Tropical Storm BLANCA

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