ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM FLORENCE DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062012 500 AM AST SUN AUG 05 2012 THE STRUCTURE OF FLORENCE HAS EVOLVED OVERNIGHT FROM A CENTRAL DENSE OVERCAST TO MORE OF A SHEAR PATTERN...WITH THE LOW-LEVEL CENTER ESTIMATED TO BE NEAR THE EASTERN EDGE OF THE DEEP CONVECTION. THIS CHANGE IN STRUCTURE IS LIKELY THE RESULT OF MODERATE SOUTHEASTELY VERTICAL WIND SHEAR. DESPITE THE STRUCTURAL CHANGES...DVORAK T-NUMBERS AT 0600 UTC WERE ESSENTIALLY THE SAME AS BEFORE...THEREFORE...THE INITIAL WIND SPEED REMAINS 50 KT. FLORENCE COULD GAIN SOME STRENGTH OVER THE NEXT 24 TO 36 HOURS... HOWEVER...SIGNIFICANT INTENSIFICATION APPEARS UNLIKELY AS THE STORM IS EXPECTED TO REMAIN OVER MARGINALLY WARM WATERS AND IN A FAIRLY STABLE AIRMASS. THE DUST PRODUCT IMAGERY FROM THE GOES-R PROVING GROUND SHOWS SOME DRY AIR WRAPPING AROUND THE PERIPHERY OF THE CIRCULATION...AND GFS AND ECMWF MODEL VERTICAL CROSS SECTIONS SUGGEST THAT THIS DRY AIR WILL CONTINUE TO AFFECT THE STORM DURING THE NEXT SEVERAL DAYS. THE SHIPS MODEL SHOWS A SUBSTANTIAL INCREASE IN WESTERLY SHEAR BY TUESDAY...AT WHICH TIME STEADY WEAKENING IS ANTICIPATED. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE AND SHOWS A SLIGHT INCREASE IN STRENGTH FOR THE NEXT DAY OR TWO...FOLLOWED BY STEADY WEAKENING DUE TO THE AFOREMENTIONED INCREASE IN SHEAR. THE CYCLONE HAS BEEN ON A STEADY WEST-NORTHWESTWARD PATH AT ABOUT 13 KT FOR THE PAST 24 HOURS. THE DYNAMICAL MODELS INSIST THAT FLORENCE WILL BEND TO THE WEST DURING THE NEXT FEW DAYS AS A LOW- TO MID-LEVEL RIDGE BUILDS WESTWARD TO THE NORTH OF THE TROPICAL STORM. THE LATEST GUIDANCE HAS SHIFTED SOUTHWARD...AND THE OFFICIAL FORECAST HAS BEEN NUDGED IN THAT DIRECTION. HOWEVER...THE NHC FORECAST LIES ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE AS MOST OF THE MODELS HAVE SHOWN A SOUTHWARD TRACK BIAS UP TO THIS POINT. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 16.6N 34.2W 50 KT 60 MPH 12H 05/1800Z 16.8N 35.9W 55 KT 65 MPH 24H 06/0600Z 17.1N 38.5W 60 KT 70 MPH 36H 06/1800Z 17.5N 41.2W 60 KT 70 MPH 48H 07/0600Z 18.0N 44.2W 55 KT 65 MPH 72H 08/0600Z 19.3N 51.0W 45 KT 50 MPH 96H 09/0600Z 21.5N 57.0W 35 KT 40 MPH 120H 10/0600Z 24.0N 62.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ FORECASTER CANGIALOSI NNNN
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Page last modified: Monday, 31-Dec-2012 12:09:19 UTC