266 AXNT20 KNHC 220000 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 759 PM 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 1800 UTC surface analysis and satellite imagery through 2345 UTC. ...TROPICAL WAVES... A tropical wave has moved off the African coast with axis along 22W between 06N-20N, moving westward at 10-15 kt. The wave is embedded within a very dry and stable environment inhibiting convection at this time. A central Atlantic tropical wave has its axis extending along 40W from 05N-18N, moving westward at 10-15 kt. This wave is also embedded within a very dry and stable environment caused by Saharan Air Layer outbreak migrating westward across the central and eastern Atlantic. Only isolated moderate convection is noted within 60 nm either side of the wave axis along 11N. A tropical wave has been repositioned based on satellite imagery and model data. The axis extends now along 60W between 09N-19N, moving westward near 15-20 kt. No significant convection is observed with this wave at this time. A western Caribbean tropical wave has its axis extending along 88W and south of 21N, moving westward at near 15 kt. Scattered moderate convection is over Central America and Yucatan Peninsula between 84W-92W. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from coast of Senegal near 14N17W to 09N23W to 09N43W. No significant convection is noted with these boundaries at this time. ...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. Latest NWS mosaic radar display shows isolated showers and thunderstorms across much of the eastern part of the gulf, mainly due to a weak trough over that area. Scattered showers and thunderstorms are observed over the far southwest section of the gulf in association with the Yucatan Peninsula trough that typically moves offshore across the southwestern gulf late at night and into the morning hours, with the added factor of an upper-level low located just east of the coast of Mexico at 22N97W. Expect for this convective activity to remain active through tonight. Otherwise, high pressure ridging will remain across the northern gulf waters, with the associated gradient producing gentle to moderate anticyclonic flow through Thu. CARIBBEAN SEA... The pressure gradient across the area will maintain fresh to strong winds over the south central Caribbean off the coast of Colombia and across the Gulf of Venezuela through Thu. Moderate to fresh trades will continue elsewhere through Thu. The tropical wave along 88W will move across the rest of the western Caribbean this evening before moving inland Central America. The tropical wave along 60W will enter the eastern Caribbean through Wed night and enter the eastern part of the central Caribbean by Thu. ATLANTIC OCEAN... Over the western Atlantic, a surface trough is analyzed from near 30N74W to the central Bahamas. An upper-level trough extends from an upper-level low at 31N66W to the central Bahamas, and to central Cuba as a shear axis. Another trough extends from 32N59W to 27N68W, and another one extends from near 32N45W to 28N50W. A small surface trough extends from near 31N54W to 28N56W. With these features in place along with a moist and unstable environment, the result is scattered shower and thunderstorm activity over the waters north of 24N between 60W and 75W, with the most concentrated activity observed north of 27N and between 70W and 76W. Isolated showers and thunderstorms are elsewhere west of 58W. A 1025 mb high center is analyzed north of these troughs at 33N58W, with a ridge extending westward to Bermuda, and southwestward from there to east-central Florida High pressure ridging will continue over the basin through the next several days. The trough extending across the central Bahamas will continue westward through this evening. The aforementioned shower and thunderstorm activity is forecast to persist through Wed. Over the eastern part of the basin, a 1026 mb high is centered near 34N42W, supporting generally moderate north to northeast winds north of 20N. Saharan dust and associated dry air, as also mentioned above under Tropical Waves, is noted mainly east of about 56W on GOES-16 Saharan Air Layer animation is inhibiting convection from developing across the eastern and central Atlantic waters. For additional information please visit http://www.hurricanes.gov/marine $$ JA/ERA