000 AXNT20 KNHC 301037 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 637 AM EDT Sat Jun 30 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 0600 UTC surface analysis and satellite imagery through 1100 UTC. ...TROPICAL WAVES... A tropical wave has an axis extending from 04N26W to just SW of the Cabo Verde Islands near 16N26W moving W around 10 kt. This wave is well defined in model diagnostics guidance and TPW animation. Scattered moderate convection is limited to a small area near the axis of this wave from 04N to 06N between 21W and 24W as it is nearly surrounded by dry Saharan air. A tropical wave has an axis extending N from 05N50W to 17N49W and is moving westward around 15 knots. Scattered moderate convection is present from 03N to 07N between 44W and 51W on the SE side of the wave. The wave shows up well in model diagnostics guidance and TPW product and has dry Saharan air on its N side. Tropical moisture associated with this wave will reach the waters E of the Windward Islands tonight, and move across the islands on Sat, increasing the likelihood of showers and tstms. A tropical wave has an axis extending N from NW Venezuela to the eastern Dominican Republic near 19N69W. This feature is moving W between 10 and 15 kt and despite its longitude has dry Saharan air on both sides. As a result, there is no significant convection currently associated with this wave. Some moisture on the SE side of this wave could enhance convection over the basin this weekend before the wave exits the basin Sun night. Another tropical wave has an axis extending N from the eastern Pacific near 07N88W to northern Belize near 18N88W. This wave is slowing down and moving W at only around 5 kt. TPW satellite imagery and model diagnostics show this wave to be poorly defined. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean from the coast of Mauritania near 17N16W and continues to 07N27W to 06N35W. The ITCZ continues from 06N35W to 03N44W to 05N49W. Aside from the convection associated with the tropical waves, scattered moderate and isolated strong convection is observed from 05N to 10N between 12W and 17W. ...DISCUSSION... GULF OF MEXICO... A surface trough curves SW from the Florida Big Bend near 30N84W over the NE Gulf to near 24N86W. Scattered showers are occurring along and up to 60 nm E of the trough axis. The remainder of the Gulf is under the influence of a weak high pressure center of 1017 mb located over the central Gulf near 27N90W. This system is producing light to gentle winds and seas of 2-3 ft over the eastern half of the Gulf, and gentle to moderate winds and seas of 3-5 ft over the western half of the Gulf. Moderate to fresh return flow is expected over the west- central and NW Gulf through the weekend. The western Atlantic high pressure is forecast to weaken on Sat and remain stretched across Florida and the eastern Gulf. A surface trough will emerge off the Yucatan Peninsula each night, enhancing nocturnal winds in the SW Gulf through early next week. CARIBBEAN SEA... A pair of tropical waves are moving across the basin. Please, see the Tropical Waves section for details. Recent scatterometer data depicted fresh to strong winds across the south-central Caribbean, while moderate to fresh trades across the remainder of the basin S of 12N between 72W-77W. Light to gentle winds are noted over the NW Caribbean. Winds and seas in the central Caribbean will gradually diminish through early next week as high pressure N of area weakens. Scattered moderate convection is seen over the SW Caribbean, mainly S of 12N between 80W-84W. Similar convection is over the eastern Caribbean due to the presence of a tropical wave. Isolated to scattered showers and tstms are over parts of Hispaniola, the Windward Passage, Jamaica and the Cayman Islands. An upper-level low centered over the Windward Passage is helping to induce this convective activity. The upper-level low will drift westward into the NW Caribbean over the weekend, and will continue to enhance convection across the area. ATLANTIC OCEAN... Two tropical waves are moving across the waters between the coast of West Africa and the Lesser Antilles. Refer to the Tropical Wave section above for details. A surface trough is over the central Atlantic and extends from 36N48W to 28N50W. Light winds are on either side of the trough's axis based on scatterometer data. This trough is a surface reflection of an upper-level low spinning near 31N49W. A 1035 mb surface high located NW of the Azores near 44N40W is in control of the remainder of the area, extending a ridge SW across the west-central Atlantic. Moderate to fresh winds are around the southern periphery of the ridge W of 48W to the Lesser Antilles. The ridge will slowly weaken through early next week. Generally benign marine conditions are expected across the region through this period. For additional information please visit http://www.hurricanes.gov/marine $$ GR