Hurricane KATIA

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HURRICANE KATIA DISCUSSION NUMBER  46
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST FRI SEP 09 2011
 
KATIA HAS MAINTAINED A RAGGED EYE FEATURE IN BOTH CONVENTIONAL AND
MICROWAVE SATELLITE IMAGERY DURING THE PAST 6 HOURS...SO THE
INTENSITY WILL REMAIN AT 75 KT...WHICH IS CONSISTENT WITH NHC AODT
AND SAB INTENSITY ESTIMATES. DESPITE THE HIGH LATITUDE OF THE
CYCLONE...KATIA CONTINUES TO HAVE A WELL-DEFINED UPPER-LEVEL
OUTFLOW PATTERN.

THE INITIAL MOTION ESTIMATE IS 050/25 KT. KATIA IS WELL NORTH OF THE
SUBTROPICAL RIDGE AXIS ORIENTED ALONG 33N LATITUDE...AND WATER
VAPOR IMAGERY INDICATES THAT THE CYCLONE IS NOW ENTERING THE FAST
WESTERLY FLOW REGIME THAT LIES NORTH OF 40N LATITUDE. AS A
RESULT...KATIA IS EXPECTED TO ACCELERATE NORTHEASTWARD THROUGH THE
REMAINDER OF THE FORECAST PERIOD. THE HURRICANE SHOULD PASS OVER
MUCH COLDER WATER BY 24 HOURS AND BECOME A POWERFUL EXTRATROPICAL
CYCLONE. THE FORECAST TRACK IS DOWN THE MIDDLE OF THE TIGHTLY
PACKED MODEL GUIDANCE...AND LIES CLOSE TO THE NHC CONSENSUS MODEL
TVCN.

KATIA WILL BE MOVING OVER WATER TEMPERATURES LESS THAN 26C BY 12
HOURS...AND OVER SSTS LESS THAN 20C BY 24 HOURS. THEREFORE...A
FAIRLY QUICK TRANSITION TO AN EXTRATROPICAL CYCLONE IS EXPECTED BY
24 HOURS WHEN THE SYSTEM WILL ALSO BE MERGING WITH AN APPROACHING
FRONTAL ZONE. ALTHOUGH KATIA IS FORECAST TO WEAKEN BELOW HURRICANE
FORCE BY 36 HOURS...THE LARGE EXTRATROPICAL LOW PRESSURE SYSTEM IS
EXPECTED TO CONTAIN STORM-FORCE WINDS WHEN IT APPROACHES THE
BRITISH ISLES IN 3 DAYS.

NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO COMPUTATIONAL
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 39.3N  65.8W   75 KT  85 MPH
 12H  10/0000Z 41.1N  60.4W   70 KT  80 MPH
 24H  10/1200Z 44.1N  49.9W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/0000Z 47.8N  37.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  11/1200Z 51.5N  26.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  12/1200Z 58.5N   7.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  13/1200Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER STEWART
 
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