[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN SEP 16 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURE...

HURRICANE NADINE IS CENTERED NEAR 30.5N 41.7W 16/1500 UTC OR
ABOUT ABOUT 985 MI...1585 KM WSW OF THE AZORES. NADINE IS MOVING
E AT 20 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB.
MAXIMUM SUSTAINED WIND SPEED IS 70 KT WITH GUSTS TO 85 KT. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/
WTNT24 KNHC FOR MORE DETAILS. MODERATE TO STRONG CONVECTION FROM
27N-34N BETWEEN 36W-42W.

...TROPICAL WAVES...

TROPICAL WAVE MOVES ACROSS THE ERN TROPICAL ATLC WITH AXIS
EXTENDING FROM WEST OF THE CAPE VERDE ISLANDS NEAR 17N27W TO
9N29W MOVING W AT 10-15 KT. THIS WAVE ALIGNS WITH A SMALL SURGE
OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER
IMAGERY. HOWEVER...THIS WAVE IS EMBEDDED IN DRY SAHARAN AIR. NO
DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE.

TROPICAL WAVE APPROACHES THE LESSER ANTILLES ANALYZED FROM
18N55W TO 11N54W MOVING W AT 10-15 KT. A 1011 MB SURFACE LOW IS
EMBEDDED ALONG THE WAVE AXIS NEAR 13N55W. THE WAVE LIES WITHIN
AN AREA OF MAXIMUM MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER
IMAGERY. THE CONVECTION ASSOCIATED TO THIS SYSTEM IS WELL TO THE
W OF THE ANALYZED FEATURE AFFECTING THE ERN CARIBBEAN AND LESSER
ANTILLES FROM GUADELOUPE S TO GRENADA BETWEEN 55W-63W. LOCALLY
HEAVY RAINS AND SQUALLS COULD AFFECT PORTIONS OF THE NRN LESSER
ANTILLES TODAY THROUGH AND MONDAY.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS IS ANALYZED FROM THE COAST OF GUINEA
NEAR 10N14W ALONG 11N21W 9N27W 10N32W TO 8N39W...WHERE THE ITCZ
AXIS CONTINUES TO 11N47W. SCATTERED MODERATE CONVECTION FROM
5N-11N BETWEEN 35W-45W...AS WELL AS FROM 5N-10N BETWEEN 20W AND
THE COAST OF WEST AFRICA.

...DISCUSSION...

GULF OF MEXICO...
A WEAK UPPER LEVEL TROUGH MOVES ACROSS THE ERN GULF ON WATER
VAPOR IMAGERY. DOPPLER RADAR IMAGERY SHOWS THIS UPPER FEATURE IS
GENERATING CLUSTERS OF SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS OVER THE WRN COASTAL WATERS OF THE FLORIDA
PENINSULA AND STRAITS E OF 84W S OF 28N. SHORT RAGE COMPUTER
MODELS KEEP THE CONVECTION IN THIS REGION DURING THE NEXT 12
HOURS...DRIFTING N ACROSS THE FLORIDA PANHANDLE OVER THE NEXT
12-24 HOURS. A SURFACE TROUGH IS ANALYZED OVER THE NW BASIN FROM
NEAR THE COAST OF TEXAS AT 27N96W TO 22N94W...PRODUCING SIMILAR
CONVECTION W OF 90W FROM 24W-28W. THE SURFACE TROUGH IS EXPECTED
TO DRIFT WNW AND WILL EVENTUALLY BE ABSORBED BY A FRONTAL
BOUNDARY THAT WILL REACH THE NW BASIN OVER THE NEXT 24 HOURS.
MOIST CONDITIONS AND BROAD SURFACE TROUGHING WILL REMAIN ACROSS
THE BASIN DURING THE FORECAST PERIOD.

CARIBBEAN SEA...
A TROPICAL WAVE AND ASSOCIATED LOW PRESSURE SYSTEM LOCATED E OF
THE LESSER ANTILLES IS GENERATING SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS OVER THE ERN CARIBBEAN ISLANDS FROM GUADELOUPE S
TO GRENADA. THIS AREA OF MODERATE TO STRONG CONVECTION WILL
SLOWLY MOVE NNW ACROSS THE NRN LEEWARD ISLANDS AND ADJACENT
WATERS DURING THE NEXT 24 HOURS. THE REMAINDER OF THE DISCUSSION
AREA IS UNDER FAIR WEATHER CONDITIONS RELATED TO DRY AIR ALOFT
AROUND AN UPPER LEVEL RIDGE CENTERED IN THE NW CARIBBEAN...AND A
DRY INVERTED UPPER TROUGH MOVING ACROSS THE CENTRAL CARIBBEAN.
THE ENVIRONMENT ALOFT IS SUPPRESSING DEEP CONVECTION AND ONLY
ALLOWING FOR A FEW ISOLATED SHOWERS OVER THE COASTAL WATERS OF
HONDURAS...NICARAGUA...AND PANAMA. THE SHOWER ACTIVITY IN THESE
AREAS ARE RELATED TO THE ERN PACIFIC MONSOON TROUGH EXTENDING
ACROSS COSTA RICA TO NRN COLOMBIA.

ATLANTIC OCEAN...
A WEAK UPPER LEVEL TROUGH MOVING ACROSS THE ERN GULF OF MEXICO
IS GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS W OF
THE NW BAHAMAS TO OVER THE FLORIDA PENINSULA AND STRAITS S OF
27N W OF 78W...EXPECTED TO LINGER AROUND THE SAME REGION DURING
THE NEXT 24 HOURS. AN UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR
IMAGERY MOVING ACROSS THE WRN ATLANTIC ALONG 60W N OF THE
DISCUSSION AREA. THIS FEATURE SUPPORTS A COLD FRONT EXTENDING
INTO OUR AREA AS A SURFACE TROUGH ALONG 30N60W 24N65W TO THE SE
BAHAMAS NEAR 21N73W. HOWEVER...THIS BOUNDARY IS MOSTLY EMBEDDED
WITH DRY AIR KEEPING SHOWER ACTIVITY AT A MINIMUM. CURRENTLY...
ISOLATED WEAK SHOWERS ARE NOTED WITHIN 60 NM ON EITHER SIDE OF
THE AXIS. THIS BOUNDARY IS EXPECTED TO WEAKEN AND DISSIPATE
DURING THE NEXT 24 HOURS...AS HIGH PRESSURE BUILDS IN ITS WAKE
THROUGH TUESDAY. TROPICAL STORM NADINE IS OVER THE CENTRAL ATLC.
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 1018 MB HIGH NEAR
25N30W. THE OVERALL FAIR WEATHER IS ENHANCED ALOFT BY THICK
LAYER OF SAHARAN DUST NOTED ON METEOSAT-9 SAL PRODUCT E OF 40W.

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

$$

GARCIA




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