[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 212028
TCDAT2
HURRICANE KARL DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT TUE SEP 21 2004

DVORAK T-NUMBERS CONTINUE TO DECREASE AS THE CONVECTIVE PATTERN
BECOMES RATHER NON-SYMMETRIC...APPARENTLY DUE TO STRONG VERTICAL
SHEAR.  THE INITIAL WIND SPEED IS 105 KT.  IN CONTRAST...THE SHIPS
MODEL DOES NOT ANALYZE VERY MUCH SHEAR UNTIL 48 HOURS AND OFFICIAL
FORECAST DOES NOT SHOW ADDITONAL WEAKENING UNTIL 36 HOURS IN
RESPECT TO THIS GUIDANCE.  IF THE PRESENT APPARENT SHEAR HOLDS
UP...KARL COULD WEAKEN MUCH FASTER THAN FORECAST.  KARL IS EXPECTED
TO ENCOUNTER COLDER WATERS BY 72 HOURS AND BECOME EXTRATROPICAL.

THE INITIAL MOTION IS 340/14.  THE TRACK FORECAST SCENARIO REMAINS
THE SAME AS IN PREVIOUS ADVISORIES.  KARL IS EXPECTED TO TURN
TOWARD THE NORTH-NORTHEAST WITH SOME ACCELERATION IN A DAY OR TWO
AROUND A RIDGE TO ITS EAST AND THEN GET DRAWN TOWARD A POWERFUL
EXTRATROPICAL MID-LEVEL LOW DROPPING SOUTHWARD OVER THE FAR NORTH
ATLANTIC.  THE FORECAST TRACK IS SOMEWHAT FASTER THAN THE PREVIOUS
ADVISORY AFTER 36 HOURS AND IS IN GOOD AGREEMENT WITH A CONSENSUS
OF THE GLOBAL TRACK MODELS.

FORECASTER LAWRENCE

FORECAST POSITIONS AND MAX WINDS

INITIAL      21/2100Z 22.9N  48.6W   105 KT
 12HR VT     22/0600Z 24.9N  49.4W   105 KT
 24HR VT     22/1800Z 27.6N  49.1W   105 KT
 36HR VT     23/0600Z 30.4N  47.4W   100 KT
 48HR VT     23/1800Z 34.1N  45.0W    90 KT
 72HR VT     24/1800Z 44.2N  42.2W    75 KT...EXTRATROPICAL
 96HR VT     25/1800Z 52.5N  37.5W    55 KT...EXTRATROPICAL
120HR VT     26/1800Z 57.5N  25.0W    45 KT...EXTRATROPICAL


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