402 AXNT20 KNHC 221206 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 806 AM EDT Sun Jul 22 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 0600 UTC surface analysis and satellite imagery through 1130 UTC. ...TROPICAL WAVES... A tropical wave is off the coast of Africa extending from 09N to 20N along roughly 17N/18N, moving W at 10-15 kt. A large area of Saharan dust is noted along the wave north of 10N. Farther south, scattered moderate convection is noted where the tropical wave intersects the monsoon trough off the coasts of Sierra Leone and Guinea, from 07N to 10N east of 09W. A tropical wave is in the central Atlantic with axis extending from 08N-22N along 40W, moving W at 15-20 kt. This tropical wave continues to be on the leading edge of a large area of Saharan dry air and dust, inhibiting large scale convection at this time. Isolated cells are noted on the southern end of the tropical wave where it intersects the monsoon trough and intertropical convergence zone. A tropical wave is in the western tropical Atlantic with axis extending from 09N-23N along 53W, moving W at 10-15 kt. The tropical wave is accompanied by Saharan dry air and dust, inhibiting large scale convection. However the northern extent of the tropical wave will be coming into phase with a broad upper trough to the northwest of the wave axis. This may allow development of isolated convection later today or tonight approximately 300 nm northeast of the Leeward Islands. A low amplitude tropical wave is moving across eastern Colombia with axis extending from 00N-11N along 75W, moving W at 15-20 kt. While no convection is noted along the wave axis, it may be interacting with overnight drainage flow to support a large area of showers and a few thunderstorms off the Pacific coast of Colombia and in the Gulf of Panama. The wave will lose some definition as it moves across the Andes today, but may emerge into the eastern Pacific off Colombia Mon. A tropical wave extends from the Gulf of Honduras into the eastern Pacific along roughly 87W. No significant convection is noted in the Caribbean related to this tropical wave. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from 08N19W and continues to 07N37W. The ITCZ begins near 07N40W and continues to 06N55W. No significant convection is observed at this time with these features. ...DISCUSSION... GULF OF MEXICO... A surface ridge extends across the basin, anchored by a 1017 mb high centered near 24N87W. To the west, surface trough extends across the Bay of Campeche from 22N30W to 19N93W with scattered showers. A shortwave trough at mid/upper levels is supporting cloudiness and a few showers over the far east Gulf waters and Florida Peninsula. A pre-frontal trough extends across the Florida from 29N80W to 28N83W. Scatterometer data depicts light to gentle anticyclonic winds over most of the basin except north of 26N and east of 89W. The weak trough across Central Florida will gradually settle southward over the next few days, bringing moderate west- southwesterly flow. The increasing westerly fetch will bring gradually higher seas in the offshore Gulf waters by early next week. Showers and thunderstorms will persist over the eastern Gulf today. A surface trough will move off the Yucatan Peninsula into the Bay of Campeche each evening, accompanied by fresh nocturnal winds and scattered showers. CARIBBEAN SEA... A tropical wave is moving across the west Caribbean. Refer to the section above for details. A recent scatterometer pass depicted fresh to strong trade winds over the central Caribbean, reaching as far north as 17N between 73W-79W. Seas are estimated to be 07 to 11 ft in this area. Aside from the thunderstorms over the southwest Caribbean due to the monsoon trough over 10N, little to no shower or thunderstorm activity is noted due to the presence of Saharan dust and dry air, mainly impacting the eastern Caribbean. For the forecast, high pressure north of the area will continue to support fresh to strong winds in the south-central Caribbean through tonight before winds diminish. ATLANTIC OCEAN... Mid to upper-level diffluent flow between a ridge in the west Atlantic and a trough along the eastern U.S. continue to support scattered showers over the west Atlantic mainly west of 70W. To the east, an upper-level low is reflected at the surface as a trough that extends from 31N55W to 23N56W. Two tropical waves extend across the basin. Refer to the section above for details. A broad high pressure prevails across the remainder of the basin centered near 40N43W. For the forecast, high pressure ridge across the northern waters will remain in place through the weekend before lifting N Mon through Wed. Scattered showers and thunderstorms will persist N of 27N and E of 78W through early next week. Fair weather is elsewhere across the Atlantic, however hazy conditions are expected S of 26N as the extensive Saharan Air Layer outbreak moves across the Atlantic tropical waters. For additional information please visit http://www.hurricanes.gov/marine $$ Christensen