ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION BLANCA DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT SUN JUN 22 2003 UNLIKE THE PREVIOUS SEVERAL NIGHTS...BLANCA HAS NOT MADE A CONVECTIVE COMEBACK. THERE HAS BEEN NO DEEP CONVECTION NEAR THE CENTER FOR THE PAST 12 HOURS OR SO. HOWEVER...IT IS NOT WISE TO KILL A TROPICAL SYSTEM AT NIGHT SINCE CONVECTION CAN ALWAYS REDEVELOP...SO BLANCA IS BEING MAINTAINED AS A TROPCIAL CYCLONE FOR ONE MORE ADVISORY UNTIL VISIBLE SATELLITE IMAGES BECOME AVAILABLE. THERE ARE NO SATELLITE INTENSITY ESTIMATES FROM ANY OF THE THREE AGENCIES... SO THE INITIAL INTENSITY IS BASED ON THE LAST QUIKSCAT PASS WHICH SHOWED A 25 KT NON-RAIN CONTAMINATED WINDSPEED AND A TIGHT LOW-CLOUD SWIRL PATTERN SEEN IN A 22/0437Z SSMI OVERPASS. THE INITIAL MOTION ESTIMATE IS 080/03. THE NHC MODEL GUIDANCE IS ALL OVER THE COMPASS...WHICH USUALLY INDICATES A SLOW FORWARD SPEED IS THE BEST COURSE OF ACTION. SINCE BLANCA HAS BECOME A SHALLOW SYSTEM...IT IS MAINLY BEING PULLED EASTWARD BY A LONG FETCH OF LOW-LEVEL SOUTHWEST TO WESTERLY FLOW FEEDING INTO MEXICO. THE GLOBAL MODELS ARE SPLIT BETWEEN A SLOW NORTHEASTWARD TO SOUTHEASTWARD MOTION. THE OFFICIAL FORECAST IS A SLOW EASTERLY COMPROMISE. THE STORM-RELATIVE SHEAR HAS ACTUALLY INCREASED ACROSS BLANCA SINCE THE CYCLONE HAS BEEN MOVING EASTWARD INTO INCREASING UPPER-LEVEL EASTERLY FLOW. UNLESS DEEP CONVECTION REDEVELOPS FAIRLY QUICKLY... THE CYCLONE WILL LIKELY DISSIPATE WITHIN THE NEXT 24 HOURS AND BE ABSORBED INTO THE BROAD CYCLONIC CIRCULATION THAT EXTENDS WESTWARD FROM THE GULF OF TEHUANTEPEC. STEADY WEAKENING AND EVENTUAL DISSIPATION IS FORECAST AND THIS IS VERY SIMILAR TO THE GFDL MODEL...WHICH DISSIPATES BLANCA IN 18-24 HOURS. THE SHIPS MODEL ACTUALLY RE-STRENGTHENS THE CYCLONE TO A TROPICAL STORM IN 48 HOURS...BUT THIS SEEMS UNLIKELY AT THIS TIME GIVEN THE PROXIMITY OF THE LARGE DISTURBANCE LOCATED TO THE EAST OF BLANCA. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 22/0900Z 15.8N 105.2W 25 KT...DISSIPATING 12HR VT 22/1800Z 15.9N 104.8W 20 KT...REMNANT LOW 24HR VT 23/0600Z 15.9N 104.4W 20 KT...REMNANT LOW 36HR VT 23/1800Z...DISSIPATED NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC