557 AXNT20 KNHC 210532 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 132 AM EDT Tue Aug 21 2018 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 0000 UTC surface analysis and satellite imagery through 0500 UTC. ...TROPICAL WAVES... An eastern Atlantic tropical wave has its axis extending from 05N36W to 18N34W, moving westward at 10-15 kt. Scattered moderate convection is noted from 08N to 10N between 25W and 32W. A tropical wave was reanalyzed to be in the eastern Caribbean along 63W to 18N, moving westward at 15 to 20 kt. The position was based to a large extent on sounding data from sites in the Lesser Antilles. No significant convection is observed. A western Caribbean tropical wave extends south of 20N along roughly 82W, moving west at 10-15 kt. No significant convection is observed. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from coast of Senegal near 14N16W to 10N20W, then to 08N40W. The intertropical convergence zone continues westward to the mouth of the Orinoco River near 09N61W. No significant convection is noted. ...DISCUSSION... GULF OF MEXICO... Weak ridging reaches across the northern Gulf of Mexico along roughly 27N, maintaining light to gentle breezes and 1 to 3 ft seas. Gentle to moderate easterly flow is noted elsewhere south of the ridge. A few showers are ongoing over the east central Gulf off Tampa Bay related to weak trough extending over the area. Scattered to numerous showers and thunderstorms are active along the coast of Mexico in the far southwest Gulf, related to the normal evening/overnight trough that sets up off Yucatan and moves westward, but also largely enhanced by an upper low centered over the southwest Gulf. The Yucatan surface trough will persist each afternoon, then drift westward across the southwest gulf waters during the overnight hours accompanied by a fresh east to southeast wind shift with the trough dissipating along 96W during the late mornings. Otherwise, the east to west ridge will persist across the northern Gulf waters between 26N and 27N overnight accompanied by gentle to moderate anticyclonic flow. A surface high will develop along the ridge near 27N93W on Tue, and meander over the western gulf waters through late Thu, as a weak trough moves southeast into the northeastern gulf waters where it will stall on Thu, and then drift west and dissipate on Fri with anticyclonic flow across the gulf waters late in the week. CARIBBEAN SEA... A scatterometer satellite pass from 0240 UTC indicated fresh to strong winds over the south central Caribbean off the coast of Colombia. A concurrent altimeter satellite pass showed seas reaching 6 to 8 ft, but this likely missed the main area of seas closer to 9 ft, off the coast of Barranquilla. Moderate to fresh winds are noted elsewhere with 3 to 6 ft seas. No significant convection is noted. The strong nocturnal easterly trades will pulse along the northwest coast of Colombia and across the Gulf of Venezuela through early Thu. The tropical wave along 83W will continue west and pass through the western Caribbean tonight. The second tropical wave along 63W will pass through the central Caribbean during mid week. A third tropical wave in the central Atlantic along 35W will reach along 55W on Thu. ATLANTIC OCEAN... Over the western Atlantic, a surface trough is analyzed from near 30N73W to 23N76W in the central Bahamas, supported in part by an upper trough over the same area. The surface trough was well defined in a pair of recent scatterometer satellite passes. A few showers and thunderstorms are noted near the northern end of the trough from 26N to 31N between 72W and 75W. A recent scatterometer satellite pass also showed another surface trough from 31N53W to 25N45W, but with no significant convection noted. The subtropical ridge is displaced slightly north to along 31N, north of the troughs. The east to west ridge will meander from near new to Port Canaveral Florida for the next several days. The trough extending across the central Bahamas will continue westward through late today. Gentle to locally moderate southerly winds are expected north of ridge, a gentle northeast to east to southeast wind shift is forecast along the trough, and moderate to fresh trades are expected south of 23N, except becoming locally strong along the north coast of Hispaniola during the late afternoon into early evening hour on Tue. Farther east, 1026 mb ridging is centered near 34N39W, supporting generally moderate N to NE winds north of 20N with 3 to 5 ft seas across the eastern Atlantic south of 32N. Moderate Saharan dust is noted mainly east of 50W in this broad area of NE winds. The dry conditions are inhibiting convective development across the region. For additional information please visit http://www.hurricanes.gov/marine $$ Christensen