Tropical Storm KAREN

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TROPICAL STORM KAREN DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122013
400 AM CDT SAT OCT 05 2013
 
KAREN REMAINS A SHEARED CYCLONE THIS MORNING...WITH THE MAIN
CONVECTIVE AREA LOCATED ABOUT 80 N MI SOUTHEAST OF THE CENTER.
EARLIER ASCAT OVERPASSES INDICATE WINDS OF AT BEST 35 KT IN THE
NORTHEASTERN QUADRANT.  THERE ARE RECENT REPORTS FROM AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT OF STRONGER WINDS IN THE
CONVECTION...BUT IT IS UNCLEAR HOW REPRESENTATIVE THESE WINDS ARE.
THE INITIAL INTENSITY IS DECREASED TO 35 KT BASED ON THE
SCATTEROMETER DATA.
 
KAREN JOGGED A BIT NORTHWESTWARD DURING THE PAST SEVERAL HOURS...BUT
IT APPEARS TO HAVE RESUMED A NORTH-NORTHWESTWARD MOTION OF 330/7.
THE LOW/MID-LEVEL RIDGE CURRENTLY STEERING KAREN SHOULD WEAKEN
TODAY AS A DEEP-LAYER TROUGH AND ASSOCIATED COLD FRONT MOVE
EASTWARD THROUGH THE CENTRAL UNITED STATES.  THIS SHOULD CAUSE
KAREN TO TURN NORTHWARD AND THEN NORTHEASTWARD DURING THE NEXT
COUPLE OF DAYS.  WHILE THE TRACK GUIDANCE AGREES WITH THIS
SCENARIO...THERE REMAINS SOME SPREAD ON THE TIMING OF THE
NORTHEASTWARD TURN.  THE NEW TRACK FORECAST IS NUDGED NORTHWARD
BASED ON THE INITIAL POSITION AND MOTION...AND IT CALLS FOR THE
CENTER TO PASS NEAR OR OVER THE MOUTH OF THE MISSISSIPPI RIVER IN
24-36 HOURS...FOLLOWED BY A FINAL LANDFALL IN ALABAMA OR THE
WESTERN FLORIDA PANHANDLE BETWEEN 36-48 HOURS.  THE NEW FORECAST
TRACK LIES NEAR THE CENTER OF THE GUIDANCE ENVELOPE.
 
THERE ARE SEVERAL POSSIBLE SCENARIOS FOR THE LOW CONFIDENCE
INTENSITY FORECAST.  THE MOST LIKELY SCENARIO...AND THE ONE USED IN
THE NEW INTENSITY FORECAST...IS THAT KAREN REMAINS A SHEARED SYSTEM
WITH LITTLE CHANGE IN STRENGTH UNTIL FINAL LANDFALL.  ONE
ALTERNATIVE IS POSSIBLE STRENGTHENING BEFORE LANDFALL DUE TO
RE-DEVELOPED CENTRAL CONVECTION.  WHILE THE DYNAMICAL MODELS
FORECAST UPPER-LEVEL WINDS THAT COULD ALLOW THIS TO HAPPEN...THEY
ARE FOR THE MOST PART SHOWING NO SIGNIFICANT STRENGTHENING AS KAREN
APPROACHES LANDFALL.   A SECOND ALTERNATIVE IS THAT KAREN WEAKENS
BELOW TROPICAL STORM STRENGTH BEFORE LANDFALL DUE TO EITHER LACK OF
CONVECTION OR THE START OF EXTRATROPICAL TRANSITION.  AFTER
LANDFALL...KAREN SHOULD WEAKEN AND BECOME EXTRATROPICAL AS IT
MERGES WITH THE COLD FRONT.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0900Z 27.1N  91.3W   35 KT  40 MPH
 12H  05/1800Z 27.6N  91.2W   35 KT  40 MPH
 24H  06/0600Z 28.4N  90.5W   35 KT  40 MPH
 36H  06/1800Z 29.5N  89.2W   35 KT  40 MPH
 48H  07/0600Z 31.2N  86.4W   30 KT  35 MPH...INLAND
 72H  08/0600Z 35.5N  80.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 96H  09/0600Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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