[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 220006
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 21 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
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS NOW A SUBTROPICAL STORM. SUBTROPICAL
STORM NADINE IS CENTERED NEAR 33.0N 27.0W AT 21/2100 UTC OR
ABOUT 300 NM S OF THE AZORES MOVING SSE AT 11 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 982 MB. MAXIMUM SUSTAINED WIND SPEED
IS 50 KT WITH GUSTS TO 60 KT. SEE LATEST NHC INTERMEDIATE PUBLIC
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/ WTNT34 AND THE FULL
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS. AREA IS VOID OF ANY SIGNIFICANT DEEP
CONVECTION. SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS COVER THE AREA FROM 30N-35N BETWEEN 21W-34W.

...TROPICAL WAVES...

TROPICAL WAVE IN THE CENTRAL TROPICAL ATLC EXTENDS FROM 17N39W
TO 11N41W MOVING W 15 KT. WAVE IS ALONG THE TRAILING EDGE OF A
SURGE OF DEEP MOISTURE AS DEPICTED ON TOTAL PRECIPITABLE WATER
IMAGERY. SCATTERED SHOWERS ARE WITHIN 120 NM W OF THE WAVE
BETWEEN 11N-15N.

TROPICAL WAVE EXTENDS FROM 20N63W THROUGH THE VIRGIN ISLANDS
INTO THE E CARIBBEAN TO 14N68W MOVING W 20-25 KT. WAVE IS
EMBEDDED WITHIN A WEAK ISOLATED SURGE OF DEEP MOISTURE AS
DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY. NO ASSOCIATED
SHOWERS/CONVECTION.

TROPICAL WAVE IN THE W CARIBBEAN EXTENDS FROM 23N84W TO 16N86W
MOVING W 15 KT. WAVE IS EMBEDDED WITHIN A BROAD AREA OF VERY
DEEP MOISTURE THAT COVERS THE W CARIBBEAN AND E GULF OF MEXICO
AS DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY. WAVE IS
EMBEDDED WITHIN A BROAD AREA OF SHOWERS/THUNDERSTORMS AND NOT
CLEARLY DEFINED AS ASSOCIATED WITH THE WAVE ITSELF.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA INTO THE E TROPICAL
ATLC NEAR 19N16W CONTINUING ALONG 11N23W TO 8N30W WHERE THE ITCZ
CONTINUES ALONG 9N37W 8N43W INTO SOUTH AMERICA NEAR 7N59W.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM WITHIN 60/75
NM OF LINE FROM 7N20W TO 6N26W.

...DISCUSSION...

GULF OF MEXICO...
THE BROAD UPPER TROUGH REMAINS OVER THE E CONUS INTO THE GULF N
OF 22N SUPPORTING A SURFACE TROUGH THAT AT 21/2100 UTC EXTENDS
FROM THE W ATLC ACROSS FLORIDA INTO THE GULF NEAR TAMPA TO
27N85W. CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE
S OF 27N E OF 88W TO OVER FLORIDA...CUBA...AND THROUGH THE
YUCATAN CHANNEL. A WEAK SURFACE TROUGH IS OVER THE W GULF
EXTENDING FROM 28N94W ALONG 23N95W INTO THE BAY OF CAMPECHE TO
NEAR 18N93W. AN UPPER RIDGE COVERS THE FAR S GULF WITH THE RIDGE
AXIS OVER S MEXICO TO BELIZE. THE W COAST SEABREEZE OVER THE
YUCATAN PENINSULA IS COMBINING WITH AN E COAST SEABREEZE TO
GENERATE NUMEROUS SHOWERS/SCATTERED THUNDERSTORMS INLAND OVER
THE YUCATAN. ISOLATED SHOWERS/THUNDERSTORMS ARE OVER THE N GULF
N OF 27N BETWEEN 86W-92W. THE W GULF SURFACE TROUGH WILL
DISSIPATE SAT AS HIGH PRESSURE BUILDS SW ACROSS THE N AND
CENTRAL GULF. THE N PORTION OF THE W CARIBBEAN TROPICAL WAVE
WILL MOVE ACROSS THE S/CENTRAL GULF TONIGHT AND INTO THE BAY OF
CAMPECHE SAT. A WEAK COLD FRONT WILL MOVE INTO THE N GULF SUN
THEN BECOME STATIONARY ACROSS THE CENTRAL GULF THROUGH TUE.

CARIBBEAN SEA...
AN UPPER RIDGE IS ANCHORED IN THE E PACIFIC REGION EXTENDING AN
AXIS ACROSS S MEXICO TO BELIZE AND IS COMBINING WITH A SECOND
UPPER RIDGE ANCHORED OVER CENTRAL CUBA EXTENDING AN AXIS S TO E
HONDURAS TO PROVIDE DIFFLUENCE ALOFT TO GENERATE CLUSTERS OF
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE NW CARIBBEAN N
OF 16N W OF 75W. THE MONSOON TROUGH EXTENDS ACROSS THE SW
CARIBBEAN S OF 10N FROM COLOMBIA INTO THE E PACIFIC REGION OVER
PANAMA/COSTA RICA GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 12N BETWEEN 77W-84W. AN UPPER LOW IS OVER THE
LESSER ANTILLES NEAR 13N61W COVERING THE E CARIBBEAN E OF 72W
GENERATING ISOLATED SHOWERS/THUNDERSTORMS FROM 12N-16N E OF 65W
ACROSS THE ISLANDS. W CARIBBEAN TROPICAL WAVE WILL MOVE OVER THE
YUCATAN PENINSULA SAT. MODERATE TRADE WINDS ACROSS THE BASIN
WILL BECOME FRESH TO STRONG ALONG THE COAST OF COLOMBIA SAT
THROUGH MON AS HIGH PRESSURE BUILDS OVER THE SE CONUS. THE
E CARIBBEAN TROPICAL WAVE WILL MOVE NW AND BECOME DIFFUSE SAT
EVENING. THE CENTRAL TROPICAL ATLC TROPICAL WAVE WILL MOVE OVER
THE E CARIBBEAN TUE AND WED.

ATLANTIC OCEAN...
AN UPPER TROUGH THAT COVERS THE E CONUS AND GULF OF MEXICO
EXTENDS OVER THE NW ATLC SUPPORTING A STATIONARY FRONT N OF THE
DISCUSSION AREA AND A SURFACE TROUGH ENTERING THE W ATLC NEAR
32N73W ALONG 29N77W ACROSS THE FLORIDA PENINSULA NEAR MELBOURNE
TO TAMPA BEFORE ENTERING THE GULF OF MEXICO. SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS ARE S OF THE TROUGH W OF 76W TO OVER
FLORIDA...CUBA...AND THROUGH THE STRAITS OF FLORIDA...AND N OF
THE TROUGH TO 32N BETWEEN 77W-81W. AN UPPER RIDGE IS ANCHORED
OVER CENTRAL CUBA EXTENDING AN AXIS N TO BEYOND 32N70W ENHANCING
THE ACTIVITY ABOVE. A LARGE DEEP LAYERED LOW IS IN THE W/CENTRAL
ATLC NEAR 33N59W SUPPORTING A 1006 MB SURFACE LOW NEAR 31N54W
WITH A SURFACE TROUGH EXTENDING ALONG 33N58W WITH A WEAK SURFACE
TROUGH EXTENDING N TO 36N57W. CLUSTERS OF SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS ARE WITHIN FROM 25N-29N BETWEEN
48W-56W...N OF 29N TO BEYOND 32N BETWEEN 47W-60W. AN UPPER LOW
IS CENTERED OVER THE LESSER ANTILLES NEAR 13N61W COVERING THE W
TROPICAL ATLC FROM 8N-20N BETWEEN 54W-63W GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 120 NM OF LINE FROM 18N59W
TO 25N53W. THIS ACTIVITY IS BEING DRAWN N TOWARD THE DEEP
LAYERED LOW IN THE SPECIAL FEATURES. A WEAK SURFACE RIDGE IS
BETWEEN THE DEEP LAYERED LOW AND SUBTROPICAL STORM NADINE. WEAK
HIGH PRESSURE WILL BUILD S SAT THROUGH SUN. A COLD FRONT WILL
MOVE INTO THE W ATLC SUN NIGHT THEN SLOWLY MOVE S TO ACROSS
CENTRAL FLORIDA THROUGH TUE.

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

$$
PAW




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