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Tropical Storm IRENE (Text)

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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
 
 
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