Tropical Storm IRENE

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TROPICAL DEPRESSION IRENE DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT TUE AUG 09 2005

ALTHOUGH IRENE APPEARED TO BE ON THE VERGE OF RE-INTENSIFYING
EARLIER TODAY...THAT TREND HAS NOT CONTINUED...AND AT THE MOMENT THE
CLOUD PATTERN IS QUITE DISORGANIZED.  ALTHOUGH WATER VAPOR IMAGES
INDICATE THE THE CYCLONE IS IN AN ENVIRONMENT OF MOSTLY NORTHERLY
MID- TO UPPER-LEVEL FLOW...THERE HAS BEEN A PLUME OF OUTFLOW CIRRUS
EMANATING NORTHWARD FROM IRENE.  IT APPEARS THAT THE NORTHERLY
FLOW...WHICH IS BELIEVED TO BE DISRUPTING THE SYSTEM...IS IN A
LAYER BELOW THE OUTFLOW LEVEL.  EVEN THOUGH WE HAVE A MARGINAL
TROPICAL CYCLONE AT THIS TIME...IF IRENE SURVIVES...THE ENVIRONMENT
IS LIKELY TO BECOME MORE FAVORABLE.  HENCE THE INTENSITY FORECAST
CALLS FOR STRENGTHENING.  THIS IS VERY SIMILAR TO THE LATEST SHIPS
AND FSU SUPERENSEMBLE PREDICTIONS...BUT IS NEVERTHELESS A LOW
CONFIDENCE FORECAST.  

THERE IS CONSIDERABLE SCATTER IN CENTER FIXES FROM THE VARIOUS
AGENCIES.  A QUIKSCAT AMBIGUITY PLOT WAS OF LITTLE HELP IN LOCATING
THE CENTER.  INITIAL MOTION IS A HIGHLY UNCERTAIN 280/9.  DYNAMICAL
GUIDANCE ARE IN GENERAL AGREEMENT ON A WEST-NORTHWESTWARD MOTION
WITHIN 12-24 HOURS AND A CONTINUATION OF THAT MOTION FOR THE NEXT
1-2 DAYS.  GLOBAL MODELS SHOW A 500 MB RIDGE BUILDING NEAR THE
SOUTHEAST U.S. COAST IN 3-5 DAYS.  A BIG QUESTION IS...HOW WILL
IRENE RESPOND TO THIS RIDGE IN THE LATTER PART OF THE FORECAST
PERIOD?  THE ECMWF GLOBAL MODEL...WHICH IS HIGHLY CREDIBLE...HAS
GENERALLY BEEN TO THE LEFT OF THE OTHER DYNAMICAL MODELS AND HAS
HAD QUITE LOW TRACK ERRORS FOR IRENE...THUS FAR.  THE OFFICIAL
FORECAST IS TO THE LEFT OF THE MODEL CONSENSUS...BUT IS NOT AS FAR
WEST AS THE ECMWF...OR THE NAVY VERSION OF THE GFDL...I.E. THE
GFDN.  THIS OFFICIAL FORECAST IS SOMEWHAT FASTER THAN THE PREVIOUS
ONE...BUT SLOWER THAN MOST OF THE TRACK MODELS.  SUBSTANTIAL
SLOWING IN FORWARD SPEED IS INDICATED LATE IN THE FORECAST PERIOD. 
THIS IS CONSISTENT WITH MUCH OF THE GUIDANCE...BUT IT IS ALSO A
REFLECTION OF THE UNCERTAINTY AS TO WHERE IRENE WILL BE HEADED BY
THAT TIME.  

FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 22.4N  55.5W    30 KT
 12HR VT     10/1200Z 23.0N  57.2W    35 KT
 24HR VT     11/0000Z 24.0N  59.4W    40 KT
 36HR VT     11/1200Z 25.0N  61.6W    45 KT
 48HR VT     12/0000Z 25.9N  63.9W    50 KT
 72HR VT     13/0000Z 27.5N  66.5W    55 KT
 96HR VT     14/0000Z 29.0N  69.0W    60 KT
120HR VT     15/0000Z 30.0N  71.0W    65 KT
 
 
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