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Tropical Storm IRWIN


ZCZC MIATCDEP1 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM IRWIN DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112011
800 PM PDT SUN OCT 09 2011

DEEP CONVECTION ASSOCIATED WITH IRWIN HAS BEEN GRADUALLY DECREASING
THIS EVENING...MUCH LIKE WHAT OCCURRED YESTERDAY AT THIS TIME. 
ASIDE FROM THE WEAKENING CONVECTION...MICROWAVE DATA INDICATE THAT
THE OVERALL STRUCTURE HAS CHANGED LITTLE DURING THE LAST SEVERAL
HOURS WITH THE LOW-LEVEL CENTER LOCATED TO THE NORTH OF A CURVED
BAND.  THE INITIAL WIND SPEED IS HELD AT 45 KT...BUT THIS COULD BE
A LITTLE GENEROUS.

THE TROPICAL STORM HAS NOW TURNED TO THE EAST AND IS MOVING A LITTLE
FASTER...AND THE LATEST INITIAL MOTION ESTIMATE IS 085/5. AN
EASTWARD OR PERHAPS EAST-SOUTHEASTWARD MOTION IS FORECAST DURING
THE NEXT COUPLE OF DAYS AS THE CYCLONE MOVES IN THE FLOW TO THE
EAST OF A SHARPENING TROUGH OR CUTOFF LOW TO THE SOUTHWEST OF THE
BAJA PENINSULA. IRWIN IS THEN FORECAST TO TRACK JUST NORTH OF DUE
EAST...BRINGING IT NEAR THE COAST OF SOUTHWESTERN MEXICO BY THE END
OF THE FORECAST PERIOD. A SLOW DOWN IS FORECAST BY DAY 5...AS MANY
OF THE GLOBAL MODELS SHOW A RIDGE BUILDING TO THE NORTH OF THE
STORM BY THAT TIME. THE OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED
SOUTHWARD...ESPECIALLY AT DAYS FOUR AND FIVE...TO COME INTO BETTER
AGREEMENT WITH THE LATEST GUIDANCE.

IRWIN IS CURRENTLY IN A RELATIVELY LOW WIND SHEAR ENVIRONMENT AND
OVER ABOUT 28C WATERS. HOWEVER...THE STORM STILL LIES NEAR STABLE
AIR AND THAT COULD BE A REASON WHY IT HAS BEEN STRUGGLING TO
STRENGTHEN RECENTLY. ALTHOUGH THE CYCLONE WILL BE MOVING INTO A
MORE MOIST ENVIRONMENT LATER THIS WEEK...THE SHIPS MODEL SHOWS
EASTERLY SHEAR INCREASING OVER IRWIN. MEANWHILE...THE FORECAST
TRACK TAKES IRWIN OVER THE COOL WATER WAKE CREATED BY HURRICANE
JOVA. THE INTENSITY MODELS ARE QUITE DIVERGENT WITH THE SHIPS/LGEM
SHOWING A GRADUAL WEAKENING...AND THE GFDL/HWRF BRINGING IRWIN TO
HURRICANE STRENGTH. GIVEN THE MIXED SIGNALS IN BOTH THE
ENVIRONMENTAL FACTORS AND THE MODELS...THE OFFICIAL FORECAST SHOWS
IRWIN REMAINING STEADY STATE THROUGHOUT THE PERIOD.   
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 15.2N 118.7W   45 KT  50 MPH
 12H  10/1200Z 15.4N 117.6W   45 KT  50 MPH
 24H  11/0000Z 15.4N 116.1W   45 KT  50 MPH
 36H  11/1200Z 15.2N 114.5W   45 KT  50 MPH
 48H  12/0000Z 15.1N 112.8W   45 KT  50 MPH
 72H  13/0000Z 16.2N 108.5W   45 KT  50 MPH
 96H  14/0000Z 17.0N 105.0W   45 KT  50 MPH
120H  15/0000Z 17.0N 103.5W   45 KT  50 MPH
 
$$
FORECASTER CANGIALOSI
 
NNNN


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Page last modified: Tuesday, 17-Jul-2012 13:44:20 UTC