Tropical Storm ANDRES

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TROPICAL STORM ANDRES DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP022009
200 AM PDT TUE JUN 23 2009
 
THE CLOUD PATTERN ASSOCIATED WITH ANDRES HAS ONLY BECOME SLIGHTLY
BETTER ORGANIZED ON SATELLITE IMAGES OVER THE PAST FEW HOURS.
THERE IS A PERSISTENT...VERY COLD-TOPPED...CDO BUT THE BANDING
FEATURES ARE NOT PARTICULARLY WELL-DEFINED.  DVORAK ESTIMATES FROM
TAFB AND SAB ARE 4.0 AND 3.5 RESPECTIVELY.  SPLITTING THE
DIFFERENCE BETWEEN THESE INTENSITY ESTIMATES YIELDS 60 KT AND THIS
IS USED FOR THE ADVISORY INTENSITY.  THE SYSTEM IS EXPECTED TO
ATTAIN HURRICANE STATUS LATER TODAY ALTHOUGH THIS MIGHT NOT OCCUR
IF ANDRES INTERACTS MORE WITH THE MEXICAN LANDMASS THAN EXPECTED.
BY 36 HOURS...THE TROPICAL CYCLONE WILL BEGIN CROSSING A
SIGNIFICANT GRADIENT OF SST AND APPROACHING A MORE STABLE AIR MASS.
THE OFFICIAL WIND SPEED FORECAST SHOWS A MORE GRADUAL WEAKENING
THAN THE SHIPS GUIDANCE...BUT IF THAT MODEL IS CORRECT THEN ANDRES
WILL NOT LAST AS LONG AS INDICATED BELOW.
 
BASED ON CONVENTIONAL SATELLITE AND MICROWAVE FIXES... THE INITIAL
MOTION ESTIMATE...320/7...IS ABOUT THE SAME AS IN THE LAST
ADVISORY.  THE STORM IS CURRENTLY MOVING ALONG THE SOUTHWESTERN
PERIPHERY OF A MID-LEVEL RIDGE.  THE DYNAMICAL GUIDANCE MODEL TRACKS
ARE IN REASONABLY GOOD AGREEMENT FOR THE NEXT DAY OR SO...BUT SINCE
ANDRES IS SO CLOSE TO THE COAST ONLY A SLIGHT DEVIATION TO THE
RIGHT OF THE MODEL CONSENSUS COULD RESULT IN THE CENTER MOVING
ONSHORE.  AS NOTED EARLIER...THE GLOBAL MODELS DISSIPATE THE SURFACE
CIRCULATION OF ANDRES WITHIN A DAY OR SO.  THIS WOULD ONLY SEEM
POSSIBLE IF THE CORE OF THE TROPICAL CYCLONE MOVES OVER LAND.  IN 3
TO 5 DAYS...AS THE SYSTEM GRADUALLY WINDS DOWN IN THE OFFICIAL
FORECAST...ANDRES OR ITS REMNANT LOW IS EXPECTED TO BE CARRIED
MAINLY WESTWARD BY THE  LOWER-TROPOSPHERIC ENVIRONMENTAL WINDS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 17.4N 103.4W    60 KT
 12HR VT     23/1800Z 18.6N 104.3W    65 KT
 24HR VT     24/0600Z 19.9N 105.9W    65 KT
 36HR VT     24/1800Z 20.9N 107.4W    60 KT
 48HR VT     25/0600Z 21.5N 109.2W    50 KT
 72HR VT     26/0600Z 22.0N 112.5W    40 KT
 96HR VT     27/0600Z 22.0N 115.5W    30 KT
120HR VT     28/0600Z 22.0N 118.0W    20 KT...REMNANT LOW
 
$$
FORECASTER PASCH
 
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