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Tropical Storm ANDRES (Text)


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TROPICAL STORM ANDRES DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 AM PDT WED MAY 21 2003
 
SEVERAL SSM/I AND AMSU OVERPASSES DURING THE NIGHT INDICATE THAT
ANDRES CONTINUES TO BE SHEARED...WITH THE LOW-LEVEL CENTER AT LEAST
PARTLY EXPOSED TO THE WEST OF THE MAIN CONVECTION.  AT THE
MOMENT...A RATHER IMPRESSIVE BURST WITH CLOUD TOPS COLDER THAN -80C
IS OCCURRING.  SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM SAB AND
35 KT FROM TAFB AND AFWA.  THE INITIAL INTENSITY REMAINS 35 KT FOR
THIS PACKAGE...ALTHOUGH GIVEN THE PROXIMITY OF THE CENTER TO THE
CONVECTIVE BURST THERE IS A CHANCE THE STORM IS A LITTLE STRONGER.

FIXES FROM THE MICROWAVE DATA INDICATE THE INITIAL MOTION IS 270/13.
ANDRES IS SOUTH OF A LARGE MID/UPPER-LEVEL ANTICYCLONE SEEN IN
WATER VAPOR IMAGERY...WHICH HAS SHIFTED A LITTLE WESTWARD SINCE
LAST NIGHT.  THIS HAS LIKELY HELPED MAINTAIN ANDRES ON A WESTERLY
COURSE TO THE SOUTH OF MOST OF THE MODEL GUIDANCE FOR THE PAST 24
HR.  LARGE-SCALE MODELS CONTINUE TO FORECAST THE RIDGE TO SHIFT
WESTWARD AND GRADUALLY WEAKEN...AND THAT ANDRES WILL TURN MORE
WEST-NORTHWESTWARD.  NHC TRACK GUIDANCE ALSO AGREES WITH THIS.
SINCE THE MODELS HAVE BEEN TOO QUICK IN MAKING THIS TURN...THE
OFFICIAL FORECAST WILL CALL FOR A WESTWARD MOTION FOR 12-24 HR
MORE...FOLLOWED BY A GRADUAL TURN TOWARD THE WEST-NORTHWEST.  THIS
TRACK IS ON THE SOUTH SIDE OF THE ENVELOPE OF GUIDANCE...AND FOR
THE FIRST 36 HR...ON THE SOUTH EDGE OF IT.

THE INTENSITY FORECAST IS PROBLEMATIC.  MODEL FORECASTS FROM LAST
NIGHT DID NOT INDICATE THE CURRENT UPPER-LEVEL WESTERLY FLOW OVER
ANDRES...AND THE RUNS FROM TONIGHT DO NOT SEEM TO INITIALIZE THOSE
WINDS WELL.  THUS...THERE IS LESS THAN NORMAL CONFIDENCE IN THE
LARGE-SCALE MODEL FORECASTS OF LIGHT SHEAR OVER ANDRES THROUGH 72
HR.  SHOULD THE MODELS VERIFY...ANDRES WOULD BE DEEP EASTERLY
FLOW...WHICH COULD ALLOW SIGNIFICANT DEVELOPMENT.  ON THE OTHER
HAND...IF THE SHEAR CONTINUES AND THE DRY AIR SEEN IN WATER VAPOR
IMAGERY NEAR ANDRES ENTRAINS INTO THE SYSTEM...LITTLE OR NO
DEVELOPMENT MAY OCCUR.  THE INTENSITY FORECAST COMPROMISES BETWEEN
THESE EXTREMES.  IT CALLS FOR NO STRENGTHENING FOR THE FIRST 12 HR
DUE TO THE CURRENT SHEAR...FOLLOWED BY GRADUAL STRENGTHENING
THROUGH 72 HR.  AFTER 72 HR...ANDRES SHOULD BE MOVING INTO COOLER
WATERS AND SHOULD BEGIN WEAKENING.

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0900Z  9.7N 109.3W    35 KT
 12HR VT     21/1800Z  9.8N 111.3W    35 KT
 24HR VT     22/0600Z 10.3N 113.9W    40 KT
 36HR VT     22/1800Z 11.0N 116.6W    45 KT
 48HR VT     23/0600Z 11.8N 119.2W    50 KT
 72HR VT     24/0600Z 13.5N 124.5W    55 KT
 96HR VT     25/0600Z 15.0N 129.0W    45 KT
120HR VT     26/0600Z 16.0N 132.5W    30 KT
 
 
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Page last modified: Monday, 07-Feb-2005 16:49:55 UTC