[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 120225
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

$$
This weather bulletin was brought to you by:
www.nashvilleweather.net