000 AXNT20 KNHC 302343 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE JUL 30 2013 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 EXTENDS FROM 08N36W TO 16N35W MOVING W AT 5 KT. OVER THE PAST FEW DAYS THIS WAVE HAS BEEN TRAPPED WITHIN THE INFLUENCE OF A MONSOONAL GYRE...BUT IT APPEARS THIS LOWER LEVEL FEATURE HAS WEAKED AND THE WAVE WILL BEGIN A MORE PROGRESSIVE WESTWARD MOVEMENT OVER THE NEXT FEW DAYS. THE WAVE ALSO COINCIDES WITH A WEAK 700 MB TROUGH WITH A VORTICITY MAXIMUM NOTED IN GLOBAL MODEL DATA IN THE VICINITY OF 14N39W TO THE WEST OF THE AXIS. OTHERWISE...CONVECTION IS NON-EXISTENT DUE TO A STRONG SAHARAN AIR LAYER COVERING A MAJORITY OF THE EASTERN TROPICAL ATLC N OF 10N E OF 37W. TROPICAL WAVE EXTENDS FROM 16N75W TO 24N73W MOVING W AT 10 KT. THE WAVE CORRESPONDS WITH BROAD MID-LEVEL TROUGHING OVER THE SW NORTH ATLC WHILE A MID-LEVEL VORTICITY MAXIMUM IN THE VICINITY OF THE REMNANTS OF DORIAN REMAINS EAST NEAR 23N69W. ENERGY ASSOCIATED WITH THE LOW-LEVEL TROPICAL WAVE HAS CONTINUED WESTWARD AND IS EXPECTED TO MOVE ACROSS THE WESTERN CARIBBEAN SEA THROUGH FRIDAY. SCATTERED MODERATE CONVECTION IS ONGOING ACROSS CUBA THIS EVENING...HOWEVER IS NOT LIKELY ASSOCIATED WITH THE WAVE AND MORE DUE TO PEAK DAYTIME HEATING AND INSTABILITY. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 20N16W TO 16N21W TO 11N24W TO 07N38W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N38W TO 06N42W TO 08N48W TO 07N52W. SCATTERED MODERATE CONVECTION IS FROM 05N-09N BETWEEN 23W-28W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL ANTICYCLONIC CIRCULATION INFLUENCES MUCH OF NORTHERN MEXICO...THE SOUTHERN U.S. PLAINS...AND PORTIONS OF THE SE CONUS CENTERED NEAR 32N103W THAT IS PROVIDING MUCH OF THE GULF WITH EAST-NORTHEASTERLY FLOW ALOFT THIS EVENING. WATER VAPOR IMAGERY ALSO INDICATES THAT MODERATELY DRY AIR AND OVERALL SUBSIDENCE PREVAILS ACROSS THE BASIN. THE UPPER LEVEL RIDGING IS SUPPORTING A SURFACE RIDGE OF HIGH PRESSRE ANCHORED BY A 1021 MB HIGH CENTERED IN THE NE GULF NEAR 28N86W. ONE EXCEPTION TO THE RIDGE IS WEAK SURFACE TROUGHING ACROSS THE FLORIDA PENINSULA WHICH IS LARGELY ASSOCIATED WITH SEABREEZE DYNAMICS. WIDELY SCATTERED SHOWERS AND TSTMS ARE OCCURRING E OF 84W IN THE FAR EASTERN GULF AND ACROSS PORTIONS OF THE FLORIDA PENINSULA. A FEW ISOLATED SHOWERS AND TSTMS ARE ALSO OCCURRING ACROSS SE LOUISIANA AND PORTIONS OF THE FLORIDA PANHANDLE. OTHERWISE...THE SURFACE RIDGE IS FORECAST TO GENERALLY REMAIN NEARLY STATIONARY OVER THE NE GULF THROUGH LATE WEDNESDAY WITH E-SE WINDS PERSISTING ACROSS THE WESTERN GULF IN THE RANGE OF 10-20 KT. CARIBBEAN SEA... A WEAK UPPER LEVEL LOW IS CENTERED OVER THE NORTHERN YUCATAN PENINSULA NEAR 19N88W AND AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE WESTERN CARIBBEAN NEAR 12N82W. MOST OF THE ACTIVE WEATHER THIS EVENING IS CONCENTRATED ACROSS THE YUCATAN PENINSULA AND ACROSS CENTRAL AMERICA S OF 16N ON THE WESTERN PERIPHERY OF THE UPPER LEVEL LOW AND WITHIN THE INFLUENCE OF THE UPPER LEVEL RIDGING WHICH IS PROVIDING AN AREA OF MAXIMUM DIFFLUENCE OVER CENTRAL AMERICA. ISOLATED SHOWERS AND TSTMS ARE OCCURRING S OF 16N BETWEEN 81W-88W WHILE SCATTERED SHOWERS AND TSTMS ARE OCCURRING ACROSS INLAND PORTIONS OF THE YUCATAN PENINSULA AND GUATEMALA. THE SOUTHERN EXTENT OF THIS CONVECTION IS LIKELY ENHANCED BY THE CLOSE PROXIMITY OF THE MONSOON TROUGH ANALYZED ALONG 10N FROM NORTHERN COLOMBIA TO CENTRAL COSTA RICA. FARTHER EAST...A TROPICAL WAVE EXTENDS FROM THE SW NORTH ATLC ACROSS EASTERN CUBA AND INTO THE NORTH-CENTRAL CARIBBEAN TO 16N75W. WATER VAPOR IMAGERY INDICATES A VERY DRY AND STABLE AIR MASS INFLUENCES MUCH OF THE CENTRAL AND EASTERN CARIBBEAN S OF 18N E OF 80W. THIS IS RESULTING IN MOSTLY CLEAR SKIES AND FAIR WEATHER CONDITIONS. THE ONLY EXCEPTIONS ARE LATE AFTERNOON AND EARLY EVENING SCATTERED SHOWERS AND TSTMS OCCURRING PRIMARILY OVER THE ISLANDS OF HISPANIOLA...JAMAICA... AND CUBA. THE ONGOING CONVECTION IS EXPECTED TO DIMINISH OVER THE NEXT FEW HOURS WITH THE LOSS OF PEAK DAYTIME HEATING AND INSTABILITY. HISPANIOLA... CURRENTLY ISOLATED SHOWERS AND TSTMS ARE OCCURRING ACROSS THE ISLAND AND THIS ACTIVITY IS EXPECTED TO DIMINISH DUE TO THE LOSS OF PEAK DAYTIME HEATING AND INSTABLITY OVER THE NEXT FEW HOURS. ON THE SYNOPTIC SCALE...AN UPPER LEVEL LOW IS CENTERED N OF HISPANIOLA NEAR 24N72W THAT IS FORECAST TO SLOWLY DRIFT NORTHWESTWARD DURING THE NEXT FEW DAYS. AS THIS OCCURS...THE ISLAND WILL GRADUALLY FALL WITHIN AN AREA OF SOUTHERLY FLOW ALOFT AND THIS WILL RESULT IN A HIGHER CHANCE FOR AFTERNOON AND EARLY EVENING SHOWERS AND TSTMS OVER THE NEXT FEW DAYS DUE TO AN OVERALL MORE DIFFLUENT ATMOSPHERE IN PLACE. IN ADDITION...THE REMNANTS OF DORIAN REMAIN NORTH OF THE ISLAND AND THE MID-LEVEL CIRCULATION WILL CONTINUE TO ADVECT MOISTURE NORTHWARD FROM THE CARIBBEAN INTO THE SW NORTH ATLC. THIS MOISTURE AND THE FAVORABLE DYNAMICS IN THE VICINITY WILL ALSO PROVIDE TO INITIATE SHOWERS AND TSTMS. ATLANTIC OCEAN... NORTHERLY UPPER LEVEL FLOW DOMINATES ON THE WESTERN PERIPHERY OF AN UPPER LEVEL LOW CENTERED NEAR 24N72W. MOST OF THE AREA W OF 72W IS UNDER FAIR CONDITIONS WITH A FEW ISOLATED SHOWERS AND TSTMS OCCURRING S OF 25N W OF 77W...AND N OF 30N BETWEEN 74W- 80W. EAST OF THE THE UPPER LEVEL LOW...A MID-LEVEL VORTICITY CENTER...THE REMNANTS OF DORIAN...IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 20N-28N BETWEEN 66W-72W. OTHERWISE...THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A WEAKENING 1024 MB HIGH CENTERED IN THE VICINITY OF BERMUDA NEAR 32N64W. FARTHER EAST...ANOTHER UPPER LEVEL LOW IS CENTERED NEAR 26N51W THAT CONTINUES TO INDUCE SURFACE TROUGHING ANALYZED FROM 20N49W TO 27N47W. ISOLATED SHOWERS ARE OCCURRING FROM 22N-28N BETWEEN 46W- 51W WITH THE BOUNDARY. FINALLY...OF NOTE...A LARGE AREA OF SUSPENDED SAHARAN DUST...OR THE SAHARAN AIR LAYER IS PRESENT ACROSS THE EASTERN ATLC. EXAMINING THE CIMSS SAL TRACKING PRODUCT THIS AREA IS N OF 10N E OF 37W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN