000 AXNT20 KNHC 061805 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 PM EDT Thu Jul 6 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...SPECIAL FEATURES... Tropical Depression Four is centered near 13.2N 42.6W at 06/1500 UTC or about 1096 nm east of the Lesser Antilles moving WNW at 18 kt. Estimated minimum central pressure is 1008 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. Scattered to isolated moderate convection is located within 315 nm of the center of the depression, primarily in the western semicircle. Please see the latest NHC Public Advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC and the full Forecast/Advisory under the AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details. ...TROPICAL WAVES... A tropical wave is just off the W coast of Africa with axis extending from 16N18W to 04N18W, moving W at 5-10 kt within the last 24 hours. The wave is in a region of favorable to neutral wind shear. However, extensive intrusion of Saharan dry air and dust to the wave environment hinder convection at the moment N of 08N. Scattered moderate convection is from 05N to 08N between 16W and 23W associated with the monsoon trough. A tropical wave is over the central Atlantic just E of the Lesser Antilles. Its axis extends from 20N58W to 08N60W and has been moving W at about 15 kt during the last 24 hours. The wave is in a region of favorable to neutral wind shear. However, intrusion of Saharan dry air and dust to the wave environment hinder deep convection at the time. Shallow moisture and upper level diffluence support isolated showers from 09N to 15N between 56W and 62W. A tropical wave located over the W Caribbean has an axis near 81W extending from 09N to 22N, moving west at around 20 kt during the past 24 hours. The wave is in a region of unfavorable wind shear. However, shallow moisture and upper level diffluent flow between a low over the SE Gulf of Mexico and a broad ridge covering the W Caribbean support scattered to isolated heavy showers and tstms W of 78W. A tropical wave is moving over the SW Gulf of Mexico with axis near 95W extending from 14N to 25N, moving westward at about 15-20 kt. The wave is in a region of favorable to neutral wind shear. Shallow moisture and upper level diffluent flow between a low over central Mexico and a broad ridge anchored in the EPAC waters support scattered heavy showers and tstms S of 26N W of 90W. ...ITCZ/MONSOON TROUGH... The Monsoon Trough extends from 11N15W to 06N20W to 04N28W. The Intertropical Convergence Zone extends from 04N28W to 03N40W to 07N51W. Aside from the convection related to Tropical Depression Four and the tropical wave off the coast of Africa, scattered showers are observed in the vicinity of the ITCZ from 01N to 07N between 37W-48W. ...DISCUSSION... GULF OF MEXICO... A weak surface ridge extends across the northern Gulf anchored by a 1022 mb high near 29N86W, which is forecast to stall through tomorrow morning. A tropical wave is in the SW basin, enhancing showers and tstms in this area, including the Bay of Campeche. Refer to the tropical waves section above for further details. Isolated showers are elsewhere in the E basin being supported by shallow moisture and diffluent flow aloft between an upper level ridge anchored in the SE CONUS and a low just N of western Cuba. Scatterometer, ship, and buoy observation indicate that the surface winds across the Gulf are light to gentle, except for moderate SE flow in the eastern Bay of Campeche associated with the aforementioned tropical wave. Little change in this pattern is expected during the next couple of days. CARIBBEAN SEA... A tropical wave is moving across the W Caribbean supporting showers and tstms W of 78W. Refer to the section above for details. The moderate pressure gradient over the Caribbean between the Azores high to the northeast and lower pressure over NW Colombia and central America is maintaining moderate to fresh tradewinds over the basin, except over the waters from 10N to 18N between 70W and 80W where fresh to strong easterlies are present. A tropical wave is entering the E Caribbean later today supporting showers across the Windward Islands and adjacent SE Caribbean waters. Little change is expected through Friday morning, but with diminishing winds Friday night. ...HISPANIOLA... Isolated showers and tstms are occuring over the western half of the Dominican Republic being supported by shallow moisture and upper level diffluent between a ridge anchored in the SW N Atlc and a low in the south-central Caribbean. No major convection is anticipated for the Island through Saturday night associated with a tropical wave. ATLANTIC OCEAN... Tropical Depression Four and two tropical waves were analyzed over the tropical North Atlantic. Refer to the Special Features and Tropical Waves sections above for details. Aside from the convection associated with Tropical Depression Four and the ITCZ previously mentioned, no other significant convection is occurring. A broad 1029 mb surface high is centered north of our area near 35N34W. This high continues to dominate the weather across the area. To the south of the high and away from Tropical Depression Four described above, moderate to fresh trade winds prevail across the basin. This synoptic pattern will change little through the next couple of days. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos