ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT SUN JUL 06 2003 THE INITIAL POSITION OF TD-04E IS RATHER UNCERTAIN DUE TO CIRRUS BLOWOFF TO THE EAST WHICH IS OBSCURING THE LOW-LEVEL CENTER. HAVING SAID THAT...THE CYCLONE LOCATION FOR THIS ADVISORY WAS BASED ON CONTINUITY WITH THE PREVIOUS FORECAST TRACK USING AN INITIAL MOTION OF 295/10...WHICH IS CLOSE TO THE AVERAGE MOTION OF THE NHC MODEL GUIDANCE...AND ASSUMING THE CENTER IS NEAR THE EAST SIDE OF THE DEEPEST CONVECTION DUE TO EASTERLY SHEAR. LITTLE CHANGE WAS MADE TO THE PREVIOUS FORECAST TRACK OTHER THAN TO BRING IT SOUTHWARD JUST A TAD AND ALSO TO ADD A 120-HOUR FORECAST POSITION. THE PREVIOUS SHIPS INTENSITY FORECAST HAD THE CYCLONE DISSIPATING IN 96-120 HOURS. HOWEVER...THAT OUTPUT WAS BASED ON THE MUCH FASTER MEDIUM BAM MODEL. THE OFFICIAL FORECAST MOVES THE DEPRESSION SLOWER THAN ALL THE BAM MODELS AND IS A BLEND OF THE GFS...UKMET...AND THE CANADIAN MODEL TRACKS BUT USING ROUGHLY THE SPEED OF THE GFS MODEL. ALL OF THE GLOBAL MODELS MAINTAIN A FAIRLY STRONG E-W ORIENTED SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE THROUGH 96 HOURS...WITH GRADUAL EROSION OF THE WESTERN PERIPHERY OF THE RIDGE BY 120 HOURS. HOWEVER...WHETHER OR NOT THE CYCLONE MOVES POLEWARD BY 120 HOURS WILL BE DETERMINED BY THE EXACT STRENGTH AND VERTICAL DEPTH OF THE SYSTEM AT THAT TIME. THE NOGAPS MODEL WAS DISCOUNTED SINCE IT MOVES THE CYCLONE VERY LITTLE FOR THE FIRST 48 HOURS FOR NO OBVIOUS PHYSICAL REASONS...ESPECIALLY GIVEN THE STRONG RIDGE TO THE NORTH AND THE PAST MOTION OF AT LEAST 10 KT. THE CYCLONE IS EXPECTED TO MOVE OVER SUB-26C SSTS IN ABOUT 24 HOURS WHICH SHOULD HELP TO PRECLUDE ANY SIGNIFICANT AND/OR RAPID INTENSIFICATION FROM OCCURRING. HOWEVER...WEAKENING SHEAR OF LESS THAN 5 KT SHOULD ALLOW GOOD OUTFLOW TO DEVELOP...WHICH IN TURN SHOULD ALLOW FOR AT LEAST SOME MODEST INTENSIFICATION TO OCCUR AS INDICATED BY THE SHIPS MODEL INTENSITY FORECAST. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 06/1500Z 14.3N 117.5W 30 KT 12HR VT 07/0000Z 14.9N 118.9W 35 KT 24HR VT 07/1200Z 15.6N 120.6W 40 KT 36HR VT 08/0000Z 16.2N 122.5W 45 KT 48HR VT 08/1200Z 16.8N 124.4W 45 KT 72HR VT 09/1200Z 17.8N 128.0W 40 KT 96HR VT 10/1200Z 19.0N 132.0W 35 KT 120HR VT 11/1200Z 20.0N 136.0W 30 KT...DISSIPATING NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC