000 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