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| #57742 (Received by flhurricane at: 9:37 AM 20.Nov.2005) TCDAT2 TROPICAL DEPRESSION GAMMA DISCUSSION NUMBER 19 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 10 AM EST SUN NOV 20 2005 CONVECTION HAS SIGNIFICANTLY WANED DURING THE PAST 6 HOURS WITH THE CLOSEST DEEP CONVECTION LOCATED A COUPLE HUNDRED MILES TO THE NORTHEAST OF THE NOW FULLY EXPOSED LOW-LEVEL CENTER. ANOTHER WEAK BAND OF CONVECTION HAS RECENTLY DEVELOPED SOUTHEAST OF THE CENTER ALONG THE HONDURAS COAST... BUT IT IS NOT SHOWING ANY SIGNS AT THIS TIME OF TRYING TO WRAP INTO THE CENTER. SATELLITE ESTIMATES HAVE DECREASED ACCORDINGLY... SO THE INITIAL INTENSITY IS SET TO 30 KT ...BASED MAINLY ON THE TIGHT SWIRL NOTED IN THE LOW-LEVEL CLOUDS. THE INITIAL MOTION IS 325/03... ALTHOUGH GAMMA APPEARS TO BE MAKING A SMALL COUNTER-CLOCKWISE LOOP. UPPER-AIR DATA AT 12Z INDICATE LITTLE CHANGE TO THE OVERALL STEERING FLOW PATTERN... EXCEPT THAT THE BREAK IN THE 500 MB RIDGE TO THE NORTH HAS FILLED IN. THIS SHOULD HELP TO KEEP GAMMA TRAPPED IN THE NORTHWESTERN CARIBBEAN FOR THE NEXT FEW DAYS UNTIL A STRONG COLD FRONT CAPTURES THE CYCLONE BY 72 HOURS. THE NOGAPS...GFDN... AND COAMPS MODELS MAINTAIN A DEEPER AND STRONGER CIRCULATION THAN DO THE REST OF THE NHC MODELS...WHICH SEEMS UNREASONABLE BASED ON THE 12Z BELIZE SOUNDING. IN CONTRAST... THE GFS AND GFS ENSEMBLE MODELS WEAKEN GAMMA OVER THE NEXT COUPLE OF DAYS AND DRIFT IT AROUND WITHIN 90 NMI OF ITS CURRENT LOCATION. THE REMAINING MODELS ALSO WEAKEN THE CYCLONE AND DRIFT IT SLOWLY EAST OR SOUTHEASTWARD. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK AND LEANS CLOSELY TOWARD THE GFS MODELS... WITH DISSIPATION POSSIBLY OCCURRING WITHIN 24 HOURS OR LESS. ADDITIONAL WEAKENING APPEARS LIKELY DUE TO INCREASING VERTICAL SHEAR... AND ENTRAINMENT OF DRY MID-LEVEL AIR FROM CENTRAL AMERICA AS NOTED IN 12Z UPPER-AIR DATA FROM BELIZE. THE SHIPS MODEL DISSIPATES GAMMA BY 24 HOURS. THIS RAPID DOWNWARD INTENSITY TREND WAS CLOSELY FOLLOWED... ESPECIALLY GIVEN THE VERY POOR APPEARANCE OF GAMMA IN THE MOST RECENT SATELLITE IMAGERY. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 20/1500Z 16.9N 85.3W 30 KT 12HR VT 21/0000Z 17.1N 85.2W 25 KT...DISSIPATING 24HR VT 21/1200Z 17.5N 84.4W 25 KT...DISSIPATING 36HR VT 22/0000Z 17.7N 83.0W 20 KT...REMNANT LOW 48HR VT 22/1200Z 17.7N 81.1W 20 KT...REMNANT LOW 72HR VT 23/1200Z...MERGED WITH FRONTAL SYSTEM |
