012 
 WTNT44 KNHC 280856
 TCDAT4
  
 TROPICAL STORM ISAAC DISCUSSION NUMBER  29
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
 400 AM CDT TUE AUG 28 2012
  
 REPORTS FROM THE AIR FORCE HURRICANE HUNTER AIRCRAFT INDICATE THAT
 THE CENTRAL PRESSURE HAS DROPPED A LITTLE MORE...BUT SO FAR...THE
 MAXIMUM FLIGHT-LEVEL AND SFMR-OBSERVED SURFACE WINDS STILL DO NOT
 QUITE SUPPORT HURRICANE INTENSITY.  THE CURRENT INTENSITY IS HELD
 AT 60 KT PENDING ADDITIONAL OBSERVATIONS FROM THE HURRICANE
 HUNTERS.  ALTHOUGH THE WIND FIELD REMAINS RATHER BROAD AND
 RELATIVELY FLAT...RECENT AIRCRAFT DATA SUGGEST THAT THE MAXIMUM
 WINDS ARE NOW OCCURRING SOMEWHAT CLOSER TO THE CENTER OVER THE
 NORTHERN SEMICIRCLE OF THE CYCLONE.  THIS WOULD SUGGEST THAT THE
 INNER CORE CIRCULATION IS BECOMING BETTER DEFINED...AND
 STRENGTHENING MIGHT BE IMMINENT.  UPPER-LEVEL OUTFLOW IS
 WELL-ESTABLISHED OVER THE SOUTHERN SEMICIRCLE OF THE SYSTEM...BUT
 CENTRAL CONVECTION CONTINUES TO FLUCTUATE.  THE LATTER IS
 PRESUMABLY DUE TO A CONTINUED INTRUSION OF DRY AIR INTO THE CORE
 REGION.  THE STATISTICAL-DYNAMICAL GUIDANCE IS A LITTLE LOWER THAN
 IN PREVIOUS RUNS...AND THE STORM HAS ONLY ABOUT 12-24 HOURS BEFORE
 MOVING INLAND.  THE OFFICIAL INTENSITY FORECAST IS JUST SLIGHTLY
 LOWER THAN THE PREVIOUS ONE.
  
 CENTER FIXES FROM THE AIRCRAFT INDICATE THAT THE STORM HAS WOBBLED
 ON A GENERALLY WESTWARD COURSE OVER THE PAST FEW HOURS.  THIS IS
 BELIEVED TO BE TEMPORARY...HOWEVER...AND THE LONGER-TERM MOTION
 ESTIMATE IS ABOUT 305/10.  THE CURRENT AND FORECAST STEERING REGIME
 ARE BASICALLY THE SAME AS IN THE PREVIOUS PACKAGE.  ISAAC IS
 EXPECTED TO MOVE INTO A WEAKNESS IN THE SUBTROPICAL RIDGE NEAR THE
 NORTH-CENTRAL GULF COAST...WITH SOME SLOWING OF FORWARD SPEED
 DURING THE NEXT COUPLE OF DAYS AS A RIDGE BUILDS A LITTLE TO THE
 NORTHWEST OF THE CYCLONE.  LATER ON...THE SYSTEM SHOULD TURN
 NORTHWARD AND NORTHEASTWARD INTO THE OHIO VALLEY REGION AS IT MOVES
 AROUND THE WESTERN PERIPHERY OF A MID-LEVEL ANTICYCLONE.
  
 ISAAC IS A LARGE TROPICAL CYCLONE.  A DANGEROUS STORM SURGE...HEAVY
 RAINFALL...AND STRONG WINDS EXTEND WELL AWAY FROM THE CENTER AND
 ARE EXPECTED TO AFFECT A LARGE PORTION OF THE NORTHERN GULF COAST. 
 FOR THIS REASON...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT CENTER
 LOCATION.  THE THREAT OF HEAVY RAINFALL AND FLOODING IS ALSO
 EXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY REGION
 DURING THE NEXT FEW DAYS.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  28/0900Z 27.5N  88.1W   60 KT  70 MPH
  12H  28/1800Z 28.5N  89.1W   70 KT  80 MPH
  24H  29/0600Z 29.5N  90.1W   75 KT  85 MPH...NEAR THE COAST
  36H  29/1800Z 30.3N  90.9W   55 KT  65 MPH...INLAND
  48H  30/0600Z 31.4N  91.5W   45 KT  50 MPH...INLAND
  72H  31/0600Z 34.5N  92.5W   25 KT  30 MPH...INLAND
  96H  01/0600Z 38.0N  91.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 120H  02/0600Z 40.5N  87.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
  
 $$
 FORECASTER PASCH