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Tropical Storm IRWIN


ZCZC MIATCDEP1 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM IRWIN DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112011
800 AM PDT MON OCT 10 2011
 
SIMILAR TO WHAT OCCURRED YESTERDAY...IRWIN HAS LOST MOST OF ITS DEEP
CONVECTION. ALL THAT REMAINS IS A PATCH OF MEAGER CONVECTION THAT
HAS RECENTLY FORMED SOUTH OF THE CIRCULATION CENTER. DVORAK
T-NUMBERS HAVE DECREASED ACCORDINGLY...AND A BLEND OF THE LATEST T-
AND CI-NUMBERS ARE USED TO SET THE INITIAL INTENSITY ESTIMATE AT 35
KT. IRWIN APPEARS TO BE PULLING IN RELATIVELY COOLER AND MORE
STABLE AIR FROM THE WEST...AS EVIDENCED BY THE SOUTHWARD
DISPLACEMENT OF THE NEARBY STRATOCUMULUS FIELD. THIS COULD
TEMPORARILY BE LIMITING ANY RE-DEVELOPMENT OF SIGNIFICANT DEEP
CONVECTION AND HENCE INTENSIFICATION. EASTERLY SHEAR IS ANOTHER
LIMITING FACTOR AND IS FORECAST BY THE DYNAMICAL MODELS TO PERSIST
AT ROUGHLY THE SAME MAGNITUDE FOR THE NEXT 3-4 DAYS AND POSSIBLY
EVEN INCREASE AT THE END OF THE FORECAST PERIOD. WHILE THE
DYNAMICAL GUIDANCE SHOWS SOME STRENGTHENING...THE OBJECTIVE
STATISTICAL OUTPUT CONTINUES TO SHOW A SLOW DECAY. THE OFFICIAL
INTENSITY FORECAST IS REDUCED A BIT FROM THE PREVIOUS ONE TO
ACCOUNT FOR THE RECENT WEAKENING. IT ALSO LEANS TOWARD A BLEND OF
SHIPS/LGEM AND THE INTENSITY CONSENSUS AIDS...GIVEN HOW MUCH THE
SYSTEM IS CURRENTLY STRUGGLING.
 
RECENT CENTER FIXES REMAIN UNCERTAIN...AND THE INITIAL MOTION
ESTIMATE APPEARS TO BE 085/06. IRWIN IS EXPECTED TO BE CARRIED ON
AN ATYPICAL EASTWARD AND THE NORTHEASTWARD TRACK FOR THE NEXT
SEVERAL DAYS AS IT BENDS CYCLONICALLY AROUND A CUT-OFF LOW
DEVELOPING SOUTHWEST OF BAJA CALIFORNIA. BY ABOUT 96 HOURS...
IRWIN...PERHAPS AS A SHALLOW CYCLONE...IS LIKELY TO BE PULLED BACK
TOWARD THE EAST AND EVEN SOUTHEAST INTO A BROAD LOW- TO MID-LEVEL
CYCLONIC GYRE OVER MEXICO. THE MODEL GUIDANCE IS IN GOOD AGREEMENT
ON THIS SCENARIO...AND THE CURRENT FORECAST IS ESSENTIALLY AN
UPDATE OF THE PREVIOUS ONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/1500Z 15.0N 117.7W   35 KT  40 MPH
 12H  11/0000Z 15.1N 116.4W   35 KT  40 MPH
 24H  11/1200Z 15.0N 114.8W   40 KT  45 MPH
 36H  12/0000Z 15.1N 112.9W   40 KT  45 MPH
 48H  12/1200Z 15.6N 110.9W   40 KT  45 MPH
 72H  13/1200Z 16.9N 107.4W   40 KT  45 MPH
 96H  14/1200Z 17.1N 105.1W   40 KT  45 MPH
120H  15/1200Z 16.4N 103.9W   35 KT  40 MPH
 
$$
FORECASTER KIMBERLAIN
 
NNNN


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Page last modified: Tuesday, 17-Jul-2012 13:44:19 UTC