[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 270859
TCDAT1
TROPICAL STORM FRANKLIN DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT WED JUL 27 2005

THE LOW LEVEL CENTER OF FRANKLIN HAS ONCE AGAIN BECOME EXPOSED... TO
THE NORTH OF A LIMITED AREA OF CONVECTION THAT IS STILL FAIRLY
DEEP... WITH TOPS AS COLD AS ABOUT -70 DEGREES CELSIUS.  WHILE THE
SYSTEM IS SHEARED... THE LOW LEVEL CENTER IS STILL CLOSE ENOUGH TO
THE CONVECTION SUCH THAT DVORAK INTENSITY ESTIMATES FROM TAFB AND
SAB REMAIN 35 KT... SO FRANKLIN HANGS ON AS A 35 KT TROPICAL STORM
ON THIS ADVISORY.

WHILE THE CONVECTION HAS NOT MOVED MUCH DURING THE PAST FEW HOURS...
THE LOW LEVEL CENTER HAS BEEN MOVING STEADILY TOWARD THE NORTH AT
ABOUT 6 KT.  THIS COULD BE THE END OF THE ERRATIC MOTION AND THE
START OF THE LONG-AWAITED ACCELERATION TO THE NORTH AND EVENTUALLY
THE NORTHEAST... AHEAD OF THE MIDLATITUDE TROUGH AND ATTENDANT COLD
FRONT NOW APPROACHING THE NORTHEASTERN UNITED STATES.  IT WILL
PROBABLY TAKE FRANKLIN ABOUT 24 MORE HOURS... WHILE A RIDGE BUILDS
TO ITS EAST AND THE TROUGH APPROACHES FROM THE WEST... TO BEGIN
MOVING MUCH FASTER AND MORE NORTHEASTWARD THAN IT IS CURRENTLY.
THE VARIOUS DYNAMICAL MODELS GENERALLY AGREE ON THIS SCENARIO...
ALTHOUGH THEY CONTINUE TO DISAGREE ON FORWARD SPEED LATER IN THE
FORECAST.  DUE TO THE FASTER THAN EXPECTED INITIAL MOTION... THE
NEW TRACK IS FASTER THAN THE PREVIOUS ADVISORY BUT SLOWER THAN THE
MODEL CONSENSUS... WITH WHICH I AM RELATIVELY COMFORTABLE GIVEN
THAT THE MODELS HAVE BEEN TOO FAST THE LAST COUPLE OF DAYS TO SEND
FRANKLIN OFF TO THE RACES.

IT DOES NOT SEEM THAT THE ENVIRONMENT... IN TERMS OF VERTICAL WIND
SHEAR... WILL BECOME MUCH MORE FAVORABLE FOR STRENGTHENING DURING
THE NEXT COUPLE OF DAYS ALONG THE FORECAST TRACK BEFORE FRANKLIN
REACHES COOLER WATERS.  THE INTENSITY FORECAST IS THEREFORE KEPT
LEVEL AT 35 KT... WHICH IS A COMPROMISE BETWEEN THE GFDL AND SHIPS
GUIDANCE... UNTIL FRANKLIN BECOMES EXTRATROPICAL AND EVENTUALLY
BECOMES ABSORBED BY A LARGER EXTRATROPICAL SYSTEM DURING THE NEXT
THREE TO FOUR DAYS.

FORECASTER KNABB


FORECAST POSITIONS AND MAX WINDS

INITIAL      27/0900Z 33.1N  68.8W    35 KT
 12HR VT     27/1800Z 34.1N  68.8W    35 KT
 24HR VT     28/0600Z 35.7N  68.2W    35 KT
 36HR VT     28/1800Z 37.6N  66.9W    35 KT
 48HR VT     29/0600Z 39.7N  64.5W    35 KT...BECOMING EXTRATROPICAL
 72HR VT     30/0600Z 43.5N  56.5W    30 KT...EXTRATROPICAL
 96HR VT     31/0600Z...ABSORBED BY EXTRATROPICAL SYSTEM


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