000
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