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 597 
 WTNT42 KNHC 011450
 TCDAT2
  
 HURRICANE KATIA DISCUSSION NUMBER  14
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
 1100 AM AST THU SEP 01 2011
  
 KATIA HAS CHANGED LITTLE IN STRUCTURE DURING THE LAST SEVERAL HOURS.
 BASED ON MICROWAVE DATA...THE LOW-LEVEL CENTER IS LOCATED NEAR THE
 WESTERN PERIPHERY OF THE CORE CONVECTION. A CURVED BAND STILL
 EXISTS OVER THE SOUTHERN SEMICIRCLE OF THE STORM...BUT CLOUD TOPS
 HAVE BEEN WARMING IN THIS BAND DURING THE PAST FEW HOURS. THE
 INITIAL WIND SPEED REMAINS AT 65 KT FOR THIS ADVISORY...IN
 AGREEMENT WITH THE LATEST SATELLITE CLASSIFICATIONS.
 
 SOUTHWESTERLY SHEAR OF ABOUT 15 KT...AS ANALYZED BY UW-CIMSS...IS
 CURRENTLY AFFECTING KATIA. THIS SHEAR IS ASSOCIATED WITH AN
 UPPER-LEVEL LOW LOCATED TO THE NORTHWEST OF THE HURRICANE. THE
 UPPER LOW IS EXPECTED TO CONTINUE TO IMPOSE MODERATE SHEAR OVER
 KATIA FOR ANOTHER 24 TO 36 HOURS. IN ADDITION...SOME DRY AIR
 APPEARS TO BE ENTRAINING INTO THE CIRCULATION OF KATIA AND
 THIS...IN COMBINATION WITH THE AFOREMENTIONED SHEAR...COULD INHIBIT
 SIGNIFICANT DEVELOPMENT IN THE SHORT-TERM. BEYOND 36 HOURS...THE
 GLOBAL MODELS SHOW THE UPPER LOW LIFTING OUT...CREATING A MORE
 FAVORABLE UPPER-LEVEL WIND PATTERN. THEREFORE...STEADY
 STRENGTHENING IS FORECAST IN THE LONGER RANGE. THE OFFICIAL
 FORECAST IS LOWERED SLIGHTLY FROM THE PREVIOUS ONE IN THE
 SHORT-TERM...BUT STILL BRINGS KATIA TO A MAJOR HURRICANE IN A FEW
 DAYS.
 
 KATIA IS MOVING WESTWARD AT 16 KT TO THE SOUTH OF A SUBTROPICAL
 HIGH. THE HURRICANE IS EXPECTED TO SLOW DOWN AND TURN TO THE
 WEST-NORTHWEST DURING THE NEXT 12-24 HOURS AS IT APPROACHES A
 WEAKNESS IN THE RIDGE. THE MODEL GUIDANCE BECOMES VERY DIVERGENT IN
 4 TO 5 DAYS WITH THE UKMET...NOGAPS...AND GFDL MODELS ON THE SOUTH
 SIDE OF THE ENVELOPE AND THE GFS...ECMWF...AND HWRF MODELS ON THE
 NORTH SIDE. THIS SPREAD APPEARS TO BE ASSOCIATED WITH THE STRENGTH
 OF A TROUGH MOVING OVER THE NORTHEASTERN UNITED STATES AND THE
 POSITION OF THE SUBTROPICAL HIGH. THE OFFICIAL TRACK FORECAST IS
 ONLY NUDGED A LITTLE TO THE LEFT...IN PART BECAUSE OF THE INITIAL
 MOTION AND POSITION...AND IS VERY NEAR THE MULTI-MODEL CONSENSUS.
   
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  01/1500Z 15.5N  47.5W   65 KT  75 MPH
  12H  02/0000Z 16.1N  49.5W   70 KT  80 MPH
  24H  02/1200Z 17.0N  51.7W   75 KT  85 MPH
  36H  03/0000Z 18.0N  53.4W   85 KT 100 MPH
  48H  03/1200Z 19.0N  55.0W   95 KT 110 MPH
  72H  04/1200Z 20.8N  58.0W  100 KT 115 MPH
  96H  05/1200Z 22.3N  61.0W  105 KT 120 MPH
 120H  06/1200Z 23.8N  64.0W  105 KT 120 MPH
  
 $$
 FORECASTER CANGIALOSI/ZELINSKY
  
 
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