ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM BLANCA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 PM PDT WED JUN 18 2003 BLANCA LOOKS A LITTLE RAGGED IN VISIBLE IMAGERY THIS AFTERNOON... WITH THE LOW-LEVEL CENTER TRYING TO BECOME EXPOSED ON THE EAST SIDE OF THE CONVECTION. HOWEVER...IR IMAGERY SHOWS THE CONVECTION IS STRONG AND PERSISTENT. SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM TAFB AND 45 KT FROM SAB AND AFWA. THE INITIAL INTENSITY IS NUDGED UPWARD TO 50 KT. THE BEST ESTIMATE OF THE INITIAL MOTION IS NOW 290/2. THERE IS LITTLE CHANGE IN THE SYNOPTIC REASONING FROM THE EARLIER PACKAGE. BLANCA IS IN A WEAKNESS IN THE SUBTROPICAL RIDGE...WITH RIDGING FORECAST TO SLOWLY BUILD NORTH OF THE CYCLONE. THIS SHOULD CAUSE IT TO MOVE WESTWARD OR WEST-NORTHWESTWARD TOWARD ANOTHER WEAKNESS IN THE RIDGE CAUSED BY A DEVELOPING TROUGH NEAR THE U. S. WEST COAST. NHC TRACK GUIDANCE GENERALLY AGREES WITH THIS SCENARIO... ALTHOUGH THERE ARE SOME SIGNIFICANT DISAGREEMENTS ON THE SPEED. THE OFFICIAL FORECAST TRACK IS NUDGED SOUTH OF THE PREVIOUS TRACK AND IS KEPT SLOW IN BEST AGREEMENT WITH THE DYNAMICAL MODELS. BLANCA REMAINS IN A EAST-SOUTHEASTERLY UPPER-LEVEL FLOW...SHOWING FAIR TO GOOD OUTFLOW OVER THE WESTERN SEMICIRCLE. LARGE-SCALE MODELS INDICATE THAT UPPER-LEVEL WINDS WILL REMAIN FAVORABLE FOR 24-36 HR. AFTER THAT...35-45 KT SOUTHEASTERLIES SHOULD DEVELOP AND SHEAR THE SYSTEM. BLANCA WILL LIKELY CONTINUE TO DEVELOP UNTIL THEN...REACHING HURRICANE STRENGTH IN ABOUT 24 HR. AFTER THAT...A COMBINATION OF SHEAR...COOLER SEA SURFACE TEMPERATURES...AND DRY AIR SEEN IN WATER VAPOR IMAGERY NORTHWEST OF THE STORM SHOULD CAUSE WEAKENING. THAT BEING SAID...THE DECAY IN THE CONVECTIVE PATTERN THIS AFTERNOON HINTS THAT THE UPPER-LEVEL FLOW MAY BE STRONGER THAN CURRENTLY ANALYZED. IF THIS CONTINUES...BLANCA MAY NOT STRENGTHEN AS MUCH AS FORECAST. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 18/2100Z 16.8N 104.5W 50 KT 12HR VT 19/0600Z 16.9N 104.9W 60 KT 24HR VT 19/1800Z 17.1N 105.4W 65 KT 36HR VT 20/0600Z 17.2N 106.0W 65 KT 48HR VT 20/1800Z 17.3N 106.6W 60 KT 72HR VT 21/1800Z 17.5N 108.5W 50 KT 96HR VT 22/1800Z 17.5N 110.5W 35 KT 120HR VT 23/1800Z 17.5N 112.5W 25 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:55 UTC