[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 030840
TCDAT5

TROPICAL STORM EMILY DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052011
500 AM AST WED AUG 03 2011

DATA FROM AN AIR FORCE HURRICANE HUNTER AIRCRAFT INDICATE THAT EMILY
HAS CHANGED LITTLE IN STRENGTH SINCE YESTERDAY.  PEAK FLIGHT-LEVEL
WINDS WERE 46 KT AND THE HIGHEST SFMR-OBSERVED SURFACE WINDS WERE 42
KT.  THE CURRENT INTENSITY ESTIMATE IS HELD AT 45 KT FOR THIS
ADVISORY.  ANALYSES FROM UW-CIMSS AND SHIPS MODEL OUTPUT INDICATE
THAT ABOUT 15 KT OF WEST-NORTHWESTERLY SHEAR IS AFFECTING THE
TROPICAL CYCLONE.  THIS IS IN AGREEMENT WITH AIRCRAFT OBSERVATIONS
WHICH INDICATED THAT THE CIRCULATION CENTER IS TILTED EASTWARD WITH
HEIGHT.  ALSO...CENTER FIXES FROM THE HURRICANE HUNTERS WERE VERY
NEAR THE WESTERN EDGE OF THE DENSE OVERCAST.  SOME STRENGTHENING IS
STILL POSSIBLE...HOWEVER...BEFORE THE CENTER REACHES HISPANIOLA.
NORTH OF THAT ISLAND...THE GLOBAL MODELS DEPICT AN UPPER-LEVEL
ENVIRONMENT THAT LOOKS MORE CONDUCIVE FOR STRENGTHENING WITH AN
UPPER-LEVEL ANTICYCLONE PREDICTED TO DEVELOP NEAR THE BAHAMAS.  THE
OFFICIAL INTENSITY FORECAST FOR 2 TO 5 DAYS IS CONSERVATIVE...
HOWEVER...AS IT IS NOT CERTAIN HOW SEVERELY EMILY WILL BE DISRUPTED
BY ITS PASSAGE ACROSS THE VERY MOUNTAINOUS TERRAIN OF HISPANIOLA.

THE INITIAL MOTION ESTIMATE REMAINS 285/12.  THE TRACK FORECAST
REASONING HAS NOT CHANGED FOR THIS ADVISORY.  OVER THE NEXT COUPLE
OF DAYS...EMILY IS EXPECTED TO TURN TOWARD THE NORTHWEST TOWARD A
WEAKNESS IN THE SUBTROPICAL RIDGE.  THEREAFTER...THE CONSENSUS OF
THE DYNAMICAL GUIDANCE CALLS FOR THE CYCLONE TO TURN TOWARD THE
NORTH AND MOVE THROUGH THE WEAKNESS IN THE RIDGE.  BY THE END OF
THE FORECAST PERIOD...EMILY SHOULD TURN TOWARD THE NORTHEAST AS IT
BEGINS TO BECOME INFLUENCED BY MID-LEVEL WESTERLIES.  IN
GENERAL...THE TRACK MODELS HAVE NOT SHIFTED CLOSER TO FLORIDA ON
THIS CYCLE...AND THE OFFICIAL FORECAST IS VERY SIMILAR TO THE
PREVIOUS ONE AND ALSO TO THE LATEST ECMWF PREDICTION.  IT SHOULD BE
NOTED HOWEVER THAT THERE IS SUBSTANTIAL SPREAD IN THE MODELS AROUND
DAY 3 AND BEYOND...SO THERE IS STILL SIGNIFICANT UNCERTAINTY IN THE
TRACK FORECAST FOR THAT TIME FRAME.



FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 16.5N  68.1W   45 KT  50 MPH
 12H  03/1800Z 17.3N  69.8W   50 KT  60 MPH
 24H  04/0600Z 19.0N  71.9W   40 KT  45 MPH...INLAND
 36H  04/1800Z 20.7N  73.7W   35 KT  40 MPH...OVER WATER
 48H  05/0600Z 22.5N  75.5W   40 KT  45 MPH
 72H  06/0600Z 26.5N  78.0W   50 KT  60 MPH
 96H  07/0600Z 30.0N  78.5W   60 KT  70 MPH
120H  08/0600Z 33.5N  74.0W   65 KT  75 MPH

$$
FORECASTER PASCH

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