563 
 WTNT42 KNHC 092042
 TCDAT2
  
 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