000 AXNT20 KNHC 092342 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON JUL 09 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 ALONG 20N27W TO 12N25W MOVING W NEAR 10 KT. THE WAVE LIES WITHIN A LARGE SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. THERE IS ALSO A CLEARING IN THE LARGE AREA OF SAHARAN DUST AROUND THE WAVE INDICATING ITS PRESENCE. ISOLATED MODERATE CONVECTION IS EMBEDDED WITHIN THE MONSOON TROUGH FROM 10N-12N BETWEEN 24W-27W. TROPICAL WAVE IS ALONG 25N63W TO 17N66W MOVING W NEAR 15 KT. THE WAVE IS WITHIN AN AREA OF ENHANCED MOISTURE. THE WAVE ALSO LIES ON THE LEADING EDGE OF A LARGE AREA OF SAHARAN DUST THAT EXTENDS ACROSS MUCH OF THE TROPICAL ATLC. THE DUST IS SUPPRESSING MOST CONVECTION NEAR THE WAVE. IT ALSO IS WITHIN AN UPPER LEVEL RIDGE WITH UPPER TROUGHS/CUT-OFF LOWS ON EITHER SIDE. ISOLATED WEAK CONVECTION IS IN THE VICINITY OF THE WAVE...BUT IS LIKELY DUE TO THE UPPER TROUGHS/LOWS AND NOT THE WAVE ITSELF. TROPICAL WAVE IS MOVING INLAND INTO ERN MEXICO ALONG 21N96W TO 15N97W MOVING W AT 12-15 KT. THERE ARE STILL ENHANCED MOISTURE VALUES NEAR THE WAVE AND ACROSS THE WRN BAY OF CAMPECHE. A LARGE BURST OF CONVECTION THAT FLARED UP EARLIER TODAY HAS MOSTLY DISSIPATED WITH ONLY SCATTERED MODERATE CONVECTION FROM 19N-21N BETWEEN 93W-97W. THERE IS ALSO ISOLATED MODERATE/STRONG CONVECTION ELSEWHERE ACROSS SRN MEXICO AND THE YUCATAN PENINSULA...BUT IT IS HARD TO SAY WHETHER IT CAN BE ATTRIBUTED TO THE WAVE OR JUST TYPICALLY AFTERNOON CONVECTION. SIMILAR ACTIVITY HAS BEEN PRESENT OVER THESE AREAS FOR SEVERAL DAYS...SO IT SEEMS TO BE MOSTLY THE RESULT OF DAYTIME HEATING AND INSTABILITY AND NOT THE WAVE. THERE IS ALSO THE INFLUENCE OF AN UPPER LEVEL TROUGH THAT CAN ALSO BE ENHANCING SOME OF THE ACTIVITY. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF GUINEA-BISSAU AT 12N17W TO 11N30W. THE ITCZ BEGINS AT 11N30W CONTINUING ALONG 7N42W 4N52W. A CLUSTER OF STRONG CONVECTION IS MOVING OFF THE COAST OF AFRICA FROM 9N-14N BETWEEN 13W-18W. ISOLATED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 13W-22W...AND WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 31W-52W. ...DISCUSSION... GULF OF MEXICO... WEAK SURFACE RIDGING IS ACROSS THE GULF OF MEXICO AROUND A 1018 MB HIGH CENTERED NEAR 26N88W. LIGHT ANTI-CYCLONIC FLOW IS AROUND THE SURFACE RIDGE WITH STRONGER WINDS IN THE SW GULF NEAR A TROPICAL WAVE MOVING INTO MEXICO. SEE TROPICAL WAVE SECTION ABOVE FOR MORE DETAILS. DRY AIR ALOFT IS KEEPING A GOOD PORTION OF THE BASIN UNDER MOSTLY FAIR CONDITIONS EXCEPT FOR AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE NRN GULF FROM 27N-29N BETWEEN 88W-95W. SIMILAR ACTIVITY IS ACROSS INLAND PORTIONS OF THE GULF COAST INCLUDING CENTRAL WRN FLORIDA....SRN ALABAMA AND ERN TEXAS WITH ISOLATED ACTIVITY ACROSS MUCH OF THE OTHER STATES. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO OVER THE YUCATAN PENINSULA AND CUBA. THE ACTIVITY ACROSS THE NRN GULF CAN BE TIED TO A MID-LEVEL TROUGH OVER LOUISIANA. THE ACTIVITY ACROSS THE YUCATAN...CUBA AND FLORIDA IS ASSOCIATED WITH DIFFLUENCE ALOFT AROUND AN UPPER LEVEL TROUGH/LOW EXTENDING FROM THE FLORIDA PANHANDLE TO A CUT-OFF UPPER LOW AT 25N85W WHERE IT THEN EXTENDS AN AXIS TO THE W TO THE BAY OF CAMPECHE NEAR 22N97W. ANOTHER UPPER TROUGH AXIS EXTENDS TOWARDS THE E TO CONNECT WITH ANOTHER CUT-OFF LOW IN THE W ATLC. WEAK SURFACE RIDGING WILL REMAIN ACROSS THE BASIN FOR THE NEXT 24 HOURS BEFORE A SURFACE TROUGH FORMS NEAR THE YUCATAN PENINSULA AND DRAWS MOISTURE ACROSS THE ERN GULF. CARIBBEAN SEA... SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS MUCH OF CUBA ALONG WITH PORTIONS OF JAMAICA...THE CAYMAN ISLANDS...AND HISPANIOLA. THIS ACTIVITY IS DUE TO THE COMBINATION OF DAYTIME HEATING AS WELL AS THE INFLUENCE OF AN ELONGATED UPPER TROUGH WITH A SERIES OF CUT-OFF UPPER LOWS THAT EXTENDS FROM THE CENTRAL ATLC INTO THE W ATLC CONTINUING N OF CUBA INTO THE ERN GULF. A TROPICAL WAVE MOVING THROUGH PUERTO RICO IS ONLY CAUSING A FEW SHOWERS/THUNDERSTORMS OVER THE ISLAND. A WEAK UPPER TROUGH HAS ALSO FORMED ACROSS THE CENTRAL CARIBBEAN BETWEEN TWO UPPER LEVEL RIDGES TO EITHER SIDE ACROSS BOTH THE WRN AND ERN CARIBBEAN. STRONG AND NUMEROUS SHOWERS/THUNDERSTORMS COVER MOST OF PANAMA AND PORTIONS OF NRN COLOMBIA ASSOCIATED WITH THE E PACIFIC MONSOON TROUGH EXTENDING S OF PANAMA TO A 1007 MB LOW OVER NRN COLOMBIA. THE CENTRAL AND ERN CARIBBEAN ARE EXPERIENCING MOSTLY FAIR CONDITIONS DUE TO DRY AIR ALOFT AROUND THE UPPER RIDGE IN THE ERN CARIBBEAN. TRADEWIND FLOW OF 15-20 KT IS PRESENT ACROSS MUCH OF THE BASIN REACHING UP TO 25 KT NEAR THE COAST OF COLOMBIA. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS. ATLANTIC OCEAN... A BROAD UPPER LEVEL RIDGE IS COVERING A PORTION OF THE W ATLC NEAR THE NRN EXTENT OF THE DISCUSSION AREA SUPPORTING WEAK SURFACE RIDGING EXTENDING FROM THE CENTRAL ATLC. AN ELONGATED UPPER TROUGH WITH SEVERAL CUT-OFF LOWS EXTENDS S OF THE RIDGE BEGINNING IN THE CENTRAL ATLC NEAR 31N33W TO AN UPPER LOW AT 29N47W TO A SECOND UPPER LOW NEAR 26N68W AND TO A THIRD UPPER LOW IN THE SE GULF OF MEXICO. THIS SERIES OF LOWS IS PRODUCING ISOLATED SHOWER/THUNDERSTORM ACTIVITY ACROSS THE WRN BAHAMAS...NEAR THE TROPICAL WAVE FROM 21N-26N BETWEEN 64W-69W...AND FROM 24N-26N BETWEEN 53W-59W. UPPER LEVEL RIDGING COVERS THE REMAINDER OF THE BASIN FROM THE TROPICAL ATLC NEAR 10N45W TO NW AFRICA. AT THE SURFACE....BROAD SURFACE RIDGING DOMINATES ANCHORED BY A 1030 MB AZORES HIGH. SATELLITE IMAGERY CONTINUES TO SHOW A LARGE AREA OF AFRICAN DUST COVERING MUCH OF THE TROPICAL ATLC BETWEEN THE TROPICAL WAVES. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON