896 
 WTNT44 KNHC 271458
 TCDAT4
  
 TROPICAL STORM ISAAC DISCUSSION NUMBER  26
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
 1000 AM CDT MON AUG 27 2012
  
 DATA FROM THE TAMPA AND KEY WEST DOPPLER RADARS...AND FROM AIR FORCE
 RESERVE AND NOAA RECONNAISSANCE AIRCRAFT DATA INDICATE THE INNER
 CORE STRUCTURE AND INTENSITY OF ISAAC HAS CHANGED LITTLE SINCE THE
 PREVIOUS ADVISORY. A RAGGED EYE FEATURE HAS OCCASIONALLY APPEARED
 IN THESE DATA...BUT IT HAS BEEN UNABLE TO PERSIST. THE CENTRAL
 PRESSURE HAS DECREASED TO AROUND 987-988 MB...BUT THIS HAS NOT
 RESULTED IN ANY INCREASE IN THE WIND SPEEDS. THE PREVIOUS INTENSITY
 OF 55 KT IS BEING MAINTAINED FOR THIS ADVISORY BASED ON THE RECON
 WIND DATA.
 
 THE INITIAL MOTION ESTIMATE IS 305/12. NO SIGNIFICANT CHANGE WAS
 MADE TO THE PREVIOUS FORECAST TRACK. THE LATEST 12Z UPPER-AIR DATA
 INDICATE 20-40 METER HEIGHT RISES AT THE 500 MB AND 400 MB LEVELS
 ACROSS THE SOUTHEASTERN AND SOUTH-CENTRAL U.S....WHICH SUGGESTS
 THAT THE SUBTROPICAL RIDGE TO THE NORTH OF ISAAC HAS STRENGTHENED
 SLIGHTLY. THIS WOULD SUPPORT A NORTHWESTWARD TO WEST-NORTHWESTWARD
 MOTION UNTIL LANDFALL IN ABOUT 36-48 HOURS...AND THIS MOTION IS
 SUPPORTED BY THE NHC MODEL CONSENSUS. AFTER 48 HOURS...HOWEVER...
 THE MODEL GUIDANCE IS WIDELY DIVERGENT WITH A SPREAD OF MORE THAN
 500 N MI BETWEEN THE GFS ON THE LEFT AND THE ECMWF ON THE RIGHT.
 THE FORECAST TRACK AT DAYS 3-5 IS ALSO SIMILAR TO THE PREVIOUS
 ADVISORY AND LIES CLOSE TO THE MODEL CONSENSUS...BUT THIS IS A LOW
 CONFIDENCE FORECAST AT THOSE TIME PERIODS.
 
 THE LACK OF STRENGTHENING APPEARS TO TO BE DUE TO THE
 LARGER-THAN-AVERAGE WIND RADII...WHICH HAVE YET TO CONTRACT
 INWARD...ALONG WITH THE PERIODIC ENTRAINMENT OF DRY MID-LEVEL AIR
 FROM THE EASTERN SEMICIRCLE INTO THE INNER-CORE REGION. UNTIL THE
 DRY AIR MIXES OUT...EROSION OF THE INNER-CORE CONVECTION WILL
 LIKELY CONTINUE UNTIL ISAAC APPROACHES THE NORTH-CENTRAL GULF COAST
 IN ABOUT 24 HOURS. AT THAT TIME...INCREASED FRICTIONAL EFFECTS FROM
 THE GULF COAST LAND MASS IS EXPECTED TO CONTRIBUTE TO AN INCREASE
 IN CONVECTION IN THE NORTHEAST QUADRANT...WHICH COULD ENABLE THE
 STRENGTHENING PROCESS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR
 TO THE PREVIOUS ADVISORY AND IS SLIGHTLY ABOVE THE INTENSITY
 CONSENSUS MODEL IV15.
  
 BECAUSE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER...IT IS
 IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  27/1500Z 26.1N  85.3W   55 KT  65 MPH
  12H  28/0000Z 27.1N  86.8W   65 KT  75 MPH
  24H  28/1200Z 28.3N  88.4W   70 KT  80 MPH
  36H  29/0000Z 29.3N  89.6W   80 KT  90 MPH
  48H  29/1200Z 30.2N  90.5W   70 KT  80 MPH...INLAND
  72H  30/1200Z 31.9N  91.7W   40 KT  45 MPH...INLAND
  96H  31/1200Z 35.2N  92.3W   25 KT  30 MPH...INLAND
 120H  01/1200Z 39.3N  91.3W   20 KT  25 MPH...INLAND
  
 $$
 FORECASTER STEWART