ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM HECTOR DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP092006 200 AM PDT WED AUG 16 2006 THE CYCLONE HAS BEEN MAINTAINING DEEP CORE CONVECTION ALL EVENING WITH INTERMITTENT BANDING...AND MICROWAVE PASSES SUGGEST THAT THE CENTER IS JUST WITHIN THE CENTRAL CONVECTIVE MASS. DVORAK CLASSIFICATIONS AT 06Z WERE T2.5...35 KT...FROM ALL AGENCIES...WITH DATA-T NUMBERS AS HIGH AS T3.5. A QUIKSCAT PASS AT 01Z CAUGHT SOME OF THE EASTERN SEMICIRCLE...AND THERE WERE A LOT OF 30 KT VECTORS OUTSIDE THE HEAVY CONVECTION IN THE SOUTHEAST QUADRANT...WITH ONE VECTOR NEAR 35 KT. THE PASS MISSED THE DEEP CONVECTION AND LIKELY THE STRONGEST WINDS...AND THE INITIAL INTENSITY IS THEREFORE SET TO 40 KT. IF THE CENTER IS WHERE I THINK IT IS...THE INITIAL MOTION IS A LITTLE TO THE LEFT OF THE PREVIOUS TRACK...AT 270/13. THERE HAS BEEN ONLY A SLIGHT SOUTHWARD ADJUSTMENT OF THE PREVIOUS FORECAST TRACK...AND THE BASIC SYNOPTIC REASONING IS UNCHANGED. HECTOR IS MOVING ALONG THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE THAT EXTENDS WESTWARD FROM MEXICO. GLOBAL MODELS ALL SHOW THE RIDGE ERODED BY A MIDDLE- TO UPPER-LEVEL TROUGH NEAR 130W OVER THE NEXT COUPLE OF DAYS...BUT DESPITE THIS EXHIBIT A FAIRLY LARGE SPREAD IN THE FORECAST TRACKS OF HECTOR. THE RIGHTMOST OUTLIERS ARE THE NOGAPS AND GFNI...WHICH START OFF THE CYCLONE WITH AN IMMEDIATE NORTHWESTWARD TRACK THAT SEEMS INCONSISTENT WITH THE CURRENT MOTION. ON THE LEFT IS THE UKMET...WHICH MARCHES HECTOR QUICKLY OFF TO THE WEST AND SUBSEQUENTLY MISSES THE TROUGH. THE INITIAL WESTWARD MOTION IN THE UKMET ALSO SEEMS INCONSISTENT WITH PRESENT TRENDS. THIS LEAVES THE GFS AND GFDL IN THE MIDDLE...AND THE OFFICIAL FORECAST IS CLOSE TO A BLEND OF THESE TWO MODELS THROUGH 96 HOURS. NEAR THE END OF THE FORECAST PERIOD...AS HECTOR PRESUMABLY WEAKENS...THE OFFICIAL FORECAST BENDS SLIGHTLY BACK TO THE WEST IN ACCORD WITH THE SHALLOW BAM. THERE STILL APPEARS TO BE SOME NORTHEASTERLY SHEAR OVER HECTOR... ALTHOUGH THIS SHEAR IS FORECAST TO ABATE SOMEWHAT OVER THE NEXT DAY OR SO. HECTOR ALSO HAS ALMOST TWO DAYS OVER WARM WATERS. THE GFDL BRINGS HECTOR TO HURRICANE STRENGTH IN 48 HOURS...BUT THE SHIPS GUIDANCE TOPS OUT AT 54 KT. THE MAIN NEGATIVE PREDICTORS SEEM TO BE ASSOCIATED WITH THE DISTRIBUTION OF COLD SATELLITE PIXEL COUNTS...WHICH I CANNOT RECONCILE WITH WHAT LOOKS LIKE A DECENT SATELLITE PRESENTATION. GIVEN THE INTENSIFICATION OVERNIGHT...I AM INCLINED TO FAVOR THE MORE AGGRESSIVE GFDL...AND NOTE THAT THE FSU SUPERENSEMBLE ALSO BRINGS HECTOR TO HURRICANE STRENGTH IN 36 HOURS. BY 72 HOURS...HECTOR IS EXPECTED TO BE DECAYING OVER COOLER WATERS. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0900Z 13.1N 116.5W 40 KT 12HR VT 16/1800Z 13.4N 118.3W 50 KT 24HR VT 17/0600Z 14.0N 120.4W 60 KT 36HR VT 17/1800Z 14.6N 122.4W 65 KT 48HR VT 18/0600Z 15.5N 124.0W 70 KT 72HR VT 19/0600Z 17.5N 127.5W 60 KT 96HR VT 20/0600Z 19.5N 130.5W 45 KT 120HR VT 21/0600Z 21.0N 134.0W 30 KT $$ FORECASTER FRANKLIN NNNN
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Page last modified: Monday, 11-Sep-2006 11:28:42 UTC