870 
 WTNT42 KNHC 180851
 TCDAT2
 HURRICANE KARL DISCUSSION NUMBER   7
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 5 AM EDT SAT SEP 18 2004
  
 KARL HAS RAPIDLY INTENSIFIED OVER THE PAST 6 HOURS OR SO BASED ON
 THE APPEARANCE OF A SMALL BUT DISTINCT 10 NMI DIAMETER EYE IN
 INFRARED SATELLITE IMAGERY. THE INITIAL INTENSITY OF 75 KT IS BASED
 ON A BLEND OF DVORAK SATELLITE INTENSITY ESTIMATES OF 90 KT...77 KT
 ...AND 65 KT...FROM TAFB...SAB...AND AFWA...RESPECTIVELY. 
 
 THE INITIAL MOTION IS 310/13. THERE REMAINS NO SIGNIFICANT CHANGE TO
 THE PREVIOUS FORECAST TRACK OR REASONING. THE NHC MODEL GUIDANCE
 REMAINS QUITE CONSISTENT ON A GENERAL NORTHWESTWARD MOTION FOR THE
 NEXT 36-48 HOURS AS KARL MOVES AROUND THE SOUTHWEST PERIPHERY OF
 THE DEEP-LAYER SUBTROPICAL RIDGE TO THE NORTH. BY 72 HOURS...A
 STRONG HIGH AMPLITUDE RIDGE IS FORECAST BY ALL THE GLOBAL MODELS TO
 DEVELOP OVER THE NORTHEASTERN U.S. AND EASTERN CANADA...WHICH
 CAUSES A STRONG MID-TROPOSPHERIC TROUGH TO DIG SOUTHWARD OVER THE
 CENTRAL ATLANTIC TO THE NORTH AND NORTHWEST OF KARL.  THE LARGE
 TROUGH IS EXPECTED TO ERODE THE SUBTROPICAL RIDGE TO THE NORTH OF
 KARL...WHICH ALLOW THE HURRICANE TO TURN NORTH-NORTHEASTWARD...AND
 POSSIBLY EVEN BEGIN RECURVATURE TO THE NORTHEAST. THE OFFICIAL
 FORECAST IS JUST A TAD TO THE LEFT OF THE PREVIOUS TRACK AND IS
 CLOSE TO THE NHC MODEL CONSENSUS.
  
 THE OUTFLOW PATTERN OVER KARL REMAINS QUITE IMPRESSIVE...ALTHOUGH
 THE CONVECTIVE CLOUD PATTERN IS ELONGATED SLIGHTLY NORTHEAST-
 SOUTHWEST. HOWEVER...THE OUTFLOW HAS CONTINUED TO EXPAND OUTWARD IN
 THE WESTERN SEMICIRCLE...SUGGESTING THAT ANY RESTRICTION THAT HAS
 CREATED THE ASYMMETRIC CLOUD PATTERN SHOULD GRADUALLY WEAKEN. KARL
 IS EXPECTED TO CONTINUE TO RAPIDLY INTENSIFY FOR THE NEXT 12 TO 18
 HOURS DUE TO THE SMALL INNER-CORE WIND FIELD...GOOD OUTFLOW PATTERN
 ...AND WARM SSTS OF AT LEAST 28C. AFTER THAT...THE INTENSITY TREND
 IS EXPECTED TO BE A LITTLE LESS ROBUST AND IS LEVELED OFF BY 72
 HOURS WHEN INCREASING SOUTHWESTERLY SHEAR IS FORECAST TO BEGIN
 AFFECTING THE HURRICANE. THE OFFICIAL INTENSITY FORECAST IS A
 LITTLE HIGHER THAN SHIPS THROUGH 24 HOURS...AND THEN MUCH LOWER
 AFTER THAT...SINCE THE SHIPS MODEL BRINGS KARL UP TO 125 KT IN 72H. 
  
 FORECASTER STEWART
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      18/0900Z 14.9N  38.6W    75 KT
  12HR VT     18/1800Z 15.8N  40.3W    90 KT
  24HR VT     19/0600Z 16.8N  42.4W   100 KT
  36HR VT     19/1800Z 18.1N  44.1W   105 KT
  48HR VT     20/0600Z 19.7N  45.3W   110 KT
  72HR VT     21/0600Z 23.0N  46.5W   110 KT
  96HR VT     22/0600Z 26.5N  47.0W   100 KT
 120HR VT     23/0600Z 31.0N  45.5W    90 KT
  
  
 $$