[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 251739
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 25 2012

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR 31.9N 30.0W AT 25/1500
UTC OR ABOUT 395 NM SSW OF THE AZORES MOVING WSW AT 5 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS. SCATTERED MODERATE CONVECTION IS WITHIN 30/45
NM OF LINE FROM 32N30W TO 31N32W.

...TROPICAL WAVES...

TROPICAL WAVE IN THE E CARIBBEAN EXTENDS FROM 17N64W TO 11N65W
MOVING W 10-15 KT. WAVE IS EMBEDDED WITHIN A BROAD AREA OF DEEP
MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
WAVE REMAINS TO THE E OF AN UPPER LOW/TROUGH COVERING THE
CENTRAL CARIBBEAN.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL
ATLC NEAR 13N16W CONTINUING ALONG 8N24W TO 10N34W. THE ITCZ IS
NOT CLEARLY DEFINED IN THE ATLC BASIN. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 10N-16N BETWEEN
18W-22W. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM
3N-7N BETWEEN 18W-24W...FROM 9N-13N BETWEEN 42W-45W...AND FROM
12N-15N BETWEEN 54W-58W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER TROUGH COVERS THE E CONUS INTO THE W ATLC
NARROWING AS IT EXTENDS ACROSS NE FLORIDA TO OVER THE E GULF
SUPPORTING A STATIONARY FRONT IN THE W ATLC THAT AT 25/1500 UTC
DISSIPATES AS IT ENTERS THE GULF OF MEXICO OVER EXTREME S
FLORIDA THEN OVER KEY WEST FLORIDA TO 23N88W. SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS ARE WITHIN 120 NM EITHER SIDE OF THE
FRONT. AN UPPER RIDGE IS BUILDING OVER THE FAR W GULF ALONG THE
COAST OF MEXICO AND TEXAS DRAWING DRY CONTINENTAL AIR OVER THE
GULF W OF A LINE FROM 23N90W TO CEDAR KEY FLORIDA. A SURFACE
TROUGH IS IN THE SW GULF EXTENDING FROM 23N97W INTO THE BAY OF
CAMPECHE TO NEAR 19N93W. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE WITHIN 120 NM E OF THE TROUGH S OF 21N. A
SURFACE RIDGE ANCHORED IN THE NW ATLC IS BUILDING SW ACROSS THE
GULF IN THE WAKE OF THE FRONT CURRENTLY IN THE SE GULF LEAVING
THE REMAINDER OF THE GULF WITH CLEAR SKIES THIS AFTERNOON. THE
FRONT WILL GRADUALLY DISSIPATE THROUGH EARLY TONIGHT. HIGH
PRESSURE BUILDING ACROSS THE GULF WILL REMAIN STRONG THROUGH WED
AND GRADUALLY WEAKEN THU THROUGH SAT.

CARIBBEAN SEA...
AN UPPER RIDGE AXIS EXTENDS FROM AN UPPER HIGH IN THE E PACIFIC
REGION ACROSS CENTRAL AMERICA AND THE GULF OF HONDURAS INTO THE
W ATLC ACROSS CENTRAL CUBA. THE DISSIPATING STATIONARY FRONT IN
THE SE GULF OF MEXICO COUPLED WITH THE UPPER RIDGE IN THE
CARIBBEAN IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
N OF 21N BETWEEN 83W-87W TO INLAND OVER CUBA AND THROUGH THE
YUCATAN CHANNEL. AN UPPER LOW IS IN THE CENTRAL CARIBBEAN
CENTERED NEAR 15N72W COVERING THE AREA BETWEEN 64W-81W
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 11N-18N
BETWEEN 63W-73W FURTHER ENHANCED BY THE E CARIBBEAN TROPICAL
WAVE. THE MONSOON TROUGH EXTENDS ACROSS THE S CARIBBEAN FROM
COLOMBIA TO COSTA RICA INTO THE E PACIFIC REGION ALONG 10N
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 14N W
OF W OF 81W. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN WITH
MOSTLY CLEAR SKIES THIS AFTERNOON. THE TROPICAL WAVE WILL REACH
THE CENTRAL CARIBBEAN EARLY WED AND THE W CARIBBEAN EARLY FRI
THEN MOVE ACROSS THE REMAINDER OF THE CARIBBEAN LATER FRI AND
SAT.

ATLANTIC OCEAN...
BROAD UPPER TROUGH COVERS THE E CONUS INTO THE NW ATLC EXTENDING
ALONG THE EASTERN SEABOARD TO NE FLORIDA SUPPORTING A COLD FRONT
N OF THE DISCUSSION AREA AND A STATIONARY FRONT ENTERING THE
REGION AT 25/1500 UTC NEAR 32N68W ALONG 28N75W TO OVER S FLORIDA
S OF MIAMI DISSIPATING AS IT ENTERS THE GULF OF MEXICO. A BROAD
UPPER RIDGE COVERS THE W ATLC ANCHORED NEAR 26N70W EXTENDING A
RIDGE AXIS SW ACROSS CENTRAL CUBA INTO THE CARIBBEAN AND NE TO
BEYOND 32N65W PROVIDING DIFFLUENCE ALOFT TO GENERATE CLUSTERS OF
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS NW OF A LINE FROM THE
COAST OF CUBA IN THE STRAITS OF FLORIDA NEAR 23N81W ALONG 27N73W
TO 31N65W AND E OF A LINE FROM SAINT AUGUSTINE FLORIDA TO
31N78W. AN UPPER LOW IS IN THE CENTRAL ATLC NEAR 24N58W
SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 24N48W TO 19N50W
AND GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN
75 NM EITHER SIDE OF THE TROUGH AXIS. A SURFACE RIDGE IS
BUILDING SW FROM A 1030 MB HIGH NW OF THE AZORES WITH A RIDGE
AXIS EXTENDING THROUGH 32N58W TO NEAR 25N73W. TROPICAL STORM
NADINE REMAINS IN THE NE ATLC...SEE SPECIAL FEATURES ABOVE. THE
W ATLC STATIONARY FRONT WILL GRADUALLY DISSIPATE BY WED AS HIGH
PRESSURE BUILDS S ACROSS THE W ATLC. A WEAK COLD FRONT WILL MOVE
ACROSS THE FAR NORTHERN WATERS FRI AND SAT.

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

$$
PAW





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