436 
 WTNT44 KNHC 221449
 TCDAT4
  
 TROPICAL STORM ISAAC DISCUSSION NUMBER   6
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
 1100 AM AST WED AUG 22 2012
  
 THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT MONITORING ISAAC
 DURING THE NIGHT REPORTED THAT THE INNER CORE WIND FIELD BECAME
 DISORGANIZED AFTER 0600 UTC.  A COUPLE OF MICROWAVE OVERPASSES
 SUGGEST THAT THE CIRCULATION CENTER BECAME ELONGATED DURING THIS
 TIME....AND THE CENTER IS NOT READILY APPARENT IN FRENCH RADAR DATA
 FROM MARTINIQUE AND GUADELOUPE.  THE INITIAL INTENSITY IS HELD AT
 40 KT BASED ON AIRCRAFT-REPORTED WINDS NORTH OF THE CENTER.  WHILE
 THE CENTRAL CORE IS DISORGANIZED...THE OVERALL STRUCTURE OF THE
 STORM IS IMPROVING...AS SATELLITE IMAGERY SHOWS A LARGE OUTER BAND
 FORMING AROUND THE CENTRAL CONVECTIVE FEATURE.
  
 THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/15...AS IT IS UNCLEAR
 HOW MUCH OF THE OBSERVED NORTHWARD NUDGE WAS DUE TO RE-FORMATION OF
 THE CENTER. OTHER THAN THAT...THERE IS NO SIGNIFICANT CHANGE TO THE
 PREVIOUS FORECAST TRACK OR REASONING DURING THE FIRST 48-72 HR OF
 THE TRACK FORECAST. THE EAST-WEST ORIENTED SUBTROPICAL RIDGE TO THE
 NORTH OF ISAAC ALONG 30N LATITUDE IS FORECAST BY ALL OF THE GLOBAL
 MODELS TO REMAIN INTACT ACROSS FLORIDA AND THE SOUTHEASTERN U.S.
 DURING THAT TIME.  THIS EARLY PART OF THE FORECAST TRACK IS AN
 UPDATE OF THE PREVIOUS FORECAST.  AFTER THAT TIME...THE RIDGE IS
 EXPECTED TO WEAKEN SOMEWHAT AS A MID/UPPER-LEVEL TROUGH MOVES ONTO
 THE EASTERN UNITED STATES.  THE MODELS DIVERGE ON THEIR FORECASTS
 OF THE RIDGE.  THE ECMWF DOES NOT BREAK THE RIDGE...AND THUS
 FORECASTS A MORE WESTWARD MOTION NEAR OR SOUTH OF CUBA.  THE
 CANADIAN AND NOGAPS HAVE A LARGE BREAK IN THE RIDGE AND TURN ISAAC
 NORTHWARD EAST OF FLORIDA.  THE UKMET HAS A BREAK IN THE RIDGE OVER
 THE NORTHERN GULF COAST AND MOVES THE CYCLONE OVER THE FLORIDA
 PENINSULA.  THE GFS SHOWS A BREAK IN THE RIDGE EAST OF FLORIDA...
 BUT FORECASTS ISAAC TO BYPASS THE BREAK AND MOVE NEAR THE SOUTHWEST
 COAST OF FLORIDA.  THIS DECREASED-CONFIDENCE PORTION OF THE
 FORECAST TRACK IS SHIFTED A LITTLE WEST OF THE PREVIOUS TRACK TO
 LIE NEAR THE CONSENSUS MODELS.
  
 WATER VAPOR IMAGERY AND MICROWAVE TOTAL PRECIPITABLE WATER DATA SHOW
 DRY AIR TO THE NORTHEAST OF ISAAC...AND A LACK OF CONVECTION IN
 THIS AREA SUGGESTS SOME OF THIS AIR IS ENTRAINING INTO THE CYCLONE.
 OTHERWISE...ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR
 INTENSIFICATION UNTIL THE CENTER REACHES HISPANIOLA IN ABOUT 48 HR.
 AFTER THAT...THE INTENSITY WILL BE DETERMINED BY HOW MUCH TIME ISAAC
 SPENDS OVER LAND.  THE NEW FORECAST IS SIMILAR TO THE PREVIOUS
 FORECAST THROUGH 48 HR...THEN IS REDUCED A LITTLE BASED ON
 INCREASED LAND INTERACTION IN THE NEW FORECAST TRACK.
  
 A HURRICANE WARNING WILL LIKELY BE REQUIRED FOR PORTIONS OF THE
 DOMINICAN REPUBLIC THIS AFTERNOON.  IT SHOULD BE NOTED THAT WHILE
 NONE OF THE FORECAST POINTS ARE OVER LAND...THE CYCLONE IS FORECAST
 TO MOVE OVER HISPANIOLA AND CUBA FROM 48-96 HR.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  22/1500Z 15.9N  59.3W   40 KT  45 MPH
  12H  23/0000Z 16.3N  61.8W   45 KT  50 MPH
  24H  23/1200Z 16.8N  64.8W   50 KT  60 MPH
  36H  24/0000Z 17.3N  67.8W   60 KT  70 MPH
  48H  24/1200Z 17.8N  70.3W   75 KT  85 MPH
  72H  25/1200Z 19.5N  74.5W   60 KT  70 MPH
  96H  26/1200Z 22.5N  78.5W   60 KT  70 MPH
 120H  27/1200Z 25.5N  81.5W   70 KT  80 MPH
  
 $$
 FORECASTER BEVEN