[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 082036
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT WED SEP 08 2004

TODAY HAS BEEN A HISTORIC DAY FOR THE DEPARTMENT OF COMMERCE/
NATIONAL OCEANIC ATMOPHERIC ADMINISTRATION/NATIONAL WEATHER
SERVICE/NATIONAL HURRICANE CENTER. THE PRESIDENT OF THE UNITED
STATES VISITED THE FACILITIES AT MIAMI FLORIDA.

A RECONNAISSANCE PLANE JUST PENETRATED THE EYE OF THE HURRICANE AND
REPORTED A MINIMUM PRESSURE OF 947 MB. SATELLITE IMAGES INDICATE
THAT THE HURRICANE CONTINUES TO BE WELL-ORGANIZED WITH A DISTINCT
EYE...SURROUNDED COMPLETELY BY VERY DEEP CONVECTION. THE OUTFLOW IS
EXCELLENT OUTFLOW. INITIAL INTENSITY REMAINS AT 120 KNOTS. IT
APPEARS THAT IVAN IS OVERCOMING THE SHEAR AND HEADING TOWARD A MORE
FAVORABLE ATMOSPHERIC AND OCEANIC ENVIRONMENT FOR STRENGTHENING.
AFTER CROSSING CUBA...THE SHEAR IS FORECAST TO INCREASE AND THE
OCEAN IS NOT AS WARM. THEREFORE SOME WEAKENING IS POSSIBLE.
HOWEVER...IVAN IS EXPECTED TO REMAIN A VERY DANGEROUS HURRICANE.

IVAN HAS BEEN MOVING TOWARD THE WEST-NORTHWEST AND IS NOW MOVING
295 DEGREES AT 15 KNOTS. AS INDICATED IN THE PREVIOUS FORECAST...
DURING THE NEXT 24 TO 48 HOURS...THE SUBTROPICAL RIDGE TO THE NORTH
OF IVAN IS EXPECTED TO CHANGE LITTLE...KEEPING IVAN ON A
WEST-NORTHWEST TRACK. THEREAFTER...THE RIDGE IS FORECAST TO WEAKEN
AND A BROAD MID-LEVEL TROUGH WILL LIKELY BECOME ESTABLISHED OVER
THE GULF OF MEXICO. THIS PATTERN SHOULD STEER THE HURRICANE ON A
NORTHWEST AND NORTH-NORTHWEST TRACK WITH A DECREASE IN FORWARD
SPEED. IT MUST BE RE-EMPHASIZED THAT THE FORECAST TRACK BEYOND 72
HOURS CONTINUES TO BE HIGHLY UNCERTAIN SINCE STEERING CURRENTS ARE
FORECAST TO BE WEAK AND NOT WELL-DEFINED IN THE FORECAST MODELS.
THE SPREAD IN THE MODELS CONTINUES IN THE LATEST 12Z RUN. SOME
MODELS BRING IVAN OVER FLORIDA AND ANOTHER GROUP MOVE THE
HURRICANE TOWARD THE GULF OF MEXICO.  THERE IS NO APPARENT REASON TO
FAVOR ONE SCENARIO OVER THE OTHER AT THIS TIME. THEREFORE...THE
OFFICIAL FORECAST REMAINS NEAR THE GLOBAL MODEL CONSENSUS AND
PRESUMES THAT THERE WILL BE ENOUGH RIDGING TO KEEP THE HURRICANE ON
A NORTHWEST TO NORTH-NORTHWEST TRACK... BRINGING DANGEROUS IVAN
OVER WESTERN CUBA IN 4 DAYS AND INTO THE EASTERN GULF OF MEXICO BY
DAY FIVE.

FORECASTER AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL      08/2100Z 13.4N  67.7W   120 KT
 12HR VT     09/0600Z 14.2N  69.8W   125 KT
 24HR VT     09/1800Z 15.5N  72.5W   120 KT
 36HR VT     10/0600Z 17.0N  74.7W   125 KT
 48HR VT     10/1800Z 18.5N  77.0W   130 KT OVER JAMAICA
 72HR VT     11/1800Z 20.5N  80.0W   130 KT
 96HR VT     12/1800Z 22.5N  82.0W   120 KT OVER WESTERN CUBA
120HR VT     13/1800Z 26.0N  83.5W   115 KT


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