844 AXNT20 KNHC 181206 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 806 AM EDT Sat Aug 18 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. ...SPECIAL FEATURES... Post-tropical Storm Ernesto is centered near 51.9N 20.0W at 18/0900 UTC or 885 nm NNE of The Azores moving ENE at 30 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. Weakening is forecast to continue, and Ernesto should merge with a frontal zone by tonight. On this forecast track the post-tropical cyclone and its remnants will move across Ireland and the United Kingdom tonight and early Sunday. See the last advisory on Ernesto under AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more details. ...TROPICAL WAVES... A tropical wave is in the central Atlc with axis extending from 04N-16N along 37W, moving W at 15-20 kt. Both CIRA LPW and GOES-16 water vapor imagery at the lower levels show dry air affecting the wave. These two factors are contributing to the lack of convection at this time. A tropical wave is entering the E Caribbean. Its axis extends from 05N-18N along 61W, moving W at 15 kt. CIRA LPW imagery show abundant low level moisture associated with it. However, some dry air intrusion is noted in the NW wave environment as shown both in CIRA LPW, and water vapor imagery at the lower levels. Scattered moderate convection is from 10N-14N between 59W-63W. A tropical wave is in the western Caribbean with axis extending from 04N-18N along 78W, moving W at 20 kt. Scattered moderate convection is in the northern wave environment N of 17N between 75W-82W. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of W Africa near 13N17W to 10N30W to 07N40W. The ITCZ begins near 07N40W and continues to 08N50W to 10N60W. Besides the convection mentioned in the tropical wave section, scattered moderate to isolated strong convection is over W Africa from 08N-14N between 04W-18W. Scattered showers are within 120 nm of the remainder of the monsoon trough and ITCZ. ...DISCUSSION... GULF OF MEXICO... A 1024 mb high is centered over the W Atlantic near 30N69W. A ridge axis extends W from the high along 30N to E Texas. 10 kt SE surface winds covers the Gulf of Mexico N of 24N. A surface trough is over the Bay of Campeche from 22N90W to 16N93W. Scattwered moderate convection is from 16N-19N between 92W-95W. In the upper levels, an upper level high is centered over SE Louisiana near 30N90W. Upper level diffluence is over the Yucatan Channel producing scattered showers. Expect, a surface trough to develop along the Yucatan Peninsula during the late afternoons, then drift westward across the southwest gulf waters during the overnight hours accompanied by a fresh east to southeast wind shift with the trough dissipating along 96W during the late mornings. Otherwise, expect an east to west ridge extends across the gulf waters along 30N accompanied by gentle to moderate anticyclonic flow that is forecast to increase to a fresh southerly breeze across the northwest gulf waters on Sun evening, and continue through sunrise on Mon. The ridge will then shift south and extend east to west across the central waters during the middle of next week. CARIBBEAN SEA... Two tropical waves are over the Caribbean Sea. See above. A surface trough extends over the Gulf of Honduras near 18N86W to the E Pacific near 10N86W. Scattered showers are within 120 nm of the trough. Surface ridging extends from the Atlantic to the northern half of the Caribbean. Fresh to strong winds are over the south-central Caribbean. In the upper levels, an upper level low is centered over central Cuba near 22N80W. Upper level diffluence is over Jamaica and E Cuba enhancing convection. Expect, strong nocturnal easterly trades along the northwest coast of Colombia through the middle of next week. A tropical wave along 76W will continue to move westward across the western Caribbean during the weekend. A second tropical wave along 60W will continue through the east Caribbean this weekend. A third tropical wave in the central Atlantic will reach along 55W on Mon night and reach the east Caribbean during the middle of next week ATLANTIC OCEAN... A tropical wave is over the Atlantic. See above. A 1024 mb high is centered over the W Atlantic near 30N69W. A surface trough is over the central Atlantic from 32N54W to 26N62W. Scattered showers are within 90 nm of the trough. A 1028 mb high is centered over the Azores near 38N29W. Expect over the W Atlantic for fresh trades to be south of 23N, except becoming locally strong along the north coast of Hispaniola during the late afternoon into early evening hours. The surface ridge axis will shift south to central Florida early next week. For additional information please visit http://www.hurricanes.gov/marine $$ MF/NR