ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM POLO DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP182008 100 AM PST MON NOV 03 2008 EARLIER MICROWAVE IMAGERY SUGGESTED THAT POLO WAS DEVELOPING A TIGHT INNER CORE...INCLUDING AN EYE-LIKE FEATURE. HOWEVER...THE APPEARANCE IN INFRARED IMAGERY HAS BECOME LESS IMPRESSIVE DURING THE PAST FEW HOURS...WITH A NOTABLE WARMING OF THE CLOUD TOPS NEAR THE CENTER. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN 35 KT. THAT WILL BE THE INITIAL INTENSITY FOR THIS ADVISORY... ALTHOUGH IT IS POSSIBLE THE STORM IS A LITTLE STRONGER THAN THAT. THE INITIAL MOTION IS 275/14. POLO IS CURRENTLY ON THE SOUTHEAST SIDE OF A MID-LEVEL RIDGE. THE LARGE-SCALE MODELS FORECAST THAT THIS RIDGE WILL BREAK DOWN DURING THE FORECAST PERIOD AND BE REPLACED BY A MID/UPPER-LEVEL TROUGH BETWEEN 125W-140W...WITH A MID-LEVEL RIDGE DEVELOPING EAST OR NORTHEAST OF POLO. THE MODELS ALSO FORECAST THE LOW-LEVEL RIDGE NORTH OF THE STORM TO WEAKEN... BUT NOT BREAK. THE TRACK GUIDANCE RESPONDS TO THIS EVOLUTION BY SPLITTING INTO TWO CAMPS...BASED MAINLY ON HOW VERTICALLY DEVELOPED POLO IS. THE GFDL...HWRF...BAMD...AND LBAR... WHICH KEEP A BETTER VERTICAL STRUCTURE...FORECAST POLO TO TURN NORTHWARD AND EVENTUALLY NORTHEASTWARD IN RESPONSE TO THE TROUGH. THE ECMWF...UKMET... CANADIAN...GFS...AND BAMS...WHICH HAVE A LESS DEVELOPED CYCLONE... FORECAST A WEST-NORTHWESTWARD OR WESTWARD MOTION. SINCE POLO IS EXPECTED TO MAINTAIN A GOOD VERTICAL STRUCTURE THROUGH 72 HR...THE FORECAST TRACK WILL CALL FOR A GRADUAL TURN TO A NORTHWESTWARD MOTION BY THAT TIME...IN BETWEEN THE TWO GUIDANCE CAMPS. AFTER 72 HR...IT IS EXPECTED THAT A WEAKENING POLO WILL BE STEERED MORE BY THE LOW-LEVEL FLOW...AND THUS THE FORECAST TRACK SHOWS A BEND TO THE LEFT. OVERALL...THE NEW TRACK IS SIMILAR TO THE PREVIOUS TRACK AND IN BEST AGREEMENT WITH THE TVCN CONSENSUS MODEL. POLO IS OVER WARM SEA SURFACE TEMPERATURES AND IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT. EXCEPT FOR THE CURRENT CONVECTIVE TRENDS...CONDITIONS APPEAR FAVORABLE FOR STRENGTHENING AS INDICATED BY ALL OF THE INTENSITY GUIDANCE. NONE OF THE GUIDANCE CURRENTLY SHOWS POLO BECOMING A HURRICANE...SO THE INTENSITY FORECAST CALLS FOR A PEAK INTENSITY OF 60 KT IN 48-72 HR IN AGREEMENT WITH THE SHIPS MODEL AND THE PREVIOUS FORECAST. IT SHOULD BE NOTED THAT THE RAPID INTENSIFICATION INDEX ATTACHED TO THE SHIPS MODEL FORECASTS A 35% CHANCE OF 25 KT STRENGTHENING DURING THE NEXT 24 HR...AND IF THE STRUCTURE OBSERVED IN THE MICROWAVE IMAGERY PERSISTS POLO COULD GET STRONGER THAN FORECAST. AFTER 72 HR...THE FORECAST TRACK TAKES POLO OVER DECREASING SEA SURFACE TEMPERATURES AND INTO INCREASING SHEAR CAUSED BY THE TROUGH. THIS COMBINATION SHOULD CAUSE THE STORM TO WEAKEN. FORECAST POSITIONS AND MAX WINDS INITIAL 03/0900Z 8.9N 112.4W 35 KT 12HR VT 03/1800Z 9.2N 114.0W 45 KT 24HR VT 04/0600Z 9.7N 115.7W 50 KT 36HR VT 04/1800Z 10.3N 117.4W 55 KT 48HR VT 05/0600Z 11.0N 118.8W 60 KT 72HR VT 06/0600Z 12.5N 121.0W 60 KT 96HR VT 07/0600Z 14.0N 123.5W 50 KT 120HR VT 08/0600Z 15.0N 126.0W 40 KT $$ FORECASTER BEVEN NNNN
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