418 AXNT20 KNHC 192357 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 757 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...TROPICAL WAVES... A tropical wave is off the coast of west Africa from 06N to 18N along 19W, moving W at 10-15 kt. 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 13N E of 24W. A tropical wave is in the central Atlantic with axis extending from 18N34W to 04N34W, moving W at 15 kt. The wave is moving across an extensive Saharan Air Layer Outbreak with dry air and dust hindering convection. A low amplitude tropical wave is over the central Atlantic with axis extending from 12N52W to 02N53W, moving W at 15 kt. Scattered moderate comvection is within 180 nm of the wave axis. A tropical wave is in the E Caribbean with axis S of 20N along 70W, moving W at 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 66W and 73W. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from W Africa near 15N17W to 08N26W to 07N40W, where the ITCZ begins and continues to South America near 05N55W. Scattered moderate convection is from 06N to 10N between 24W and 30W, and from 04N to 08N between 46W and 50W. ...DISCUSSION... GULF OF MEXICO... The Azores high continues to extend a ridge axis SW across the southern half of the Florida Peninsula to the central Gulf of Mexico. This is supporting maily light to gentle winds over the Gulf S of 27N. In the NE Gulf, a surface trough continues to generate scattered moderate convection and isolated tstms. The trough is being supported by upper level level diffluent flow. The Bay of Campeche has shallow moisture as depicted by low level water vapor imagery. 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 for the remainder of the weekend. In addition, a surface trough will move westward off the Yucatan Peninsula each night, enhancing nocturnal winds over the eastern half of the Bay of Campeche. CARIBBEAN SEA... A tropical wave is over the E Caribbean. See above. Upper level diffluent flow over Puerto Rico and eastern Hispaniola along with abundant shallow moisture supports this wave. The remainder of the basin is under dry, stable, air as indicated by the low level water vapor imagery of GOES-16. RGB imagery from GOES-16 also shows 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 an upper level trough is over the W Atlantic at 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 over E Hispaniola supports scattered showers and tstms S of 22N between 61W and 70W. The remainder of the Atlantic N of 18N is under the influence of the Azores high supporting fair weather conditions. No major changes expected during the next two days. For additional information please visit http://www.hurricanes.gov/marine $$ Formosa