000 AXNT20 KNHC 132339 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON AUG 13 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. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 12N21W TO 21N21W MOVING W AT 15 KT. THE WAVE IS EMBEDDED WITHIN A LOW-LEVEL CYCLONIC GYRE OF THE MONSOON TROUGH WHICH IS CENTERED NEAR THE SOUTHERN EXTENT OF THE WAVE AXIS NEAR 12N. THE WAVE ALSO COINCIDES WITH A 700 MB LOW NEAR 10N22W THAT EXTENDS A TROUGH AXIS NORTHWARD FROM THE LOW TO 21N WITH TOTAL PRECIPITABLE WATER IMAGERY INDICATING MAXIMUM DEEP LAYERED MOISTURE FROM 08N-15N BETWEEN 16W-22W. ISOLATED MODERATE CONVECTION IS FROM 11N-14N BETWEEN 16W-23W. TROPICAL WAVE EXTENDS FROM 20N45W TO 28N43W MOVING WNW AT 15-20 KT. A WEAK 1016 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 24N44W AND COINCIDES WITH AN AREA OF MAXIMUM DEEP LAYERED MOISTURE NOTED IN TOTAL PRECIPITABLE WATER IMAGERY FROM 20N-25N BETWEEN 42W-49W. HOWEVER...DRY AIR AND DUST SURROUND THE WAVE LIMITING DEEP CONVECTION AT THIS TIME. ISOLATED SHOWERS ARE POSSIBLE FROM 22N-26N BETWEEN 42W-51W. TROPICAL WAVE EXTENDS FROM 11N78W TO 19N75W MOVING W AT 20 KT. SATELLITE PRESENTATION AND ASSOCIATED SURFACE OBSERVATIONS INDICATE CYCLONIC FLOW IN THE VICINITY OF THE AXIS. THIS WAS CONFIRMED EARLIER BY A 13/1418 UTC ASCAT PASS IN THE WATERS SOUTH OF THE WINDWARD PASSAGE ALONG 75W. SCATTERED MODERATE CONVECTION IS FROM 17N-20N BETWEEN 66W-70W...INCLUDING PUERTO RICO AND THE MONA PASSAGE...AND FROM 14N-20N BETWEEN 70W-79W...INCLUDING HISPANIOLA AND PORTIONS OF THE WINDWARD PASSAGE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM NEAR 11N23W TO 08N36W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N36W TO 11N50W TO 08N60W. SCATTERED MODERATE CONVECTION IS FROM 06N-10N BETWEEN 20W-32W. ISOLATED MODERATE CONVECTION IS FROM 07N-13N BETWEEN 47W-56W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH IS PROGRESSING EASTWARD OVER THE MISSISSIPPI RIVER VALLEY THIS EVENING WITH THE TROUGH AXIS EXTENDING SOUTHWARD INTO THE NORTH-CENTRAL GULF N OF 25N BETWEEN 84W-93W. THIS MIDDLE TO UPPER LEVEL TROUGHING IS PROVIDING A GENERAL SYNOPTIC-SCALE WEAKNESS IN THE UPPER LEVEL RIDGE THAT EXTENDS FROM THE SW NORTH ATLC NEAR 26N77W TO 19N95W TO 32N103W. THE COLD FRONT ASSOCIATED WITH THIS TROUGH IS WELL INLAND ACROSS ARKANSAS AND TEXAS THIS EVENING...AND IS FORECAST TO WEAKEN BEFORE APPROACHING THE NW AND NORTHERN GULF WATERS. HOWEVER... MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO ADVECT NORTH- NORTHEASTWARD ACROSS MUCH OF THE GULF AND ALONG WITH DAYTIME HEATING AND MAXIMUM INSTABILITY CONTINUES TO GENERATE ISOLATED SHOWERS AND TSTMS ACROSS THE FLORIDA PENINSULA AND PORTIONS OF THE FLORIDA STRAITS FROM 22N-25N BETWEEN 81W-84W...AND OVER THE CENTRAL GULF FROM 24N-31N BETWEEN 85W-93W. WITH THE UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER SOUTHERN MEXICO NEAR 19N95W...DIFFLUENCE IS MAXIMIZED AND IS GENERATING SCATTERED SHOWERS AND TSTMS S OF 25N W OF 91W. WITH MUCH OF THIS WEATHER ASSOCIATED WITH THE MIDDLE TO UPPER LEVELS OF THE ATMOSPHERE... AT THE SURFACE...A RIDGE AXIS EXTENDS FROM THE SW NORTH ATLC ALONG 27N TO A 1020 MB HIGH CENTERED NEAR 27N86W THEN SW TO A 1018 MB HIGH ALONG THE COAST OF MEXICO CENTERED NEAR 21N97W. CARIBBEAN SEA... AN UPPER LEVEL LOW IS CENTERED NEAR 11N80W AND CONTINUES TO AID IN ADVECTION OF MOISTURE INTO THE TROPICAL WAVE ALONG 77W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING MOSTLY EAST OF THE WAVE AXIS...HOWEVER THIS ACTIVITY STRETCHES W OVER JAMAICA. OVERALL THE ACTIVITY IS FOUND FROM 14N-20N BETWEEN 66W-80W. FARTHER SOUTH...THE TROPICAL WAVE IN TANDEM WITH THE MONSOON TROUGH AXIS ALONG 09N IS GENERATING SCATTERED SHOWERS AND TSTMS ACROSS THE SW CARIBBEAN S OF 13N BETWEEN 73W-82W...INCLUDING NORTHERN COLOMBIA AND MUCH OF PANAMA. OTHERWISE THE NW CARIBBEAN IS UNDER FAIRLY DRY AND STABLE CONDITIONS THIS EVENING DUE TO VERY DRY AIR ALOFT W OF 80W AS NOTED ON WATER VAPOR IMAGERY. WITH THE APPROACH OF THE TROPICAL WAVE IN THE NEXT FEW DAYS... THE CHANCE FOR PRECIPITATION ACROSS CENTRAL AMERICA IS FORECAST TO INCREASE. EAST OF 65W...MOST OF THE FAR EASTERN CARIBBEAN AND LESSER ANTILLES ARE UNDER FAIR SKIES THIS EVENING AS AN AREA OF DRY AIR ALOFT MOVES WESTWARD FROM THE TROPICAL ATLC. ATLANTIC OCEAN... AN UPPER LEVEL SHORTWAVE TROUGH IS LOCATED NORTH OF THE REGION IN THE VICINITY OF 34N69W AND SUPPORTS A SURFACE TROUGH ANALYZED FROM 32N71W TO 29N75W. WITH AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED SOUTHWEST OF THIS SHORTWAVE TROUGHING... UPPER LEVEL DIFFLUENCE IS MAXIMIZED NEAR THE SURFACE TROUGH GENERATING SCATTERED SHOWERS AND TSTMS FROM 27N-32N BETWEEN 68W-74W. UPPER LEVEL DIFFLUENCE IS ALSO LARGELY INFLUENCING SCATTERED SHOWERS AND TSTMS OCCURRING OVER THE FLORIDA PENINSULA AND ADJACENT COASTAL ATLC WATERS THIS EVENING N OF 25N W OF 77W. ELSEWHERE THE REMAINDER OF THE CENTRAL AND EASTERN ATLC ARE UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE ANCHORED BY A STATIONARY 1025 MB HIGH CENTERED NEAR 33N46W. PRIMARILY STABLE CONDITIONS AND FAIR WEATHER ARE OCCURRING OVER MUCH OF THIS AREA WITH THE ONLY WEAKNESS FOUND WORKING TO ERODE THE RIDGING IS THE TROPICAL WAVE ALONG 44N MENTIONED ABOVE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN