ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IRWIN DISCUSSION NUMBER 25 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011 200 AM PDT WED OCT 12 2011 IRWIN HAS BECOME LESS ORGANIZED DURING THE PAST SEVERAL HOURS WITH ONLY A PUNY AREA OF CONVECTION NEAR THE CENTER. DVORAK CLASSIFICATIONS SUPPORT REDUCING THE WIND SPEED TO 35 KT FOR THIS ADVISORY. MODERATE-TO-STRONG EASTERLY SHEAR SHOULD AFFECT THE TROPICAL CYCLONE FOR THE NEXT COUPLE OF DAYS...AND IRWIN IS FORECAST TO MOVE INTO SOMEWHAT COOLER WATERS DUE TO THE WAKE OF HURRICANE JOVA. THESE FACTORS SHOULD CAUSE IRWIN TO WEAKEN INTO A TROPICAL DEPRESSION WITHIN 24 HOURS...AND THE NHC FORECAST REFLECTS THIS LIKELIHOOD. HOWEVER...THE INTENSITY FORECAST GETS RATHER DIFFICULT IN THE MEDIUM RANGE AS IRWIN SHOULD EVENTUALLY MOVE OVER RATHER WARM WATERS WITH SOME GLOBAL MODELS SHOWING A LESSENING OF THE EASTERLY SHEAR. WHILE SOME RESTRENGTHENING IS NOT OUT OF THE QUESTION...THERE PROBABLY WILL NOT BE MUCH LEFT OF IRWIN TO TAKE ADVANTAGE OF THE MORE FAVORABLE CONDITIONS AT THAT TIME. THUS THE NHC FORECAST WILL CONTINUE TO SHOW THE CYCLONE BECOMING A REMNANT LOW BY DAY 4. IRWIN APPEARS TO HAVE TURNED A LITTLE NORTH OF DUE EAST...AND THE INITIAL MOTION ESTIMATE IS 075/9. A MID-LEVEL LOW LOCATED A FEW HUNDRED MILES TO THE SOUTHWEST OF THE BAJA PENINSULA SHOULD STEER THE STORM ON A FASTER MOTION TOWARD THE EAST-NORTHEAST FOR A DAY OR SO. THEREAFTER...THE CYCLONE IS EXPECTED TO BE DRAWN TO THE EAST AND EAST-SOUTHEAST AS IT BECOMES MORE ENTANGLED WITH THE EASTERN PACIFIC MONSOON TROUGH...AND EVENTUALLY BEGINS TO MOVE WESTWARD IN THE LONGER RANGE DUE TO A REBUILDING RIDGE OVER MEXICO. FOR SUCH A COMPLICATED STEERING PATTERN...THE MODELS ARE IN FAIR AGREEMENT... AND THE OFFICIAL FORECAST IS CLOSE TO THE PREVIOUS ONE...BETWEEN THE ECMWF MODEL AND THE MULTI-MODEL CONSENSUS EXCLUDING THE HWRF MODEL. FORECAST POSITIONS AND MAX WINDS INIT 12/0900Z 15.2N 112.3W 35 KT 40 MPH 12H 12/1800Z 16.0N 110.7W 35 KT 40 MPH 24H 13/0600Z 17.2N 108.4W 30 KT 35 MPH 36H 13/1800Z 17.3N 106.1W 30 KT 35 MPH 48H 14/0600Z 16.8N 104.5W 30 KT 35 MPH 72H 15/0600Z 16.0N 104.0W 30 KT 35 MPH 96H 16/0600Z 15.5N 105.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 17/0600Z 15.5N 107.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ FORECASTER BLAKE NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:19 UTC