000 AXNT20 KNHC 292352 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN JUL 29 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES ALONG 21N56W TO 9N58W MOVING W NEAR 20 KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES THAT THE WAVE LIES WITHIN A SURGE OF DEEP LAYER MOISTURE WITH MAXIMUM VALUES NEAR THE AXIS. SURFACE OBSERVATIONS ALSO INDICATE LOW LEVEL CYCLONIC FLOW IS AROUND THE WAVE AXIS. CURRENTLY ISOLATED MODERATE CONVECTION IS FROM 13N-20N BETWEEN 52W-57W. SIMILAR ACTIVITY IS FROM 12N-17N BETWEEN 57W-61W. TROPICAL WAVE IS MOVING W THROUGH THE CENTRAL CARIBBEAN ALONG 19N73W TO 11N74W AT 20 KT. THE WAVE IS MOVING THROUGH A VERY DRY ENVIRONMENT EVEN UNDER THE E SIDE OF AN UPPER LEVEL TROUGH OVER THE WESTERN HALF OF THE CARIBBEAN. TOTAL PRECIPITABLE WATER DOES GIVE SOME INDICATION THAT THE WAVE IS PRESENT DUE TO ENHANCED MOISTURE VALUES OVER THE EXTREME SRN CARIBBEAN AS WELL AS MODERATE VALUES NEAR THE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OVER HISPANIOLA FROM 18N-20N BETWEEN 70W-73W. THIS ACTIVITY MAY BE MORE ASSOCIATED WITH DAYTIME HEATING THAN THE ACTUAL WAVE. A LARGE CLUSTER OF STRONG CONVECTION IS INLAND OVER COLOMBIA FROM 9N-11N BETWEEN 73W-76W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF GUINEA BISSAU AT 12N16W CONTINUING ACROSS ATLC WATERS THROUGH A 1009 MB SURFACE LOW AT 9N32W TO 8N41W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-12N BETWEEN 16W-24W. SIMILAR ACTIVITY IS NEAR THE SURFACE LOW FROM 7N-10N BETWEEN 31W-41W. ...DISCUSSION... GULF OF MEXICO... STRONG SHOWERS/THUNDERSTORMS COVER NRN FLORIDA ASSOCIATED WITH AN UPPER LEVEL TROUGH EXTENDING DOWN THE EASTERN SEABOARD AND ALONG THE NRN GULF COAST. THE UPPER TROUGH SUPPORTS A SURFACE TROUGH FROM 31N83W TO 27N87W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE NEAR THE WESTERNMOST POINT OF THE TROUGH FROM 24N-27N BETWEEN 88W-91W. THE REMAINDER OF THE BASIN IS INFLUENCED BY WEAK SURFACE RIDGING AROUND A 1020 MB HIGH NEAR 26N90W. THE HIGH IS SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED OVER THE CENTRAL UNITED STATES. A PAIR OF UPPER LEVELS LOWS IS ACROSS THE SOUTHERN GULF WITH ONE CENTERED OVER THE MEXICAN COAST NEAR 23N98W AND THE SECOND OVER THE FLORIDA STRAITS NEAR 24N81W. THE WESTERN UPPER LOW IS SUPPORTING ISOLATED SHOWERS AND THUNDERSTORMS OVER THE SW GULF AND BAY OF CAMPECHE. THE SE GULF LIES UNDERNEATH THE WESTERN SIDE OF THE SECOND UPPER LOW...AND THUS IS MOSTLY CLEAR. EXPECT WEAK SURFACE RIDGING TO REMAIN ACROSS THE BASIN FOR THE NEXT SEVERAL DAYS. SHOWERS AND THUNDERSTORMS WILL LIKELY REMAIN OVER THE NE CORNER. CARIBBEAN SEA... THE CARIBBEAN WATERS REMAIN MOSTLY DRY THIS EVENING DESPITE THE PRESENCE OF A TROPICAL WAVE IN THE CENTRAL CARIBBEAN. DRY AIR ALOFT IS SUPPRESSING MOST OF THE ACTIVITY ALONG WITH SAHARAN DUST THAT IS BEING REPORTED BY MANY SURFACE STATIONS. HOWEVER...OVER LAND...MANY AREAS ARE EXPERIENCING SHOWERS AND THUNDERSTORMS. SHOWERS/THUNDERSTORMS ARE CURRENTLY OVER CUBA AND HISPANIOLA TIED TO A BROAD UPPER LEVEL LOW CENTERED OVER THE FLORIDA STRAITS. THE ACTIVITY OVER HISPANIOLA MAY ALSO BE INFLUENCED BY THE TROPICAL WAVE. STRONG SHOWERS/THUNDERSTORMS ARE ALSO OVER PORTIONS OF COSTA RICA AND PANAMA WITH MORE SCATTERED ACTIVITY OVER THE REST OF CENTRAL AMERICA. THE EASTERN CARIBBEAN IS COVERED BY UPPER LEVEL RIDGING EXTENDING FROM THE TROPICAL ATLC. SHOWERS/THUNDERSTORMS ARE BEGINNING TO IMPACT THE LESSER ANTILLES AHEAD OF ANOTHER TROPICAL WAVE STILL E OF THE ISLANDS. THIS ACTIVITY WILL LIKELY CONTINUE UNTIL AFTER THE WAVE PASSES. EXPECT LITTLE CHANGE ELSEWHERE. ATLANTIC OCEAN... SHOWERS/THUNDERSTORMS ASSOCIATED WITH AN UPPER LEVEL TROUGH EXTENDING DOWN THE EASTERN SEABOARD ARE JUST N OF THE DISCUSSION AREA IN THE W ATLC. WEAK SURFACE RIDGING AROUND A 1021 MB HIGH NEAR 28N71W...AND A 1023 MB HIGH NEAR 31N56W COVERS THE REMAINDER OF THE W ATLC PROVIDING MOSTLY FAIR CONDITIONS. HOWEVER...AN UPPER LEVEL LOW CENTERED NEAR 26N66W IS SUPPORTING A SURFACE TROUGH FROM 27N64W TO 23N67W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE W OF THE AXIS FROM 24N-27N BETWEEN 65W-68W. ANOTHER UPPER LEVEL LOW IS CENTERED OVER THE FLORIDA STRAITS...BUT IS NOT CAUSING ANY SIGNIFICANT WEATHER OVER THE BASIN. FARTHER E...A THIRD UPPER LEVEL LOW CENTERED NEAR 28N42W IS SUPPORTING A SURFACE LOW STILL N OF THE DISCUSSION AREA...AND POSSIBLE ISOLATED SHOWERS TO THE S FROM 26N-30N BETWEEN 43W-48W. THE REMAINDER OF THE EASTERN ATLC IS DOMINATED BY SURFACE RIDGING AROUND A 1024 MB AZORES HIGH THAT IS PROVIDING FAIR CONDITIONS ACROSS MUCH OF THE AREA. IT IS SUPPORTED BY THE LARGE UPPER LEVEL RIDGE THAT COVERS MUCH OF THE BASIN CENTERED NEAR 38N51W. SATELLITE IMAGERY CONTINUES TO SHOW A LARGE AREA OF SAHARAN DUST THAT EXTENDS FROM THE COAST OF AFRICA TO NEAR 50W...WHICH FURTHER SUPPORTS FAIR WEATHER. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON