000 AXNT20 KNHC 201211 TWDAT Tropical Weather Discussion...UPDATED NWS National Hurricane Center Miami FL 810 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. ...UPDATED TO PLACE TROPICAL WAVE IN SPECIAL FEATURES SECTION... Based on 0600 UTC surface analysis and satellite imagery through 1030 UTC. ...SPECIAL FEATURES... A tropical wave extends across the central Caribbean with axis extending from 19N72W to a 1008 mb surface low near 14N72W to 11N73W. This system was previously T.S Harvey. Scattered moderate convection has developed during the past few hours near the low center mainly from 12N-17N between 73W-77W. 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. ...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. A tropical wave was introduced to this map over the eastern Caribbean, after analyzing upper-air soundings across the islands and model guidance. The wave's axis extends from 19N65W to 10N64W, moving west at 10-15 kt. Scattered showers are noted over the northern portion of the wave mainly north of 16N between 62W-66W affecting the Leeward Islands, the U.S. Virgin Islands, and Puerto Rico. A tropical wave is over the western Caribbean with axis extending from western Cuba along 84W to near 10N84W, 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 currently located over the Florida Peninsula. The wave is enhancing showers near Honduras, Belize and adjacent waters. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the African coast near 15N17W to a 1008 mb low near 13N20W to 11N41W. The Intertropical Convergence Zone extends from 11N51W 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 over the Florida Straits. The western half of the Gulf is under the influence of a surface ridge, anchored by a 1016 mb high pressure centered near 29N90W. 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 today. CARIBBEAN SEA... Three 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 area increasing the likelihood of showers and thunderstorms today. Scatterometer data depicts moderate trades across the basin, with the strongest winds remaining east of 70W. ...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 currently extending across southeast Florida. This trough is generating scattered showers and thunderstorms west of 76W, and will continue to move westward through the day. Another surface trough is analyzed northeast of the Leeward Islands extending from 25N65W to 20N65W. This trough continues to produce disorganized showers and thunderstorms from 19N-25N between 61W-66W. 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. An area of fresh to strong winds is noted per scatterometer data on the northern side of this trough. The remainder of the Atlantic is under the influence of a surface ridge, anchored by a 1023 mb high centered near 32N39W. 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