[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED JUL 18 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.

...TROPICAL WAVES...

TROPICAL WAVE MOVES ACROSS THE ERN TROPICAL ATLC WITH AXIS
ANALYZED FROM 19N29W TO THE MONSOON TROUGH AXIS NEAR 13N28W.
LIMITED MOISTURE SURROUNDS THE WAVE AXIS ON TOTAL PRECIPITABLE
WATER IMAGERY...AS A LAYER OF DRY/SAHARAN AIR CONTINUES TO
OVERTAKE THE WAVE. THEREFORE...ANY CONVECTIVE ACTIVITY IS
CONFINED TO THE EXTREME SRN PORTION OF THE WAVE AXIS ATTACHED TO
THE MONSOON TROUGH.

TROPICAL WAVE IS HEADING TOWARDS THE LESSER ANTILLES WITH AXIS
EXTENDING FROM 19N55W TO 11N54W MOVING W AT 15-20 KT. THE WAVE
PRECEDES A NARROW SURGE OF MOISTURE NOTED ON TOTAL PRECIPITABLE
WATER IMAGERY WITH LIMITED SHOWER ACTIVITY DUE TO SAHARAN DUST
AROUND THE WAVE AXIS.

TROPICAL WAVE IS IMPACTING THE ERN COASTAL WATERS AND INLAND
PORTIONS OF THE YUCATAN PENINSULA WITH AXIS EXTENDING FROM
23N84W TO 16N85W MOVING W AT ABOUT 15 KT. SCATTERED SHOWERS AND
THUNDERSTORMS W OF 85W TO INLAND ACROSS THE YUCATAN PENINSULA.
THE SHOWER ACTIVITY IS ENHANCED BY A WEAK UPPER LEVEL CYCLONIC
CIRCULATION MOVING ACROSS THE NRN YUCATAN PENINSULA.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS INLAND ACROSS WEST AFRICA...PASSING
THROUGH DAKAR SENEGAL TO 12N21W 12N30W 11N36W TO 8N43W...WHERE
THE ITCZ CONTINUES ALONG 9N50W TO THE COAST OF GUYANA NEAR
8N58W. SCATTERED MODERATE CONVECTION IS FROM 8N-12N BETWEEN
30W-40W AND FROM 7N-12N BETWEEN 22W-28W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL CYCLONIC CIRCULATION CENTERED OVER ERN GEORGIA
CONTINUES TO DOMINATE THE NE GULF WATERS THIS AFTERNOON. THIS
FEATURE SUPPORTS A SURFACE TROUGH EXTENDING ACROSS THE SE CONUS
INTO THE GULF BASIN ALONG 30N83W TO 27N84W. THIS SYSTEM IS
GENERATING SCATTERED SHOWERS AND THUNDERSTORMS N OF 27N E OF
90W. SIMILAR CONVECTION IS FOUND OVER THE WRN GULF COAST W OF
94W N OF VERACRUZ MEXICO. THE ACTIVITY IN THIS REGION IS
ASSOCIATED TO AN UPPER LEVEL LOW SPINNING OVER THE NRN MEXICO
REGION. RELATIVELY STABLE CONDITIONS ARE ELSEWHERE ACROSS THE
AREA THIS AFTERNOON. AS THE UPPER LOW OVER THE SE CONUS DRIFTS
NNE...SHORT RANGE COMPUTER MODELS SUGGEST THE RAIN ACTIVITY OVER
THE NE GULF WILL SLOWLY MOVE N DURING THE NEXT 24 HOURS. FAIR
WEATHER IS EXPECTED TO REMAIN CONSTANT ACROSS THE REMAINDER OF
THE GULF DURING THE FORECAST PERIOD.

CARIBBEAN SEA...
THE TWO MAIN AREAS OF ACTIVE WEATHER ARE FOUND OVER THE FAR NW
AND SW CORNERS OF THE BASIN THIS AFTERNOON. A TROPICAL WAVE IS
APPROACHING THE ERN COAST OF THE YUCATAN PENINSULA WITH
SCATTERED SHOWERS AND THUNDERSTORMS W OF 85W TO INLAND ACROSS
THE YUCATAN PENINSULA. THE SHOWER ACTIVITY IS ENHANCED BY A WEAK
UPPER LEVEL CYCLONIC CIRCULATION MOVING ACROSS THE NRN YUCATAN
PENINSULA...PROVIDING FURTHER LIFTING AND INSTABILITY ACROSS
THIS AREA. SIMILAR CONVECTION IS S OF 11N W OF 77W ASSOCIATED TO
THE MONSOON TROUGH AXIS EXTENDING ACROSS NRN COLOMBIA TO THE SRN
COASTAL WATERS OF PANAMA AND WRN COSTA RICA. THE REMAINDER OF
THE DISCUSSION AREA IS UNDER FAIR WEATHER ASSOCIATED TO AN
ELONGATED UPPER LEVEL CYCLONIC CIRCULATION CENTERED NE OF PUERTO
RICO NEAR 21N64W. MODERATE TO FRESH EASTERLY TRADE WINDS ARE
OBSERVED ACROSS THE AREA WITH SOME STRONGER WINDS GUSTING TO
NEAR GALE FORCE CRITERIA OVER THE NRN COASTAL WATERS OF COLOMBIA.

ATLANTIC OCEAN...
THE UPPER LEVEL LOW CONTINUES TO WOBBLE OVER THE SE CONUS THIS
AFTERNOON...NOW CENTERED OVER ERN GEORGIA. HOWEVER...THE SHOWER
AND THUNDERSTORM ACTIVITY OVER THE WRN ATLC HAVE DECREASED
CONSIDERABLY COMPARED TO 24 HOURS AGO. ONLY A FEW ISOLATED
SHOWERS AND THUNDERSTORMS ARE OBSERVED N OF 27N BETWEEN 76W-79W.
AN UPPER LEVEL ANTI-CYCLONE CENTERED W OF BERMUDA CONTINUES TO
SUPPORT A WEAKENING 1024 MB HIGH AROUND 29N67W. HOWEVER...AN
ELONGATED UPPER LEVEL CYCLONIC CIRCULATION CENTERED NE OF PUERTO
RICO NEAR 21N64W IS GENERATING SCATTERED SHOWERS AND POSSIBLE
ISOLATED THUNDERSTORMS WITHIN 72 NM ON EITHER SIDE OF A LINE
EXTENDING FROM 30N58W TO 20N68W. OTHERWISE...A LARGE AREA OF
HIGH PRESSURE DOMINATES THE REMAINDER OF THE ATLC DISCUSSION
AREA ANCHORED BY A 1030 MB HIGH CENTERED WSW OF THE AZORES
ISLANDS NEAR 37N31W. THE WEATHER IN THIS REGION IS FURTHER
ENHANCED BY A LAYER SAHARAN DUST ALOFT NOTED ON METEOSAT-9 E OF
55W. WHILE SOME CONVECTION FROM THE NE GULF IS EXPECTED TO MOVE
OVER THE WRN ATLC DURING THE AFTERNOON AND EVENING HOURS OF
TODAY... THE OVERALL WEATHER PATTERN IS EXPECTED TO FURTHER
IMPROVE OVER THE NEXT 24 HOURS...AS THE UPPER LOW SLOWLY LIFTS
NNE AND A SURFACE RIDGE AXIS REBUILDS ACROSS THE WRN ATLC.

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

$$

GARCIA




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