120
WTNT41 KNHC 312038
TCDAT1
TROPICAL STORM NOEL DISCUSSION NUMBER 17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL162007
500 PM EDT WED OCT 31 2007
THE CENTER OF NOEL DRIFTED WESTWARD FOR A FEW HOURS AROUND
MIDDAY...BUT RECENTLY HAS BEEN NEARLY STATIONARY...OR PERHAPS
MAKING A SMALL CYCLONIC LOOP...JUST OFFSHORE OF THE NORTH COAST OF
CUBA. THE CENTER IS NOT AS WELL CONNECTED TO THE DEEP CONVECTION AS
IT WAS SEVERAL HOURS AGO...BUT THE OFFICIAL FORECAST PRESUMES THAT
THE TWO WILL NOT COMPLETELY SEPARATE. INDEED...THERE WAS SOME
EVIDENCE IN THE RECON DATA AROUND 18Z THAT A SECOND VORTICITY
CENTER WAS TRYING TO DEVELOP IN THE CONVECTION TO THE NORTHEAST OF
THE SURFACE CENTER. SOUTHWESTERLY FLOW AHEAD OF A MID-LEVEL TROUGH
IN THE GULF OF MEXICO IS ADVANCING TOWARD THE CYCLONE...AND THIS IS
EXPECTED TO INDUCE A NORTHWARD AND THEN NORTHEASTWARD ACCELERATION
OF NOEL. THE OFFICIAL FORECAST FOLLOWS A GFDL/HWRF/GFS
BLEND...EXCEPT FOR BEING A LITTLE SLOWER THAN THE GUIDANCE AND THE
PREVIOUS FORECAST DURING THE FIRST 24 HOURS.
THE INITIAL INTENSITY REMAINS 45 KT BASED ON FLIGHT-LEVEL AND SFMR
DATA. THERE COULD BE SOME STRENGTHENING DURING THE NEXT 24
HOURS...BEFORE SOUTHWESTERLY SHEAR INCREASES AND EXTRATROPICAL
TRANSITION BEGINS. GLOBAL MODEL GUIDANCE CONTINUES TO INDICATE
NOEL WILL BECOME A VIGOROUS EXTRATROPICAL CYCLONE.
WINDS ASSOCIATED WITH THE ENVIRONMENTAL PRESSURE GRADIENT HAVE
DECREASED BELOW GALE FORCE ALONG THE SOUTHEAST FLORIDA COAST.
RECONNAISSANCE DATA INDICATE THAT THE WIND FIELD OF NOEL HAS
EXPANDED IN THE NORTHWEST QUADRANT...AND THE OFFICIAL FORECAST NOW
BRINGS TROPICAL STORM WINDS TO NEAR THE SOUTHEAST FLORIDA COAST.
SINCE ANY SUBSEQUENT INCREASE IN WINDS AT THE COAST WOULD BE
ASSOCIATED WITH THE TROPICAL STORM...A TROPICAL STORM WATCH IS
BEING ISSUED AT THIS TIME. WHILE A WATCH IS USUALLY ASSOCIATED WITH
A LONGER LEAD TIME THAN A WARNING...IT ALSO CONVEYS THE
POSSIBILITY...AS OPPOSED TO THE EXPECTATION...OF TROPICAL STORM
CONDITIONS. BECAUSE THE TROPICAL STORM FORCE WIND RADII ARE
FORECAST TO REMAIN OFFSHORE...A WATCH IS MORE APPROPRIATE THAN A
WARNING. THE NEED FOR A WARNING WILL BE REASSESSED THIS EVENING.
FORECAST POSITIONS AND MAX WINDS
INITIAL 31/2100Z 22.6N 78.8W 45 KT
12HR VT 01/0600Z 23.5N 79.0W 50 KT
24HR VT 01/1800Z 25.3N 78.1W 55 KT
36HR VT 02/0600Z 28.0N 76.0W 50 KT
48HR VT 02/1800Z 31.5N 72.5W 55 KT...EXTRATROPICAL
72HR VT 03/1800Z 39.0N 66.0W 60 KT...EXTRATROPICAL
96HR VT 04/1800Z 49.0N 57.5W 60 KT...EXTRATROPICAL
120HR VT 05/1800Z 60.0N 47.5W 60 KT...EXTRATROPICAL
FORECASTER FRANKLIN
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