[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 030248
TCDAT1

HURRICANE OPHELIA DISCUSSION NUMBER  42
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
1100 PM AST SUN OCT 02 2011

THE SATELLITE PRESENTATION OF OPHELIA HAS CONTINUED TO DETERIORATE
THIS EVENING...WITH CLOUD TOPS WARMING AND DRY AIR WORKING ITS WAY
INTO THE CORE OF THE CYCLONE FROM THE SOUTH. ALSO...RECENT
MICROWAVE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT THE
LOW-LEVEL CENTER IS DISPLACED ABOUT A DEGREE TO THE SOUTH-SOUTHWEST
OF THE MID-LEVEL CIRCULATION AND THE REMAINING DEEP CONVECTION.
THIS TILT IS DUE TO THE 30 KT OF SOUTHWESTERLY SHEAR SHOWN OVER THE
CYCLONE IN ANALYSES FROM THE SHIPS MODEL AND UW-CIMSS. THE INITIAL
INTENSITY IS LOWERED TO 70 KT FOR THIS ADVISORY...LEANING TOWARD
THE HIGH END OF A BLEND OF DVORAK CI- AND FINAL-T NUMBERS FROM TAFB
AND SAB. OPHELIA SHOULD CONTINUE TO STEADILY WEAKEN OVER THE NEXT
12 TO 24 HOURS AS THE CYCLONE MOVES OVER VERY COLD WATERS AND THE
SHEAR INCREASES EVEN MORE. BY 24 HOURS...OPHELIA WILL BE
EXTRATROPICAL AND SLOWLY WEAKEN UNTIL IT IS ABSORBED BY A FRONTAL
SYSTEM IN ABOUT 48 HOURS.

BASED ON MICROWAVE FIXES AND SURFACE OBSERVATIONS...THE INITIAL
MOTION ESTIMATE IS A RATHER UNCERTAIN 025/29. HOWEVER...THE TRACK
FORECAST REASONING REMAINS STRAIGHTFORWARD. OPHELIA WILL TURN
TOWARD THE NORTHEAST OVERNIGHT AS IT MOVES AROUND THE NORTHWESTERN
SIDE OF THE SUBTROPICAL RIDGE. THIS MOTIONS WILL BRING THE CENTER
OF OPHELIA NEAR THE AVALON PENINSULA OF NEWFOUNDLAND ON MONDAY
MORNING. AFTER THAT TIME...OPHELIA WILL BECOME EMBEDDED IN THE
MID-LATITUDE WESTERLIES AND ACCELERATE TOWARD THE EAST-NORTHEAST
UNTIL IT IS ABSORBED IN 36 TO 48 HOURS. THE NEW NHC TRACK FORECAST
IS SIMILAR TO THE PREVIOUS ONE AND CLOSE TO A BLEND OF THE ECMWF
AND GFS MODELS.

THE TROPICAL-STORM-FORCE WIND RADII HAVE BEEN ADJUSTED INWARD BASED
ON RECENT SURFACE OBSERVATIONS.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 43.9N  58.6W   70 KT  80 MPH
 12H  03/1200Z 46.6N  53.7W   55 KT  65 MPH
 24H  04/0000Z 49.8N  43.7W   45 KT  50 MPH...POST-TROP/EXTRATROP
 36H  04/1200Z 53.0N  32.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  05/0000Z...DISSIPATED

$$
FORECASTER BRENNAN



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