485 AXNT20 KNHC 220606 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 206 AM EDT Sat Sep 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 0000 UTC surface analysis and satellite imagery through 0515 UTC. ...Special Features... The well defined low east of the Windward Islands has developed into Tropical Depression Eleven, centered near 13.1N 53.4W at 22/0300 UTC, or 440 nm E of the Windward Islands, moving WNW at 5 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC for more details. A low pressure system is located at about 550 miles south- southeast of the Cabo Verde Islands. Although the low is currently producing only limited shower and thunderstorm activity, the system appears to have become better organized today and a tropical depression could form during the next day or two. This system is expected to move westward at 15 to 20 mph across the low latitudes of the eastern and central tropical Atlantic Ocean through early next week. The system has now a medium chance of tropical cyclone formation within the next 48 hours. Please refer to the latest Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information. A 1010 mb non-tropical low is located near 30N64W, or about 850 miles west-southwest of the Azores. Conditions are expected to be conducive for the low to acquire subtropical or tropical characteristics, and a subtropical or tropical cyclone is likely to form early next week while the low meanders over the central Atlantic Ocean. The system has now a medium chance of tropical cyclone formation within the next 48 hours. Please refer to the latest Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information. ...TROPICAL WAVES... The tropical wave has its axis along 38W from 04N-16N and is moving west at 10-15 kt. The wave corresponds nicely with a maximum in TPW imagery. Model analyses depict an associated 700 mb trough along 38W. Isolated showers are noted within 120 nm of the wave axis from 10N-13N. Little change is expected with this wave over the next 24-48 hours. A western Caribbean Sea tropical wave has its axis along 82W, moving west at 10-15 kt. This wave is well depicted in model guidance and TPW imagery shows abundant moisture in its environment. Scattered showers are noted within 75 nm on either side of the wave's axis. ...MONSOON TROUGH/ITCZ... The monsoon trough extends across Africa along 17N. The trough begins over the Atlantic near 07N21W to 07N36W. The ITCZ begins near 07N40W to 10N52W. Scattered showers are noted within 75 nm north of the ITCZ between 43W-52W. ...DISCUSSION... GULF OF MEXICO... An upper-level cyclonic circulation centered near 28N85W is enhancing convection across the eastern half of the basin mainly east of 90W. A surface trough was analyzed from 27N88W to 23N88W. Another trough is located from 27N82W to 24N82W. Surface ridging prevails across the remaining of the basin. The ridge will support gentle to moderate easterly winds and seas 3 ft or less across most of the Gulf of Mexico through the middle of next week. It is possible that a typical nocturnal surface trough, that will be moving westward across the southwestern corner of the Gulf of Mexico, may produce locally fresh winds through Saturday. CARIBBEAN SEA... A tropical wave is moving across the western Caribbean. Please see the Tropical Waves section for more details. The eastern Pacific monsoon trough combined with diffluence aloft is helping to induce scattered showers over portions of Costa Rica and Panama. Plenty of moisture will persist over the southwest Caribbean through Saturday as the tropical wave, currently along 82W, moves west through the weekend. The pressure gradient between central Atlantic high pressure and the lower pressure near the west Caribbean tropical wave will support moderate to fresh trades across the area. Winds will diminish over most of the Caribbean this weekend. ATLANTIC OCEAN... Currently, there are two tropical waves and a tropical depression between the west coast of Africa and the Lesser Antilles. Please see the Special Features/Tropical Waves sections for more details. A weakening frontal boundary extends from a 1010 mb low near 30N64W to 27N68W. Minimal convection is observed along the frontal boundary. The front will dissipate by this morning. The low is currently producing moderate to fresh winds north of 27N between 60W-66W. The low is expected to drift south and then west over the forecast area between 60W-70W while weakening. The remainder of the Atlantic forecast area is under the influence of a surface ridge, anchored by a pair of 1017 mb highs centered near 24N63W and 24N47W. For additional information please visit http://www.hurricanes.gov/marine $$ ERA