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Tropical Storm ISAAC (Text)

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TROPICAL STORM ISAAC DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 AM AST THU AUG 23 2012
 
THE SATELLITE APPEARANCE OF ISAAC HAS IMPROVED SOMEWHAT THIS
MORNING...WITH MULTIPLE CONVECTIVE BANDS DEVELOPING AROUND THE
CENTER.  HOWEVER...REPORTS FROM AIR FORCE RESERVE AND NOAA
HURRICANE HUNTER AIRCRAFT INDICATE THAT THE CENTRAL CORE OF ISAAC
REMAINS POORLY ORGANIZED...WITH MULTIPLE LOW-LEVEL VORTICITY CENTERS
ROTATING AROUND A LARGE AREA OF LIGHT WINDS.  IN ADDITION...THE
CENTER IN AIRCRAFT DATA IS NORTH OF THE CENTER SUGGESTED BY THE
SATELLITE IMAGERY.  A COMBINATION OF FLIGHT-LEVEL...DROPSONDE...AND
SFMR WINDS SUGGEST THAT THE INITIAL INTENSITY IS NEAR 35 KT.

THE OVERALL CIRCULATION OF ISAAC IS A LITTLE FARTHER SOUTH THAN 12
HR AGO.  HOWEVER...IT SEEMS TO HAVE RESUMED A WESTWARD MOTION AT
ABOUT 13 KT.  THE TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT THAT
ISAAC SHOULD MOVE WEST-NORTHWESTWARD FOR THE NEXT 36-48 HR...
STEERED BY THE SUBTROPICAL RIDGE TO THE NORTH.  AFTER THAT...THE
STORM SHOULD APPROACH A WEAKNESS OR BREAK IN THE RIDGE OVER FLORIDA
AND THE EASTERN GULF OF MEXICO. THE NEW FORECAST TRACK IS SHIFTED A
LITTLE TO THE WEST OF THE PREVIOUS TRACK BASED ON CURRENT POSITION
AND LIES DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE NEAR THE
CONSENSUS MODELS.  IT SHOULD BE NOTED...THOUGH...THAT NEAR THE 96
HR POINT THE GUIDANCE MODELS ARE SPREAD BETWEEN SOUTHEASTERN
FLORIDA AND WESTERN CUBA...AND AT 120 HR THEY ARE BETWEEN
NORTHEASTERN FLORIDA AND THE CENTRAL GULF OF MEXICO.  THUS...
SIGNIFICANT UNCERTAINTY REMAINS ABOUT THE THREAT ISAAC POSES TO
FLORIDA.

IN THE SHORT TERM...THE STRUCTURE OF ISAAC SUGGESTS THAT ONLY SLOW
STRENGTHENING IS LIKELY.  HOWEVER...THE ENVIRONMENTAL CONDITIONS
ARE FAVORABLE FOR RAPID INTENSIFICATION...WHICH COULD OCCUR IF THE
CYCLONE DEVELOPS A WELL-DEFINED INNER CORE.  BASED ON THIS...THE
INTENSITY FORECAST CONTINUES TO SHOW HURRICANE STRENGTH BEFORE THE
SYSTEM REACHES HISPANIOLA IN ABOUT 36 HR.  AFTER THAT...PASSAGE OVER
HISPANIOLA AND CUBA SHOULD CAUSE SOME WEAKENING...FOLLOWED BY
LITTLE CHANGE OF STRENGTH FROM 48-72 HR.  THE INTENSITY FORECAST
SHOWS A LITTLE MORE STRENGTHENING OVER THE GULF OF MEXICO DUE TO
THE FORECAST TRACK BEING A LITTLE FARTHER FROM THE FLORIDA
PENINSULA THAN BEFORE.  THE INTENSITY FORECAST IS BASED ON A BLEND
OF THE PREVIOUS FORECAST AND THE SHIPS/LGEM MODELS...AND IT IS WELL
ABOVE THE INTENSITY CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 15.6N  65.4W   35 KT  40 MPH
 12H  24/0000Z 16.1N  67.4W   40 KT  45 MPH
 24H  24/1200Z 16.9N  70.0W   50 KT  60 MPH
 36H  25/0000Z 18.0N  72.4W   65 KT  75 MPH
 48H  25/1200Z 19.3N  74.6W   55 KT  65 MPH
 72H  26/1200Z 22.0N  78.5W   55 KT  65 MPH...INLAND
 96H  27/1200Z 24.5N  81.5W   65 KT  75 MPH...OVER WATER
120H  28/1200Z 27.5N  84.5W   75 KT  85 MPH
 
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FORECASTER BEVEN
 
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