[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221151
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU SEP 22 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED 13.4N 47.0W AT 22/0900 UTC OR
885 NM E-SE OF THE LEEWARD ISLANDS MOVING W AT 12 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 994 MB. MAXIMUM SUSTAINED WIND
SPEED IS 55 KT WITH GUSTS TO 70 KT. SCATTERED MODERATE TO STRONG
CONVECTION IS FROM 13N-18N BETWEEN 42W-47W LOCATED MAINLY IN THE
NE QUADRANT...WHILE SCATTERED MODERATE CONVECTION IS WITHIN 120
NM EITHER SIDE OF A LINE FROM 13N42W TO 08N50W. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 19N25W TO 10N30W MOVING W AT
10-15 KT. THE WAVE IS EMBEDDED WITHIN A POLEWARD EXTENSION OF
DEEP LAYER MOISTURE AS DEPICTED BY TOTAL PRECIPITABLE WATER
IMAGERY FROM 05N-25N BETWEEN 22W-31W. NO SIGNIFICANT DEEP
CONVECTION IS ATTRIBUTED TO THE WAVE AT THIS TIME.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO
13N21W. SCATTERED MODERATE CONVECTION IS FROM 04N-13N BETWEEN
11W-20W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER LEVEL TROUGH COVERS THE CENTRAL CONUS WHICH
EXTENDS INTO THE WESTERN GULF PROVIDING WEST TO SOUTHWESTERLY
FLOW ALOFT. WATER VAPOR IMAGERY INDICATES THAT MODERATE TO
STRONG DRY AIR IS LOCATED W OF 90W...HOWEVER E OF 90W...
LOW-LEVEL MOISTURE AND MIDDLE TO UPPER LEVEL DIFFLUENCE IS
SUPPORTIVE OF SCATTERED SHOWERS AND TSTMS OCCURRING N OF 25N E
OF 90W. A SURFACE TROUGH IS ANALYZED FROM 29N87W TO 20N90W WHICH
IS ALSO AIDING IN MAXIMIZING LOW-LEVEL MOISTURE CONVERGENCE E OF
THE TROUGH AXIS. ANOTHER WEAK SURFACE TROUGH IS LOCATED EAST OF
THE YUCATAN PENINSULA S OF 23N ALONG 87W AND IS PROVIDING FOCUS
FOR ISOLATED SHOWERS OVER THE SE GULF...THE YUCATAN CHANNEL...S
OF 23N BETWEEN 85W-87W. OTHERWISE THIS MORNING...A RELATIVELY
WEAK PRESSURE GRADIENT REMAINS ACROSS THE GULF WITH GENERALLY
LIGHT AND BROAD CYCLONIC FLOW AROUND THE SURFACE TROUGH ALONG
90W. BY FRIDAY...A COLD FRONT IS FORECAST TO ENTER THE NW GULF
WATERS AND EVENTUALLY WEAKEN AS IT SKIRTS THE NORTH-CENTRAL AND
NE GULF.

CARIBBEAN SEA...
A WEAK SURFACE TROUGH IS ANALYZED FROM 18N TO 23N ALONG 87W IN
THE VICINITY OF THE YUCATAN CHANNEL AND REMAINS THE FOCUS FOR
ISOLATED SHOWERS N OF 17N BETWEEN 85W-88W. AN UPPER LEVEL RIDGE
EXTENDS FROM THE E PACIFIC ACROSS SOUTHERN MEXICO AND THE
YUCATAN PENINSULA TO WESTERN CUBA WHICH IS PROVIDING MARGINAL
SUPPORT FOR THIS CONVECTIVE ACTIVITY OVER THE NW CARIBBEAN THIS
MORNING. FARTHER EAST...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM
OVER THE WINDWARD PASSAGE NEAR 20N75W TO 11N84W. MIDDLE TO UPPER
LEVEL DIFFLUENCE EAST OF THE TROUGH AXIS ALONG WITH LOW-LEVEL
SPEED CONVERGENCE OF EASTERLY TRADES IS GENERATING ISOLATED
SHOWERS AND TSTMS FROM 09N-18N BETWEEN 76W-84W. THE REMAINDER OF
THE EASTERN CARIBBEAN IS UNDER THE INFLUENCE OF AN UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED NEAR 12N70W. HOWEVER...AT THE
SURFACE..A WEAK 1011 MB LOW IS CENTERED OVER PUERTO RICO NEAR
18N66W WHICH CONTINUES TO MOVE SWIFTLY WESTWARD WITH ISOLATED
SHOWERS AND TSTMS FROM 15N-19N BETWEEN 64W-68W. ANOTHER BAND OF
LOW-LEVEL MOISTURE AND ISOLATED SHOWERS IS ACROSS THE LESSER
ANTILLES AND ADJACENT COASTAL WATERS THIS MORNING FROM 11N-20N
BETWEEN 59W-64W.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE IS ANCHORED IN THE SW NORTH ATLC NEAR
29N71W WITH AN UPPER LEVEL LOW POSITIONED TO THE S OVER THE SE
BAHAMAS NEAR 23N74W. THIS IS GENERATING A LARGE AREAL COVERAGE
OF ISOLATED SHOWERS AND POSSIBLE ISOLATED TSTMS N OF 20N W OF
69W. FARTHER EAST OVER THE REMAINDER OF W ATLC...AN UPPER LEVEL
RIDGE AXIS EXTENDS FROM N OF PUERTO RICO NEAR 20N66W TO THE
PREVIOUSLY MENTIONED UPPER LEVEL RIDGE NEAR 29N71W. AN OVERALL
DIFFLUENT ENVIRONMENT FROM 22N-27N BETWEEN 55W-69W IS GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 22N-28N BETWEEN
55W-69W. OTHERWISE THE REMAINDER OF THE CENTRAL AND EASTERN ATLC
IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1028 MB
HIGH CENTERED NEAR 38N59W WHICH IS FORECAST TO REMAIN QUASI-
STATIONARY THROUGH EARLY SATURDAY.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
HUFFMAN



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