265 AXNT20 KNHC 191802 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 202 PM EDT Thu Jul 19 2018 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 coming off west Africa. Its axis extends from 06N to 19N along 17W. The wave is being engulfed by Saharan dry air and dust and is mainly in a strong deep layer wind shear environment. However, shallow moisture and upper level diffluence is supporting scattered moderate convection from 06N to 15N E of 20W. The wave is forecast to move at 5-10 kt within the next 24 hours. A tropical wave is in the central Atlc with axis extending from 05N34W to 17N33W, moving westward at 10-15 kt. The wave is moving across an extensive Saharan Air Layer Outbreak, which dry air and dust hinder convection. A tropical wave is in the E Caribbean with axis S of 20N along 68W, moving westward at 15 to 20 kt. The wave is in a strong deep layer wind shear environment. However, abundant shallow moisture and upper level diffluence in the NE Caribbean support scattered showers and tstms N of 13N between 62W and 71W. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from W Africa near 16N16W to 09N23W to 07N40W, where the ITCZ begins and continues to South America near 06N57W. Scattered moderate convection is from 06N to 10N between 20W and 30W, and from 04N to 07N W of 45W. ...DISCUSSION... GULF OF MEXICO... The Azores high continues to extend a ridge axis SW across the southern half of the Florida Peninsula then westward to 90W. This is supporting maily south to southwest light to gentle winds S of 27N. In the NE Gulf, a surface pre-frontal trough continues to generate scattered moderate convection and isolated tstms being supported by middle level diffluent flow. Except for the Bay of Campeche where both CIRA LPW and GOES-16 low level water vapor imagery show shallow moisture, the remainder of the Gulf is under dry stable air which supports fair weather. The trough is forecast to dissipate late Friday night and convection associated with it will cease by early Sat. However, an upper level trough will extend from the SE CONUS into the E Gulf and will support the development of showers over the remainder weekend. Otherwise, a surface trough will move westward off the Yucatan Peninsula at night, enhancing nocturnal winds over the eastern half of the Bay of Campeche. CARIBBEAN SEA... A tropical wave is between Puerto Rico and the eastern Dominican Republic with axis along the Mona Passage to NW Venezuela. Upper level diffluent flow over Puerto Rico and eastern Hispaniola along with abundant shallow moisture associated with this wave support scattered showers and tstms N of 13N between 62W and 72W. The remainder basin is under dry, stable air as indicated by the low level water vapor imagery of GOES-16. RGB imagery from GOES-16 also show a thin layer of Saharan Dust moving across the central and western portions of the basin. These factors along with strong deep layer wind shear contribute to a lack of convection elsewhere. The wave will cross Hispaniola tonight and continue to bring showers at the island and adjacent waters through early Friday. The convection will then shift to the SW basin during the weekend as the wave continues to move westward. Otherwise, fresh to strong winds will prevail in the central basin through the weekend as the Azores high remains nearly-stationary. Near gale force winds will be likely along the coast of Colombia. ATLANTIC OCEAN... The base of a middle to upper level trough extends to nearly 30N. This upper trough supports a cold front N of the area. Diffluent flow between the trough and a middle to upper level anticyclone over the Bahamas support scattered showers and tstms N of 28N W of 69W. Isolated showers are also across Andros Island and adjacent waters. A tropical wave moving between Puerto Rico and Hispaniola support scattered showers and tstms S of 22N between 61W and 70W. The remainder Atlc N of 18N is under the influence of the Azores high, which in part is supporting fair weather conditions. No major changes expected during the next two days. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos