000 AXNT20 KNHC 061712 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE AUG 06 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 1745 UTC. ...TROPICAL WAVES... A TROPICAL WAVE AXIS EXTENDS FROM 20N62W TO 11N63W MOVING W-NW ABOUT 20 KT. THE NORTHERN PORTION OF THE WAVE HAS FRACTURED WITH A SURFACE TROUGH EXTENDING FROM 28N59W TO 22N62W. METEOSAT-9 SAL TRACKING IMAGERY INDICATED THAT THE WAVE IS EMBEDDED WITHIN A VERY DRY STABLE ENVIRONMENT WHICH ALONG WITH STRONG SOUTHWESTERLY WIND SHEAR IS HINDERING CONVECTION. A CLUSTER OF MODERATE CONVECTION IS INDICATED ALONG THE TROUGH AXIS WITHIN 60 NM OF 26.5N59W. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM THE COAST OF MAURITANIA NEAR 21N17W TO 12N25W TO 08N38W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM NEAR 08N38W AND CONTINUES INTERMITTENTLY THROUGH 11N46W TO 12N55W TO 11N62W. A SURFACE TROUGH ASSOCIATED WITH A 1012 MB LOW NEAR 12N49W EXTENDS FROM 09N TO 16N. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NOTED WITHIN 120 NM EITHER SIDE OF A LINE FROM 012N17W TO 08N28W...AND FROM 10N-12N BETWEEN 51W-54W. ...DISCUSSION... THE GULF OF MEXICO... AS OF 1500 UTC...ANTICYCLONIC FLOW IN THE RANGE OF 5-15 KT SPREADS ACROSS MOST OF THE BASIN ANCHORED BY A 1018 MB HIGH NEAR 26N89W WHICH IS BEING SUPPORTED BY A BROAD MIDDLE TO UPPER LEVEL RIDGE AND ANTICYCLONE CENTERED OVER THE NW GULF NEAR 29N95W. A WEAK SURFACE TROUGH EXTENDS FROM A 1015 MB LOW BEAR THE BIG BEND OF FLORIDA TO 28N86W TO 29N88W. SCATTERED TSTMS WERE ERUPTING ALONG THE SURFACE TROUGH WITH NUMEROUS LIGHTNING STRIKES WITHIN THE PAST HOUR. A SURFACE PREFRONTAL TROUGH EXTENDS THROUGH THE STRAITS OF FLORIDA TO 25N84W. THIS WAS ENHANCING SCATTERED SHOWERS AND TSTMS IN THE FLORIDA STRAITS. THE SURFACE TROUGH OVER THE BAY OF CAMPECHE HAS DISSIPATED WITH THE ASSOCIATED CONVECTION DISSIPATING. OTHERWISE...DRY AIR IN THE LOWER AND MIDDLE LEVELS IS SUPPORTING FAIR WEATHER OVER THE WESTERN AND SOUTHERN-CENTRAL GULF. THE CENTER OF HIGH PRESSURE IS EXPECTED TO DRIFT NW AND PERSIST OVER THE GULF UNTIL THURSDAY MORNING. THE TROUGH OVER THE BAHAMAS IS EXPECTED TO MOVE WESTWARD AND PROVIDE TROUGHINESS TO THE EASTERN GULF UNTIL VERY EARLY THURSDAY. SCATTERED SHOWERS AND TSTMS ARE LIKELY TO CONTINUE OVER THE EASTERN GULF. THE CARIBBEAN SEA... DEEP LAYERED DRY AIR FROM A SAHARAN OUTBREAK AT THE LOW LEVELS AND SUBSIDENCE IN THE MID TO UPPER LEVELS CONTINUES TO SPREAD ACROSS MOST OF THE BASIN. THE DRY AIR WAS FOCUSED WITHIN 180 NM N AND W OF AN UPPER LEVEL TROUGH WHICH EXTENDED FROM A CYCLONIC CIRCULATION N OF HISPANIOLA THROUGH 15N73W TO THE COAST OF NICARAGUA. A TROPICAL WAVE ALONG 62W/63W IS MOVING INTO THE FAR E CARIBBEAN IS EMBEDDED WITHIN THIS DRY STABLE ENVIRONMENT WITH ONLY SCATTERED LOW CLOUDS AND ISOLATED WARM TOPPED SHOWERS NOTED ACROSS THE LEEWARD ISLANDS. TRADEWINDS RANGING FROM 20-25 KT ARE OVER THE CENTRAL-SOUTHERN CARIBBEAN NEAR THE COAST OF COLOMBIA WHILE WINDS OF 5-15 KT ARE ELSEWHERE IN THE BASIN. WEAKENING ISOLATED MODERATE CONVECTION WITHIN 60 NM OFF THE COASTS OF COSTA RICA AND PANAMA IS ASSOCIATED WITH THE MONSOON TROUGH AXIS. WINDS OVER THE CENTRAL-SOUTHERN CARIBBEAN ARE EXPECTED TO SUBSIDE TONIGHT. RAINSHOWERS ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE ARE EXPECTED TO DEVELOP S OF PUERTO RICO...THE MONA PASSAGE AND DOMINICAN REPUBLIC THIS AFTERNOON BEING ENHANCED BY AN UPPER LEVEL LOW CENTERED IN THE BASIN. HISPANIOLA... IN THE UPPER LEVELS...AN ELONGATED CYCLONIC CIRCULATION EXTENDS ACROSS THE ISLAND FROM THE W ATLC TO THE SOUTHERN CARIBBEAN. THIS IS SUPPORTING LOW VALUES OF WIND SHEAR OVER THE ISLAND...HOWEVER DRY AIR SUBSIDENCE IS CURRENTLY ENHIBITING CONVECTION. A FEW DIURNALLY DRIVEN SHOWERS AND TSTMS ARE EXPECTED THIS AFTERNOON/EARLY EVENING POSSIBLY ENHANCED BY SOME MOISTURE CARRIED TOWARDS THE ISLAND BY THE TROPICAL WAVE THAT HAS ENTERED THE EASTERN CARIBBEAN. THE WAVE IS EXPECTED TO START MOVING ACROSS THE ISLAND WEDNESDAY MORNING WITH INCREASING SHOWERS AND TSTMS LIKELY TO DEVELOP/CONTINUE THROUGH EARLY THURSDAY. THE ATLANTIC OCEAN... AS OF 1500 UTC...A WEAKENING STATIONARY FRONT WAS OVER THE SW N ATLC FROM 31N70W TO 29N81W TO A 1015 MB LOW NEAR THE FLORIDA BIG BEND. A PREFRONTAL TROUGH EXTENDS ACROSS THE NORTH CENTRAL BAHAMAS TO THE STRAITS OF FLORIDA ALONG 28N75W TO 24N81W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE SOUTHERN AND CENTRAL BAHAMAS S OF THE SURFACE TROUGH EXTENDING INTO THE STRAITS OF FLORIDA. A SURFACE TROUGH ASSOCIATED WITH A 1012 MB LOW IS EMBEDDED WITHIN THE ITCZ AXIS NEAR 12N48W ASSOCIATED WITH A SURFACE TROUGH ALONG 48W WITH ONLY ISOLATED MODERATE CONVECTION ASSOCIATED WITH IT AT THIS TIME. ELSEWHERE SURFACE RIDGING AND FAIR WEATHER SUPPORTED BY LOWER-MIDDLE LEVEL DRY AIR DOMINATE THE REMAINDER BASIN. EASTERLY WAVE DIAGNOSTICS AND 12Z RAOB DATA FROM DAKAR SUGGESTS A NEW TROPICAL WAVE IS EXPECTED TO EMERGE OFF THE WEST AFRICAN COAST LATER TODAY. THIS FEATURE MAY BE INTRODUCED IN THE 18 UTC ANALYSIS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ COBB