[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 290232
TCDAT4

TROPICAL STORM DON DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042011
1000 PM CDT THU JUL 28 2011

BOTH NOAA AND AIR FORCE RECONNAISSANCE PLANES HAVE BEEN
INVESTIGATING TROPICAL STORM DON AND FOUND THAT THE CYCLONE HAD
JOGGED TO THE WEST DURING THE PAST FEW HOURS AND THAT THE CYCLONE
IS A LITTLE BIT STRONGER. THE MINIMUM CENTRAL PRESSURES REPORTED BY
NOAA AND AIR FORCE PLANE EARLIER THIS EVENING WERE 996 AND 998
RESPECTIVELY. MORE RECENTLY A HIGHER PRESSURE WAS REPORTED BUT THE
DROPSONDE DID NOT HIT THE VERY SMALL CENTER. SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB HAVE INCREASED TO 3.0 AND 3.5 ON THE
DVORAK SCALE. THE INITIAL HAS BEEN INCREASED TO 45 KNOTS PRIMARILY
BASED ON A BELIEVABLE 43-KNOT SFMR REPORT. THE CYCLONE HAS BEEN
UNDER THE INFLUENCE OF NORTHERLY SHEAR AND THE LOW-LEVEL CENTER IS
STILL TILTED SOUTHWARD WITH HEIGHT AS REPORTED BY BOTH PLANES.
SINCE NO SIGNIFICANT DECREASE OF THE SHEAR IS ANTICIPATED AND THE
CYCLONE IS INTERACTING WITH DRY AIR OVER THE WESTERN GULF OF
MEXICO...ONLY A SMALL AMOUNT OF STRENGTHENING IS FORECAST BEFORE
LANDFALL. IN FACT NONE OF THE GUIDANCE SUGGEST IMPORTANT CHANGES IN
INTENSITY.

DURING THE PAST FEW HOURS...DON HAS BEEN MOVING BETWEEN THE WEST AND
WEST-NORTHWEST AT 12 KNOTS. A STRONG HIGH PRESSURE SYSTEM OVER THE
SOUTHERN UNITED STATES HAS BEEN CONTROLLING THE TRACK OF THE
CYCLONE. SINCE THIS HIGH IS FORECAST BY MOST OF THE GLOBAL MODELS
TO PERSIST...A CONTINUATION OF A GENERALLY WEST-NORTHWESTWARD TRACK
IS ANTICIPATED UNTIL LANDFALL. THE OFFICIAL TRACK HAS BEEN SHIFTED
SOUTHWARD A LITTLE BIT AND THIS DUE TO THE INITIAL WESTWARD JOG AND
NOT DUE TO ANY IMPORTANT CHANGE IN THE STEERING PATTERN. GIVEN THE
SMALL SOUTHWARD SHIFT OF THE TRACK...THE TROPICAL STORM WATCH FOR
THE SOUTHERN TEXAS COAST HAS BEEN REPLACED WITH A TROPICAL STORM
WARNING.

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

FORECAST POSITIONS AND MAX WINDS

INIT  29/0300Z 24.7N  92.5W   45 KT  50 MPH
 12H  29/1200Z 25.5N  94.3W   50 KT  60 MPH
 24H  30/0000Z 26.6N  96.6W   55 KT  65 MPH
 36H  30/1200Z 27.5N  99.0W   30 KT  35 MPH...INLAND
 48H  31/0000Z 28.5N 101.5W   25 KT  30 MPH...INLAND
 72H  01/0000Z...DISSIPATED

$$
FORECASTER AVILA


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