028 AXNT20 KNHC 201806 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 206 PM EDT Mon Aug 20 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. ...TROPICAL WAVES... A far eastern Atlantic tropical wave has its axis extending from 05N34W to 13N34W to 19N32W, moving westward at 10-15 kt. Isolated moderate convection is from 05N to 17N. Scattered moderate convection is within 120 nm west of the wave axis from 05N to 06N. Isolated showers and thunderstorms are within 180 nm east of the wave axis from 05N to 08N. A central Atlantic tropical wave has its axis extending from 05N52W to 13N52W to 18N51W, moving westward at 15 kt. Scattered moderate convection is within 60 nm east of the wave axis from 09N to 10N. Isolated showers and thunderstorms are within 60 nm of the axis from 12N to 16N. A western Caribbean Sea tropical wave has its axis extending from southern Costa Rica northward to 15N78W and to eastern Cuba near 20N76W. It is moving westward at 10-15 kt. Isolated moderate convection is within 60 nm east of the wave from 20N-21N. The northern portion of an eastern Pacific tropical wave extends along 94W northward to the Bay of Campeche to 19N. It is moving westward near 20 kt. Only isolated showers are noted within 60 nm of the wave. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from western Africa at 13N17W to 10N28W to 09N40W, where scatterometer data indicates the ITCZ axis begins and extends to just east to the east of the central Atlantic tropical wave. It resumes at 09N52W to just inland the coast of S America at 07N59W. Scattered moderate convection is within 120 nm south of the axis between 21W and 25W and also between 27W and 29W. ...DISCUSSION... GULF OF MEXICO... A 1023 mb high is centered over the western Atlantic at 32N62W, with a ridge axis extending WSW from the high to central Florida and to the eastern gulf waters. The associated gradient is allowing for generally moderate southerly flow to persist over much of the gulf, except for lighter SW to W flow, in the 5-10 kt range over the far northeastern gulf waters. Widely scattered moderate convection is over the N Florida Peninsula N of 27N. The northern portion of a tropical wave is over the Bay of Campeche. No deep convection is occurring with this wave. See above for details. Scattered moderate to isolated strong convection is from 15N to 21N between 92W and 95W. A small upper-level low is centered over the Yucatan Channel near 22N86W enhancing the convection over western Cuba and the NW Caribbean Sea. Expect, a surface high to develop over the Gulf near 27N91W on Tue. This high will meander over the western gulf waters through Thu. A weak trough will stall over the eastern Gulf waters, then drifts west and dissipates on Fri. CARIBBEAN SEA... A tropical wave is over the western section of the central Caribbean. See above for details. A surface trough is evident along a position from 19N69W to near 14N72W. Latest satellite imagery shows an area of scattered showers and isolated thunderstorms within 60 nm east of the trough from 15N to 16N. This activity is being further aided by an upper-level disturbance that is quickly moving westward in moderate to strong east winds that are located to the south of an upper anticyclone centered just north of the Dominican Republic. Otherwise, the pressure gradient associated with surface ridging that extends from the Atlantic to the northern half of the basin supports fresh to strong winds in the south-central Caribbean. Expect scattered shower showers and convection to persist over the southwestern Caribbean through at least Wed. Also expect strong to near gale force nocturnal easterly trades along the northwestern coast of Colombia and across the Gulf of Venezuela through the middle of the week. ATLANTIC OCEAN... A surface trough is analyzed from near 32N51W to 28N60W to near 27N65W. A second surface trough is analyzed from near 32N45W to 27N50W and to near 23N56W. Meanwhile, an elongated upper-level low is near 32N62W. The present factors of a very moist and unstable atmosphere and upper divergence to the east and southeast of the low along with the presence of the first surface trough is leading to scattered moderate convection from 26N to 29N between 62W and 65W. Isolated showers and thunderstorms are seen within 60 nm south of the first trough between 57W and 62W. Yet a third surface trough is analyzed along a position from near 28N69W to the southeastern Bahamas near 22N74W. A shortwave trough passing just to its NNE is providing additional atmospheric lift leading to clusters of weakening scattered moderate convection from 25N to 29N and between 71W and 73W. Isolated showers and thunderstorms are elsewhere within 90 nm of the surface trough from 22N to 25N. The third trough is forecast to move westward across the Bahamas through Tue, then weaken by Tue night and into Wed. An upper- level anticyclone is identified to be just north of the Dominican Republic near 21N70W. Its associated subsidence is suppressing deep convection from developing in that general area. E of the lower Windward Islands, scattered moderate convection is seen within 45 nm either side of a line from 09.5N55W to 10N58W to 11N62W. A 1023 mb high is centered over the western Atlantic near 32N62W, with a ridge extending WSW to central Florida. A surface trough from 32N79W to just east of central Florida briefly interrupts the ridge. Scattered showers and thunderstorms are within 30 nm of the trough. This activity is likely to continue into tonight. A 1027 mb high is centered to the southwest of the Azores near 35N35W. It is allowing for ridging and generally fair weather to persist over the eastern Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre