000 AXNT20 KNHC 312336 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE JUL 31 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 2300 UTC. ...SPECIAL FEATURES... A TROPICAL WAVE IS ALONG 16N40W TO A 1010 MB SURFACE LOW AT 10N41W. THE WAVE/LOW IS MOVING W AT ABOUT 10-15 KT. THE WAVE IS FAIRLY LOW AMPLITUDE ALIGNING WITH AN EQUALLY LOW AMPLITUDE SURGE IN TOTAL PRECIPITABLE WATER. HOWEVER...AN ANALYSIS OF THE SAHARAN AIR LAYER CONTINUES TO SHOW A CLEARING IN THE WIDESPREAD DUST NEAR THE WAVE AXIS INDICATING ITS PRESENCE. CONVECTION HAS INCREASED AROUND THE LOW CENTER FROM 24 HOURS AGO. CURRENTLY SCATTERED MODERATE/STRONG CONVECTION IS MAINLY W OF THE SYSTEM FROM 7N-11N BETWEEN 41W-46W. ENVIRONMENTAL CONDITIONS ARE CONDUCIVE FOR SLOW DEVELOPMENT OF THIS SYSTEM. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 17N21W TO A 1010 MB SURFACE LOW EMBEDDED IN THE MONSOON TROUGH AT 12N23W. THE WAVE/LOW IS MOVING W AT 10-15 KT. A CLEARING IN THE WIDESPREAD DUST TO THE N OF THE WAVE INDICATES THE PRESENCE OF THE WAVE. THERE IS ALSO A SMALL NORTHWARD SURGE IN THE DEEP LAYER MOISTURE INDICATED BY TOTAL PRECIPITABLE WATER IMAGERY. NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE. TROPICAL WAVE NEAR 40/41 W IS DESCRIBED IN THE SPECIAL FEATURES SECTION ABOVE. ACTIVE TROPICAL WAVE IS PUSHING INTO THE CENTRAL CARIBBEAN FROM 23N70W TO 10N72W MOVING W NEAR 15 KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES THAT THE WAVE LIES ON THE W SIDE OF A LARGE SURGE OF DEEP LAYER MOISTURE THAT COVERS THE EASTERN CARIBBEAN. THE WAVE LIES UNDERNEATH AN AREA OF DIFFLUENCE ALOFT THAT IS HELPING ENHANCE CONVECTION. CURRENTLY SCATTERED MODERATE CONVECTION IS FROM 15N-23N BETWEEN 62W-72W...EXCEPT FOR TWO LARGE CLUSTERS OF STRONG CONVECTION FROM 15N-18N BETWEEN 66W-68W...AND FROM 16N-18N BETWEEN 69W-71W. TROPICAL WAVE IS MOVING ACROSS GUATEMALA INTO THE E PACIFIC BASIN FROM 17N89W TO 10N90W. THE WAVE IS HELPING PRODUCE SCATTERED SHOWERS/THUNDERSTORMS ACROSS NORTHERN GUATEMALA AND PORTIONS OF THE YUCATAN PENINSULA. SEE TWDEP FOR MORE DETAILS ON THE WAVE IN THE E PACIFIC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF MAURITANIA AT 19N16W OVER ATLC WATERS TO A 1010 MB LOW NEAR 12N23W TO 8N31W TO A SECOND 1010 MB SURFACE LOW AT 10N41W TO 8N52W. THE ITCZ BEGINS AT 8N48W TO 8N59W. THE TWO SURFACE LOWS ARE CONNECTED TO TROPICAL WAVES. SEE TROPICAL WAVE SECTION ABOVE. SCATTERED MODERATE CONVECTION IS FROM 5N-10N BETWEEN 27W-29W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 8N-11N BETWEEN 50W-59W. ...DISCUSSION... GULF OF MEXICO... SCATTERED SHOWERS/THUNDERSTORMS COVER MUCH OF THE NE GULF AND THE FLORIDA PENINSULA ASSOCIATED WITH AN UPPER LEVEL TROUGH EXTENDING JUST OFF THE EASTERN SEABOARD. THE UPPER TROUGH SUPPORTS A SURFACE TROUGH ALONG 31N81W TO 27N84W. THE MOST CONCENTRATED SHOWERS/THUNDERSTORMS ARE W OF THE TROUGH FROM 25N-28N BETWEEN 85W-90W. SIMILAR ACTIVITY IS FOUND OVER S OF THE TROUGH OVER FLORIDA. ISOLATED SHOWERS ARE ACROSS THE REMAINDER OF THE NE GULF. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO OVER THE YUCATAN PENINSULA TIED TO A TROPICAL WAVE TO THE S ALONG WITH TYPICAL DAYTIME HEATING. THE WESTERN AND SOUTHERN GULF ARE MOSTLY DRY DUE TO DRY AIR ALOFT AROUND THE W SIDE OF AN UPPER LEVEL LOW OVER CUBA...AND AN UPPER LEVEL RIDGE COVERING MUCH OF THE NORTHERN GULF CENTERED OVER NORTHERN TEXAS. THE UPPER RIDGE ALSO SUPPORTS A WEAK SURFACE RIDGE AROUND A 1019 MB HIGH NEAR 26N93W. LIGHT ANTI-CYCLONIC FLOW IS AROUND THE HIGH CENTER. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS. CARIBBEAN SEA... AN ACTIVE TROPICAL WAVE IS BRINGING THE NE CARIBBEAN SHOWERS/THUNDERSTORMS COVERING MUCH OF HISPANIOLA AND PUERTO RICO. THE REMAINDER OF THE BASIN IS FAIRLY DRY BESIDES A FEW AFTERNOON STORMS OVER CUBA AND CENTRAL AMERICA. A LARGER CLUSTER OF SHOWERS IS JUST OFFSHORE OF COSTA RICA DUE TO DIFFLUENCE FLOW ALOFT BETWEEN EASTERLY FLOW ALOFT OVER THE E PACIFIC AND NORTHERLY FLOW AROUND AN UPPER LEVEL RIDGE OVER THE CENTRAL CARIBBEAN. A DRY UPPER LEVEL LOW IS COVERED OVER WESTERN CUBA AND MAY BE CONTRIBUTING TO THE SHOWERS ACROSS THE ISLAND. EXPECT THE WAVE TO CONTINUE TO MOVE WESTWARD DRAWING MOISTURE BEHIND IT. ATLANTIC OCEAN... A FEW SHOWERS/THUNDERSTORMS ARE OFFSHORE OF FLORIDA ASSOCIATED WITH AN UPPER LEVEL TROUGH N OF THE DISCUSSION AREA...WHICH IS SUPPORTING A SURFACE TROUGH ACROSS NORTHERN FLORIDA. A SMALL AREA OF SHOWERS/THUNDERSTORMS IS ALSO FROM 28N-30N BETWEEN 73W-74W...SUPPORTED BY DIFFLUENCE ALOFT BETWEEN AN UPPER LEVEL LOW CENTERED OVER CUBA AND AN UPPER LEVEL LOW CENTERED NEAR 31N66W. UPPER LEVEL RIDGING IS TO THE S...N OF THE EASTERN CARIBBEAN. IT IS DRAWING MOISTURE INTO THE ATLC ALONG WITH SHOWERS AND POSSIBLE THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE IN THE CENTRAL CARIBBEAN. THE UPPER RIDGE ALSO SUPPORTS A WEAK SURFACE RIDGE AROUND A 1023 MB HIGH NEAR 32N61W. A THIRD UPPER LEVEL LOW IS CENTERED NEAR 27N44W SUPPORTING A WEAK SURFACE TROUGH ALONG 35N46W TO 27N52W. POSSIBLE ISOLATED SHOWERS ARE NEAR THE TROUGH AXIS. THE REMAINDER OF THE EASTERN ATLC IS COVERED BY SURFACE RIDGING AROUND A 1024 MB HIGH NEAR 34N37W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE TO THE N...AS WELL AS AN UPPER LEVEL RIDGE COVERING THE TROPICAL ATLC. SATELLITE IMAGERY CONTINUES TO SHOW A LARGE AREA OF SAHARAN DUST THAT EXTENDS FROM THE COAST OF AFRICA TO NEAR 60W...WHICH FURTHER SUPPORTS FAIR WEATHER. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON