954 
 WTNT44 KNHC 100836
 TCDAT4
  
 TROPICAL STORM SEAN DISCUSSION NUMBER   9
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL192011
 400 AM EST THU NOV 10 2011
 
 INFRARED AND MICROWAVE SATELLITE IMAGERY THIS MORNING SHOWS THAT
 SEAN IS SLOWLY BECOMING BETTER ORGANIZED...WITH INCREASING
 CONVECTIVE BANDING AROUND THE CENTER AND OCCASIONAL ATTEMPTS AT EYE
 FORMATION.  SATELLITE INTENSITY ESTIMATES FROM SAB AND TAFB ARE 55
 KT...AND THAT REMAINS THE INITIAL INTENSITY.  THE CYCLONE CURRENTLY
 HAS GOOD CIRRUS OUTFLOW IN THE NORTH SEMICIRCLE.
 
 SEAN CONTINUES ITS NORTHERLY TRACK WITH AN INITIAL MOTION OF 355/7. 
 WATER VAPOR IMAGERY SHOWS SOUTHWESTERLY MID/UPPER-LEVEL FLOW
 ASSOCIATED WITH A TROUGH OVER THE EASTERN UNITED STATES APPROACHING
 THE CYCLONE...AND THE GUIDANCE IS IN GOOD AGREEMENT THAT THIS
 SHOULD CAUSE SEAN TO TURN NORTHEASTWARD IN THE NEXT 12 HOURS. 
 AFTER THAT...THE CYCLONE SHOULD ACCELERATE NORTHEASTWARD DURING THE
 REMAINDER OF ITS LIFETIME.  THE NEW FORECAST TRACK FOLLOWS THIS
 SCENARIO AND IS SIMILAR TO...BUT NORTH OF...THE PREVIOUS TRACK. 
 THE FORECAST TRACK IS NEAR THE CENTER OF THE TRACK GUIDANCE
 ENVELOPE.
  
 THERE IS PERHAPS 12-24 HOURS FOR SEAN TO STRENGTHEN BEFORE STRONG
 VERTICAL WIND SHEAR IMPACTS THE STORM.  GIVEN THE CURRENT
 STRUCTURE...THE INTENSITY FORECAST CALLS FOR SEAN TO REACH HURRICANE
 STRENGTH IN 24 HOURS IN AGREEMENT WITH THE PREVIOUS FORECAST. 
 AFTER THAT...STRONG SHEAR AND THE START OF EXTRATROPICAL TRANSITION
 SHOULD CAUSE WEAKENING.  EXTRATROPICAL TRANSITION IS EXPECTED TO BE
 COMPLETE BY 48 HOURS...AND BY 72 HOURS SEAN IS EXPECTED TO BE
 ABSORBED BY A LARGER BAROCLINIC SYSTEM TO ITS NORTH.  AS NOTED IN
 THE PREVIOUS DISCUSSION...IT IS POSSIBLE THAT SEAN COULD DISSIPATE
 EARLIER THAN CURRENTLY FORECAST.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  10/0900Z 30.2N  70.9W   55 KT  65 MPH
  12H  10/1800Z 31.2N  69.8W   60 KT  70 MPH
  24H  11/0600Z 33.4N  67.2W   65 KT  75 MPH
  36H  11/1800Z 37.0N  63.0W   55 KT  65 MPH
  48H  12/0600Z 41.5N  56.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
  72H  13/0600Z...ABSORBED BY EXTRATROPICAL LOW
  
 $$
 FORECASTER BEVEN