000 AXNT20 KNHC 211756 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 156 PM EDT THU JUL 21 2016 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...TROPICAL WAVES... A tropical wave is in the east Tropical Atlantic extending from 08N-20N with axis near 23W, moving W at 15 kt over the past 24 hours. Enhanced Meteosat imagery show Saharan dry air and dust over the northern wave environment, thus hindering convection in the Cape Verde Islands. CIRA LPW imagery from the surface to 850 mb show a moderate moist environment S of 14N that along with divergence aloft support scattered showers from 07N-12N E of 26W. Similar convection is from 14N-20N E of 21W. A tropical wave is in the central Caribbean extending from 12N-18N with axis near 68W, moving W at 20 kt over the past 24 hours. CIRA LPW imagery from the surface to 850 mb show the wave is embedded in a moderate to high moist environment that along with divergent flow aloft support showers and tstms over Puerto Rico, Hispaniola and adjacent waters southern waters to 13N. A tropical wave is in the western Caribbean extending from 13N to 24N with axis near 83W, moving W at 20 kt over the past 24 hours. Water vapor imagery show dry air subsidence from aloft over the western Caribbean. Shallow moisture in the wave environment support isolated showers N of 16N W of 76W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends across Africa into the east Tropical Atlantic near 14N16W and then continues along 10N25W to 07N40W. The ITCZ begins near 07N40W and then extends to 08N51W to the coast of Venezuela near 08N60W. Aside the convection associated with the tropical wave in the eastern Atlc, numerous moderate convection is from 04N-10N between 27W and 43W. ...DISCUSSION... GULF OF MEXICO... Weak surface ridging prevails in the northern half of the basin providing mainly gentle to moderate easterly flow, which advects moisture from the SW N Atlc into the Gulf. This moisture is supporting isolated heavy showers and tstms across southern and central Florida and in the basin N of 23N. Similar convection is across the Florida straits being enhanced by a tropical wave over the western Caribbean. A surface trough extends over SE Mexico coastal waters generating scattered showers and tstms S of 26N W of 94W. The tropical wave over the Caribbean will move across the southern Gulf Friday and enter southern Mexico late Friday night into Saturday. Showers across the basin are expected to continue through early Saturday. CARIBBEAN SEA... An inverted trough in the upper levels covers the western half of the basin where water vapor imagery show dry air. An upper level ridge covers the NE basin being centered near the Mona passage. Diffluence aloft being generated by these two features along with abundant moisture associated with a tropical wave with axis along 68W support showers and isolated tstms over Puerto Rico, Hispaniola and adjacent southern waters to 13N. A second tropical wave is in the western Caribbean, however dry air subsidence from aloft limits in part the convection to isolated showers N of 16N W of 76W. Scattered heavy showers and tstms are in the SW basin S of 11N E of 80W associated with the monsoon trough. For further details see tropical waves section. Scatterometer data depict gentle to moderate trades across most of the Caribbean waters except S of 16N between 70W and 78W where fresh to strong winds prevail due to a tighter pressure gradient. Showers are forecast to continue in the central and SW Caribbean through Friday. Little change is expected elsewhere. ...HISPANIOLA... Scattered showers and isolated tstms are across the Island and southern adjacent waters being supported by both a tropical wave moving into central Caribbean waters and a diffluent environment aloft. Model guidance indicate showers will continue through late Friday as the wave continue to move west during the next 24 hours. ATLANTIC OCEAN... A middle to upper level trough over W Atlc waters extends S to a base over SW N Atlc waters. The trough aloft is supporting a weak surface trough in the region that along with moisture being advected by SE flow generate scattered to isolated showers W of a line from 30N68W to 23N80W. Aside from the tropical wave in the east Atlc, surface ridging prevails elsewhere. For additional information please visit http://www.hurricanes.gov/marine $$ RAMOS