[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 050849
TCDAT3
TROPICAL STORM HARVEY DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI AUG 05 2005

CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE HARVEY IS
EXPERIENCING SIGNIFICANT WEST-SOUTHWESTERLY UPPER-LEVEL SHEAR...
WHICH HAS CAUSED THE LOW-LEVEL CIRCULATION TO LAG BEHIND TO THE
SOUTHWEST OF THE MID- AND UPPER-LEVEL CIRCULATIONS. THE OVERALL
CONVECTIVE PATTERN HAS ALSO BECOME LESS DISTINCT...ALTHOUGH A BURST
OF DEEP CONVECTION HAS REDEVELOPED OVER AND JUST NORTHEAST OF THE
SURFACE CENTER DURING THE PAST COUPLE OF HOURS. THE INTENSITY IS
BEING MAINTAINED AT 55 KT BASED ON DVORAK T-NUMBERS OF T3.5/55 KT
FROM BOTH TAFB AND SAB...AND A COUPLE OF 55 KT UNFLAGGED WIND
VECTORS NOTED IN A 04/2228Z QUIKSCAT OVERPASS.

THE INITIAL MOTION ESTIMATE IS 070/08. THE INITIAL POSITION WAS
ADJUSTED ABOUT 30 NMI SOUTH OF THE PREVIOUS POSITIONS AND FORECAST
TRACK. OTHER THAN THAT...THE FORECAST TRACK AND REASONING REMAINS
UNCHANGED FROM THE PAST FEW ADVISORIES. A SHORTWAVE TROUGH TO THE
NORTH OF HARVEY THAT HAD BEEN MOVING THE CYCLONE ALONG AT A DECENT
CLIP HAS NOW LIFTED OUT TO THE NORTHEAST AS NOTED IN WATER VAPOR
IMAGERY. THIS HAS RESULTED IN A WEAKENING OF THE STEERING FLOW.
HOWEVER...ANOTHER UPSTREAM SHORTWAVE CURRENTLY MOVING OVER
SOUTHEASTERN CANADA IS EXPECTED TO DIG SOUTHWARD AND SLOWLY LIFT
HARVEY NORTHEASTWARD BY 36 HOURS...WITH GRADUAL ACCELERATION OVER
COOLER WATER EXPECTED AFTER THAT. THE OFFICIAL FORECAST TRACK IS
SIMILAR TO THE PREVIOUS ADVISORY...AND IS A LITTLE SLOWER AND TO
THE RIGHT OF THE NHC MODEL CONSENSUS.

THE VERTICAL SHEAR IS FORECAST TO WEAKEN TO LESS THAN 10 KT BY 24
HOURS...SO LITTLE CHANGE IN INTENSITY IS EXPECTED BEFORE THEN.
AFTERWARDS...HOWEVER...THE VERTICAL SHEAR WILL GRADUALLY INCREASE
TO 30 KT OR MORE BY 96 HOURS AS HARVEY ALSO MOVES OVER SUB-26C
SSTS. THIS SHOULD BRING ABOUT STEADY WEAKENING AND POSSIBLE
TRANSITION TO AN EXTRATROPICAL LOW BY 96 HOURS.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      05/0900Z 32.5N  59.0W    55 KT
 12HR VT     05/1800Z 32.9N  57.9W    55 KT
 24HR VT     06/0600Z 33.5N  57.0W    55 KT
 36HR VT     06/1800Z 34.6N  56.1W    50 KT
 48HR VT     07/0600Z 36.0N  55.0W    50 KT
 72HR VT     08/0600Z 39.1N  50.5W    45 KT
 96HR VT     09/0600Z 42.5N  44.0W    40 KT...BECOMING EXTRATROPICAL
120HR VT     10/0600Z 47.0N  34.0W    30 KT...EXTRATROPICAL

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