ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IRWIN DISCUSSION NUMBER 32 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011 800 PM PDT THU OCT 13 2011 TONIGHT WE HAVE RECEIVED UNCOMMON BUT WELCOME DATA. THERE ARE 3 DIFFERENT SHIPS LOCATED NEAR AND TO THE EAST OF IRWIN THAT REPORTED AT THE SAME TIME...AND THEY ALL MEASURED WINDS OF TROPICAL STORM FORCE. ALTHOUGH THE CLOUD PATTERN HAS NOT BECOME ANY BETTER ORGANIZED AND THE DVORAK T-NUMBERS REMAIN UNCHANGED...THE INITIAL INTENSITY HAS BEEN INCREASED TO 40 KNOTS BASED ON THESE SHIP OBSERVATIONS. SOME MODELS SUGGEST THAT IRWIN SHOULD BEGIN TO STRENGTHEN SLIGHTLY...BUT THERE IS AN UNFAVORABLE MID-LEVEL DRY ENVIRONMENT SURROUNDING THE CYCLONE. THE LOW SHEAR AND THE WARM OCEAN COULD COMPENSATE FOR THE DRY AIR...SO IRWIN IS KEPT AS A 35- TO 40-KT TROPICAL STORM THROUGH 5 DAYS IN THIS ADVISORY. THE CENTER HAS BEEN MEANDERING DURING THE PAST SEVERAL HOURS...AND LITTLE MOTION IS ANTICIPATED DURING THE NEXT 12 TO 24 HOURS. THEREAFTER...LIGHT MID-LEVEL NORTHERLY AND NORTHEASTERLY FLOW SHOULD DEVELOP NEAR THE CYCLONE AS SUGGESTED BY GLOBAL MODELS...AND THIS PATTERN SHOULD FORCE IRWIN ON A VERY SLOW SOUTHWARD AND SOUTHWESTWARD TRACK THROUGH 5 DAYS. MOST OF GUIDANCE UNANIMOUSLY FAVOR SUCH MOTION. GIVEN THE SMALL AREA OF TROPICAL STORM FORCE WINDS...THE FACT THAT IRWIN IS BASICALLY STATIONARY...AND THAT IT IS FORECAST TO MOVE AWAY FROM MEXICO OVER THE NEXT COUPLE OF DAYS...TROPICAL STORM WATCHES OR WARNINGS ARE NOT REQUIRED FOR THE COAST OF MEXICO AT THIS TIME. HOWEVER...DATA FROM THESE SHIPS INDICATE THAT THE TROPICAL STORM FORCE WINDS ARE NOT TOO FAR FROM THE MEXICAN COAST. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 19.2N 106.6W 40 KT 45 MPH 12H 14/1200Z 19.0N 106.5W 35 KT 40 MPH 24H 15/0000Z 18.0N 106.2W 35 KT 40 MPH 36H 15/1200Z 16.8N 106.2W 35 KT 40 MPH 48H 16/0000Z 15.8N 107.0W 40 KT 45 MPH 72H 17/0000Z 15.0N 108.0W 40 KT 45 MPH 96H 18/0000Z 15.0N 109.0W 40 KT 45 MPH 120H 19/0000Z 15.0N 109.5W 40 KT 45 MPH $$ FORECASTER AVILA NNNN
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