ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GUILLERMO DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 AM PDT FRI AUG 08 2003 GUILLERMO HAD DEVELOPED A COLD AND PERSISTENT CONVECTIVE OVERCAST THIS MORNING WITH CLOUD TOPS TO -80C NEAR THE CENTER. THE CYCLONE SHOWS GOOD CIRRUS OUTFLOW OVER THE WESTERN SEMICIRCLE AND POOR ELSEWHERE. SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND SAB...AND 35 KT FROM AFWA. THE INITIAL INTENSITY IS INCREASED TO 45 KT. THE INITIAL MOTION IS 270/6. GUILLERMO IS ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE...WHICH LARGE SCALE MODELS FORECAST TO PERSIST AND PERHAPS STRENGTHEN SLIGHTLY DURING THE FORECAST PERIOD. THIS SHOULD KEEP THE STORM ON A GENERAL WESTWARD COURSE FOR THE NEXT SEVERAL DAYS. NHC TRACK GUIDANCE AGREES WITH THIS SCENARIO... ALTHOUGH THERE IS A FAIR AMOUNT OF SPREAD IN THE SPEED. THE OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS FORECAST...AND SOMEWHAT FASTER AFTER 48 HR. IT SHOULD BE NOTED THAT WHILE THIS FORECAST IS FASTER THAN THE PREVIOUS FORECAST...IT IS STILL SLOWER THAN THE UKMET...BAM MODELS...AND LBAR. LARGE-SCALE MODELS SUGGEST THAT GUILLERMO SHOULD REMAIN IN A LIGHT/MODERATE VERTICAL SHEAR ENVIRONMENT DURING THE FORECAST PERIOD. THUS...THE MAIN PART OF THE INTENSITY FORECAST PROBLEM IS WHAT WILL THE SEA SURFACE TEMPERATURE UNDER THE STORM BE. THE FORECAST TRACK TAKES GUILLERMO OVER 26C SSTS ROUGHLY PARALLEL TO THE ISOTHERMS. IF IT MOVES NORTH OF THE TRACK...IT WILL MOVE INTO COOLER WATER AND WEAKEN. IF IT MOVES SOUTH OF THE TRACK...IT COULD FIND WARMER WATER. THE LOW-CONFIDENCE INTENSITY FORECAST CALLS FOR SLOW STRENGTHENING TO 55 KT FOLLOWED BY AN EVEN SLOWER WEAKENING ON THE PREMISE THAT GUILLERMO WILL MOVE CLOSE ENOUGH TO THE COLD WATER FOR IT TO HAVE AN EFFECT. THIS FORECAST IS IN GOOD AGREEMENT WITH THE SHIPS MODEL. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 08/1500Z 16.6N 118.7W 45 KT 12HR VT 09/0000Z 16.6N 120.0W 50 KT 24HR VT 09/1200Z 16.7N 122.0W 55 KT 36HR VT 10/0000Z 16.8N 124.2W 55 KT 48HR VT 10/1200Z 16.9N 126.7W 55 KT 72HR VT 11/1200Z 17.0N 130.5W 50 KT 96HR VT 12/1200Z 17.0N 134.5W 50 KT 120HR VT 13/1200Z 17.0N 138.5W 45 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC