[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 132341
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 13 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
2335 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR 24.0N 53.0W 13/2100 UTC
OR ABOUT 765 MI...1230 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MOVING NW AT 14 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990
MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO
STRONG CONVECTION IS FROM 22N-27N BETWEEN 48W-55W.

...TROPICAL WAVES...

A TROPICAL WAVE AXIS IS ANALYZED FROM 15N43W ALONG A 1012 MB LOW
LEVEL CENTER NEAR 10N41W TO 7N38W MOVING W 10-15 KT. THIS SYSTEM
IS EMBEDDED IN A SURGE OF MODERATE MOISTURE VALUES ON TOTAL
PRECIPITABLE WATER IMAGERY. THIS SYSTEM IS ALSO EMBEDDED IN DRY
SAHARAN AIR ALOFT LIMITING THE CONVECTIVE ACTIVITY NEAR THE
CENTER. ONLY A SMALL AREA OF SCATTERED WEAK CONVECTION IS N OF
THE LOW LEVEL CENTER FROM 11N-15N BETWEEN 40W-45W.

...ITCZ/MONSOON TROUGH...

THE OCEANIC MONSOON TROUGH IS ANALYZED FROM THE NRN COAST OF
GUINEA NEAR 11N15W TO 9N27W...WHERE THE ITCZ AXIS CONTINUES TO
11N37W. THE ITCZ REDEVELOPS SW OF A TROPICAL WAVE NEAR 8N44W TO
7N55W. SCATTERED MODERATE CONVECTION IS FROM 5N-11N E OF 30W.
ISOLATED WEAK CONVECTION IS WITHIN 50 NM ON EITHER SIDE OF THE
ITCZ BETWEEN 44W-50W.

...DISCUSSION...

GULF OF MEXICO...
SEVERAL AREAS OF CONVECTION ARE KEEPING THE WEATHER ACROSS THE
GULF UNSETTLED THIS EVENING. AN ELONGATED UPPER LEVEL LOW IS
NOTED ON WATER VAPOR IMAGERY MOVING ACROSS THE SE CONUS. THIS
FEATURE EXTENDS AN UPPER TROUGH INTO THE CENTRAL GULF PROVIDING
FOCUS FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 26N
BETWEEN 85W-89W. UPPER LEVEL DIVERGENCE OVER THE WRN GULF IS
GENERATING SIMILAR CONVECTION NEAR THE COASTAL WATERS OF MEXICO
FROM 21N-26N W OF 95W. THE REMNANTS OF A DISSIPATING STATIONARY
FRONT ANALYZED FROM THE WRN NORTH ATLANTIC TO OVER THE STRAITS
OF FLORIDA CONTINUE TO PROVIDE SCATTERED SHOWERS TO THE ERN GULF
AND THE YUCATAN CHANNEL E OF 85W S OF 28N. THIS LEAVES THE
CENTRAL GULF AND BAY OF CAMPECHE THE ONLY AREAS WHERE FAIR
WEATHER CONDITIONS PREVAIL. MARINE OBSERVATIONS ACROSS THE GULF
SHOW EASTERLY WINDS 10-15 KT ACROSS THE BASIN...OCCASIONALLY
GUSTING TO 20 KT. SHORT RANGE COMPUTER MODELS SUGGEST THE
WEATHER ACROSS THE GULF WILL REMAIN UNSTABLE DURING THE NEXT 24
HOURS.

CARIBBEAN SEA...
THE REMNANTS OF A DISSIPATING STATIONARY FRONT N OF CUBA
COASTAL WATERS CONTINUE TO GENERATE SCATTERED SHOWERS INLAND W
OF 80W...SOME OF THESE REACHING THE WATERS NEAR THE YUCATAN
CHANNEL. THE REMAINDER OF THE NW AND CENTRAL BASIN ARE DOMINATED
BY DRY AIR AND STRONG SUBSIDENCE ALOFT PROVIDED BY A BROAD UPPER
RIDGE CENTERED OVER THE NW BAHAMAS...SUPPRESSING DEEP CONVECTION
AND ONLY ALLOWING FOR A FEW ISOLATED LOW-TOP SHOWERS DOTTING THE
DISCUSSION AREA TONIGHT. HOWEVER...AN ELONGATED UPPER LOW DRIFTS
WESTWARD CENTERED JUST A FEW MILES N OF PUERTO RICO GENERATING
SCATTERED MODERATE TO HEAVY SHOWERS N OF 15N E OF 68W EVIDENT ON
SAN JUAN DOPPLER RADAR IMAGERY. SIMILAR CONVECTION IS NOTED S
OF 13N W OF 75W...ASSOCIATED TO THE ERN PACIFIC MONSOON TROUGH
EXTENDING ACROSS COSTA RICA TO NRN COLOMBIA. FAIR WEATHER
CONDITIONS WITH A FEW ISOLATED SHOWERS WILL PREDOMINATE ACROSS
THE DISCUSSION AREA DURING THE NEXT 24 HOURS. MODERATE TO
ISOLATED STRONG CONVECTION WILL LINGER OVER THE SW BASIN DURING
THE FORECAST PERIOD.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH CONTINUES TO MOVE ACROSS THE WRN NORTH
ATLANTIC SUPPORTING A STATIONARY FRONT EXTENDING INTO OUR
DISCUSSION AREA AS A SURFACE TROUGH ALONG 31N63W 24N70W TO
ACROSS THE BAHAMAS AS A DISSIPATING STATIONARY FRONT NEAR 24N75W
AND INTO THE FAR ERN GULF OF MEXICO ACROSS THE STRAITS OF
FLORIDA. SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS
ARE NOTED WITHIN 90-120 NM ON EITHER SIDE OF THE FRONT W OF 75W.
ISOLATED WEAK SHOWERS ARE ALSO WITHIN 80 NM ON EITHER SIDE E OF
70W. THIS FRONTAL BOUNDARY IS EXPECTED TO CONTINUE TO WEAKEN
OVER THE NEXT 12-24 HOURS. TROPICAL STORM NADINE IS WELL TO THE
ENE OF THE LESSER ANTILLES. SEE SPECIAL FEATURE ABOVE FOR MORE
DETAILS ON NADINE. THE REMAINDER OF THE ATLC BASIN DISCUSSION
AREA IS DOMINATED BY A SURFACE RIDGE OF HIGH PRESSURE ANCHORED
BY A 1021 MB HIGH NEAR 32N44W. THE OVERALL FAIR WEATHER IS
ENHANCED ALOFT BY THICK LAYER OF SAHARAN DUST NOTED ON
METEOSAT-9 SAL PRODUCT E OF 50W.

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

$$

GARCIA




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