266 
 WTNT43 KNHC 040254
 TCDAT3
 TROPICAL STORM HANNA DISCUSSION NUMBER  29
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082008
 1100 PM EDT WED SEP 03 2008
  
 HANNA HAS BEEN A TENACIOUS TROPICAL CYCLONE. SINCE ITS FORMATION IT
 HAS FOUGHT TWO UPPER-LEVEL LOWS...STRONG NORTHERLY SHEAR AND THE
 EFFECTS OF LAND. FURTHERMORE...AT TIMES HANNA HAS RESEMBLED A
 SUBTROPICAL CYCLONE.  SURFACE AND AIRCRAFT OBSERVATIONS TONIGHT
 CONTINUE TO SHOW THAT HANNA HAS A LARGE CIRCULATION AND SATELLITE
 IMAGES SUGGEST THAT THE SHEAR IS DECREASING AND HANNA IS DEVELOPING
 UPPER-LEVEL OUTFLOW. THESE CHANGES IN THE UPPER FLOW OVER HANNA
 HAVE BEEN ACCURATELY FORECAST BY MOST OF THE NUMERICAL WEATHER
 PREDICTION MODELS.  THE INITIAL INTENSITY IS 55 KNOTS...AND IS
 BASED ON A 68 KT FLIGHT-LEVEL WIND MEASURED AS THE PLANE DEPARTED
 THE CYCLONE. WITH THE MORE FAVORABLE UPPER-LEVEL ENVIRONMENT...SOME
 INTENSIFICATION IS INDICATED IN THE OFFICIAL FORECAST.  HANNA IS
 FORECAST TO REGAIN HURRICANE STATUS IN A DAY OR TWO BUT IT COULD
 OCCUR EARLIER. NONE OF THE GUIDANCE INTENSIFIES HANNA BEYOND 70
 KNOTS.   
 
 THE CENTER HAS BEEN ROTATING AROUND A LARGE CYCLONIC GYRE AND FIXES
 FROM THE RECONNAISSANCE PLANE AND DATA FROM A NOAA BUOY SUGGEST
 THAT THE INITIAL MOTION IS 335/11. SOME OF THIS MOTION COULD HAVE
 RESULTED FROM REFORMATION OF THE CENTER. SINCE THE SUBTROPICAL RIDGE
 IS EXPANDING TO THE NORTHEAST OF HANNA...A NORTHWEST MOTION SHOULD
 CONTINUE DURING THE NEXT DAY OR TWO WITH A GRADUAL TURN TO THE
 NORTH AROUND THE WESTERN EDGE OF THE HIGH.  THE TRACK
 MODELS ARE NOT TIGHTLY CLUSTERED AND THE CONFIDENCE IN THE TRACK
 FORECAST IS NOT VERY HIGH. HOWEVER...THE MIDDLE OF THE GUIDANCE
 ENVELOPE HAS HANNA MOVING OVER OR VERY CLOSE TO THE COAST OF THE
 CAROLINAS.  BECAUSE HANNA IS A LARGE CYCLONE...A HURRICANE WATCH
 WILL LIKELY BE REQUIRED FOR A PORTION OF THE SOUTHEASTERN UNITED
 STATES COAST EARLY THURSDAY. 
 
 A NOAA JET HAS SAMPLED THE ENVIRONMENT TONIGHT AND THE DATA IS BEING
 USED TO INITIALIZE THE 00Z GLOBAL MODEL RUNS. 
  
 
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      04/0300Z 23.2N  72.1W    55 KT
  12HR VT     04/1200Z 24.7N  73.1W    55 KT
  24HR VT     05/0000Z 26.9N  75.0W    60 KT
  36HR VT     05/1200Z 29.3N  77.3W    65 KT
  48HR VT     06/0000Z 32.0N  79.0W    70 KT
  72HR VT     07/0000Z 39.5N  74.0W    50 KT...INLAND
  96HR VT     08/0000Z 46.5N  63.0W    35 KT...EXTRATROPICAL
 120HR VT     09/0000Z 49.0N  47.0W    35 KT...EXTRATROPICAL
  
 $$
 FORECASTER AVILA