Tropical Storm IRWIN

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TROPICAL STORM IRWIN DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112011
800 AM PDT SUN OCT 09 2011
 
IRWIN COULD BE MAKING A COMEBACK. DEEP CONVECTION HAS CONTINUED TO
REDEVELOP IN A CURVED BAND IN THE SOUTHERN SEMICIRCLE DURING THE
LAST SEVERAL HOURS. HOWEVER...THE OVERALL STRUCTURE OF THE CYCLONE
HAS NOT CHANGED MUCH. GIVEN THAT DVORAK T-NUMBERS ARE ABOUT THE
SAME AS SIX HOURS AGO...THE INITIAL INTENSITY IS HELD AT 40 KT.
 
THE SCATTER OF THE LATEST FIXES MAKES ESTIMATING THE CENTER LOCATION
DIFFICULT...BUT THE INITIAL MOTION APPEARS TO BE THE SAME AS
BEFORE...055/04. IRWIN IS EXPECTED TO BE STEERED GENERALLY EASTWARD
DURING THE NEXT DAY OR TWO BY LOW- TO MID-LEVEL WESTERLY FLOW. FROM
48-96 HOURS...THE GFS AND ECMWF MODELS CONTINUE TO SHOW A BINARY
INTERACTION BETWEEN IRWIN AND A PIECE OF SHORTWAVE ENERGY CUTTING
OFF SOUTHWEST OF BAJA CALIFORNIA...WHICH COULD IMPART A TEMPORARY
SOUTH-OF-EAST MOTION AND THEN A TURN TOWARD THE NORTHEAST. BY 120
HOURS...THE STEERING FLOW AROUND IRWIN BEGINS TO CHANGE...WITH THE
GFS SHOWING THE CYCLONE COMING TO A HALT AND THE OTHER GUIDANCE
FAVORING A BEND TOWARD THE EAST OR EAST-SOUTHEAST. THE OFFICIAL
TRACK FORECAST IS A HAIR TO THE RIGHT OF THE PREVIOUS ONE...IN
FAVOR OF THE MORE RELIABLE GFS/ECMWF SOLUTIONS AND FOLLOWING THE
MULTI-MODEL CONSENSUS. THERE CONTINUES TO BE A LARGE AMOUNT OF
SPREAD IN THE MODEL SOLUTIONS...PRIMARILY LATE IN THE FORECAST
PERIOD...WHICH MAKES THE FORECAST CONFIDENCE LOW AT THAT TIME.
 
ALTHOUGH THE RETURN OF DEEP CONVECTION COULD SIGNAL SOME RE-
INTENSIFICATION...THE EFFECTS OF EASTERLY SHEAR...THE INGESTION OF
A MORE STABLE AIR MASS TO ITS NORTH...AND THE CURRENT LARGE RMW
COULD BE LIMITING FACTORS DURING THE NEXT DAY OR TWO. A PERSISTENCE
OF THE EASTERLY SHEAR AND THE POTENTIAL ADVERSE EFFECTS OF THE SST
WAKE ASSOCIATED WITH JOVA COULD BE CONSIDERATIONS BEYOND 72 HOURS.
ALTHOUGH THE GFDL AND HWRF FORECASTS ARE AGAIN MORE AGGRESSIVE...
THE LGEM/SHIPS GUIDANCE CONTINUE TO SHOW A GRADUAL DECAY. THE
OFFICIAL INTENSITY FORECAST ASSUMES THAT IRWIN WILL HOLD ITS OWN IN
THE SHORT TERM AND...SIMILAR TO THE PREVIOUS ADVISORY...CALLS FOR
SOME POSSIBILITY OF RE-INTENSIFICATION LATER ON.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 15.2N 119.8W   40 KT  45 MPH
 12H  10/0000Z 15.5N 118.9W   40 KT  45 MPH
 24H  10/1200Z 15.8N 117.6W   40 KT  45 MPH
 36H  11/0000Z 15.8N 116.2W   40 KT  45 MPH
 48H  11/1200Z 15.5N 114.8W   40 KT  45 MPH
 72H  12/1200Z 15.8N 111.3W   40 KT  45 MPH
 96H  13/1200Z 17.6N 107.8W   45 KT  50 MPH
120H  14/1200Z 19.0N 106.5W   50 KT  60 MPH
 
$$
FORECASTER KIMBERLAIN
 
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