076 
 WTNT42 KNHC 072051
 TCDAT2
  
 HURRICANE KATIA DISCUSSION NUMBER  39
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
 500 PM AST WED SEP 07 2011
  
 THE CLOUD TOPS ASSOCIATED WITH KATIA WARMED DURING THE EARLY
 AFTERNOON...BUT SINCE THAT TIME A NEW BURST OF DEEP CONVECTION
 HAS FORMED TO THE NORTHEAST OF THE CENTER.  AN EARLIER TRMM PASS
 ONCE AGAIN SHOWED A SMALL REMNANT OF THE INNER EYEWALL WITH A LARGE
 BAND OF CONVECTION OVER THE NORTH AND EAST SEMICIRCLES OF THE
 CIRCULATION.  SUBJECTIVE AND OBJECTIVE DVORAK T- AND CI-NUMBERS
 CONTINUE TO SLOWLY DECREASE...THEREFORE THE INITIAL INTENSITY IS
 LOWERED TO 70 KT.  THERE HAS BEEN LITTLE CHANGE TO THE INTENSITY
 FORECAST REASONING.  MODERATE WESTERLY SHEAR CURRENTLY OVER THE
 SYSTEM IS FORECAST TO DECREASE ON THURSDAY...HOWEVER THIS IS LIKELY
 TO BE NEGATED BY SLIGHTLY COOLER SSTS THAT THE HURRICANE WILL BE
 MOVING OVER.  OVERALL...LITTLE CHANGE IN STRENGTH IS FORECAST
 DURING THE NEXT COUPLE OF DAYS.  KATIA IS EXPECTED TO BECOME A
 LARGE AND POWERFUL EXTRATROPICAL CYCLONE IN ABOUT 72 HOURS.
  
 THE INITIAL MOTION ESTIMATE IS 320/9.  THE MODELS REMAIN IN VERY
 GOOD AGREEMENT MOVING KATIA AROUND THE WEST SIDE OF A
 MID/UPPER-LEVEL RIDGE OVER THE CENTRAL ATLANTIC DURING THE NEXT
 24-36 HOURS.  AFTER 48 HOURS...THE CYCLONE IS EXPECTED TO
 ACCELERATE NORTHEASTWARD AHEAD OF A BROAD TROUGH MOVING ACROSS
 THE CANADIAN MARITIMES.  THE GFS AND ECMWF MODELS ARE STILL IN
 REMARKABLY GOOD AGREEMENT ON THE EXTRATROPICAL PORTION OF THE
 TRACK.  THE OFFICIAL FORECAST HAS BEEN NUDGED NORTHWARD AT 36 HOURS
 AND BEYOND AND IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  07/2100Z 29.9N  69.7W   70 KT  80 MPH
  12H  08/0600Z 31.3N  70.1W   70 KT  80 MPH
  24H  08/1800Z 33.8N  70.0W   70 KT  80 MPH
  36H  09/0600Z 36.6N  68.5W   70 KT  80 MPH
  48H  09/1800Z 39.2N  64.5W   70 KT  80 MPH
  72H  10/1800Z 44.5N  46.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
  96H  11/1800Z 53.0N  26.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 120H  12/1800Z 60.0N   7.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
  
 $$
 FORECASTER BROWN