250 
 WTNT44 KNHC 120230
 TCDAT4
 TROPICAL STORM IRENE DISCUSSION NUMBER  30
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 11 PM EDT THU AUG 11 2005
 
 OVER THE PAST SEVERAL HOURS....THERE HAS NOT BEEN MUCH CHANGE IN THE
 ORGANIZATION OF THE STORM AS SHOWN BY SATELLITE IMAGES.  IRENE
 CONTINUES TO HAVE SOME BANDING FEATURES OVER ITS EASTERN
 SEMICIRCLE...BUT THE CLOUD TOPS ARE NOT VERY COLD AND THE DEEP
 CONVECTION ENCOMPASSES A RATHER SMALL AREA.  DVORAK INTENSITY
 ESTIMATES FROM TAFB AND SAB ARE UNCHANGED FROM THE PREVIOUS
 PACKAGE...SO THE CURRENT INTENSITY ESTIMATE REMAINS AT 45 KT. 
 UPPER-LEVEL OUTFLOW OVER THE SOUTHEASTERN QUADRANT IS WEAK BUT
 APPEARS WELL-DEFINED OVER THE REMAINDER OF THE CIRCULATION. 
 ACCORDING TO THE GLOBAL MODELS...IRENE WILL BE MOVING THROUGH AN
 ENVIRONMENT CHARACTERIZED BY ANTICYCLONIC UPPER-LEVEL FLOW AND WEAK
 VERTICAL SHEAR OVER THE FORECAST PERIOD.  THE OFFICIAL INTENSITY
 FORECAST IS A BLEND OF THE SHIPS...GFDL...GFDN...AND THE FSU
 SUPERENSEMBLE GUIDANCE...ALL OF WHICH SHOW IRENE STRENGTHENING INTO
 A HURRICANE DURING THE NEXT COUPLE OF DAYS.
 
 LOCATING THE STORM CENTER REMAINS A CHALLENGE...ESPECIALLY WITH
 INFRARED IMAGERY.  THUS THE INITIAL MOTION ESTIMATE...300/13...IS
 AN EDUCATED GUESS.  NWP MODELS SHOW A 500 MB HIGH BUILDING NEAR
 BERMUDA DURING THE NEXT DAY OR TWO...AND THEN RETROGRADING WESTWARD
 LATER IN THE FORECAST PERIOD.  AS IRENE APPROACHES THE RIDGE...
 STEERING CURRENTS ARE LIKELY TO WEAKEN...SO THE TROPICAL CYCLONE
 WILL LIKELY BE MOVING VERY SLOWLY IN 3 TO 5 DAYS.  BEYOND 36
 HOURS...THE TRACK MODEL GUIDANCE DIVERGES SIGNIFICANTLY.  THE GFDL
 AND GFDN ARE NOW SHOWING A MORE WESTWARD TRACK AND ARE ON THE LEFT
 SIDE OF THE DYNAMICAL SUITE.  THE U.K. MET OFFICE AND NOGAPS
 SOLUTIONS SHOW A NORTHWARD TURN...AS DOES THE GFS.  HOWEVER THE
 LATTER MODEL ESSENTIALLY DISSIPATES THE TROPICAL CYCLONE BY THE END
 OF THE PERIOD.  THE OFFICIAL FORECAST IS FAIRLY SIMILAR TO THE
 PREVIOUS ONE...AND ALSO SHOWS CONSIDERABLE SLOWING OF THE FORWARD
 SPEED BY 72 HOURS. THIS IS IN REASONABLE AGREEMENT WITH THE LATEST
 FSU SUPERENSEMBLE TRACK.
 
 FIVE-DAY TROPICAL CYCLONE FORECASTS HAVE CONSIDERABLE UNCERTAINTY IN
 BOTH LOCATION AND INTENSITY...SO IT IS STILL TOO EARLY TO TALK
 ABOUT SPECIFIC THREATS TO THE EAST COAST OF THE UNITED STATES.
 
 FORECASTER PASCH
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      12/0300Z 26.4N  64.9W    45 KT
  12HR VT     12/1200Z 27.3N  66.3W    50 KT
  24HR VT     13/0000Z 28.3N  67.9W    55 KT
  36HR VT     13/1200Z 29.0N  69.2W    60 KT
  48HR VT     14/0000Z 29.8N  70.5W    65 KT
  72HR VT     15/0000Z 31.5N  72.0W    70 KT
  96HR VT     16/0000Z 33.0N  73.0W    75 KT
 120HR VT     17/0000Z 35.0N  74.0W    75 KT
  
  
 $$