000 AXNT20 KNHC 201001 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 601 AM EDT SAT AUG 20 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 0600 UTC surface analysis and satellite imagery through 1000 UTC. ...SPECIAL FEATURES... Tropical Storm Fiona is centered near 19.2N 46.7W at 20/0900 UTC or about 869 nm east of the Leeward Islands, moving west- northwest at 11 kt. Estimated minimum central pressure is 1008 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Convection has significantly reduced in the last couple of hours. Scattered showers and isolated tstms are from 17N-22N between 43W- 47W. Please see the latest NHC Intermediate Public Advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC and the full Forecast/Advisory under the AWIPS/WMO headers MIATCPAT1/WTNT21 KNHC for more details. ...TROPICAL WAVES... Tropical wave is in the central Atlantic extending from 05N35W to a 1009 mb low near 11N35W to 16N33W, moving W at 15 kt within the last 24 hours. Intrusion of Saharan dry air and dust to the wave environment continue to limit the convection to scattered showers and isolated tstms from 05N-16N between 30W and 40W. Any development of this system during the next couple of days should be slow to occur due to its proximity to dry air. Environmental conditions are forecast to be more conducive for development after that time, and a tropical depression could form by the middle of next week while the system moves westward across the tropical Atlantic Ocean and into the eastern Caribbean Sea. Tropical wave in the eastern Caribbean extends from 10N-18N with axis near 67W, moving W at 20 kt within the last 24 hours. Even though the wave is in a region of favorable deep layer wind shear, strong dry air subsidence from aloft and Saharan dry air in the wave environment hinder convection at the time. Tropical wave in the western Caribbean extends from 08N-19N with axis near 83W, moving W at 20-25 kt within the last 24 hours. CIRA LPW imagery from surface to 850 mb show the wave is associated with moderate moisture. However, strong dry air subsidence from aloft and mainly unfavorable deep layer wind shear limits the convection to isolated showers and tstms S of 17N W of 81W. ...ITCZ/MONSOON TROUGH... The monsoon trough extends across Africa into the east Tropical Atlantic near 13N17W through the 1009 mb low to near 11N42W. The ITCZ begins near 11N45W and continues along 09N55W to 10N62W. The monsoon trough/ITCZ is disrupted by Tropical Storm Fiona. Aside from the convection associated with the tropical wave, scattered heavy showers and isolated tstms are from 05N-15N E of 22W. ...DISCUSSION... GULF OF MEXICO... Weak surface ridging prevails across the Gulf waters N of 22N, being anchored by a 1017 mb high near 27N84W. The ridge continue to provide gentle variable flow across the E-NE basin and E-SE gentle to moderate flow elsewhere. The surface trough that was along the western Yucatan Peninsula has moved to the E Bay of Campeche waters where it extends from 21N90W to 17N92W and provide NE moderate wind. The trough also generates isolated showers S of 21N E of 96W and across portions of the Yucatan Peninsula. An elongated upper level trough extending across the SW and SE Gulf support isolated showers and tstms across the Florida straits. Dry air subsidence and unfavorable deep layer wind shear support fair weather elsewhere. Mostly gentle to moderate E-SE winds are expected through the weekend. The diurnal surface trough will form each evening over the Yucatan peninsula supporting fresh winds along the northwest coast of the Yucatan. CARIBBEAN SEA... Water vapor imagery continue to show mostly dry air and stable conditions in the central and eastern Caribbean. Two tropical waves are the main features in the basin. However, none represent a threat in terms of winds and precipitation. Due to the presence of divergent flow aloft, low level moisture and favorable deep layer wind shear the westernmost wave is associated with isolated showers and tstms S of 17N W of 80W. For more details about the waves see the tropical waves section. The E pacific monsoon trough support scattered showers and tstms in the SW basin S of 10N. Otherwise...fresh to strong trades are from 11N-14N between 73W and 78W with near gale force winds along the coast of Colombia. These winds are forecast to prevail for the rest of the weekend. ...HISPANIOLA... Remnant moisture associated with the passage of a tropical wave and divergent flow aloft support cloudiness across portions of Haiti and the Windward Passage. Model guidance indicate showers will develop across the western Island tonight. Fair weather for the entire Island is forecast for Sunday. ATLANTIC OCEAN... The primary concern in the Atlantic waters S of 30N continue to be Tropical Storm Fiona. Please see the Special Features section above for more details. Over the SW N Atlantic, an elongated area of low pressure is centered by a 1015 mb low near 28N69W. Farther east, scattered showers and isolated thunderstorms are N of 28N between 46W and 52W. The remainder of the basin is dominated by a surface ridge anchored by a 1019 mb high near 28N33W. For additional information please visit http://www.hurricanes.gov/marine $$ RAMOS