000
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