[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 131434
TCDAT1

TROPICAL STORM FRANKLIN DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062011
1100 AM EDT SAT AUG 13 2011

SINCE THE LAST ADVISORY...A SIGNIFICANT BURST OF DEEP CONVECTION HAS
PERSISTED NEAR AND JUST NORTH OF THE CENTER OF FRANKLIN. PASSIVE
MICROWAVE SATELLITE IMAGES INDICATED A PRONOUNCED MID-LEVEL
EYE-LIKE FEATURE HAD DEVELOPED BETWEEN 08Z AND 10Z...AND THAT COULD
BE WHEN FRANKLIN POSSIBLY REACHED A PEAK INTENSITY OF NEAR 45 KT.
SINCE THAT TIME...HOWEVER...THE CONVECTIVE PATTERN HAS ERODED
SOMEWHAT DUE TO THE EFFECTS OF INCREASING SOUTHWESTERLY UPPER-LEVEL
SHEAR AND COOLER WATER BENEATH THE CYCLONE. THE INITIAL INTENSITY
OF 40 KT IS BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES OF
T3.0/45 KT FROM TAFB...T2.5/35 KT FROM SAB...38 KT FROM
CIRA-AMSU...AND 39 KT FROM UW-CIMSS ADT.

THE INITIAL MOTION ESTIMATE IS 060/19 BASED PRIMARILY ON MICROWAVE
SATELLITE FIXES. FRANKLIN IS EMBEDDED WITHIN DEEP WESTERLY
MID-LATITUDE FLOW AHEAD OF A LARGE MID-TROPOSPHERIC TROUGH THAT IS
MOVING EASTWARD OFF OF THE U.S. NEW ENGLAND COAST. THIS PROGRESSIVE
PATTERN IS EXPECTED TO CONTINUE FOR THE NEXT FEW DAYS...WHICH
SHOULD KEEP FRANKLIN MOVING IN A GENERAL EASTERLY DIRECTION. THE
OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK
AND IS NEAR THE CENTER OF THE TIGHTLY PACKED NHC MODEL GUIDANCE.

FRANKLIN LIKELY PEAKED EARLIER THIS MORNING AND IS NOW ENTERING A
WEAKENING PHASE AS IT MOVES OVER WATER COOLER THAN 26C AND WESTERLY
VERTICAL WIND SHEAR GRADUALLY INCREASES. FRANKLIN IS FORECAST TO
MERGE WITH A COLD FRONT IN 24-36 HOURS INDUCING EXTRATROPICAL
TRANSITION...BUT IT APPEARS THAT THERE WILL NOT BE ENOUGH
BAROCLINIC ENERGY TO CAUSE FRANKLIN TO RE-STRENGTHEN AS A
SIGNIFICANT EXTRATROPICAL LOW PRESSURE SYSTEM. THE INTENSITY
FORECAST IS IDENTICAL TO THE PREVIOUS ADVISORY AND REMAINS LOWER
THAN ALL OF THE AVAILABLE INTENSITY GUIDANCE.

FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 39.0N  57.9W   40 KT  45 MPH
 12H  14/0000Z 39.9N  54.7W   40 KT  45 MPH
 24H  14/1200Z 40.6N  50.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 36H  15/0000Z 40.6N  45.6W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  15/1200Z 40.0N  41.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  16/1200Z...DISSIPATED

$$
FORECASTER STEWART


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