Tropical Storm FRANKLIN

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TROPICAL STORM FRANKLIN DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT THU JUL 28 2005
 
DURING THE PAST 6 HOURS...DEEP CONVECTION HAS DEVELOPED NEAR THE
LOW-LEVEL CENTER IN THE NORTHWEST QUADRANT WITH A BAND OF MODERATE
CONVECTION WRAPPING AROUND THE EASTERN SEMICIRCLE. SATELLITE
INTENSITY ESTIMATES HAVE BEEN FLUCTUATING BETWEEN 45 AND 55 KT FROM
TAFB AND SAB...AND AN EARLIER AMSU CIMSS PRESSURE ESTIMATE CAME IN
AT 998 MB..OR 48 KT. GIVEN THE OVERALL IMPROVED APPEARANCE OF
FRANKLIN AND THE FASTER FORWARD SPEED POSSIBLY ADDING ANOTHER 5 KT
TO THE TOTAL WIND FIELD ON THE EAST SIDE...THE INITIAL INTENSITY
HAS BEEN INCREASED TO 50 KT.
 
THE INITIAL MOTION ESTIMATE IS 040/15...AS FRANKLIN HAS COME UNDER
THE INFLUENCE OF INCREASING DEEP-LAYER SOUTHWESTERLY STEERING FLOW
AHEAD OF AN EASTWARD MOVING MID-LATITUDE FRONTAL SYSTEM. THE NHC
MODEL GUIDANCE IS IN OUTSTANDING AGREEMENT ON THE DIRECTION OF
MOTION...BUT THERE IS A RANGE OF FORWARD SPEEDS WITH THE CANADIAN
...GFS AND GFDL MODELS BEING THE FASTEST...WHILE THE NOGAPS AND
GFDN MODELS ARE MUCH SLOWER. THE OFFICIAL FORECAST TRACK LEANS
TOWARD THE NOGAPS AND GFDN MODELS GIVEN THEIR BETTER OVERALL
PERFORMANCE THUS FAR...AND THE FACT THAT FRANKLIN WILL BE MOVING
OVER 13-17C SST WATER BY 36 HOURS WHICH SHOULD CAUSE THE LOW-LEVEL
CIRCULATION TO DECOUPLE AND REMAIN BEHIND THE FASTER MOVING MID- TO
UPPER-LEVEL CIRCULATION.

NOW THAT FRANKLIN IS MOVING NORTHEASTWARD...THE VERTICAL SHEAR ON
THE SYSTEM SHOULD REMAIN RELATIVELY LOW FOR ANOTHER 18 HOURS OR
SO...WHICH IS ALSO ABOUT THE TIME THAT THE CYCLONE REACHES MUCH
COLDER WATER. THEREFORE...SOME ADDITIONAL STRENGTHENING IS POSSIBLE
...WHICH IS ALSO INDICATED NOW BY THE GFDL MODEL. BY 24 HOURS...
THOUGH...INCREASING VERTICAL SHEAR AND MUCH COLDER WATER SHOULD
INDUCE RAPID WEAKENING...ALONG WITH A TRANSITION TO AN
EXTRATROPICAL LOW. IT IS POSSIBLE THAT BY 48 HOURS FRANKLIN COULD
ALREADY BE ASORBED BY THE APPROACHING FRONTAL SYSTEM.
 
THE OFFICIAL FORECAST TRACK BRINGS TROPICAL STORM-FORCE WINDS VERY
CLOSE TO THE EXTREME SOUTHEASTERN TIP OF NEWFOUNDLAND IN 48 HOURS.
 
FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/2100Z 37.6N  67.5W    50 KT
 12HR VT     29/0600Z 39.3N  65.3W    55 KT
 24HR VT     29/1800Z 41.3N  62.0W    50 KT...BECOMING EXTRATROPICAL
 36HR VT     30/0600Z 43.2N  57.9W    40 KT...EXTRATROPICAL
 48HR VT     30/1800Z 45.3N  53.0W    35 KT...EXTRATROPICAL
 72HR VT     31/1800Z...ABSORBED BY FRONTAL SYSTEM

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