[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 291433
TCDAT4

TROPICAL STORM DON DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042011
1000 AM CDT FRI JUL 29 2011

SATELLITE IMAGES SHOW THAT DON HAS BECOME A LITTLE BETTER ORGANIZED
THIS MORNING WITH INCREASED CONVECTIVE BANDING AROUND THE CENTRAL
CONVECTION...ESPECIALLY IN THE SOUTHERN SEMICIRCLE.  HOWEVER...THE
STORM CONTINUES TO EXPERIENCE 10-15 KT OF NORTHERLY VERTICAL WIND
SHEAR...WITH AN ELONGATED OVERALL CLOUD PATTERN AND A STREAM OF ARC
CLOUDS IN THE EASTERN AND NORTHEASTERN QUADRANTS OF THE CYCLONE.
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS REPORTED 850 MB
FLIGHT-LEVEL WINDS OF 51 KT...AND THE CENTRAL PRESSURE ESTIMATED
FROM THE AIRCRAFT DATA IS NEAR 1002 MB.  THE INITIAL INTENSITY
REMAINS 45 KT.

THE INITIAL MOTION IS NOW 300/12.  DEEP-LAYER RIDGING OVER THE
SOUTHEASTERN UNITED STATES SHOULD STEER DON GENERALLY
WEST-NORTHWESTWARD UNTIL THE CYCLONE DISSIPATES OVER LAND IN
36-48 HR.  THE NEW FORECAST TRACK HAS CHANGED LITTLE FROM THE
PREVIOUS TRACK AND IS NEAR THE CENTER OF THE TRACK GUIDANCE
ENVELOPE.

DON SHOULD CONTINUE TO EXPERIENCE MODERATE SHEAR UNTIL THE CENTER
MAKES LANDFALL IN ABOUT 18 HR.  IN ADDITION...WATER VAPOR IMAGERY
AND MICROWAVE PRECIPITABLE WATER DATA SHOW DRY AIR CLOSE TO THE
WESTERN SIDE OF DON.  THIS COMBINATION SHOULD CONTINUE TO IMPEDE
SIGNIFICANT STRENGTHENING BEFORE LANDFALL...AND THUS THE INTENSITY
FORECAST SHOWS ONLY SLIGHT STRENGTHENING.  DON SHOULD WEAKEN
STEADILY AFTER LANDFALL...AND THE SYSTEM IS EXPECTED TO DISSIPATE
COMPLETELY BY 48 HR IN AGREEMENT WITH THE DYNAMICAL MODEL GUIDANCE.

INTERESTS IN EXTREME NORTHEAST MEXICO SHOULD CONTINUE TO CLOSELY
MONITOR THE PROGRESS OF DON. ANY SMALL DEVIATION TO THE SOUTH OF
THE FORECAST TRACK COULD NECESSITATE THE ISSUANCE OF WARNINGS FOR
THE EXTREME NORTHEASTERN COAST OF MEXICO.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 26.2N  94.9W   45 KT  50 MPH
 12H  30/0000Z 26.8N  96.7W   50 KT  60 MPH
 24H  30/1200Z 27.7N  99.1W   35 KT  40 MPH...INLAND
 36H  31/0000Z 28.3N 101.6W   25 KT  30 MPH...INLAND
 48H  31/1200Z...DISSIPATED

$$
FORECASTER BEVEN


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