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| #7968 (Received by flhurricane at: 10:36 PM 11.Sep.2004) TCDAT4 HURRICANE IVAN DISCUSSION NUMBER 39 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SAT SEP 11 2004 THE HURRICANE HAS DEEPENED A LITTLE MORE THIS EVENING AND THE LAST CENTRAL PRESSURE OBSERVATION...BY DROPSONDE FROM THE HURRICANE HUNTERS...WAS 910 MB. IVAN RANKS SIXTH FOR LOWEST ATLANTIC BASIN CENTRAL PRESSURE BEHIND CAMILLE IN 1969 AND MITCH IN 1998 AT 905 MB EACH...ALLEN IN 1980 AT 899 MB...THE 1935 LABOR DAY HURRICANE AT 892 MB...AND GILBERT IN 1988 AT 888 MB. BOTH THE ATMOSPHERIC AND OCEANIC ENVIRONMENT ARE EXPECTED TO REMAIN FAVORABLE FOR THE NEXT DAY OR SO...AND IVAN COULD STRENGTHEN EVEN MORE. HOWEVER...THERE IS NO SKILL IN PREDICTING INTENSITY CHANGES FOR SUCH EXTREME TROPICAL CYCLONES. IT SUFFICES TO SAY THAT IVAN IS LIKELY TO HAVE A DEVASTATING IMPACT OVER PORTIONS OF THE CAYMAN ISLANDS AND WESTERN CUBA. AFTER IVAN MOVES INTO THE GULF OF MEXICO...THE SHIPS MODEL SHOWS INCREASING SHEAR...SO SOME WEAKENING IS FORECAST IN 2-3 DAYS. NOTWITHSTANDING...IVAN IS EXPECTED TO REMAIN A POWERFUL AND DANGEROUS HURRICANE WHEN IT MAKES LANDFALL SOMEWHERE ALONG THE GULF COAST OF THE UNITED STATES. THE EYE HAS BEEN WOBBLING OVER THE PAST FEW HOURS...BUT THE AIRCRAFT FIXES GIVE AN OVERALL MOTION OF ABOUT 285/7. AS A WEAK LOW MOVES SOUTHEASTWARD FROM THE LOWER MISSISSIPPI VALLEY REGION...THE MID-TROPOSPHERIC RIDGE TO THE NORTH OF THE HURRICANE IS FORECAST TO WEAKEN...SO A GRADUAL TURN TOWARD THE NORTHWEST IS PREDICTED. LATER IN THE PERIOD...IVAN SHOULD TURN NORTHWARD AND MOVE THROUGH THE WEAKNESS IN THE RIDGE. THE CURRENT NHC TRACK FORECAST HAS BEEN ADJUSTED VERY SLIGHTLY TO THE LEFT OF THE PREVIOUS ONE...BUT IT IS ON THE EASTERN SIDE OF THE LATEST MODEL GUIDANCE SUITE. BEAR IN MIND THAT 3-4 DAY FORECASTS ARE FAR FROM EXACT...SO THERE IS STILL CONSIDERABLE UNCERTAINTY AS TO JUST WHEN AND WHERE IVAN WILL MAKE LANDFALL IN THE UNITED STATES. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 12/0300Z 18.3N 80.0W 145 KT 12HR VT 12/1200Z 19.0N 81.0W 145 KT 24HR VT 13/0000Z 20.3N 82.4W 145 KT 36HR VT 13/1200Z 21.6N 83.7W 145 KT 48HR VT 14/0000Z 23.3N 84.5W 130 KT 72HR VT 15/0000Z 27.0N 85.5W 115 KT 96HR VT 16/0000Z 31.0N 85.5W 70 KT...INLAND 120HR VT 17/0000Z 36.0N 83.0W 20 KT...INLAND |
