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.