ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM CALVIN DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 PM PDT MON JUN 27 2005 ACAPULCO RADAR IMAGES SUGGEST LITTLE CHANGE IN ORGANIZATION OVER THE LAST SEVERAL HOURS. IN FACT...THE SPIRAL BANDING IS NOT AS WELL DEFINED AS IT WAS THIS MORNING. GEOSTATIONARY SATELLITE IMAGES ALSO SUGGEST LITTLE CHANGE. DVORAK T-NUMBERS REMAIN AT 3.0 AND THE CURRENT INTENSITY ESTIMATE IS HELD AT 45 KT FOR THIS PACKAGE. CALVIN IS EXPECTED TO REMAIN IN AN ENVIRONMENT OF MODERATE EASTERLY VERTICAL SHEAR OVER THE NEXT FEW DAYS SO ONLY SLOW STRENGTHENING IS ANTICIPATED. THE OFFICIAL WIND SPEED FORECAST IS A BLEND OF THE LATEST GFDL AND SHIPS MODEL OUTPUT. BY 72 HOURS...THE CYCLONE WILL BE TRAVERSING COOLER WATERS AND ENCOUNTERING A MORE STABLE AIR MASS SO WEAKENING SHOULD HAVE COMMENCED BY THAT TIME. THERE IS A LOT OF SCATTER IN THE CENTER FIXES BUT THE STORM HAS APPARENTLY TURNED TOWARD THE WEST-NORTHWEST. INITIAL MOTION ESTIMATE IS 300/9. THE TRACK FORECAST APPEARS TO BE RELATIVELY STRAIGHTFORWARD...WITH A MID-LEVEL RIDGE EXPECTED TO PERSIST TO THE NORTH OF THE TROPICAL CYCLONE...AND PROVIDING AN EAST-SOUTHEASTERLY STEERING FLOW. BECAUSE OF THE FASTER INITIAL MOTION ESTIMATE... THIS OFFICIAL TRACK FORECAST IS SOMEWHAT FASTER THAN THE PREVIOUS ONE DURING THE FIRST FEW DAYS OF THE FORECAST PERIOD. LATER IN THE PERIOD...THE WEAKENING CYCLONE IS FORECAST TO TURN WESTWARD UNDER THE INFLUENCE OF SHALLOW-LAYER FLOW. THE WEST-NORTHWESTWARD MOTION REDUCES THE THREAT TO THE COAST...AND THE TROPICAL STORM WATCH CAN PROBABLY BE DISCONTINUED LATER TODAY. HOWEVER...LOCALLY HEAVY RAINFALL ASSOCIATED WITH THE OUTER CIRCULATION IS EXPECTED TO CONTINUE TO AFFECT PORTIONS OF THE SOUTHERN COAST OF MEXICO OVER THE NEXT DAY OR SO. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 27/2100Z 15.4N 100.9W 45 KT 12HR VT 28/0600Z 15.8N 102.2W 50 KT 24HR VT 28/1800Z 16.3N 104.2W 55 KT 36HR VT 29/0600Z 16.8N 106.5W 60 KT 48HR VT 29/1800Z 17.3N 108.6W 60 KT 72HR VT 30/1800Z 18.0N 112.0W 50 KT 96HR VT 01/1800Z 18.0N 115.0W 30 KT 120HR VT 02/1800Z 18.0N 117.5W 20 KT $$ NNNN
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Page last modified: Monday, 27-Jun-2005 20:40:02 UTC