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Tropical Storm KAREN


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TROPICAL STORM KAREN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122013
400 PM CDT THU OCT 03 2013
 
THE SATELLITE APPEARANCE OF KAREN REMAINS LESS THAN IMPRESSIVE...AS
THE CENTER HAS BEEN PARTIALLY EXPOSED TO THE WEST OF THE REMAINING
DEEP CONVECTION. THE SHIPS MODEL CONTINUES TO ANALYZE ABOUT 20 KT
OF SOUTHWESTERLY SHEAR OVER KAREN...AND DRY AIR IS PRESENT IN THE
MID/UPPER LEVELS OVER THE WESTERN SEMICIRCLE. DESPITE THESE NEGATIVE
FACTORS...KAREN CONTINUES TO MAINTAIN ITS INTENSITY. THE NOAA
HURRICANE HUNTERS JUST MEASURED A CENTRAL PRESSURE OF 999 MB...AND
FLIGHT-LEVEL AND SFMR WINDS FROM BOTH THE NOAA AND AIR FORCE
RESERVE AIRCRAFT SUPPORT MAINTAINING THE INITIAL INTENSITY AT 55
KT. MODERATE SHEAR IS EXPECTED TO CONTINUE...AND ONLY GRADUAL
STRENGTHENING IS EXPECTED BEFORE THE SHEAR INCREASES FURTHER IN
ABOUT 48 HOURS. SOME WEAKENING IS THEN ANTICIPATED AS KAREN
APPROACHES THE GULF COAST...BUT THE STORM COULD STILL BE NEAR
HURRICANE STRENGTH AT LANDFALL. THE NHC FORECAST IS CLOSE TO THE
SHIPS AND LGEM MODELS AND THE IVCN INTENSITY CONSENSUS THROUGH THE
PERIOD. KAREN SHOULD BE EXTRATROPICAL BY ABOUT 4 DAYS AND ABSORBED
BY DAY 5...IF NOT SOONER.
 
THE INITIAL MOTION ESTIMATE IS A MORE CONFIDENT 330/10 BASED ON
AIRCRAFT FIXES AND SATELLITE IMAGERY. THE TRACK FORECAST REASONING
REMAINS UNCHANGED...AS KAREN WILL MOVE AROUND THE PERIPHERY OF THE
SUBTROPICAL RIDGE DURING THE NEXT DAY OR SO...WITH A DECREASE IN
FORWARD SPEED AS A MID-LEVEL RIDGE BUILDS BRIEFLY TO THE NORTHEAST
OF THE CYCLONE. A NORTHEASTWARD ACCELERATION IS EXPECTED AFTER 48
HOURS AHEAD OF A MID/UPPER-LEVEL TROUGH. THE TRACK GUIDANCE HAS
AGAIN SHIFTED A LITTLE TO THE WEST THIS CYCLE...AND THERE REMAINS
CONSIDERABLE EAST/WEST SPREAD...WITH THE HWRF AND GFS TO THE EAST
AND THE ECMWF TO THE WEST. THE NHC TRACK HAS BEEN ADJUSTED TO THE
WEST ABOUT A HALF A DEGREE BUT STILL LIES A LITTLE TO THE EAST OF
THE LATEST TCVA CONSENSUS...AND IS CLOSE TO THE FSU SUPERENSEMBLE
THROUGH LANDFALL.
 
THE 34-KT WIND RADII HAVE BEEN ADJUSTED OUTWARD IN THE EASTERN
SEMICIRCLE BASED ON AN EARLIER ASCAT PASS.
 
GIVEN THE NEW NHC TRACK AND INTENSITY FORECAST...A TROPICAL STORM
WARNING HAS BEEN ISSUED FOR A PORTION OF SOUTHEASTERN LOUISIANA.

FORECAST POSITIONS AND MAX WINDS
 
INIT  03/2100Z 23.3N  88.5W   55 KT  65 MPH
 12H  04/0600Z 24.6N  89.3W   60 KT  70 MPH
 24H  04/1800Z 26.2N  89.9W   60 KT  70 MPH
 36H  05/0600Z 27.6N  89.8W   65 KT  75 MPH
 48H  05/1800Z 28.8N  89.3W   60 KT  70 MPH
 72H  06/1800Z 32.0N  86.0W   40 KT  45 MPH...INLAND
 96H  07/1800Z 36.0N  80.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
120H  08/1800Z...ABSORBED BY FRONT
 
$$
FORECASTER BRENNAN
 
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