000 AXNT20 KNHC 180555 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Fri Aug 18 2023 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 31N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 0000 UTC surface analysis and satellite imagery through 0530 UTC. ...SPECIAL FEATURES... Eastern Tropical Atlantic (AL98): Showers and thunderstorms continue to show some signs of organization in association with a broad area of low pressure located a few hundred miles west of the Cabo Verde Islands. Environmental conditions appear generally favorable for additional development of this system, and a tropical depression is likely to form over the weekend while it moves toward the west-northwest or northwest at about 10 kt across the eastern tropical Atlantic. By early next week, upper-level winds over the system are forecast to increase, and further development is not expected. This system has a medium chance of tropical cyclone development within 48 hours. Central Tropical Atlantic (AL99): An elongated trough of low pressure located more than 1000 miles west-southwest of the Cabo Verde Islands is producing some disorganized showers and thunderstorms. Environmental conditions are only marginally conducive for further development of this system, but a tropical depression could still form during the next couple of days while it moves west-northwestward at 10 to 15 mph across the central tropical Atlantic. Thereafter, upper- level winds are forecast to become unfavorable for any further development.This system has a medium chance of tropical cyclone development within 48 hours. Please refer to the latest NHC Tropical Weather Outlook at www.hurricanes.gov for more details on both special features. ...TROPICAL WAVES... Please see the SPECIAL FEATURES section above for information on a tropical wave near 30W that has induced low pressure formation and that has a potential for tropical development and on a central Atlantic area of low pressure with a low near 12N40W. A western Atlantic tropical wave has its axis near 50W from 06N to 19N. It is moving westward near 15 kt. Scattered moderate and isolated strong convection is depicted from 07N to 14N between 48W and 55W. A Caribbean tropical wave has its axis near 73W, or from the western part of Haiti to just inland Colombia. It is moving westward around 13 kt. The wave has helped to set off scattered to numerous moderate convection over parts of Colombia. ...MONSOON TROUGH/ITCZ... The monsoon trough axis enters the Atlantic near 18N17W and continues to 17N22W to a low pressure near 15N29W, to a low pressure near 13N41W, and ends near 11N54W. Outside of convection associated to the SPECIAL FEATURES and TROPICAL WAVES, scattered moderate convection south of the trough is depicted between 18W and 21W. GULF OF MEXICO... A weak surface trough extends across Florida and is producing scattered moderate convection in the nearshore and offshore waters of southwest Florida and the Florida Keys. Another surface trough is located near the Campeche Bay. However, no significant convection is depicted in association with this trough. Otherwise, high pressure prevails across the Gulf waters, with a weak pressure gradient supporting light to gentle winds and seas of 1 to 2 ft. For the forecast, a surface ridge over the Gulf waters will support mostly gentle to moderate winds and slight seas across the basin through Sat night. Looking ahead, a surface trough is expected to move across the Gulf from east to west Sun through early next week. The trough could form into a broad area of low pressure in the central or W Gulf by the beginning of next week. Some slow development of this system is possible thereafter as it moves westward and approaches the western Gulf of Mexico coastline by the middle of next week. CARIBBEAN SEA... Scattered showers and thunderstorms are depicted in the southwestern Caribbean Sea near the offshore waters of Panama, Costa Rica, and Nicaragua in association with the eastern end of the Pacific Monsoon Trough. Elsewhere, no significant convection is depicted at this time. The pressure gradient between the subtropical ridge in the central Atlantic and low pressure over NW Colombia is supporting fresh easterly trade winds in the south central Caribbean. Moderate to locally fresh winds are over the north central and eastern Caribbean. Gentle to moderate winds are in the western Caribbean. Seas are in the 5 to 6 ft range in the central Caribbean, with 3 to 5 ft seas elsewhere, except for lower seas of 2 to 4 ft seas in the NW basin. For the forecast, moderate to fresh trade winds will prevail over the eastern and central Caribbean during the next few days. A strong tropical wave is likely to approach the E Caribbean this weekend and spread fresh to strong winds and building seas over the NE Caribbean Sat night into Tue. ATLANTIC OCEAN... Please refer to the SPECIAL FEATURES and the MONSOON TROUGH/ITCZ sections above for details on the two low pressure systems in the central and eastern Atlantic that could become tropical cyclones. And convection in the tropical Atlantic. A weak surface trough off the coasts of east Florida is producing isolated moderate convection near the western Bahamas. An expansive subtropical ridge dominates the tropical and subtropical Atlantic waters N of 20N. Fresh to locally strong winds, and seas of 7 to 9 ft, are noted from 15N to 24N between 35W and 74W. Gentle to moderate winds, and seas of 4 to 6 ft are noted elsewhere. The exception is a zone of fresh to locally strong south-southwest winds north of 29N, ahead of a stationary front that extends from the southeastern U.S. to just along the coast of Louisiana and northwestward from there to eastern Texas. For the forecast W of 55W, Fresh to locally strong tradewinds will pulse off Hispaniola each evening into early next week. Fresh tradewinds south of 25N today will persist through Sat. A strong tropical wave could enhance winds and seas near the Leeward and Virgin Islands over the weekend, and north of Puerto Rico early next week. $$ KRV