000 AXNT20 KNHC 202333 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI JUL 20 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 2245 UTC. ...TROPICAL WAVES... TROPICAL WAVE APPEARS TO HAVE LEFT THE COAST OF AFRICA AND WILL LIKELY BE ADDED TO THE 0000 UTC SURFACE ANALYSIS. TROPICAL WAVE IS ALONG 18N49W TO 8N53W MOVING W NEAR 20 KT. WAVE COINCIDES WITH THE MAXIMUM MOISTURE VALUES SEEN IN A BROAD SURGE OF MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. A LARGE AREA OF DUST TO THE N OF THE WAVE IS DAMPENING ANY DEEP CONVECTION NEAR THE AXIS EXCEPT FOR A SMALL AREA OF ISOLATED MODERATE CONVECTION W OF THE AXIS FROM 9N-11N BETWEEN 53W-56W. TROPICAL WAVE IS MOVING THROUGH THE N CENTRAL CARIBBEAN ALONG 23N80W TO 14N75W MOVING W NEAR 20-25 KT. THE WAVE LIES ON THE W SIDE OF A TILTED SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY...WHICH EXPLAINS THE TILT OF THE WAVE. THE WAVE IS ALSO INTERACTING WITH A BROAD UPPER LEVEL LOW OVER THE NW CARIBBEAN CENTERED S OF CUBA NEAR 20N82W. THE COMBINATION OF THE WAVE AND DIFFLUENCE ALOFT AROUND THE UPPER LOW IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 16N-19N BETWEEN 75W-80W. SIMILAR ACTIVITY COVERS HISPANIOLA FROM 18N-20N BETWEEN 67W-73W. LARGE CLUSTERS OF STRONG CONVECTION ARE ALSO OVER CUBA FROM 20N-21N BETWEEN 76W-79W...AND FROM 22N-23N BETWEEN 80W-86W. IT IS HARD TO SAY WHETHER THE ACTIVITY IS MORE ASSOCIATED WITH THE UPPER LOW OR THE WAVE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM A 1007 MB LOW OVER AFRICA NEAR 24N14W TO 11N22W 6N32W. THE ITCZ BEGINS AT 6N32W AND CONTINUES ALONG 5N42W 8N51W. SCATTERED MODERATE CONVECTION IS FROM 8N-11N BETWEEN 13W-23W. ...DISCUSSION... GULF OF MEXICO... DESPITE SURFACE RIDGING AROUND A 1021 MB SURFACE HIGH NEAR 26N94W...THE NRN GULF OF MEXICO IS IMPACTED BY AN AREA OF STRONG SHOWERS/THUNDERSTORMS. THE STORMS ARE SUPPORTED BY AN UPPER LEVEL SHORTWAVE TROUGH THAT PARALLELS THE NRN GULF COASTLINE. THE TROUGH SUPPORTS A SURFACE TROUGH ALONG 31N89W TO 27N92W. THE COMBINATION OF THE UPPER AND LOWER TROUGHS IS SUPPORTING A LARGE AREA OF STRONG SHOWERS/THUNDERSTORMS FROM 28N-31N BETWEEN 89W-93W...COVERING MUCH OF SRN LOUISIANA. ISOLATED SHOWERS/THUNDERSTORMS CONTINUE N OF 26N BETWEEN 84W-94W. THE REMAINDER OF THE BASIN IS FAIRLY DRY SUPPORTED BY DRY AIR ALOFT WRAPPING AROUND AN UPPER LEVEL RIDGE COVERING THE MAJORITY OF THE BASIN. HOWEVER...AN UPPER LEVEL LOW OVER SRN MEXICO NEAR 18N94W...AND A BROAD UPPER LOW OVER THE NW CARIBBEAN ARE SUPPORTING STRONG SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN PENINSULA AND CUBA WITH ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE SE GULF AND EXTREME SW GULF. LIGHT ANTI-CYCLONIC SURFACE WINDS AROUND THE SURFACE HIGH...EXCEPT NEAR THE THUNDERSTORMS IN THE NRN GULF WHERE WIND SPEEDS WILL BE HIGHER. SURFACE RIDGING WILL REMAIN ACROSS THE BASIN WITH A WEAK SURFACE TROUGH ALONG THE NRN GULF. SHOWERS/THUNDERSTORMS WILL REMAIN ACROSS THE NRN GULF...AND WILL LIKELY INCREASE OVER THE SRN GULF AS MOISTURE ASSOCIATED WITH A TROPICAL WAVE IN THE CARIBBEAN APPROACHES THE GULF. CARIBBEAN SEA... TWO UPPER LEVEL LOWS CENTERED OVER SRN MEXICO AND THE NW CARIBBEAN NEAR 18N94W AND 20N82W RESPECTIVELY ARE HELPING PRODUCE CLUSTERS OF STRONG SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN PENINSULA...CUBA...AND HISPANIOLA. SOME OF THE STORMS ARE ALSO ENHANCED BY A TROPICAL WAVE EXTENDING FROM CENTRAL CUBA INTO THE CENTRAL CARIBBEAN. SEE TROPICAL WAVE SECTION ABOVE FOR MORE DETAILS. A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE YUCATAN CHANNEL AND JAMAICA. STRONG SHOWERS/THUNDERSTORMS COVER PORTIONS OF COSTA RICA AND PANAMA ASSOCIATED WITH THE E PACIFIC MONSOON TROUGH THAT EXTENDS THROUGH BOTH COUNTRIES TO A 1008 MB LOW OVER NRN COLOMBIA. THE REMAINDER OF THE BASIN IS EXPERIENCING MOSTLY FAIR WEATHER DUE TO DRY AIR ALOFT ACROSS THE S CENTRAL CARIBBEAN AND AROUND AN UPPER LEVEL RIDGE COVERING THE ERN CARIBBEAN. A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE NOTED OVER THE NRN LESSER ANTILLES DUE TO SOME MOISTURE DRAGGED AHEAD OF THE NEXT TROPICAL WAVE STILL IN THE ERN ATLC. SOME DUST IS STILL PRESENT ACROSS MUCH OF THE BASIN EVIDENT IN SATELLITE IMAGERY AND SURFACE OBSERVATIONS. EXPECT MOIST CONDITIONS TO REMAIN OVER THE NRN CARIBBEAN AS THE TROPICAL WAVE MOVES WWD. DUSTY CONDITIONS WILL TRAIL BEHIND THE WAVE. ATLANTIC OCEAN... FAIR CONDITIONS ARE ACROSS THE WRN AND CENTRAL ATLC DUE TO DRY AIR ALOFT AROUND A PAIR OF UPPER LEVEL RIDGES CENTERED NEAR 36N67W AND 25N57W THAT SUPPORT A SURFACE RIDGE ANCHORED BY A 1027 MB HIGH NEAR 32N48W. A FEW SHOWERS/THUNDERSTORMS ACROSS HISPANIOLA ARE MOVING TO THE N NEAR THE SE BAHAMAS. THE SAME HIGH CENTER ALONG WITH A 1024 MB AZORES HIGH ARE PROVIDING THE ERN ATLC WITH FAIR WEATHER AS WELL. THE AZORES HIGH IS SUPPORTED BY ANOTHER UPPER LEVEL RIDGE CENTERED NEAR 41N31W. AN UPPER HIGH ALSO COVERS THE ERN TRPCL ATLC CENTERED NEAR THE CAPE VERDE ISLANDS. AN UPPER LEVEL TROUGH IS ALONG 42W SANDWICHED BETWEEN THE RIDGE OVER THE CENTRAL ATLC AND THE CAPE VERDE RIDGE...BUT IS NOT CAUSING ANY SIGNIFICANT WEATHER. SATELLITE IMAGERY CONTINUES TO SHOW A LARGE AREA OF AFRICAN DUST EXTENDING ALL THE WAY FROM THE COAST OF AFRICA TO N OF THE CENTRAL CARIBBEAN...WHICH IS FURTHER SUPPORTING THE FAIR SURFACE CONDITIONS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON