303 
 WTNT42 KNHC 292100
 TCDAT2
 HURRICANE GUSTAV DISCUSSION NUMBER  20
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
 500 PM EDT FRI AUG 29 2008
  
 VISIBLE IMAGERY HAS OCCASIONALLY REVEALED AN EYE TRYING TO
 FORM...BUT THAT FEATURE HAS NOT BEEN PERSISTENT. 
 NEVERTHELESS...THE CYCLONE CONTINUES TO INCREASE IN
 ORGANIZATION...WITH SOLID CONVECTIVE BANDS AND UPPER-LEVEL OUTFLOW
 THAT IS WELL-DEVELOPED IN ALL QUADRANTS. THE UNDERLYING WATERS OF
 THE NORTHWESTERN CARIBBEAN SEA ARE QUITE WARM...AND TO SOME DEPTH
 BENEATH THE SURFACE...SO THERE ARE NO APPARENT IMPEDIMENTS TO
 ADDITIONAL STRENGTHENING BEFORE GUSTAV REACHES WESTERN CUBA. EVEN
 RAPID INTENSIFICATION IS POSSIBLE...AS SUPPORTED BY THE LATEST
 SHIPS-BASED RAPID INTENSIFICATION INDEX THAT SHOWS A 35 PERCENT
 CHANCE OF AN INTENSITY INCREASE OF 30 KT OR MORE DURING THE NEXT 24
 HOURS...SO IT IS POSSIBLE THAT GUSTAV COULD REACH MAJOR HURRICANE
 STATUS PRIOR TO CROSSING WESTERN CUBA.  PASSAGE OVER CUBA WILL NOT
 LIKELY HAVE MUCH IMPACT ON THE STORM'S STRENGTH...AND ALL GUIDANCE
 FORECASTS A STRENGTHENING TREND OVER THE SOUTHERN GULF...WITH
 SLIGHT WEAKENING POSSIBLE IN THE NORTHERN GULF.  THE OFFICIAL
 FORECAST AGAIN CALLS FOR A MAJOR HURRICANE OVER THE GULF...AND
 DESPITE THE WEAKENING IMPLIED BY THE LESSER INTENSITY OVER LAND AT
 96 HOURS...GUSTAV COULD MAKE FINAL LANDFALL ALONG SOME PORTION OF
 THE NORTHERN GULF COAST AS A MAJOR HURRICANE.
  
 GUSTAV HAS TURNED MORE TO THE RIGHT AND SPED UP A LITTLE...NOW
 MOVING AT ABOUT 305/10...AS IT HEADS FOR A BREAK IN THE SUBTROPICAL
 RIDGE OVER THE EASTERN GULF OF MEXICO.  THE PORTION OF THAT RIDGE
 THAT IS INTACT OVER THE SOUTHERN PLAINS OF THE UNITED STATES IS
 FORECAST BY ALL MODELS TO EVOLVE INTO A DEEP-LAYER HIGH THAT WILL
 REACH THE NORTHEASTERN U.S. IN A FEW DAYS.  THERE ARE IMPORTANT
 DIFFERENCES AMONG THE MODELS...HOWEVER...IN HOW MUCH RIDGING WILL
 EXTEND SOUTHWESTWARD FROM THAT HIGH TOWARD TEXAS...AND IN HOW STRONG
 THE UPPER-LEVEL TROUGH CURRENTLY OVER THE CENTRAL GULF WILL BE OVER
 THE WESTERN GULF IN A FEW DAYS.  THESE VARYING SOLUTIONS LEAD TO
 DIFFERENT TRACKS FOR GUSTAV OVER THE NORTHERN GULF.  MODELS WITH
 THE RIDGE EXTENSION AND A STRONGER UPPER-LEVEL TROUGH WEST OF
 GUSTAV...SUCH AS THE NOGAPS AND UKMET...FORECAST GUSTAV TO TURN
 WESTWARD TOWARD TEXAS.  OTHERS INCLUDING THE GFS...GFDL...AND
 HWRF...DO NOT SHOW THE RIDGE EXTENSION NOR A STRONG UPPER-LEVEL
 TROUGH...AND FORECAST GUSTAV TO BE PULLED INTO THE NORTHERN GULF
 COAST FARTHER EAST.  THE NEW OFFICIAL FORECAST LEANS TOWARD THE
 LATTER SOLUTIONS AND IS EAST OF THE CONSENSUS...AND REPRESENTS NO
 SIGNIFICANT CHANGE TO THE PREVIOUS ADVISORY.  DUE TO THE NOTABLE
 MODEL SPREAD LATE IN THE FORECAST PERIOD...IT IS ONCE AGAIN
 IMPORTANT TO RESTATE THAT IT IS SIMPLY NOT YET POSSIBLE TO
 DETERMINE EXACTLY WHERE AND WHEN GUSTAV WILL MAKE FINAL LANDFALL.
 
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      29/2100Z 19.2N  79.7W    65 KT
  12HR VT     30/0600Z 20.1N  80.9W    75 KT
  24HR VT     30/1800Z 21.7N  82.8W    90 KT...OVER ISLE OF YOUTH
  36HR VT     31/0600Z 23.4N  84.8W   100 KT
  48HR VT     31/1800Z 25.2N  86.8W   110 KT
  72HR VT     01/1800Z 28.0N  90.0W   105 KT
  96HR VT     02/1800Z 30.5N  92.5W    85 KT...INLAND
 120HR VT     03/1800Z 32.0N  94.0W    55 KT...INLAND
  
 $$
 FORECASTER KNABB