ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM SERGIO DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP212006 800 AM PDT TUE NOV 14 2006 AN AMSR-E MICROWAVE PASS AT 09Z SHOWED A WELL-DEFINED CORE BAND. DVORAK INTENSITY ESTIMATES WERE 30 KT FROM TAFB AND AFWA ...AND 35 KT FROM SAB. BASED ON THE STRONG MICROWAVE PRESENTATION...THE ADVISORY INTENSITY WILL FAVOR THE HIGHER ESTIMATE...AND THE DEPRESSION IS UPGRADED TO A TROPICAL STORM. THIS IS THE FIRST TIME SINCE 1961 THAT TWO TROPICAL STORMS HAVE FORMED IN THE EASTERN PACIFIC BASIN IN NOVEMBER...AND ONLY FIVE STORMS HAVE FORMED LATER IN THE SEASON THAN SERGIO. A REPRESENTATIVE INITIAL MOTION MIGHT BE 315/3...SLOWER THAN BEFORE. GLOBAL MODEL GUIDANCE SUGGESTS THAT THE ALREADY WEAK RIDGING TO THE NORTH OF SERGIO WILL CONTINUE TO BREAK DOWN...AND ALL OF THE PRIMARY DYNAMICAL MODELS INDICATE A LOOP OR A STALL OVER THE NEXT COUPLE OF DAYS. AFTER THAT...A MID- TO UPPER-LEVEL LOW IS FORECAST TO DROP SOUTHWARD ACROSS BAJA CALIFORNIA TO THE WEST OF THE CYCLONE...WHICH SHOULD INDUCE A NORTH OR NORTHWESTWARD MOTION TO RESUME. WITHIN THIS BASIC SCENARIO THERE IS CONSIDERABLE MODEL SPREAD...HOWEVER...WITH THE GFDL ON THE RIGHT WITH A TRACK VERY CLOSE TO THE MEXICAN COAST...AND THE ECMWF ON THE LEFT WELL OFFSHORE. THE OFFICIAL FORECAST IS SLOWER THAN THE PREVIOUS ADVISORY EARLY IN THE FORECAST PERIOD...AND SHIFTED A LITTLE TO THE RIGHT LATER ON TO BE IN BETTER AGREEMENT WITH THE DYNAMICAL MODEL CONSENSUS. FIRST VISIBLE SATELLITE IMAGES SEEM TO CONFIRM THE GOOD CORE BANDING STRUCTURE SEEN IN THE EARLIER MICROWAVE DATA...AND SERGIO IS UNDERNEATH AN UPPER ANTICYCLONE WITH LIGHT SHEAR. WATER TEMPERATURES ARE ABOVE 29C...AND THE ENVIRONMENT IS MOIST. I DON'T SEE ANY REASON WHY THIS SYSTEM SHOULD NOT DEVELOP FURTHER IN THE SHORT RUN...AND PERHAPS QUITE RAPIDLY. THE SHIPS R-I INDEX CONTINUES TO INDICATE A STRONG POSSIBILITY OF RAPID INTENSIFICATION...AS DOES THE GFDL MODEL. THE OFFICIAL INTENSITY FORECAST IS ADJUSTED UPWARD AND IS CLOSE TO AN AVERAGE OF THE SHIPS AND GFDL GUIDANCE. WHILE THERE IS UNFAVORABLE SHEAR TO THE NORTH OF THE CYCLONE...THE CURRENT FORECAST PRESUMES THAT SERGIO WILL REMAIN FAR ENOUGH TO THE SOUTH TO AVOID THE SHEAR. FORECAST POSITIONS AND MAX WINDS INITIAL 14/1500Z 13.2N 104.5W 35 KT 12HR VT 15/0000Z 13.4N 104.7W 45 KT 24HR VT 15/1200Z 13.5N 105.0W 55 KT 36HR VT 16/0000Z 13.5N 105.0W 65 KT 48HR VT 16/1200Z 14.0N 105.0W 70 KT 72HR VT 17/1200Z 15.5N 105.5W 70 KT 96HR VT 18/1200Z 17.0N 106.0W 70 KT 120HR VT 19/1200Z 18.5N 107.0W 65 KT $$ FORECASTER FRANKLIN/BLAKE NNNN
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Page last modified: Tuesday, 14-Nov-2006 14:35:03 UTC