAKENING.  THE NEW NHC INTENSITY
FORECAST IS ADJUSTED UPWARD THROUGH 48 HOURS BASED ON
CURRENT TRENDS AND IS ABOUT THE SAME AS THE PREVIOUS FORECAST AFTER
THAT TIME.  THE FORECAST IS IN EXCELLENT AGREEMENT WITH THE LATEST
SHIPS/LGEM OUTPUT.

THE INITIAL MOTION ESTIMATE IS 295/13. A MID-LEVEL RIDGE OVER THE
EASTERN ATLANTIC IS EXPECTED TO BUILD WESTWARD DURING THE NEXT
SEVERAL DAYS...WHICH WILL CAUSE THE TRACK OF FLORENCE TO BEND TOWARD
THE WEST.  LATE IN THE FORECAST PERIOD...THE CYCLONE IS EXPECTED TO
ENCOUNTER A WEAKNESS IN THE SUBTROPICAL RIDGE OVER THE CENTRAL
ATLANTIC WHICH SHOULD INDUCE A WEST-NORTHWESTERLY HEADING. ALTHOUGH
THE SPREAD IN THE TRACK GUIDANCE HAS DECREASED THIS CYCLE...IT
REMAINS FAIRLY SIGNIFICANT BEYOND 72 HOURS.  THE DIFFERENCE IN TRACK
SOLUTIONS AT LATER TIMES APPEARS DEPENDENT ON THE VERTICAL DEPTH/
STRENGTH OF THE CYCLONE...WITH THE ECMWF/GFDL/HWRF FORECASTING A
WEAKER VERSION OF FLORENCE AND THE GFS FAVORING A STRONGER SYSTEM.
THE NEW NHC FORECAST TRACK REMAINS IN BETWEEN THESE TWO EXTREMES
BUT HAS BEEN ADJUSTED TOWARD THE CAMP OF MODELS FAVORING A WEAKER
CYCLONE GIVEN THE SHEAR FORECAST.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 16.1N  33.0W   50 KT  60 MPH
 12H  05/1200Z 16.5N  34.8W   55 KT  65 MPH
 24H  06/0000Z 17.0N  37.2W   60 KT  70 MPH
 36H  06/1200Z 17.5N  39.7W   60 KT  70 MPH
 48H  07/0000Z 18.1N  42.6W   60 KT  70 MPH
 72H  08/0000Z 19.3N  49.0W   45 KT  50 MPH
 96H  09/0000Z 20.9N  55.1W   35 KT  40 MPH
120H  10/0000Z 23.5N  60.5W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
FORECASTER KIMBERLAIN


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