[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222358
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT SEP 22 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
2345 UTC.

...SPECIAL FEATURES...

POST-TROPICAL CYCLONE NADINE IS CENTERED OVER THE NORTHEASTERN
ATLC ANALYZED AS A 987 MB SURFACE LOW NEAR 30N26W MOVING SE AT
5-10 KT. ISOLATED MODERATE CONVECTION IS NEAR THE LOW CENTER AND
TO THE NE FROM 30N-32N BETWEEN 24W-26W. CONDITIONS ARE EXPECTED
TO BE MARGINALLY FAVORABLE FOR REGENERATION OF THIS SYSTEM INTO
A TROPICAL OR SUBTROPICAL CYCLONE AS IT MOVES OVER SLIGHTLY
WARMER WATERS DURING THE NEXT DAY OR TWO.  THIS SYSTEM HAS A
MEDIUM CHANCE OF BECOMING A TROPICAL OR SUBTROPICAL CYCLONE
AGAIN DURING THE NEXT 48 HOURS. ADDITIONAL INFORMATION ON
POST-TROPICAL CYCLONE NADINE CAN BE FOUND IN HIGH SEAS FORECASTS
ISSUED BY METEO FRANCE.

...TROPICAL WAVES...

TROPICAL WAVE MOVES ACROSS THE CENTRAL TROPICAL ATLC WITH AXIS
FROM 15N45W TO 10N50W MOVING W AT ABOUT 15-20 KT. THE WAVE LIES
WITHIN A HORIZONTALLY ELONGATED AREA OF DEEP LAYER MOISTURE. A
WEAK LOW LEVEL CIRCULATION AROUND THE WAVE AXIS IS NOTED ON
INFRA-RED IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 12N-15N
BETWEEN 45W-48W.

TROPICAL WAVE EXTENDS FROM THE ERN BAY OF CAMPECHE OVER THE GULF
OF MEXICO AT 21N90W TO THE ERN PACIFIC NEAR 11N94W...ENHANCING
INLAND LOCAL PRECIPITATION ACROSS THE YUCATAN PENINSULA. OVER
THE NEXT 24 HOURS...THE NORTHERN HALF OF THE WAVE AXIS WILL
LIKELY DISSIPATE OVER THE ERN SIERRA MADRE MOUNTAINS AS THE
SOUTHERN PORTION CONTINUES IN THE E PACIFIC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO A 1008 MB
SURFACE LOW ALONG THE COAST OF SENEGAL AT 16N15W AND CONTINUES
OVER ATLC WATERS ALONG 10N23W 6N34W. THE ITCZ BEGINS AT 6N34W
AND CONTINUES ALONG 7N38W 8N47W 7N61W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-8N BETWEEN
16W-28W. NO OTHER DEEP CONVECTION IS NOTED.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH CONTINUES TO SLOWLY MOVE ACROSS THE ERN
CONUS THIS EVENING PROVIDING SOUTHWESTERLY FLOW ACROSS THE
ENTIRE BASIN. THIS PATTERN IS BRINGING DRY AIR AND STRONG
SUBSIDENCE ALOFT OVER THE NW AND MOST OF THE CENTRAL PORTION OF
THE GULF. HOWEVER...AN AREA OF STRONG DIFFLUENCE ASSOCIATED WITH
THE UPPER TROUGH EXTENDS INTO THE SE GULF SUPPORTING A SURFACE
TROUGH ANALYZED FROM 27N83W TO THE YUCATAN CHANNEL NEAR 21N86W.
SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE OVER
THIS REGION S OF 26N E OF 86W...AS WELL AS INLAND PORTIONS OF
CENTRAL AND SOUTH FLORIDA PENINSULA. A WEAK TROPICAL WAVE IS
ENTERING THE ERN BAY OF CAMPECHE...ENHANCING INLAND LOCAL
PRECIPITATION ACROSS THE YUCATAN PENINSULA. SEE TROPICAL WAVE
SECTION FOR MORE DETAILS. TO THE W OF THIS TROPICAL WAVE...A
SURFACE TROUGH IS ANALYZED FROM 24N96W TO 20N94W GENERATING
SIMILAR CONVECTION S OF 25N W OF 93W. FAIR WEATHER WITH A FEW
ISOLATED WEAK SHOWERS ARE ACROSS THE REMAINDER OF THE GULF
SUPPRESSED BY THE DRY/SUBSIDENT AIR ALOFT AND A SURFACE RIDGE
ANCHORED INLAND OVER SW LOUISIANA. THE WEATHER WILL REMAIN
UNSETTLED ACROSS THE SRN HALF OF THE GULF DURING THE NEXT 24
HOURS.

CARIBBEAN SEA...
THE SAME DIFFLUENT PATTERN ALOFT ACROSS THE S-ERN GULF OF MEXICO
EXTENDS INTO THE NW CARIBBEAN SUPPORTING A SURFACE TROUGH THAT
EXTENDS OVER THE SE GULF TO THE YUCATAN CHANNEL NEAR 21N86W.
SCATTERED SHOWERS AND THUNDERSTORMS ARE NOTED ACROSS THIS AREA N
OF 17N W OF 80W. THIS PATTERN WILL SLOWLY LIFT N ALLOWING FOR
DRYER WEATHER TO TAKE PLACE. SIMILAR ACTIVITY IS NOTED ACROSS
THE SW BASIN S OF 12N W OF 75W ASSOCIATED TO THE ERN PACIFIC
MONSOON TROUGH EXTENDING ACROSS CENTRAL AMERICA OVER COSTA RICA
TO NRN COLOMBIA. FAIR WEATHER WITH A FEW ISOLATED SHOWERS ARE
NOTED ACROSS THE REMAINDER OF THE BASIN DUE TO DRY AIR ALOFT
BETWEEN A WEAK UPPER LEVEL RIDGE OVER THE NW CARIBBEAN AND A DRY
ELONGATED UPPER LEVEL LOW MOVING ACROSS THE EASTERN CARIBBEAN
NEAR 14N63W. TRADEWIND FLOW OF 15-20 KT IS PRESENT ACROSS MUCH
OF THE BASIN. EXPECT MOIST CONDITIONS TO REMAIN ACROSS THE SW
CARIBBEAN FOR THE NEXT 24 HOURS.

ATLANTIC OCEAN...
THE UPPER LEVEL TROUGH OVER THE EASTERN CONUS IS GENERATING AN
AREA CONVECTION OFF THE SE CONUS COAST. A SURFACE TROUGH IS
ANALYZED FROM 33N72W TO 27N78W ENHANCING THE AREA OF CONVECTION
N OF 24N W OF 74W...INCLUDING THE NW BAHAMAS. THE ENVIRONMENT IS
EXPECTED TO REMAIN FAVORABLE FOR THE DEVELOPMENT OF CONVECTION
DURING THE NEXT 24 HOURS AS IT DRIFTS EASTWARD. AN UPPER LEVEL
RIDGE IS TO THE E OF THIS AREA OF CONVECTION OVER THE WRN
ATLANTIC PROVIDING FAIR CONDITIONS W OF 60W. OVER THE PAST 6
HOURS THE UPPER LEVEL LOW NEAR 32N59W HAS BEEN SHOWING SIGNS OF
ELONGATION AND THE ASSOCIATED CONVECTION HAS DETACHED
SIGNIFICANTLY. SHOWERS AND ISOLATED THUNDERSTORMS ARE LOCATED N
OF 26N AND BETWEEN 52W-60W. ANOTHER AREA OF SCATTERED
SHOWERS/THUNDERSTORMS IS LOCATED FARTHER SOUTH FROM 22N-26N
BETWEEN 55W-58W. UPPER LEVEL RIDGING DOMINATES THE CENTRAL ATLC
CENTERED NEAR 33N40W. POST-TROPICAL STORM NADINE IS LOCATED OVER
THE EASTERN ATLANTIC ATTACHED TO AN UPPER LEVEL TROUGH PRODUCING
SOME SHOWER ACTIVITY TO THE E AND NE OF THE CENTER AS WELL AS
GALE FORCE WINDS IN THE NW QUADRANT.

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

$$

GARCIA/DELGADO




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