Tropical Storm BLANCA

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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
 
 
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