ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DEBBY DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042012 400 PM CDT SAT JUN 23 2012 AIRCRAFT RECONNAISSANCE...SATELLITE...AND BUOY DATA INDICATE THAT THE CIRCULATION ASSOCIATED WITH THE AREA OF LOW PRESSURE IN THE GULF OF MEXICO HAS BECOME SUFFICIENTLY DEFINED TO CLASSIFY THIS SYSTEM AS A TROPICAL STORM. THE INITIAL INTENSITY IS BASED ON A HIGHEST 1000-FT FLIGHT-LEVEL WIND OF 61 KT AND SFMR WINDS NEAR 45 KT. THESE WINDS ARE ONLY OCCURRING TO THE EAST OF THE CENTER. DEBBY IS MOVING SLOWLY NORTHWARD...OR 360 DEGREES AT 5 KT. THE CYCLONE IS IN A WEAK STEERING ENVIRONMENT BETWEEN TWO MID-LEVEL RIDGES LOCATED OVER THE GREATER ANTILLES AND THE SOUTHERN UNITED STATES...AND DEBBY IS NOT EXPECTED TO MOVE MUCH DURING THE NEXT COUPLE OF DAYS. THE TRACK GUIDANCE IS SPLIT IN TWO BRANCHES...WITH THE GFS AND GFDL SHOWING AN EASTWARD MOTION ACROSS FLORIDA...AND THE REST OF THE MODELS BRINGING DEBBY WESTWARD ACROSS THE NORTHERN GULF TOWARDS TEXAS. EVEN THOUGH THE DETERMINISTIC GFS SHOWS AN EASTWARD TRACK...MORE THAN HALF OF THE GFS ENSEMBLE MEMBERS ARE IN AGREEMENT WITH THE WESTWARD-MOVING MODELS...MAKING THE WESTWARD SCENARIO SEEM MORE LIKELY. IT IS IMPORTANT TO NOTE TOO THAT THE ECMWF MODEL SHOWS A FASTER WESTWARD MOTION THAN INDICATED IN THE NHC FORECAST...SO IT IS POSSIBLE THAT DEBBY COULD REACH THE COAST EARLIER THAN INDICATED. DEBBY IS CURRENTLY A SHEARED CYCLONE WITH NEARLY ALL OF THE DEEP CONVECTION LOCATED IN A CURVED BAND TO THE EAST OF THE CENTER. HOWEVER...AN UPPER-LEVEL LOW OVER THE NORTHWESTERN GULF OF MEXICO IS FORECAST TO DIG SOUTHWESTWARD...WHICH WILL RESULT IN A DECREASE OF VERTICAL SHEAR AFFECTING THE SYSTEM...AND A GREATER CHANCE OF INTENSIFICATION OVER THE NEXT FEW DAYS. BECAUSE THE OFFICIAL TRACK FORECAST IS SO DIFFERENT FROM THE GFS SOLUTION...THE GFS FIELDS USED BY THE SHIPS AND LGEM MODELS ARE NOT LIKELY TO BE REPRESENTATIVE OF THE CONDITIONS ENCOUNTERED BY DEBBY. THE NHC FORECAST THEREFORE SHOWS MORE STRENGTHENING THAN INDICATED BY THE INTENSITY GUIDANCE. DEBBY IS THE EARLIEST 4TH STORM IN THE HISTORICAL RECORDS... SURPASSING HURRICANE DENNIS OF 2005...WHICH BECAME A TROPICAL STORM ON JULY 5TH. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 26.2N 87.6W 45 KT 50 MPH 12H 24/0600Z 26.9N 87.8W 45 KT 50 MPH 24H 24/1800Z 27.3N 88.1W 50 KT 60 MPH 36H 25/0600Z 27.4N 88.5W 50 KT 60 MPH 48H 25/1800Z 27.5N 89.5W 55 KT 65 MPH 72H 26/1800Z 27.5N 91.5W 55 KT 65 MPH 96H 27/1800Z 27.5N 93.5W 60 KT 70 MPH 120H 28/1800Z 27.5N 95.0W 60 KT 70 MPH $$ FORECASTER BERG/AVILA NNNN
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Page last modified: Monday, 31-Dec-2012 12:09:11 UTC