566 AXNT20 KNHC 180008 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 808 PM EDT Fri Aug 17 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. ...SPECIAL FEATURES... Tropical Storm Ernesto centered near 49.1N 29.8W at 17/2100 UTC or 680 nm N of The Azores moving NE at 27 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. A rapid northeast or east-northeast motion is expected during the next day or so. On the forecast track, the post-tropical cyclone and its remnants will move across Ireland and the United Kingdom Saturday night and early Sunday. Ernesto is expected to become post-tropical this evening, and some gradual weakening is forecast to occur Saturday and Saturday night. The post-tropical cyclone is expected to merge with a frontal zone by early Sunday. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more details. ...TROPICAL WAVES... A tropical wave is in the E Atlc with axis extending from 06N-18N along 30W, moving W at 10-15 kt. The wave is in a low deep layer wind shear environment, however 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 in the central Atlc with axis extending from 05N-16N along 58W, moving W at 15-20 kt. The wave is in a low deep layer wind shear environment, and CIRA LPW imagery shows 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 isolated strong convection is from 10N-14N between 54W-61W. A tropical wave is in the central Caribbean with axis extending from 10N-20N along 74W, moving W at 10-15 kt. The wave is in a moderate deep layer wind shear environment. GOES-16 water vapor imagery at the lower levels show very dry air over the central Caribbean. This is limiting convection to scattered moderate convection over W Hispaniola from 18N-21N between 72W-74W. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of W Africa near 14N17W to 10N28W. The ITCZ begins near 10N35W and continues to 09N46W to 11N56W. Besides the convection mentioned in the tropical wave section, scattered moderate to strong convection is over W Africa and the coast from 08N-15N between 00W-18W. Isolated moderate convection is from 10N- 12N between 24W-27W, and from 10N-12N between 36W-49W. ...DISCUSSION... GULF OF MEXICO... The Bermuda high extends a ridge axis SW across Florida and large portions of the Gulf into eastern Mexico. The ridge is providing return flow in the range of 5-10 kt across the region except in the north-central Gulf where scattered heavy showers and tstms enhance the winds to fresh. Widely scattered moderate convection is N of 25N between 85W-92W. This convection is being supported by the inflow of shallow moisture from the Caribbean with southeasterly winds, and middle level diffluent flow. Elsewhere, scattered moderate to isolated strong convection is over the Yucatan Peninsula and the E Bay of Campeche from 17N-22N between 88W-93W. Surface ridging will prevail across the basin through early next week. Showers over the NE basin are forecast to continue through Sat night. CARIBBEAN SEA... CIRA LPW imagery shows abundant shallow moisture across most of the Caribbean. In the western basin, an upper level anticyclone provides divergent flow aloft, which supports a broad area of isolated moderate convection from 15N-23N between 83W-88W. A tropical wave is moving across the central basin. SAn area of scattered moderate convection is S of Puerto Rico from 15N-17N between 65W-68W. Otherwise, surface ridging extending from the Atlantic to the northern half of the basin, continues to support fresh to strong winds in the south-central Caribbean. The next tropical is forecast to move across the Lesser Antilles Sat morning. Showers will prevail in the E Caribbean through the weekend. ATLANTIC OCEAN... Two tropical waves are over the Atlantic. See above. The Bermuda high and the Azores high covers most of the Atlc ocean mainly supporting fair weather. A weakness in the ridge is analyzed as a surface trough that extends from 31N55W SW to 26N61W to 24N72W. Scattered showers and tstms are within 105 nm either side of the trough. Isolated showers are across the Bahamas. A large area of disorganized showers and thunderstorms is SE of the Windward Islands associated with a tropical wave. For additional information please visit http://www.hurricanes.gov/marine $$ Formosa