[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 201448
TCDAT2
HURRICANE KARL DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT MON SEP 20 2004

SATELLITE IMAGES INDICATE THAT KARL IS NOT AS CIRCULAR AS YESTERDAY
WITH THE CLOUD SHIELD SHOWING ASYMMETRIES IN THE EASTERN AND
NORTHERN SEMICIRCLES.  THIS PATTERN SUGGESTS SOME SHEAR IS
PRESENT...CONFIRMED BY THE GFS AND CIMSS ANALYSES SHOWING ABOUT
10-15 KT OF SHEAR FROM THE SOUTHWEST.  THE CLOUD PATTERN NEAR THE
INNER CORE REMAINS RAGGED AND T-NUMBERS ARE FALLING.  HOWEVER A
RECENT SSMI OVERPASS SHOWED NO EVIDENCE OF THE INNER EYEWALL SEEN
ON EARLIER MICROWAVE IMAGES.  THIS SUGGESTS THAT THE PREVIOUS
EYEWALL CYCLE IS COMPLETE.  ON THE OTHER HAND THE EYE WAS ALSO OPEN
ON THE SOUTH SIDE.  GIVEN THE ABOVE FACTORS...THE INTENSITY IS
DECREASED A BIT TO 105 KT FOR THIS ADVISORY.

A MIDDLE TO UPPER LEVEL TROUGH ALONG 54W IS APPROACHING THE CYCLONE.
THE GFS INDICATES THAT SHEAR WILL REMAIN NEAR CURRENT LEVELS UNTIL
AFTER 24 HOURS WHEN THE TROUGH RETROGRADES AWAY FROM KARL.  THIS
SCENARIO SHOULD PROVIDE A PERIOD OF VERY LOW SHEAR OVER WARM WATER
NEAR THE CYCLONE'S RECURVATURE POINT... ALL INGREDIENTS FOR
INTENSIFICATION BETWEEN 24-48 HOURS.  THE OFFICIAL FORECAST IS A
COMPROMISE BETWEEN THE SHIPS AND PREVIOUS INTENSITY FORECAST.  WIND
RADII HAVE BEEN INCREASED BASED ON A 0900 UTC QUIKSCAT PASS AND THIS
LARGE SIZE IS HELD CONSTANT THOUGH THE PERIOD.

KARL IS STILL MOVING WEST-NORTHWEST OVER THE PAST 6-12 HOURS BUT
RECENT SATELLITE PICTURES SUGGEST THAT A MORE NORTHWESTERLY MOTION
MAY HAVE BEGUN.  THERE REMAINS NO SIGNIFICANT CHANGE TO THE TRACK
FORECAST PHILOSOPHY.  A DEEP-LAYERED TROUGH CURRENTLY OVER THE
WESTERN ATLANTIC IS FORECAST TO DIG SOUTHWARD AND BECOME ANCHORED
ALONG 55W.  THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS
ADVISORY AND IS IN BETWEEN CONU AND THE PREVIOUS FORECAST.  THE
FORECAST TRACK SHOWS A BIT OF A BEND TO THE LEFT BEYOND 3 DAYS TO
REFLECT A DEEP MID-LATITUDE CYCLONE CAPTURING KARL RATHER THAN THE
TROPICAL CYCLONE STAYING A SEPARATE ENTITY.

FORECASTER BLAKE/LAWRENCE

FORECAST POSITIONS AND MAX WINDS

INITIAL      20/1500Z 17.9N  46.3W   105 KT
 12HR VT     21/0000Z 18.7N  47.4W   105 KT
 24HR VT     21/1200Z 20.4N  48.8W   110 KT
 36HR VT     22/0000Z 22.5N  49.7W   120 KT
 48HR VT     22/1200Z 25.0N  49.8W   120 KT
 72HR VT     23/1200Z 32.0N  47.0W   110 KT
 96HR VT     24/1200Z 41.0N  44.0W    90 KT
120HR VT     25/1200Z 51.0N  45.0W    65 KT...EXTRATROPICAL


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