000 WTPZ42 KNHC 230831 TCDEP2 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