000
WTPZ41 KNHC 120852
TCDEP1
 
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