000 AXNT20 KNHC 200528 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 128 AM EDT Sun Aug 20 2017 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. ...TROPICAL WAVES... A tropical wave extends its axis from 20N45W to 10N46W, moving west at 15-20 kt. Satellite imagery indicates a large area of cloudiness but convection is limited in association with this wave due to Saharan dust intrusion. This system coincides with a well defined 700 mb trough, and a high amplitude northward bulge of moisture is noted on the TPW product. T.S. Harvey has been degraded to an open tropical wave with axis extending from 19N70W to a 1007 mb surface low near 14N71W to 11N71W. An Air Force Reserve Hurricane Hunter aircraft investigated Harvey earlier this evening and was unable to close off a center of circulation. Maximum surface winds, as measured by the plane, remain near 30 kt around the wave's axis. A fast westward motion is expected to continue with this system for the next couple of days as the wave moves along the southern periphery of the subtropical ridge. A tropical wave is over the western Caribbean with axis extending from western Cuba along 83W to near 10N83W, moving west at 10-15 kt. The wave shows up very well on the TPW animation and 700 mb streamline analysis. Energy from the wave has fractured to the northeast and is analyzed as a surface trough between the northern Bahamas and the Florida peninsula, from 28N79W to 24N80W. Currently, the wave is enhancing showers and thunderstorms over west Cuba and near the Cayman Islands. Showers and thunderstorms are also noted ahead of the wave's axis affecting portions of Honduras and adjacent waters. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 14N17W to 10N36W. The Intertropical Convergence Zone extends from 11N48W to 09N61W. Scattered moderate convection is observed within 100 nm on either side of the monsoon trough. ...DISCUSSION... GULF OF MEXICO... A large and well defined upper-level low centered over the southeast Gulf near 25N85W continues to generate scattered showers particularly between 88W-92W and the Florida Straits area. A surface trough, reflection of this upper-level low, is analyzed from 30N84W to 26N85W. A scatterometer pass showed very well the wind shift associated with this trough. The western half of the Gulf is under the influence of a surface ridge, anchored by a 1016 mb high pressure centered near 29N93W. Isolated showers and light to gentle anticyclonic winds prevail west of 90W. The upper-low will drift westward reaching the central Gulf by Monday. This system will continue to enhance showers and thunderstorms across the Gulf waters on Sunday. CARIBBEAN SEA... Two tropical waves are moving across the basin. Refer to the section above for details. Moisture associated with these tropical waves will continue to affect the central Caribbean, central America and northwest Caribbean increasing the likelihood of showers and thunderstorms today. ...HISPANIOLA... Daytime heating, local sea breezes, and mountain upslope lifting will combine with available moisture to produce scattered showers and thunderstorms across the island mainly during the afternoon and evening hours through the weekend. ATLANTIC OCEAN... As previously mentioned, the northern part of the tropical wave currently moving across the western Caribbean is analyzed as a trough between the northwest Bahamas and the Florida peninsula. This trough is generating scattered showers and thunderstorms west of 76W, and will continue to move westward across south Florida and the Straits of Florida tonight and Sunday accompanied by active weather. Showers and thunderstorms are forecast to increase across south Florida tonight and continue on Sunday with possible locally heavy rain. Another surface trough is analyzed northeast of the Leeward Islands extending from 24N62W to 20N63W. This trough continues to produce disorganized showers and thunderstorms from 17N-21N between 60W-65W. Environmental conditions are not expected to be conducive for development of this system during the next couple of days while it moves west-northwestward at 15 to 20 kt. Conditions could become slightly more conducive for development once the system is near the northern Bahamas or Florida around the middle of next week. An area of fresh to strong winds is noted per scatterometer data on the northern side of this trough from 19N-24N between 57W-63W. The remainder of the Atlantic is under the influence of a surface ridge, anchored by a 1024 mb high centered near 33N39W. Fresh to strong northerly winds are also noted between the coast of Africa and the Madeira/Canary Islands. These winds are the result of the pressure gradient between the Atlantic ridge and lower pressures over west Africa. For additional information please visit http://www.hurricanes.gov/marine $$ ERA