Tropical Storm KAREN

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TROPICAL STORM KAREN DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122007
1100 PM EDT TUE SEP 25 2007

AFTER LOOKING RATHER UNIMPRESSIVE IN INFRARED SATELLITE IMAGERY
DURING THE AFTERNOON...DEEP CONVECTION HAS REDEVELOPED NEAR
THE CENTER OF KAREN AND BANDING FEATURES HAVE BECOME A LITTLE
BETTER DEFINED WITHIN THE PAST COUPLE OF HOURS.  HOWEVER...
SATELLITE INTENSITY ESTIMATES AND QUIKSCAT DATA SUGGEST THAT THE
MAXIMUM WINDS REMAIN 35 KT.  

THE INITIAL MOTION IS 285/12.  THE TRACK FORECAST SCENARIO REMAINS
THE SAME WITH KAREN MOVING WEST-NORTHWESTWARD SOUTH OF A DEEP-LAYER
RIDGE DURING THE NEXT COUPLE OF DAYS.  THEREAFTER...A WEAKNESS IN
THE RIDGE IS EXPECTED TO DEVELOP OVER THE CENTRAL ATLANTIC...
ALLOWING A TURN TOWARD THE NORTHWEST.  THE GFS AND UKMET
MODELS...WHICH HAVE PERFORMED WELL IN THE ATLANTIC SO FAR THIS
YEAR...ARE ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE AND THE
OFFICIAL FORECAST LEANS TOWARDS THESE SOLUTIONS.

THE LARGE AND BROAD CIRCULATION OF KAREN HAS LIKELY INHIBITED
STRENGTHENING DURING THE PAST 24 HOURS.  WITH THE RECENT
DEVELOPMENT OF CONVECTION NEAR THE CENTER AND THE FACT THAT
THE UPPER-LEVEL OUTFLOW HAS CONTINUED TO BECOME BETTER
ESTABLISHED...IT APPEARS THAT KAREN SHOULD STRENGTHEN DURING
THE NEXT DAY OR TWO.  THEREAFTER...IT REMAINS UNCLEAR AS TO EXACTLY
WHAT ROLE A DEVELOPING UPPER-LEVEL TROUGH NORTHEAST OF THE LEEWARD
ISLANDS WILL HAVE ON THE CYCLONE.  THE GFS DEVELOPS THIS TROUGH A
LITTLE FARTHER WEST THAN THE REMAINDER OF THE DYNAMICAL MODELS AND
KEEPS A MORE FAVORABLE OUTFLOW PATTERN OVER KAREN FOR A LITTLE
LONGER.  HOWEVER...BY DAYS 4-5...KAREN IS FORECAST TO MOVE CLOSE
ENOUGH TO THE UPPER-LEVEL TROUGH THAT SOUTHWESTERLY SHEAR WOULD
INCREASE.  DESPITE THIS SEEMINGLY UNFAVORABLE ENVIRONMENT LATE IN
THE FORECAST PERIOD...THE GFDL AND HWRF MODELS CONTINUE TO
STRENGTHEN KAREN TO A HURRICANE.  THE SHIPS AND LGEM MODELS SHOW
LITTLE CHANGE IN STRENGTH AFTER 48-72 HOURS.  THE OFFICIAL
INTENSITY FORECAST BLENDS THE STATISTICAL MODELS AND SHOWS A 
LITTLE LESS INTENSIFICATION THAN IN THE PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0300Z 11.1N  41.0W    35 KT
 12HR VT     26/1200Z 11.6N  43.0W    40 KT
 24HR VT     27/0000Z 12.6N  45.5W    45 KT
 36HR VT     27/1200Z 13.8N  47.6W    50 KT
 48HR VT     28/0000Z 15.3N  49.4W    55 KT
 72HR VT     29/0000Z 17.7N  51.4W    55 KT
 96HR VT     30/0000Z 20.0N  53.0W    50 KT
120HR VT     01/0000Z 22.5N  54.5W    50 KT
 
$$
FORECASTER BROWN
 
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