Tropical Storm KAREN

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TROPICAL STORM KAREN DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122007
500 PM EDT FRI SEP 28 2007
 
NOT SURPRISINGLY...THIS AFTERNOON...KAREN IS ATTEMPTING TO MAKE A
COMEBACK.  DEEP CONVECTION IS DEVELOPING JUST TO THE NORTHEAST OF
THE CENTER.  A 1328Z ASCAT OVERPASS HAPPENED TO CAPTURE THE
MAJORITY OF THE SYSTEM AND INDICATED 30 KT WINDS OVER THE NORTHEAST
QUADRANT.  HOWEVER...THIS PARTICULAR PASS WAS A FEW HOURS BEFORE
THE CONVECTIVE CANOPY BEGAN TO EXPAND AND INTENSIFY.  THE DVORAK
SATELLITE CURRENT INTENSITY ESTIMATES HAVE INCREASED TO 35 KT AND
THE INITIAL INTENSITY REMAINS AT 35 KT.
 
THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE
AND IS A BLEND OF THE SHIPS AND THE LGEM...INDICATING WEAKENING
UNDER STRONG UPPER LEVEL SOUTHWESTERLY FLOW DURING THE NEXT 24
HOURS...THEN LITTLE CHANGE THROUGH DAY 5...DUE TO AN UNFAVORABLE
UPPER WIND ENVIRONMENT.
 
INITIAL MOTION IS ESTIMATED AT 310/10.  THE UNPREDICTED TEMPORARY
NORTHWARD MOTION COULD BE DUE TO A COMBINATION OF SLIGHT
STRENGTHENING OF THE LOW- LEVEL RIDGE BETWEEN TROPICAL DEPRESSION
14 AND KAREN AND SOUTHERLY FLOW WITH A TROUGH WEST OF THE CYCLONE. 
CONSEQUENTLY...IT IS UNCLEAR IF OR WHEN THE SYSTEM WILL RETURN TO
ITS PREVIOUS NORTHWESTWARD MOTION THAT THE DYNAMICAL MODELS
CONTINUE TO SUGGEST.  THEREFORE...BASED ON A BLEND OF THE
LARGE-SCALE MODELS AND THE GFDL...THE OFFICIAL FORECAST
SHOWS A TURN BACK MORE TO THE NORTHWEST DURING THE NEXT 12
HOURS.  THE MODELS HAVE SPLIT INTO TWO POSSIBLE SCENARIOS
AGAIN...WITH THE GFS AND THE HWRF INDICATING MORE OF A NORTHWARD
MOTION AT THE END OF THE FORECAST PERIOD IN RESPONSE TO AN
APPROACHING MID-LATITUDE TROUGH FROM THE NORTHWEST.  THE OTHER
CLUSTER CONSISTS OF THE UKMET...ECMWF...AND NOGAPS WHICH REFLECTS A
TURN MORE TOWARD THE WEST-NORTHWEST.  BASED ON THE CONSTANT
INCONSISTENCIES FROM ONE MODEL RUN TO THE OTHER...THE OFFICIAL
FORECAST IS BASED ON A DYNAMICAL MODEL CONSENSUS AND IS ADJUSTED TO
THE RIGHT OF THE PREVIOUS FORECAST DUE TO THIS MORNING'S NORTHWARD
JOG.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/2100Z 16.4N  49.9W    35 KT
 12HR VT     29/0600Z 17.1N  50.9W    35 KT
 24HR VT     29/1800Z 18.2N  52.4W    30 KT
 36HR VT     30/0600Z 19.2N  53.7W    30 KT
 48HR VT     30/1800Z 20.3N  55.0W    30 KT
 72HR VT     01/1800Z 22.5N  57.5W    30 KT
 96HR VT     02/1800Z 24.0N  59.5W    30 KT
120HR VT     03/1800Z 25.5N  61.5W    30 KT
 
$$
FORECASTER ROBERTS
 
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