[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 292037
TCDAT1

HURRICANE OPHELIA DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
500 PM AST THU SEP 29 2011

SATELLITE IMAGES AND MICROWAVE DATA INDICATE THAT THE CLOUD PATTERN
HAS CONTINUED TO ACQUIRE ORGANIZATION. THERE IS A CYCLONICALLY
CURVED CONVECTIVE BAND WRAPPING AROUND THE CENTER AND THE
UPPER-LEVEL OUTFLOW HAS EXPANDED IN ALL QUADRANTS. THERE HAS BEEN
AN EYE FEATURE INTERMITTENTLY APPEARING ON VISIBLE IMAGES...BUT
THERE IS DEFINITELY A DISTINCT ONE AT THE MID-LEVELS ON EARLIER
MICROWAVE DATA. T-NUMBERS FROM TAFB AND SAB HAVE INCREASED TO 4.0
ON THE DVORAK SCALE AND ON THIS BASIS...OPHELIA HAS BEEN UPGRADED
TO HURRICANE STATUS...THE FOURTH OF THE 2011 SEASON.

OPHELIA HAS KICKED OUT THE SHEAR AND GLOBAL MODELS INSIST ON KEEPING
AN UPPER-LEVEL RIDGE OVER THE CYCLONE. THIS PATTERN SHOULD ALLOW
SOME ADDITIONAL STRENGTHENING DURING THE NEXT DAY OR SO. THE
OFFICIAL FORECAST CONTINUE TO BE VERY SIMILAR TO THE STATISTICAL
LGEM...ALTHOUGH SOME MODELS FORECAST A STRONGER HURRICANE.
BEYOND 72 HOURS THE SHEAR IS FORECAST TO INCREASE SIGNIFICANTLY...
AND THE SEA SURFACE TEMPERATURES WILL DECREASE. THIS SHOULD RESULT
IN WEAKENING...AND MOST LIKELY OPHELIA WILL BECOME POST-TROPICAL BY
96 HOURS OR SOONER.

OPHELIA HAS BEEN MOVING TOWARD THE NORTH-NORTHWEST OR 340 DEGREES AT
8 KNOTS. THERE HAS BEEN NO CHANGE IN THE STEERING TO REPORT. THE
OFFICIAL FORECAST REMAINS UNCHANGED AND CONTINUES IN THE MIDDLE OF
THE GUIDANCE ENVELOPE IN BETWEEN THE GFS AND THE ECMWF FOR THE NEXT
2 TO 3 DAYS. OPHELIA SHOULD GRADUALLY TURN TO THE NORTH BY FRIDAY
AND THEN RECURVE NEAR THE LATITUDE OF BERMUDA IN ABOUT 48 HOURS.
THE WESTERN EDGE OF THE GUIDANCE ENVELOPE BARELY REACHES BERMUDA
AT THIS TIME.


FORECAST POSITIONS AND MAX WINDS

INIT  29/2100Z 21.4N  62.3W   65 KT  75 MPH
 12H  30/0600Z 22.8N  62.9W   75 KT  85 MPH
 24H  30/1800Z 25.0N  63.5W   75 KT  85 MPH
 36H  01/0600Z 27.5N  63.5W   80 KT  90 MPH
 48H  01/1800Z 30.5N  63.0W   75 KT  85 MPH
 72H  02/1800Z 41.0N  59.5W   70 KT  80 MPH
 96H  03/1800Z 51.5N  48.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  04/1800Z 53.0N  30.0W   30 KT  35 MPH...POST-TROP/EXTRATROP

$$
FORECASTER AVILA


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