[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 220554
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED 13.7N 46.2W AT 22/0300 UTC OR
925 NM E OF THE LEEWARD ISLANDS MOVING W AT 13 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND
SPEED IS 50 KT WITH GUSTS TO 60 KT. SCATTERED MODERATE TO STRONG
CONVECTION IS FROM 13N-18N BETWEEN 41W-46W CLOSEST TO THE
CENTER...WHILE SCATTERED MODERATE CONVECTION IS FROM 08N-13N
BETWEEN 40W-45W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/
WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 16N25W TO 07N32W 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-23N BETWEEN 20W-20W. ISOLATED MODERATE
CONVECTION IS OCCURRING WITHIN 30 NM EITHER SIDE OF A LINE FROM
15N27W TO 12N31W AND FROM 07N-10N BETWEEN 32W-37W.

...ITCZ/MONSOON TROUGH...

NO SPECIFIC ITCZ OR MONSOON TROUGH AXIS IS OBSERVED HOWEVER
SCATTERED MODERATE AND WIDELY SCATTERED STRONG CONVECTION IS
MOVING OFF THE COAST OF W AFRICA FROM 04N-16N BETWEEN 11W-18W.

...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 WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS
OCCURRING N OF 24N E OF 90W. A SURFACE TROUGH IS ANALYZED S OF
27N ALONG 90W...WHICH IS ALSO AIDING IN LOW-LEVEL MOISTURE
CONVERGENCE E OF THE TROUGH AXIS. ANOTHER WEAK SURFACE TROUGH IS
LOCATED EAST OF THE YUCATAN PENINSULA S OF 23N ALONG 86W AND IS
PROVIDING FOCUS FOR WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS
OVER THE SE GULF...THE YUCATAN CHANNEL...AND THE ADJACENT
COASTAL GULF WATERS OF WESTERN CUBA S OF 24N BETWEEN 81W-87W.
OTHERWISE THIS EVENING...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 86W IN
THE VICINITY OF THE YUCATAN CHANNEL AND REMAINS THE FOCUS FOR
ISOLATED SHOWERS AND TSTMS N OF 18N BETWEEN 81W-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 EVENING. FARTHER EAST...AN UPPER LEVEL TROUGH
AXIS EXTENDS FROM OVER EASTERN CUBA NEAR 20N77W 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 13N-17N BETWEEN
73W-81W. 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 1012 MB LOW IS
CENTERED EAST OF PUERTO RICO NEAR 18N64W WHICH CONTINUES TO MOVE
WESTWARD SWIFTLY WITH ISOLATED SHOWERS AND TSTMS WITHIN 120 NM
EITHER SIDE OF A LINE FROM 19N65W TO 11N62W. ANOTHER AREA OF
LOW-LEVEL MOISTURE AND ISOLATED SHOWERS IS EAST OF THE LEEWARD
ISLANDS OCCURRING FROM 14N-20N BETWEEN 58W-61W WHICH IS FORECAST
TO BRING THE POSSIBILITY OF ISOLATED OVERNIGHT SHOWERS TO THE
LESSER ANTILLES.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE IS ANCHORED IN THE SW NORTH ATLC NEAR
29N72W WITH AN UPPER LEVEL LOW POSITIONED TO THE S OVER THE SE
BAHAMAS NEAR 23N75W. THIS IS GENERATING A LARGE AREAL COVERAGE
OF ISOLATED SHOWERS AND POSSIBLE ISOLATED TSTMS N OF 22N W OF
70W. FARTHER EAST OVER THE REMAINDER OF W ATLC...AN UPPER LEVEL
RIDGE AXIS EXTENDS FROM N OF PUERTO RICO NEAR 20N67W TO THE
PREVIOUSLY MENTIONED UPPER LEVEL RIDGE NEAR 29N72W. AN OVERALL
DIFFLUENT ENVIRONMENT FROM 20N-27N BETWEEN 57W-70W IS GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 20N-26N BETWEEN
61W-70W. OTHERWISE THE REMAINDER OF THE CENTRAL AND EASTERN ATLC
IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1027 MB
HIGH CENTERED NEAR 38N60W 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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