Expires:No;;211713 AXNT20 KNHC 171747 TWDAT
Tropical Weather Discussion NWS National Hurricane Center Miami FL 147 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 1200 UTC surface analysis and satellite imagery through 1745 UTC. ...SPECIAL FEATURES... The center of Tropical Storm Ernesto at 17/1500 UTC is near 47.1N 32.9W or 605 nmi to the NNW of the Azores. Ernesto is moving NE at 26 knots. The estimated minimum central pressure is 1005 mb. The maximum sustained wind speeds are 40 knots with gusts to 50 knots. Scattered moderate convection is N of 44N between 26W and 34W. Ernesto is expected to become a post-tropical cyclone by tonight and then become extratropical as it merges with a frontal zone on Saturday. The post-tropical cyclone or its remnants will move across Ireland and the United Kingdom Saturday night. Please read the 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 57W, 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 shown both in CIRA LPW and water vapor imagery at the lower levels. This dry air limits the area of scattered moderate isolated strong convection from 10N-15N between 54W-61W. A tropical wave is in the central Caribbean with axis extending from 10N-20N along 70W, 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 isolated showers and tstms over Dominican Republic adjacent waters.
A tropical wave is the SW Gulf of Mexico with axis S of 20N along 95W, moving W at 10-15 kt. GOES-16 water vapor imagery at the lower levels show dry air over this region, which is hindering convection in the Bay of Campeche at this time. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of W Africa near 10N15W to 07N20W to 07N28W. The ITCZ begins near 09N32W and continues to 08N40W to 07N48W to 10N52W. Scattered moderate convection is from 04N-10N E of 21W and from 05N-11N between 38W-46W. For more information about convection, see the tropical waves section. ...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. The area of convection is N of 25N between 85W and 92W and is being supported by inflow of shallow moisture from the Caribbean by southeasterly wind and middle level diffluent flow. Otherwise, a tropical wave moving over the EPAC waters south of southern Mexico reaches the Bay of Campeche, however is not supporting convection at the time. 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 scattered showers and tstms from 12N-21N between 83W-90W. A tropical wave is moving across the central basin, however low level dry air suppress the development of deep convection at the time. Scattered to isolated showers and tstms are occurring across Hispaniola and adjacent waters being supported by shallow moisture and middle level diffluence. Scattered showers and tstms are in the eastern Caribbean associated with a tropical wave approaching the Lesser Antilles. 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 center of high pressure SW of the Bahamas will stall the next several days, which will allow the continuation of these winds in the south-central basin. The axis of the tropical wave supporting showers in the E Caribbean is forecast to move across the Lesser Antilles Sat morning. Showers will prevail in the E Caribbean through the weekend. ATLANTIC OCEAN... 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. Environmental conditions are becoming less conducive and development of this system is not expected while it moves westward. This system is forecast to move through the Windward Islands on Saturday where it could bring locally heavy rainfall to portions of the area this weekend. For further information associated with the tropical waves, see section above.
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