000 AXNT20 KNHC 190005 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 PM EDT Tue Jul 18 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 1800 UTC surface analysis and satellite imagery through 2345 UTC. ...SPECIAL FEATURES... Tropical Storm Don is centered near 11.7N 60.0W at 18/2100 UTC moving westward or 275 degrees at 19 kt. Estimated minimum central pressure is 1010 mb with maximum sustained winds of 35 kt with gusts to 45 kt. Scattered moderate convection associated with Don is from 09N to 14N between 59W and 68W. The center of Don will move across the Windward Islands this evening, and then move westward across the southeastern Caribbean Sea late tonight and Wednesday. Don is expected to produce total rain accumulations of 3 to 6 inches, with isolated higher amounts across Barbados, Trinidad and Tobago, and the southern Windward Islands through Wednesday. Therefore, there is a high potential for life-threatening flash floods and mudslides, especially in mountainous areas. Please refer to the latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more details. ...TROPICAL WAVES... A tropical wave associated with a center of low pressure is in the central Atlc. Its axis extends from 17N38W a 1012 mb low near 10N39W to 04N39W, moving westward at 5-10 kt within the last 24 hours. The wave is in a region of favorable wind shear. However, its environment continue to be affected by intrusion of Saharan dry air and dust, which is limiting the convection to scattered showers from 07N to 13N between 38W and 48W. Some slow development of this system is possible during the next day or two while it moves toward the west-northwest or northwest. Potential for tropical cyclone development from this system remain low through the next two days. A tropical wave is in the E Caribbean with axis extending from 20N65W to inland Venezuela near 08N65W, moving west at 20 kt within the last 24 hours. The wave is in a region of unfavorable wind shear, and Saharan dry air and dust are affecting the northern half of the wave environment. This set up is limiting the convection to isolated showers across Puerto Rico and adjacent waters as well as the Dominican Republic. ...ITCZ/MONSOON TROUGH... The monsoon trough axis extends from 12N16W to 11N30W to 07N45W. The ITCZ then extends from 07N45W to 07N57W. Aside from the convection associated with the tropical wave and attendant low, scattered moderate to isolated strong convection is from 05N to 11N between 15W and 26W. ...DISCUSSION... GULF OF MEXICO... The atmosphere across the Gulf remains very moist and unstable as low to middle level southeasterly flow continue to advect moisture from the Caribbean. Latest scatterometer data showed the presence of a surface trough along the northern Gulf waters from 29N84W to 28N88W to 27N92W with fresh to strong northerly flow between the trough axis and the Florida Panhandle. Scattered to isolated showers are within 90 nm either side of the trough. Former scattered showers and thunderstorms over the SW Gulf are now reaching the NW Gulf waters underneath diffluent flow. This area of showers and tstms are over adjacent waters of S Texas from 23N to 26N W of 93W. Similar shower activity is across Florida being supported by a surface trough. Little change is expected in the shower and thunderstorm activity over the next couple of days as moist and unstable conditions continue, and a mid to upper trough just north of the basin begins to shift southward. CARIBBEAN SEA... The main feature of concern for the SE Caribbean is Tropical Storm Don that is moving across the Windward Islands. Don is expected to produce total rain accumulations of 3 to 6 inches, with isolated higher amounts, which may result in potential life-threatening flash floods and mudslides, especially in mountainous areas. See the special features section for details. Scattered to isolated heavy showers and tstms are confined to the far SW Caribbean. This activity is being supported by the combination of diffluence aloft along with low-level forcing from low-level wind speed convergence. In addition, the presence of the the eastern segment of the eastern Pacific monsoon trough across much of Costa Rica and Panama is providing added instability to this convective activity. This activity will remain quite active through the next 24-48 hours. ...HISPANIOLA... A fast moving tropical wave over the eastern Caribbean Sea is supporting isolated showers across the Dominican Republic and adjacent waters, including the Mona Passage. The wave will move into the vicinity of the island tonight and into Wednesday morning. Shower and thunderstorm activity associated with the wave are to be mainly of the scattered to isolated nature. However, any moisture from the wave that does mix in with local effects may result in a bit more shower and thunderstorm activity in some locations of the island through Wednesday. ATLANTIC OCEAN... Middle level diffluence continue to support scattered showers across the northern Bahamas and northward adjacent waters beyond 30N. Central Atlantic high pressure centered near 34N50W extends a ridge south across the entire basin N of 20N. Otherwise, a tropical wave with low potential of tropical cyclone development within the next two days is in the central tropical basin. See the waves section for further details. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos