[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 080833
TCDAT4

TROPICAL STORM MARIA DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142011
500 AM AST THU SEP 08 2011

MARIA CURRENTLY HAS A RATHER DISORGANIZED APPEARANCE ON SATELLITE
IMAGES...AND CONSISTS PRIMARILY OF A RATHER SHAPELESS CLUSTER OF
DEEP CONVECTION WITH A FEW THUNDERSTORMS TO THE WEST-SOUTHWEST OF
THE CLUSTER.  THERE IS LITTLE...IF ANY...EVIDENCE OF BANDING
FEATURES.  AN ASCAT PASS FROM SEVERAL HOURS AGO INDICATED THAT THE
MAXIMUM WINDS REMAIN NEAR 45 KT.  HOWEVER...DATA FROM THIS PASS ALSO
CAST SOME DOUBT AS TO WHETHER THE SYSTEM HAS A CLOSED CIRCULATION
AT THIS TIME.  VISIBLE IMAGERY AND AN AIRCRAFT MISSION LATER TODAY
SHOULD GIVE MORE INFORMATION ON THE STATUS OF MARIA.

NO CHANGE IS MADE TO THE INTENSITY FORECAST.  AN UPPER-LEVEL LOW OR
TROUGH TO THE NORTHWEST OF THE STORM HAS BEEN IMPARTING ABOUT 20 KT
OF SOUTH-SOUTHWESTERLY SHEAR OVER THE TROPICAL CYCLONE...AND
INHIBITING STRENGTHENING.  GLOBAL MODELS INDICATE THAT THIS
LOW/TROUGH WILL MOVE MORE OR LESS IN TANDEM WITH MARIA THROUGH
ABOUT 72 HOURS...AND CONTINUE TO PRODUCE SIGNIFICANT SHEAR ON THE
SYSTEM.  THE OFFICIAL FORECAST SHOWS NO STRENGTHENING THROUGH 72
HOURS FOLLOWED BY SOME INCREASE IN INTENSITY AS THE IMPACT OF THE
AFOREMENTIONED UPPER-LEVEL LOW IS EXPECTED TO LESSEN.  THE NHC WIND
SPEED FORECAST IS ROUGHLY BETWEEN THE LATEST LGEM GUIDANCE AND THE
INTENSITY MODEL CONSENSUS.

THE CENTER IS QUITE DIFFICULT TO FIND...BUT IT IS PRESUMED THAT
MARIA HAS BEEN MAINTAINING A MOTION OF 275/20. A CONTINUED WESTWARD
MOTION IS LIKELY FOR ANOTHER DAY OR SO AS THE STORM MOVES ON THE
SOUTHERN SIDE OF A SUBTROPICAL RIDGE. SOME DECELERATION IS
PREDICTED AS THE RIDGE WEAKENS A LITTLE WITH TIME. IN 48 TO 72
HOURS...MARIA SHOULD BE NEARING A WEAKNESS IN THE RIDGE AND TURN
WEST-NORTHWESTWARD. AS USUAL...THERE IS A FAIR AMOUNT OF
UNCERTAINTY IN THE TRACK 4 TO 5 DAYS FROM NOW. A BROAD 500 MB
TROUGH...MOVING OFF THE U.S EAST COAST...IS SHOWN BY THE GLOBAL
MODELS TO WEAKEN THE RIDGE ENOUGH TO CAUSE MARIA TO TURN
NORTHWESTWARD BY 96 HOURS. IF THE TROUGH TURNS OUT TO BE WEAKER
THAN CURRENTLY PREDICTED...IT COULD DELAY THE NORTHWESTWARD TURN.
THE OFFICIAL FORECAST IS VERY CLOSE TO THE PREVIOUS ONE AND ROUGHLY
IN THE MIDDLE OF THE TRACK GUIDANCE ENVELOPE...BRACKETED BY THE
U.K. MET OFFICE MODEL ON THE LEFT AND BY THE GFS AND HWRF MODELS ON
THE RIGHT.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 13.5N  48.2W   45 KT  50 MPH
 12H  08/1800Z 13.8N  51.2W   45 KT  50 MPH
 24H  09/0600Z 14.5N  54.7W   45 KT  50 MPH
 36H  09/1800Z 15.3N  57.8W   45 KT  50 MPH
 48H  10/0600Z 16.7N  60.8W   45 KT  50 MPH
 72H  11/0600Z 19.5N  65.5W   45 KT  50 MPH
 96H  12/0600Z 23.0N  69.0W   50 KT  60 MPH
120H  13/0600Z 26.0N  72.0W   60 KT  70 MPH

$$
FORECASTER PASCH


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