ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ANDRES DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP022009 800 PM PDT SUN JUN 21 2009 VISIBLE AND INFRARED SATELLITE IMAGERY INDICATES THAT THE CYCLONE HAS CONTINUED TO ORGANIZE DURING THE LAST 6 HOURS...WITH BANDING FEATURES INCREASING AND A RECENT BURST OF CONVECTION OVER THE CENTER IN WHAT APPEARS TO BE A DEVELOPING CENTRAL DENSE OVERCAST. DVORAK T-NUMBERS AT 0000 UTC WERE 2.0 AND 2.5 FROM TAFB AND SAB. THE INITIAL INTENSITY IS SET AT THE HIGHER ESTIMATE GIVEN THE IMPROVEMENT IN THE SATELLITE PRESENTATION OF THE SYSTEM. THIS MARKS THE LATEST FORMATION OF THE FIRST NAMED STORM IN THE EASTERN NORTH PACIFIC BASIN SINCE 1971. RECENT FIXES INDICATE AN INITIAL MOTION OF 275/05...WHICH IS TO THE LEFT OF MOST OF THE GUIDANCE. THE MOST RECENT GFDL AND HWRF RUNS IMMEDIATELY TAKE ANDRES ON A MORE NORTHERLY COURSE VERY CLOSE TO THE SOUTHWESTERN COAST OF MEXICO DURING THE NEXT 24 TO 48 HOURS. THESE TWO SOLUTIONS ARE WELL TO THE RIGHT OF THE REST OF THE MODEL GUIDANCE...AND IT IS NOT CLEAR FROM MODEL FIELDS WHAT IS CAUSING THIS MOTION. THE FORECAST WAS ADJUSTED ONLY SLIGHTLY TO THE RIGHT OF THE PREVIOUS TRACK THROUGH 72 HOURS...BUT REMAINS LEFT OF THE MODEL CONSENSUS. BY 72 HOURS...THE MODELS ARE IN BETTER AGREEMENT THAT THE SUBTROPICAL RIDGE SHOULD GUIDE ANDRES ON A MORE WEST-NORTHWESTERLY TRACK AWAY FROM THE COAST. ULTIMATELY...AS ANDRES WEAKENS LATE IN THE PERIOD...THE CYCLONE WILL BE STEERED WESTWARD WITH THE LOW-LEVEL FLOW. SEA SURFACE TEMPERATURES REMAIN WARM ALONG THE FORECAST TRACK THROUGH ABOUT 48-72 HOURS...WITH A FAIRLY RAPID DROP OFF IN OCEANIC HEAT CONTENT THEREAFTER. HOWEVER...THE SHIPS MODEL INDICATES THAT NORTHEASTERLY TO EASTERLY SHEAR WILL DEVELOP OVER THE CYCLONE DURING THE NEXT COUPLE OF DAYS...AND NONE OF THE GUIDANCE SHOWS ANDRES REACHING HURRICANE INTENSITY. THE OFFICIAL FORECAST HAS ANDRES PEAKING IN INTENSITY IN A COUPLE OF DAYS...WITH A STEADY DECREASE IN STRENGTH BEYOND 72 HOURS AS THE CYCLONE ENCOUNTERS INCREASINGLY COOLER WATERS AND A MORE STABLE AIRMASS. GIVEN THE FORECAST TRACK AND WIND RADII OF ANDRES...THE GOVERNMENT OF MEXICO HAS ISSUED A TROPICAL STORM WATCH FOR A PORTION OF THE SOUTHWESTERN COAST OF MEXICO. FORECAST POSITIONS AND MAX WINDS INITIAL 22/0300Z 14.8N 101.9W 35 KT 12HR VT 22/1200Z 15.1N 102.4W 40 KT 24HR VT 23/0000Z 15.8N 103.2W 50 KT 36HR VT 23/1200Z 16.6N 103.8W 55 KT 48HR VT 24/0000Z 17.8N 104.8W 60 KT 72HR VT 25/0000Z 20.5N 108.5W 50 KT 96HR VT 26/0000Z 21.5N 113.0W 40 KT 120HR VT 27/0000Z 21.5N 117.5W 30 KT $$ FORECASTER KIMBERLAIN NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:15 UTC