[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 230242
TCDAT1

TROPICAL STORM OPHELIA DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
1100 PM AST THU SEP 22 2011

ALTHOUGH THE LOW-LEVEL CENTER OF OPHELIA HAS BECOME BETTER DEFINED
AS COMPARED TO EARLIER TODAY...THE DEEP CONVECTION HAS BECOME
FURTHER REMOVED FROM THE CENTER DUE TO STRONG SOUTHWESTERLY SHEAR.
SATELLITE CURRENT INTENSITY ESTIMATES FROM TAFB AND SAB ONLY
SUPPORT A 35-KT TROPICAL STORM.  SINCE THE WINDS FROM THIS STORM
HAVE HISTORICALLY BEEN HIGHER THAN THE SATELLITE PRESENTATION WOULD
SUGGEST...THE INITIAL INTENSITY IS BEING CONSERVATIVELY REDUCED TO
45 KT ON THIS ADVISORY.

IT APPEARS THAT OPHELIA MAY BE MAKING A LITTLE MORE NORTHWARD
PROGRESS AND IS NOW MOVING TO THE WEST-NORTHWEST AT 10 KT.  THE
TRACK MODEL GUIDANCE IS IN GENERALLY GOOD AGREEMENT ON TURNING
OPHELIA NORTHWESTWARD WITHIN THE NEXT 24 HOURS AND THEN MAINTAINING
THAT HEADING THROUGH DAY 5.  HOWEVER...THERE ARE SOME SPEED
DIFFERENCES THAT APPEAR TO BE RELATED TO THE ORIENTATION OF THE
MID-LEVEL HIGH RELATIVE TO THE CYCLONE.  MOST NOTABLY...THE ECMWF
SHOWS THE HIGH WEAKENING AND SLIDING SOUTHEASTWARD MORE THAN THE
OTHER MODELS BY DAYS 4 AND 5 AND THEREFORE HAS OPHELIA MAKING MORE
NORTHWESTWARD PROGRESS DURING THAT TIME.  THE NEW OFFICIAL FORECAST
IS JUST A LITTLE SLOWER THAN THE PREVIOUS ONE BUT IS STILL FASTER
THAN THE VARIOUS CONSENSUS MODELS.

AS FAR AS INTENSITY...OPHELIA HAS A TOUGH ROAD AHEAD OF IT...AND
THE CYCLONE IS ALREADY WEAKENING DUE TO ABOUT 25 KT OF
SOUTHWESTERLY SHEAR.  THE UPPER-LEVEL TROUGH RESPONSIBLE FOR THIS
SHEAR IS EXPECTED TO CUT-OFF AND MOVE WESTWARD IN TANDEM WITH
OPHELIA...REMAINING ABOUT 600 N MI NORTHWEST OF THE STORM AT LEAST
FOR THE NEXT 3 DAYS.  YOU WOULD THINK THAT OPHELIA WOULD NOT
SURVIVE AN ENVIRONMENT LIKE THIS...BUT IT IS OFTEN HARD TO TELL IF
SYSTEMS LIKE THIS WILL HANG BY A THREAD DESPITE THE CONDITIONS.
DUE TO THE HIGH UNCERTAINTY...THE OFFICIAL INTENSITY FORECAST SHOWS
VERY LITTLE CHANGE FOR THE NEXT 5 DAYS.  IT WOULD NOT BE
SURPRISING...HOWEVER...IF OPHELIA DEGENERATED INTO A REMNANT LOW
OVER THE NEXT DAY OR TWO.

FORECAST POSITIONS AND MAX WINDS

INIT  23/0300Z 14.1N  49.9W   45 KT  50 MPH
 12H  23/1200Z 14.8N  51.6W   45 KT  50 MPH
 24H  24/0000Z 16.2N  53.8W   40 KT  45 MPH
 36H  24/1200Z 17.5N  55.8W   40 KT  45 MPH
 48H  25/0000Z 18.8N  57.6W   40 KT  45 MPH
 72H  26/0000Z 21.0N  61.0W   40 KT  45 MPH
 96H  27/0000Z 22.5N  63.0W   40 KT  45 MPH
120H  28/0000Z 25.0N  65.0W   40 KT  45 MPH

$$
FORECASTER BERG



This weather bulletin was brought to you by:
www.nashvilleweather.net