Tropical Storm ISAAC

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TROPICAL STORM ISAAC DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM EDT SUN AUG 26 2012

ALTHOUGH SATELLITE AND RADAR IMAGES HAVE SUGGESTED THAT THE TROPICAL
CYCLONE WAS BECOMING A LITTLE BETTER ORGANIZED...AN AIR FORCE
HURRICANE HUNTER AIRCRAFT INVESTIGATING ISAAC THIS AFTERNOON HAVE
FOUND THAT THERE HAS BEEN NO STRENGTHENING OF THE STORM. 
FLIGHT-LEVEL AND SFMR-OBSERVED WINDS SUPPORT AN INTENSITY OF 50 KT. 
THERE IS STILL A WELL-ESTABLISHED UPPER-LEVEL OUTFLOW PATTERN OVER
THE SYSTEM...AND VERTICAL SHEAR SHOULD REMAIN FAIRLY LIGHT FOR THE
NEXT COUPLE OF DAYS.  INTENSIFICATION STILL SEEMS LIKELY AS ISAAC
MOVES OVER THE EASTERN GULF...AND POSSIBLY OVER THE HIGHER HEAT
CONTENT OF THE LOOP CURRENT.  THE OFFICIAL INTENSITY FOREAST IS
CLOSE TO THE LATEST LGEM GUIDANCE...AND NOT MUCH DIFFERENT FROM THE
PREVIOUS NHC FORECAST.    

ISAAC HAS MOVED A LITTLE TO THE LEFT OF PREVIOUS PROJECTIONS AND
CENTER FIXES YIELD A 6- TO 12-HOUR AVERAGED MOTION OF 295/15.   THE
TRACK FORECAST CONTINUES TO BE CHALLENGING.  THE DYNAMICAL MODELS
SHOW THE TROPICAL STORM/HURRICANE GRADUALLY TURNING TO THE RIGHT
AND HEADING FOR A BREAK IN THE SUBTROPICAL RIDGE.  HOWEVER...THERE
ARE SUBSTANTIAL DIFFERENCES AMONG THE MOST RELIABLE MODELS AS TO
WHERE ISAAC MIGHT CROSS THE NORTHERN GULF COAST.  THE U.K. MET.
OFFICE AND ECMWF MODELS ARE ABOUT 300 N MI TO THE EAST OF THE GFS
AT LANDFALL.  IT SHOULD BE NOTED THAT NEARLY ALL OF THE GFS ENSMEBLE  
MEMBERS ARE EAST OF THE GFS CONTROL TRACK.  BECAUSE OF THE WIDE
MODEL SPREAD...THERE CONTINUES TO BE GREATER THAN USUAL TRACK
FORECAST UNCERTAINTY.  
 
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK DUE TO FORECAST UNCERTAINTIES AND THE FACT THAT
SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER.

THE OFFICIAL FORECAST TRACK AND WIND RADII NECESSITATE THE ISSUANCE
OF A HURRICANE WARNING FOR THE NORTHERN GULF COAST AT THIS TIME. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/2100Z 24.2N  82.3W   50 KT  60 MPH
 12H  27/0600Z 25.1N  83.9W   55 KT  65 MPH
 24H  27/1800Z 26.3N  85.9W   60 KT  70 MPH
 36H  28/0600Z 27.7N  87.6W   70 KT  80 MPH
 48H  28/1800Z 28.9N  88.5W   80 KT  90 MPH
 72H  29/1800Z 30.7N  89.5W   85 KT 100 MPH...INLAND
 96H  30/1800Z 32.5N  90.0W   30 KT  35 MPH...INLAND
120H  31/1800Z 34.5N  90.0W   20 KT  25 MPH...INLAND
 
$$
FORECASTER PASCH
 
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