ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM BLANCA DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 PM PDT TUE JUN 17 2003 THE INNER CORE CONVECTION OF TROPICAL STORM BLANCA HAS WAXED AND WANED DURING THE PAST 12 HOURS...WITH ANOTHER CONVECTIVE BURST HAVING OCCURRED NEAR THE CENTER DURING THE PAST COUPLE OF HOURS. A 17/1948Z TRMM OVERPASS INDICATED AN 80 PERCENT LOW-LEVEL EYEWALL HAD FORMED AT THAT TIME. THE CURRENT INTENSITY OF 45 KT IS BASED ON CONSENSUS T3.0 OR 45 KT INTENSITY FROM ALL 3 SATELLITE AGENCIES. THE INITIAL MOTION IS A HIGHLY UNCERTAIN 290/2. THE TREND IN MICROWAVE POSITIONS THE PAST 18 HOURS ACTUALLY SUGGESTS A SLOW WESTWARD DRIFT HAS OCCURRED. IT ALSO APPEARS THAT THE EASTERLY UPPER-LEVEL FLOW ACROSS THE CYCLONE IS ACTING TO NUDGE THE SYSTEM SLOWLY WESTWARD. HOWEVER...THE GLOBAL MODELS ARE IN FAIR AGREEMENT THAT THE WEAKNESS IN THE SUBTROPICAL RIDGE IN WHICH BLANCA IS CURRENTLY EMBEDDED WILL WEAKEN A LITTLE MORE AS THE MID-LEVEL TROUGH OVER BAJA CALIFORNIA DIGS A LITTLE FARTHER SOUTH DURING THE NEXT 24 HOURS AND ALLOW BLANCA TO MOVE SLIGHTLY POLEWARD. BY 36 HOURS...THE TROUGH IS FORECAST TO LIFT OUT AND ALLOW THE RIDGE TO BUILD WESTWARD TO THE NORTH OF BLANCA...WHICH SHOULD ACT TO KEEP THE CYCLONE MOVING IN A MORE WESTWARD DIRECTION TOWARD COOLER WATER. THE OFFICIAL FORECAST TRACK IS A LITTLE SLOWER AND SLIGHTLY TO THE LEFT OF THE PREVIOUS TRACK AND IS CLOSE TO A BLEND OF THE MEDIUM BAM...NOGAPS...GFDN...AND GFS ENSEMBLE MODELS. EARLIER CIRRUS OUTFLOW FROM A DYING CONVECTIVE COMPLEX ALONG THE MEXICAN COAST EAST OF BLANCA HAS BEEN ACTING TO ENHANCE THE UPPER-LEVEL SHEAR ACROSS THE CYCLONE. HOWEVER...WATER VAPOR IMAGERY INDICATES THE SHEAR HAS ABATED SLIGHTLY AND THIS HAS ALLOWED DEEP CONVECTION TO REFORM NEAR THE CYCLONE CENTER. SINCE BLANCA IS EXPECTED TO REMAIN OVER WARM SSTS AND IN A RELATIVELY LOW SHEAR ENVIRONMENT... ADDITIONAL STRENGTHENING IS FORECAST WITH MOST OF THAT OCCURRING DURING THE NEXT 12 HOURS OR SO. THE OFFICIAL FORECAST IS CLOSE TO THE SHIPS MODEL WHICH BRINGS BLANCA UP TO HURRICANE STRENGTH IN 36 HOURS...BEFORE WEAKENING ENSUES AFTERWARDS AS THE CYCLONE BEGINS MOVING OVER COOLER WATER. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 18/0300Z 16.6N 103.8W 45 KT 12HR VT 18/1200Z 16.8N 104.2W 55 KT 24HR VT 19/0000Z 17.0N 104.7W 60 KT 36HR VT 19/1200Z 17.3N 105.2W 65 KT 48HR VT 20/0000Z 17.5N 105.8W 65 KT 72HR VT 21/0000Z 17.8N 106.8W 60 KT 96HR VT 22/0000Z 18.0N 108.0W 45 KT 120HR VT 23/0000Z 18.0N 109.5W 30 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:55 UTC