[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU AUG 18 2011

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 1715 UTC.

...SPECIAL FEATURE...
AN ACTIVE TROPICAL WAVE IS MOVING THROUGH THE WRN CARIBBEAN
ALONG 19N82W 15N80W 11N80W MOVING W NEAR 13 KT. THERE IS A
WELL-DEFINED MID-LEVEL CIRCULATION JUST E OF THE WAVE AXIS AT
16N. THE SYSTEM IS BECOMING MORE ORGANIZED AND SURFACE PRESSURES
HAVE BEEN DROPPING INDICATING THAT A SURFACE CIRCULATION MAY BE
FORMING. CURRENTLY NUMEROUS MODERATE/SCATTERED STRONG CONVECTION
IS FROM 15N-18N BETWEEN 78W-81W WITH SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 11N-14N BETWEEN 82W-84W. INTERESTS IN THE
NRN CENTRAL AMERICA AND YUCATAN PENINSULA COASTS SHOULD MONITOR
THIS SYSTEM.

...TROPICAL WAVES...

WELL DEFINED TROPICAL WAVE IS ACROSS THE CENTRAL TRPCL ATLC
ALONG 17N39W TO THE MONSOON TROUGH NEAR 13N39W MOVING W 10-15
KT. SATELLITE IMAGERY SHOWS DISTINGUISHABLE LOW-LEVEL CYCLONIC
FLOW AROUND THE WAVE AXIS CONCENTRATED AT THE INTERSECTION WITH
THE MONSOON TROUGH. THE WAVE IS EMBEDDED WITHIN A SURGE OF DEEP
LAYER MOISTURE EXTENDING TO 20N. SCATTERED MODERATE/STRONG
CONVECTION IS FROM 13N-17N BETWEEN 39W-43W.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 20N16W
ALONG 13N28W TO S OF A TROPICAL WAVE NEAR 13N39W TO 9N47W. THE
ITCZ CONTINUES FROM 9N47W TO 9N62W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 7N-15N BETWEEN 13W-20W. SIMILAR
ACTIVITY IS FROM 8N-12N BETWEEN 20W-24W...AND FROM 6N-9N BETWEEN
32W-46W.

...DISCUSSION...

THE GULF OF MEXICO...
UPPER LEVEL RIDGING COVERS MUCH OF THE GULF OF MEXICO CENTERED
OVER NW TEXAS. WATER VAPOR IMAGERY ALSO INDICATES MOSTLY DRY AIR
ALOFT COVERING THE AREA. THIS IS MAINTAINING MOSTLY FAIR WEATHER
AND LIGHT SURFACE FLOW. WEAK SURFACE RIDGING COVERS THE WRN GULF
CENTERED AROUND A 1016 MB HIGH NEAR 26N95W. A WEAK SURFACE
TROUGH COVERS THE ERN AND CENTRAL GULF WITH AXIS ALONG 29N84W
27N88W TO 25N91W. SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE NE
GULF NEAR THE TROUGH AXIS FROM 27N-30N BETWEEN 83W-85W. SIMILAR
ACTIVITY IS BETWEEN THE TROUGH AND THE HIGH PRESSURE CENTER FROM
23N-28N BETWEEN 91W-94W. ISOLATED SHOWERS ARE ALSO OVER THE SE
GULF S OF 27N E OF 97W. EXPECT WEAK SURFACE FLOW TO REMAIN
ACROSS THE BASIN WITH THE SURFACE RIDGE DISSIPATING.

THE CARIBBEAN SEA...
AN ACTIVE TROPICAL WAVE IS IMPACTING THE WRN CARIBBEAN. SEE
SPECIAL FEATURES ABOVE FOR MORE DETAILS. BESIDES THE CONVECTION
ASSOCIATED WITH THE WAVE...A FEW CLUSTERS OF
SHOWERS/THUNDERSTORMS ARE OVER WRN CUBA FROM 21N-23N BETWEEN
81W-84W...AND ACROSS JAMAICA FROM 17N-20N BETWEEN 75W-78W. A
CLUSTER IS ALSO IN THE FAR SW CARIBBEAN N OF PANAMA AND W OF
COLOMBIA FROM 9N-11N BETWEEN 76W-78W. ALOFT...AN UPPER LEVEL
RIDGE COVERS THE WRN CARIBBEAN CENTERED S OF WRN CUBA. THE ERN
CARIBBEAN IS UNDER MOSTLY FAIR CONDITIONS WITH MODERATE DRY AIR
ALOFT. A FEW ISOLATED SHOWERS ARE EMBEDDED WITHIN THE TRADEWIND
FLOW. EXPECT THE TROPICAL WAVE TO CONTINUE TO MOVE WWD OVER THE
NEXT 24 HOURS WITH POSSIBLE IMPACTS TO NRN CENTRAL AMERICA.

THE ATLANTIC OCEAN...
A LARGE AREA OF SCATTERED SHOWERS/THUNDERSTORMS IS OVER THE WRN
ATLC W OF 75W ACROSS THE NW BAHAMAS ASSOCIATED WITH A DEEP LAYER
TROUGH EXTENDING DOWN 75W. THE UPPER TROUGH SUPPORTS A
STATIONARY FRONT THAT EXTENDS SLIGHTLY INTO THE DISCUSSION AREA
ALONG 32N78W TO 29N80W. FARTHER E...AN UPPER LEVEL LOW IS
SPINNING NEAR 25N57W SUPPORTING ISOLATED SHOWERS FROM 25N-31N
BETWEEN 54W-61W. AN AREA OF ISOLATED SHOWERS/THUNDERSTORMS IS
ALSO E OF THE LESSER ANTILLES FROM 10N-16N BETWEEN 56W-61W
ASSOCIATED WITH AN AREA OF ENHANCED MOISTURE EVIDENT IN TOTAL
PRECIPITABLE WATER IMAGERY. THE REMAINDER OF THE BASIN IS
COVERED BY WEAK SURFACE RIDGING AROUND A PAIR OF 1025 MB HIGHS
NEAR THE AZORES ISLANDS PROVIDING MOSTLY FAIR WEATHER.
ALOFT...UPPER LEVEL RIDGING COVERS MUCH OF THE ERN ATLC WITH
CENTERS NEAR 23N41W AND 36N34W. A NARROW UPPER LEVEL TROUGH IS
OVER THE FAR ERN ATLC WITH AXIS FROM N OF THE MADEIRA ISLANDS TO
JUST SW OF THE CANARY ISLANDS. TWO AREAS OF AFRICAN DUST ARE
ACROSS THE ATLC BASIN. THE FIRST IS N OF THE TROPICAL WAVE IN
THE CENTRAL TRPCL ATLC AND E OF 55W. THE SECOND IS N OF THE ERN
CARIBBEAN BETWEEN 61W-70W.

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

$$
WALTON





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