000
WTNT42 KNHC 280857
TCDAT2
TROPICAL STORM KAREN DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122007
500 AM EDT FRI SEP 28 2007
 
THE SATELLITE PRESENTATION OF KAREN HAS DETERIORATED DURING THE LAST
SIX HOURS...AND THE BURST OF DEEP CONVECTION THAT HAD PREVIOUSLY
OBSCURED THE LOW-LEVEL CENTER HAS WEAKENED.  LATEST CONVENTIONAL
AND MICROWAVE IMAGERY SUGGESTS THAT THE LOW-LEVEL CIRCULATION
CENTER IS TO THE SOUTH OF THE PREVIOUS ADVISORY POSITION...AND THE
INITIAL POSITION HAS BEEN ADJUSTED ACCORDINGLY.  CURRENT DVORAK
INTENSITY CLASSIFICATIONS REMAIN AT 35 KT FROM BOTH TAFB AND
SAB...AND THE INITIAL INTENSITY HAS BEEN LOWERED TO A POSSIBLY
GENEROUS 40 KT.
 
AS A RESULT OF THE RELOCATION OF THE CENTER...THE INITIAL MOTION IS
AN UNCERTAIN 290/9.  KAREN IS EXPECTED TO MOVE ON A GENERAL
WEST-NORTHWESTWARD TO NORTHWESTWARD TRACK FOR THE NEXT TWO TO THREE
DAYS IN RESPONSE TO A LOW- TO MID-LEVEL RIDGE TO THE NORTH OF THE
CYCLONE.  IN 48-72 HOURS...A MID-LATITUDE TROUGH IS EXPECTED TO
APPROACH THE CYCLONE FROM THE WEST...AND IT IS DIFFICULT TO
DETERMINE HOW MUCH OF A NORTHWARD STEERING INFLUENCE THE TROUGH
WILL HAVE ON KAREN.  BY DAY 4...MOST OF THE GUIDANCE AGREES THAT A
MORE WEST-NORTHWESTWARD TO WESTWARD MOTION COULD OCCUR AS THE
TROUGH MOVES EAST AND HIGH PRESSURE BUILDS BACK IN TO THE NORTH OF
THE CYCLONE.  THE OFFICIAL TRACK FORECAST IS TO THE WEST OF THE
PREVIOUS ADVISORY...PRIMARILY DUE TO THE INITIAL RELOCATION...AND
FOLLOWS MOST CLOSELY WITH THE GFDL AND GFS GUIDANCE.
 
THE STRONG WESTERLY SHEAR CURRENTLY AFFECTING THE CYCLONE IS
EXPECTED TO PERSIST FOR THE NEXT 48 HOURS OR SO.  ONCE THE
AFOREMENTIONED MID-LATITUDE TROUGH MOVES EAST OF KAREN... THE SHEAR
IS FORECAST TO RELAX AS RIDGING TO THE NORTH RETURNS.  IF KAREN IS
ABLE TO SURVIVE THE SHEAR FOR THE NEXT 48 HOURS...  RESTRENGTHENING
COULD OCCUR IN THE LATER FORECAST PERIODS.  TAKING A BLEND OF THE
GFDL...HWRF...AND SHIPS INTENSITY GUIDANCE YIELDS THE OFFICIAL
INTENSITY FORECAST FOR THIS ADVISORY.
 
IT SHOULD BE NOTED THAT THERE ARE LARGE UNCERTAINTIES IN BOTH THE
TRACK AND INTENSITY AT THE LONGER FORECAST PERIODS.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/0900Z 14.1N  49.8W    40 KT
 12HR VT     28/1800Z 14.8N  50.9W    35 KT
 24HR VT     29/0600Z 16.0N  52.4W    35 KT
 36HR VT     29/1800Z 17.3N  53.8W    35 KT
 48HR VT     30/0600Z 18.5N  55.0W    35 KT
 72HR VT     01/0600Z 20.5N  56.4W    40 KT
 96HR VT     02/0600Z 22.0N  57.5W    45 KT
120HR VT     03/0600Z 22.5N  60.0W    50 KT
 
$$
FORECASTER MAINELLI