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Tropical Storm OPHELIA (Text)

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TROPICAL STORM OPHELIA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
500 AM AST THU SEP 22 2011

ALTHOUGH OPHELIA IS NOT WELL ORGANIZED ON SATELLITE IMAGES WITH ALL
OF THE CONVECTION LOCATED NORTHEAST OF THE CENTER...NOAA BUOY 41041
REPORTED PEAK ONE-MINUTE SUSTAINED WINDS OF 54 KT WITH A GUST TO 68
KT DURING THE PAST COUPLE OF HOURS.  THUS THE INITIAL INTENSITY IS
INCREASED TO 55 KT FOR THIS ADVISORY...AND THIS MIGHT BE A LITTLE
CONSERVATIVE GIVEN THE REMOTE CHANCES OF MEASURING THE INTENSITY OF
A SYSTEM WITH JUST ONE OBSERVING STATION.

THE INTENSIFICATION OF OPHELIA IS EXPECTED TO BE SHORT-LIVED AS 
SOUTHWESTERLY VERTICAL WIND SHEAR SHOULD INCREASE OVER THE NEXT DAY
OR SO.  GLOBAL MODELS ARE IN GOOD AGREEMENT ON A MID-OCEANIC
UPPER-LEVEL TROUGH REMAINING ENHANCED FOR THE NEXT SEVERAL
DAYS...WHICH SHOULD CAUSE SOME WEAKENING OF THE TROPICAL CYCLONE. 
AT THE END OF THE FORECAST PERIOD...THE MID-OCEANIC TROUGH COULD
FRACTURE...RESULTING IN A LOWER SHEAR ENVIRONMENT MORE CONDUCIVE
FOR STRENGTHENING.  THE NHC INTENSITY FORECAST SHOWS WEAKENING
EARLY ON...AND IS CLOSEST TO THE FSU SUPERENSEMBLE...ON THE LOW
SIDE OF THE GUIDANCE ENVELOPE.  IT WOULD NOT BE SURPRISING IF
OPHELIA ENDED UP WEAKENING FASTER THAN SHOWN BELOW GIVEN THE
SOMEWHAT HOSTILE UPPER-LEVEL WINDS EXPECTED.  
 
MICROWAVE AND ASCAT DATA INDICATED THAT THE CENTER IS A LITTLE
FARTHER SOUTH THAN ANTICIPATED...WHICH REQUIRED A SMALL
REPOSITIONING OF THE CENTER.  THIS CHANGE RESULTS IN AN ESTIMATED
MOTION OF 275/12.  MOST OF THE RELIABLE GUIDANCE SHOW OPHELIA
TURNING TO THE WEST-NORTHWEST BY FRIDAY MORNING AS THE MID-LEVEL
RIDGE WEAKENS SOMEWHAT.  A TURN TO THE NORTHWEST IS ANTICIPATED
OVER THE WEEKEND DUE TO THE TROPICAL CYCLONE REACHING THE
SOUTHWESTWARD EDGE OF THE SUBTROPICAL RIDGE...WITH A MORE POLEWARD
TRACK ANTICIPATED FOR EARLY NEXT WEEK.  THERE IS FAIR AGREEMENT IN
THE GLOBAL MODEL GUIDANCE ON THIS SOLUTION...THOUGH THE SPEED
DIFFERENCES ARE NOTABLE BY DAY 5.  THE NHC TRACK FORECAST IS
SHIFTED TO THE RIGHT AFTER 24 HOURS...BUT REMAINS TO THE WEST OF
THE DYNAMICAL MODEL CONSENSUS...AND THE TOP-PERFORMING ECMWF/GFS
MODELS.   
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/0900Z 13.4N  47.0W   55 KT  65 MPH
 12H  22/1800Z 13.8N  49.0W   55 KT  65 MPH
 24H  23/0600Z 14.5N  51.6W   50 KT  60 MPH
 36H  23/1800Z 15.4N  53.8W   50 KT  60 MPH
 48H  24/0600Z 16.7N  55.8W   45 KT  50 MPH
 72H  25/0600Z 19.3N  59.6W   45 KT  50 MPH
 96H  26/0600Z 21.5N  63.0W   45 KT  50 MPH
120H  27/0600Z 24.5N  65.5W   50 KT  60 MPH
 
$$
FORECASTER BLAKE
 
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