[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 070850
TCDAT4

TROPICAL DEPRESSION FOURTEEN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142011
500 AM AST WED SEP 07 2011

DATA FROM AN EARLIER ASCAT PASS SUGGESTED THAT THE CYCLONE WAS NEAR
TROPICAL STORM STRENGTH.  HOWEVER...THE CLOUD PATTERN HAS NOT BECOME
SIGNIFICANTLY BETTER ORGANIZED AND DVORAK T-NUMBERS FROM BOTH
AGENCIES ARE 2.0...WHICH DO NOT SUPPORT NAMING THE SYSTEM AT THIS
TIME.  NORMALLY WE WOULD EXPECT SIGNIFICANT STRENGTHENING OF A
TROPICAL CYCLONE IN THIS LOCATION AT THIS TIME OF YEAR.  MOST OF THE
INTENSITY GUIDANCE...HOWEVER...DOES NOT CALL FOR MUCH OF AN INCREASE
IN STRENGTH FOR THE NEXT 72 HOURS OR SO.  THE REASONS FOR THIS ARE
NOT CLEAR...BUT WATER VAPOR IMAGERY DOES SHOW A WEAK UPPER-LEVEL
TROUGH OR SHEAR AXIS ABOUT 500 MILES TO THE NORTHWEST OF THE
DEPRESSION...AND THIS COULD BE AN INHIBITING FACTOR.  LATE
IN THE FORECAST PERIOD...THE GFDL MODEL SHOWS CONSIDERABLE
INTENSIFICATION...BUT IT IS ONE OF FEW MODELS TO DO SO. THE NHC
INTENSITY FORECAST IS ABOVE THE OPERATIONAL MODEL CONSENSUS BUT
QUITE CLOSE TO A CONSENSUS THAT INCLUDES THE HURRICANE FORECAST
IMPROVEMENT PROJECT...HFIP...MODELS.  THIS IS ALSO THE SAME AS THE
PREVIOUS OFFICIAL WIND SPEED FORECAST.

THERE HAS BEEN SOME SCATTER IN THE CENTER FIXES...BUT A SMOOTHED
ESTIMATE OF THE INITIAL MOTION IS 280/17.  OVER THE NEXT DAY OR
TWO...THE TROPICAL CYCLONE WILL BE MOVING TO THE SOUTH OF A
STRENGTHENING SUBTROPICAL RIDGE WHICH IS LIKELY TO CAUSE SOME
ADDITIONAL INCREASE IN FORWARD SPEED.  BY DAYS 2-3...HOWEVER...THE
RIDGE BEGINS TO WEAKEN AND THE CYCLONE SHOULD BEGIN A GRADUAL TURN
TO THE RIGHT WITH DECREASING FORWARD SPEED.  THE TRACK GUIDANCE
CONTINUES TO SHOW QUITE A BIT OF SPREAD...WITH THE GFDL AND GFS
AMONG THE FASTEST OF THE MODELS AND THE ECMWF AND HWRF
SIGNIFICANTLY SLOWER.  THE OFFICIAL FORECAST FOR THIS PACKAGE IS
ONLY SLIGHTLY FASTER THAN THE PREVIOUS ONE AND NEAR OR A LITTLE TO
THE LEFT OF THE MULTI-MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 12.0N  39.9W   30 KT  35 MPH
 12H  07/1800Z 12.6N  42.7W   35 KT  40 MPH
 24H  08/0600Z 13.3N  46.8W   40 KT  45 MPH
 36H  08/1800Z 14.0N  51.0W   45 KT  50 MPH
 48H  09/0600Z 14.6N  54.5W   50 KT  60 MPH
 72H  10/0600Z 16.7N  60.5W   55 KT  65 MPH
 96H  11/0600Z 19.5N  65.5W   60 KT  70 MPH
120H  12/0600Z 22.5N  69.5W   65 KT  75 MPH

$$
FORECASTER PASCH



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