ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM BLANCA DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 PM PDT THU JUN 19 2003 BLANCA LIKELY PEAKED AROUND 15Z-16Z WHEN SSMI AND AMSU MICROWAVE DATA INDICATED A LOW- AND MID-LEVEL EYE FEATURE. SINCE THEN...IT HAS BEEN ALL DOWN HILL. SATELLITE IMAGERY INDICATES VIRTUALLY NO CENTRAL DEEP CONVECTION...ALTHOUGH SOME CONVECTION HAS RE-DEVELOPED WELL SOUTH OF THE CENTER. THE INITIAL INTENSITY HAS BEEN DECREASED TO 40 KT BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 35 KT FROM TAFB AND 45 KT FROM BOTH SAB AND AFWA. THE INITIAL MOTION ESTIMATE CONTINUES TO BE 225/03. NOW THAT BLANCA HAS LOST ITS CENTRAL DEEP CONVETCION...THE VERTICAL CIRCULATION HAS LIKELY DECREASED AND THE SYSTEM IS NOW BEING STEERED MORE BY THE NORTHEASTERLY LOW- TO MID-LEVEL FLOW ON THE SOUTH SIDE OF THE WEAK SUBTROPICAL RIDGE LOCATED OVER MEXICO. A SLOW SOUTHWEST TO WESTWARD DRIFT IS FORECAST BY ALL OF THE NHC MODEL GUIDANCE FOR THE NEXT 48-72 HOURS...AND THEN THE MODELS DIVERGE SIGNIFICANTLY AFTER THAT. BLANCA IS EXPECTED TO DRIFT SOUTHWESTWARD FOR THE NEXT 24 HOURS AND THEN TURN MORE WESTWARD...WHICH IS SIMILAR TO THE GLOBAL AND REGIONAL TRACK MODELS AND THE PREVIOUS OFFICIAL FORECAST TRACK. SOUTHEASTERLY UPPER-LEVEL FLOW HAS BEEN INCREASING OVER BLANCA...BUT AS THE CYCLONE DRIFTS FARTHER SOUTHWEST...THE SHEAR COULD ACTUALLY WEAKEN SLIGHTLY FOR THE NEXT 12-24 HOURS. AFTER THAT...HOWEVER... BLANCA SHOULD BEGIN EXPERIENCING 30-40 KT UPPER-LEVEL SOUTHEASTERLY SHEAR AS INDICATED BY ALL OF THE GLOBAL MODELS. THERE MAY BE BRIEF PERIODS OF CONVECTIVE DEVELOPMENT OR BURSTING...ESPECIALLY AT NIGHT...FOR THE NEXT 36-48 HOURS. HOWEVER...THE GENERAL TREND SHOULD BE FOR CONTINUED WEAKENING TO OCCUR DUE TO INCREASING SHEAR...DRY AIR ENTRAINMENT...AND THE CYCLONE MOVING INTO A FIELD OF STABLE STRATOCUMULUS CLOUDS. IF CENTRAL DEEP CONVECTION DOES NOT RE-DEVELOP...THEN A FASTER RATE OF WEAKENING WILL OCCUR. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 20/0300Z 15.8N 105.2W 40 KT 12HR VT 20/1200Z 15.7N 105.6W 35 KT 24HR VT 21/0000Z 15.6N 106.2W 35 KT 36HR VT 21/1200Z 15.6N 106.9W 30 KT 48HR VT 22/0000Z 15.8N 107.6W 30 KT 72HR VT 23/0000Z 15.9N 108.9W 25 KT...DISSIPATING 96HR VT 24/0000Z 15.9N 110.5W 20 KT...REMNANT LOW 120HR VT 25/0000Z 15.9N 112.0W 20 KT...REMNANT LOW NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:55 UTC