000 AXNT20 KNHC 200605 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 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 0000 UTC surface analysis and satellite imagery through 0545 UTC. ...SPECIAL FEATURES... Tropical Storm Fiona is centered near 18.7N 45.5W at 20/0300 UTC or about 934 nm east of the Leward Islands moving west-northwest at 10 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Numerous heavy showers and isolated tstms are from 18N-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 a 1009 mb low near 10N33W to 15N31W, 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 06N-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 11N-18N with axis near 66W, 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 09N-19N with axis near 82W, 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 80W. ...ITCZ/MONSOON TROUGH... The monsoon trough extends across Africa into the east Tropical Atlantic near 16N16W through the 1009 mb low to near 12N39W. The ITCZ begins near 11N45W and continues along 10N56W 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 08N-14N E of 20W. ...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 NE basin and E-SE gentle to moderate flow elsewhere. A heat surface trough extending along the western Yucatan Peninsula provide NE moderate wind to the central and eastern Bay of Campeche. The trough also generates scattered to isolated showers S of 21N E of 94W and across the Yucatan Peninsula. An elongated upper level low centered N of the Yucatan Peninsula 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 in the SW basin S of 10N E of 80W. Otherwise...fresh to strong trades prevail between 69W-81W with near gale force trades along the coast of Colombia. ...HISPANIOLA... Remnant moisture associated with the passage of a tropical wave and divergent flow aloft support cloudiness and isolated showers along Haiti and the Windward Passage. Model guidance indicate these showers will cease before the sunrise today and will resume Saturday night. Fair weather for the entire Island is expected 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 28N70W. Farther east, scattered showers and isolated thunderstorms are N of 28N between 47W-52W. The remainder of the basin is dominated by a surface ridge. For additional information please visit http://www.hurricanes.gov/marine $$ RAMOS