471 
 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
  
  
 $$