000 AXNT20 KNHC 041758 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN AUG 04 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... A BROAD TROPICAL WAVE EXTENDS FROM 10N38W TO 21N40W MOVING W AT ABOUT 20 KT. THE WAVE IS PART OF A LARGER AREA OF OVERALL BROAD TROUGHING IN THE CENTRAL ATLANTIC AND IS COUPLED WITH MID- LATITUDE MID-LEVEL TROUGHING NOTED TO THE NW OF THE WAVE IN THE VICINITY OF 21N47W. WHILE NEITHER FEATURE EXHIBITS A STRONG SIGNAL ON SATELLITE IMAGERY AND IN GLOBAL MODEL DATA...ENERGY ASSOCIATED WITH EACH ARE FORECAST TO MERGE WITHIN THE NEXT 12 TO 24 HOURS ACROSS THE CENTRAL ATLC AND CONTINUE A FAIRLY RAPID WESTWARD MOVEMENT TOWARD THE LESSER ANTILLES REACHING 60W BY TUE. THE WAVE IS SURROUNDED BY A MASSIVE AREA OF SUSPENDED SAHARAN DUST AT THIS TIME WITH NO DEEP CONVECTION OCCURRING IN THE VICINITY OF THE WAVE. GOES-R PROVING GROUND SAL AND AIRMASS IMAGERY SUGGESTED THIS DUST OUTBREAK WAS FAIRLY SIGNIFICANT. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM THE COAST OF MAURITANIA NEAR 16N17W TO 14N25W TO 10N33W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N33W TO 10N45W TO 06N55W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF A LINE FROM 11N16W TO 10N25W. SCATTERED MODERATE CONVECTION WAS NOTED WITHIN 180 NM S OF THE ITCZ BETWEEN 33W AND 46W. ...DISCUSSION... GULF OF MEXICO... A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER NORTH-CENTRAL TEXAS NEAR 33N99W AND IS PROVIDING THE GULF WITH NORTHEAST TO EASTERLY FLOW ALOFT. WATER VAPOR IMAGERY INDICATES IT REMAINS MODERATELY DRY AND STABLE WITH UPPER LEVEL CONVECTIVE DEBRIS CLOUDINESS COVERING THE EAST-CENTRAL GULF FROM 22N-28N E OF 90W. OTHERWISE...THE GULF IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED OVER THE CENTRAL GULF NEAR 25N88W. VISIBLE SATELLITE IMAGERY AND COASTAL WSR-88D IMAGERY ARE INDICATING WIDELY SCATTERED POPCORN SHOWERS AND TSTMS ARE OCCURRING WITHIN 120 NM OF THE COAST FROM GALVESTON TEXAS AROUND THE GULF TO THE SW COAST OF FLORIDA NEAR FORT MYERS. THE ACTIVITY APPEARED TO BE MORE CONCENTRATED OVER NORTH-CENTRAL FLORIDA. LOOKING AHEAD...RIDGING WILL DOMINATE OVER THE BASIN THROUGH WEDNESDAY WITH SOUTHERLY WINDS PREVAILING W OF 90W IN THE RANGE OF 10-20 KT. CARIBBEAN SEA... A MID TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE WESTERN CARIBBEAN NEAR 13N82W. EASTERLY FLOW ON THE SOUTH SIDE OF THE FEATURE WAS ADVECTING MOISTURE WESTWARD OVER CENTRAL AMERICA. LOW LEVEL CONVERGENT FLOW ALONG THE COAST FROM NICARAGUA TO PANAMA IN COMBINATION WITH UPPER LEVEL DIFFLUENCE AND THE PRESENCE OF THE MONSOON TROUGH AXIS WAS RESULTING IN SCATTERED SHOWERS AND TSTMS IN THE AREA. ON THE EASTERN PERIPHERY OF THE UPPER LEVEL ANTICYCLONE...A DRIER NORTHWESTERLY FLOW PREVAILS BETWEEN 70W-80W WITH MOSTLY CLEAR SKIES AND FAIR CONDITIONS. FINALLY...OVER THE EASTERN CARIBBEAN AN UPPER LEVEL LOW IS CENTERED NORTH OF PUERTO RICO NEAR 23N66W WAS RESULTING IN BROAD TROUGHING E OF 70W. WATER VAPOR IMAGERY INDICATES THE TROUGHING EXHIBITS RELATIVELY DRY AIR ALOFT AND THIS IS RESULTING IN ONLY A FEW ISOLATED LOW-TOPPED SHOWERS OCCURRING FROM 16N-18N BETWEEN 69W-73W...AND E OF 66W...INCLUDING THE LESSER ANTILLES. OTHERWISE...THE EXTENSIVE SAHARAN AIR LAYER/DUST IS CONTRIBUTING TO THE OVERALL STABILITY OF THE BASIN E OF 80W. HISPANIOLA... VISIBLE SATELLITE IMAGERY INDICATED ONLY A FEW STREETS OF LOW CLOUDS IN AND AROUND HISPANIOLA WITH SIGNIFICANT SAHARAN DUST NOTED AS WELL. SURFACE OBSERVATIONS SO FAR DO NOT INDICATE ANY RESTRICTIONS TO VISIBILITIES AS A RESULT OF THE SAHARAN DUST. NONETHELESS THE SAHARAN AIR LAYER WILL PROVIDE AN OVERALL STABLE ATMOSPHERE OVER THE NEXT FEW DAYS WITH VERY LITTLE IN THE WAY OF CONVECTIVE ACTIVITY EXPECTED. ATLANTIC OCEAN... NORTHEASTERLY UPPER LEVEL FLOW IS NOTED ON WATER VAPOR IMAGERY BETWEEN 70W AND THE SE CONUS. A NARROW SHEARED MID-LEVEL TROUGH IS IN THE VICINITY OF 28N77W WAS WEAKENING AS IT APPROACHED A COL IN THE SW NORTH ATLC. THIS TROUGH SUPPORTS A 1010 MB LOW CENTERED NEAR 34N73W AND A SURFACE TROUGH EXTENDING FROM THE LOW TO 29N77W. GENERALLY AN OVERALL WEAKNESS IN THE SURFACE RIDGING EXTENDING FROM THE CENTRAL ATLC TO THE GULF OF MEXICO... MAXIMUM MIDDLE TO UPPER LEVEL DIFFLUENCE IN THE REGION IS GENERATING OVERCAST CLOUDINESS WITH ISOLATED SHOWERS AND TSTMS WITHIN 150 NM EITHER SIDE OF A LINE FROM 32N71W TO 25N79W. THIS AREA OF TROUGHING...ALONG WITH THE LOW PRESSURE CENTER IS EXPECTED TO MOVE NORTHEAST WELL NORTH OF THE DISCUSSION AREA OVER THE NEXT 12 HOURS. OTHERWISE THE REMAINDER OF THE SW NORTH ATLC...CENTRAL ATLC...AND EASTERN ATLC ARE UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1022 MB HIGH CENTERED NEAR 29N58W AND A 1030 MB HIGH CENTERED S OF THE AZORES NEAR 34N30W. EMBEDDED WITHIN THE SOUTHERN PERIPHERY OF THE RIDGE... MID-LATITUDE MID-LEVEL ENERGY IS LOCATED IN THE VICINITY OF 21N47W. WHILE NO SIGNIFICANT CONVECTION IS OCCURRING WITH THIS FEATURE...IT IS FORECAST TO MERGE WITH ENERGY ASSOCIATED WITH THE TROPICAL WAVE ALONG 38W/40W OVER THE NEXT 24 HOURS. FINALLY...ONE OF THE MORE EXTENSIVE AREAS OF SAHARAN DUST THUS FAR THIS SEASON COVERS MUCH OF THE TROPICAL ATLC AND IS PROVIDING OVERALL STABLE CONDITIONS THIS MORNING. AS NOTED ABOVE...GOES R PROVING GROUND PRODUCTS HAVE BEEN INSTRUMENTAL IN IDENTIFYING THE EXTENT OF THIS LATEST DUST OUTBREAK. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ COBB