ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM CALVIN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT MON JUN 27 2005 ON SATELLITE IMAGES...THE ORGANIZATION OF THE DEEP CONVECTION IS NOT IMPRESSIVE AT THIS TIME. HOWEVER...RADAR IMAGES FROM THE COMISION NACIONAL DEL AGUA ACAPULCO REVEAL A RATHER WELL-DEFINED SPIRAL RAIN BAND STRUCTURE. THE INTENSITY IS INCREASED TO 45 KT FOR THIS ADVISORY IN AGREEMENT WITH THE LATEST DVORAK ESTIMATES. CALVIN IS IN A MODERATE EASTERLY SHEAR ENVIRONMENT...SO ONLY SLOW STRENGTHENING IS EXPECTED. THE OFFICIAL WIND SPEED FORECAST IS SIMILAR TO THAT FROM THE PREVIOUS PACKAGE AND IS IN GENERAL AGREEMENT WITH THE SHIPS GUIDANCE. BY 72 HOURS...THE CYCLONE WILL BEGIN TO MOVE OVER COOLER WATERS...SO WEAKENING IS PROBABLE AFTER THAT TIME. CALVIN HAS BEGUN TO TURN TOWARD THE LEFT AND THE MOTION ESTIMATE IS NOW 310/7. SYNOPTIC REASONING FOR THE TRACK FORECAST IS ABOUT THE SAME AS IN THE PREVIOUS ADVISORY. A MID-LEVEL RIDGE TO THE NORTH OF THE TROPICAL CYCLONE SHOULD INDUCE A MOSTLY WEST-NORTHWESTWARD MOTION UNTIL LATE IN THE PERIOD...WHEN A MORE WESTWARD TRACK OF THE WEAKENING CYCLONE...FOLLOWING THE LOW-LEVEL EASTERLIES...IS LIKELY. THE LEFTWARD TURN REDUCES THE THREAT TO THE COAST...AND IF A MORE WEST-NORTHWESTWARD MOTION IS ESTABLISHED...THE TROPICAL STORM WATCH COULD BE DISCONTINUED LATER TODAY. LOCALLY HEAVY RAINFALL IS EXPECTED TO CONTINUE TO AFFECT PORTIONS OF THE SOUTHERN COAST OF MEXICO TODAY. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 27/1500Z 14.8N 99.5W 45 KT 12HR VT 28/0000Z 15.3N 100.2W 50 KT 24HR VT 28/1200Z 15.9N 102.1W 50 KT 36HR VT 29/0000Z 16.5N 104.3W 55 KT 48HR VT 29/1200Z 17.1N 106.5W 55 KT 72HR VT 30/1200Z 18.0N 110.0W 55 KT 96HR VT 01/1200Z 18.5N 113.5W 35 KT 120HR VT 02/1200Z 18.5N 116.5W 25 KT $$ NNNN
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Page last modified: Monday, 27-Jun-2005 14:40:02 UTC