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Hurricane KATIA


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HURRICANE KATIA DISCUSSION NUMBER  47
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST FRI SEP 09 2011
 
DESPITE ITS HIGH LATITUDE LOCATION...KATIA HAS MAINTAINED A LARGE
RAGGED EYE FEATURE IN BOTH CONVENTIONAL AND MICROWAVE SATELLITE
IMAGERY. THE INITIAL INTENSITY REMAINS 75 KT BASED ON CONSENSUS
SATELLITE CURRENT INTENSITY ESTIMATES OF T4.5/77 KT FROM TAFB AND
SAB...AND NHC AODT INTENSITY ESTIMATES.
 
THE INITIAL MOTION ESTIMATE IS 060/33 KT. KATIA IS NOW EMBEDDED
WITHIN DEEP-LAYER WEST-SOUTHWESTERLY FLOW AHEAD OF A SHARP
MID-UPPER-LEVEL TROUGH AND ASSOCIATED COLD FRONT MOVING QUICKLY
SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA. THE LARGE HURRICANE IS
EXPECTED TO CONTINUE TO ACCELERATE TOWARD THE EAST-NORTHEAST
THROUGH THE REMAINDER OF THE FORECAST PERIOD. KATIA IS MOVING OVER
COOLER WATER AND IN 18-24 HOURS AND IT IS EXPECTED TO BECOME A
POWERFUL EXTRATROPICAL CYCLONE OVER THE FAR NORTH ATLANTIC. THE
FORECAST TRACK IS DOWN THE MIDDLE OF THE TIGHTLY PACKED NHC MODEL
GUIDANCE...AND LIES CLOSE TO THE CONSENSUS TRACK MODEL TVCN.
 
KATIA WILL BE MOVING OVER WATER TEMPERATURES LESS THAN 22C BY 12
HOURS...AND THE CYCLONE COULD BECOME EXTRATROPICAL AT THAT TIME.
HOWEVER...THE LARGE CIRCULATION IS EXPECTED TO TRANSPORT WARM
UNSTABLE AIR SOUTH OF 40N LATITUDE NORTHWARD INTO THE EASTERN
SEMICIRCLE...WHICH COULD HELP MAINTAIN CONVECTION A LITTLE LONGER
THAN USUAL FOR SYSTEMS AT SUCH A HIGH LATITUDE. REGARDLESS...
TRANSITION TO AN EXTRATROPICAL CYCLONE SHOULD BE COMPLETED BY
24 HOURS WHEN THE SYSTEM WILL HAVE MERGED WITH THE AFOREMENTIONED
COLD FRONT AND BE OVER SSTS LESS THAN 20C. 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.
INTERESTS IN AND AROUND THE BRITISH ISLES AND NORTHERN EUROPE
SHOULD MONITOR PRODUCTS ISSUED BY THE UKMET OFFICE AT
WWW.METOFFICE.GOV.UK/WEATHER/.
 
NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/2100Z 40.6N  62.7W   75 KT  85 MPH
 12H  10/0600Z 42.6N  55.9W   70 KT  80 MPH
 24H  10/1800Z 46.0N  44.9W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/0600Z 49.6N  33.3W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  11/1800Z 53.2N  22.9W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  12/1800Z 60.1N   4.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  13/1800Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER STEWART
 
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