[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 240247
TCDAT2
HURRICANE KARL DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU SEP 23 2004

KARL IS NOW EXPERIENCING STRONG SOUTHWESTERLY SHEAR AND THE
LOW-LEVEL CENTER IS BECOMING DETACHED FROM THE MORE OBVIOUS
MID-LEVEL CIRCULATION. AS SUCH...THE INITIAL POSITION IS BECOMING
MORE UNCERTAIN. CI NUMBERS HAVE FALLEN TO 5.5...5.0...AND 4.0 FROM
TAFB...SAB...AND AFWA SO THE INITIAL INTENSITY IS SET AT A
COMPROMISE OF 80 KT. A DRIFTING BUOY NEAR THE CENTER REPORTED A
PRESSURE OF 963 MB...WHICH WOULD NORMALLY SUPPORT A STRONGER
TROPICAL CYCLONE...BUT THIS PRESSURE-WIND RELATIONSHIP IS ALLOWABLE
FOR A HIGH-LATITUDE STORM. THE CLOUD PATTERN SUGGESTS THAT KARL IS
IN THE FIRST STAGES OF EXTRATROPICAL TRANSITION...WHICH SHOULD BE
COMPLETED WITHIN THE NEXT 12-24 HOURS AS THE SYSTEM BECOMES
ENVELOPED WITHIN THE BELT OF STRONG WESTERLIES SOUTH OF GREENLAND.
THE OFFICIAL INTENSITY FORECAST CLOSELY FOLLOWS THE GFDL...WHICH
SEEMS TO HAVE BEEN CORRECTLY FORECASTING THE HURRICANE'S RECENT
INTENSITY TRENDS. THIS IS SLIGHTLY HIGHER THAN THE SHIPS GUIDANCE.

KARL IS STILL ACCELERATING WITH AN INITIAL MOTION OF 020/26. THE
SYSTEM WILL CONTINUE MOVING IN A NORTH-NORTHEASTWARD DIRECTION FOR
THE NEXT 24 HOURS BUT WILL THEN MAKE A RAPID TURN TO THE NORTHEAST
AS IT MOVES INTO THE STRONG UPPER LEVEL WESTERLIES. THE OFFICIAL
FORECAST TRACK IS A TAD TO THE WEST OF THE PREVIOUS TRACK AFTER 24
HOURS...DUE TO A WESTWARD SHIFT IN THE MODEL CONSENSUS. KARL IS
EXPECTED TO MERGE WITH ANOTHER EXTRATROPICAL LOW NORTH OF THE
BRITISH ISLES BY 72 HOURS.

FORECASTER BERG/AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL      24/0300Z 38.7N  41.5W    80 KT
 12HR VT     24/1200Z 42.6N  40.9W    75 KT...BECOMING EXTRATROPICAL
 24HR VT     25/0000Z 47.5N  39.4W    65 KT...EXTRATROPICAL
 36HR VT     25/1200Z 52.2N  35.4W    55 KT...EXTRATROPICAL
 48HR VT     26/0000Z 57.0N  27.0W    50 KT...EXTRATROPICAL
 72HR VT     27/0000Z...MERGED WITH ANOTHER EXTRATROPICAL LOW


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