000 AXNT20 KNHC 161728 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 128 PM EDT Sat Jun 16 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 1715 UTC. ...TROPICAL WAVES... Three tropical waves are noted between the W coast of Africa and the Lesser Antilles. A tropical wave is added to the 1200 UTC analysis/surface map along 18W/19W based on the Hovmoller Diagram that shows the westward propagation of the wave. This system is also well defined on the TPW product, and model diagnostics guidance. Scattered moderate to isolated strong convection is near the southern end of the wave's axis from 5N-9N between 16W-19W. A tropical wave is in the E Atlantic, with axis extending from 13N33W to 04N34W, moving W at 10 kt. A modest surge of moistened air is noted in association with the wave in TPW imagery. Scattered showers are where the wave meets the ITCZ axis. A tropical wave is in the central Atlantic, with axis extending from 15N47W to 04N48W, moving W at 10 kt. The wave coincides with a high amplitude bulge of moisture as depicted in the TPW product. Currently, shallow moisture and isolated showers are observed near the wave's axis. This wave will move across the waters E of the Lesser Antilles Sun night through Mon night, and the eastern Caribbean Tue through Wed night. A tropical wave is moving westward across the eastern Caribbean. Its axis extends along 66W/67W. African dust surrounds the wave. As a result, shallow moisture with embedded showers is associated with the wave. This wave will move across the remainder of the eastern Caribbean through Sun, the central Caribbean Sun night through Tue and the western Caribbean Tue night through Wed night. A tropical wave is moving across Central America, with axis along 87W/88W from 11N-20N, moving W at 10 kt. Scattered moderate to isolated strong convection is near the southern end of the wave's axis affecting parts of Nicaragua, Honduras, and El Salvador. The GFS model indicates plenty of moisture over Central America and the Yucatan Peninsula this weekend. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of Africa near 11N15W to 07N30W. The ITCZ continues from 07N30W to 08N34W to 06N42W to the coast of Guyana near 7N59W. Besides the convection mentioned in the Tropical Waves section, isolated moderate convection is within about 90 nm on either side of the monsoon trough between 22W-25W. ...DISCUSSION... GULF OF MEXICO... A strong surface trough extends from 23N91W to the eastern Bay of Campeche. Fresh to locally strong winds are near the trough axis. A large cluster of moderate to strong convection follows the trough covering the far NW Caribbean, the Yucatan Channel, the NE portion of the Yucatan Peninsula and the Gulf waters S of 24N between 85W-90W. Although environmental conditions are not expected to be favorable for significant tropical cyclone development, heavy rains and gusty winds are likely to spread across the central Gulf of Mexico later today and will reach portions of the Texas and southwestern Louisiana coasts on Sunday. The trough is interacting with an upper-level low located over the western Gulf. Scattered moderate convection is noted near the northern end of the trough while scattered showers and isolated tstms are seen over the SW Gulf in association with the upper level-low. The remainder of the Gulf is under the influence of a ridge. The trough will move WNW through early Sun night accompanied by numerous showers and thunderstorms that could produce rough seas. A tightening of the pres gradient between the trough and high pres that extends westward from the Atlantic will support fresh to strong SE winds over the west-central Gulf waters, increasing to strong to near gale force over the central Gulf this afternoon. These winds will spread westward through Tue while gradually diminishing with the trough shifting inland over Texas. CARIBBEAN SEA... As previously mentioned, a cluster of moderate to strong convection covers the far NW Caribbean, including the Yucatan Channel, mainly N of 19N W of 85W. A line of tstms has persisted this morning along the E coast of the Yucatan Peninsula. Cancun and Cozumel have been reporting rain for several hours. This convective activity is the result of a trough interacting with an upper- level low over the Gulf of Mexico. Strong trades across the central Caribbean between 69W and 83W will slowly diminish through Sun night. The strongest winds will become confined to the S central waters, with similar pulsing winds continuing in the vicinity of the Gulf of Honduras. Two tropical waves are noted across the basin. Please, see Tropical Wave section for details. A tropical wave is forecast to reach the waters E of the Lesser Antilles Sun night through Mon night, and the eastern Caribbean Tue through Wed night. It is expected to be accompanied by scattered showers and thunderstorms. As the wave moves across the Lesser Antilles into the eastern Caribbean, the moisture field is forecast by the GFS computer model to expand over the Leeward Islands, the UK/US Virgin Islands and Puerto Rico, bringing an increase in showers and tstms with likely gusty winds Tue and Wed. ATLANTIC OCEAN... As of 1500 UTC, a cold front enters the forecast waters and extends from 31N68W to 30N73W to 31N77W. A surface trough remains offshore northern and central Florida and stretches from 30N77W to the NW Bahamas. Scattered showers and tstms are roughly affecting the waters N of 28N between 65W-77W. Another surface trough is analyzed ahead of the front from 30N64W to 26N72W. High pressure of 1032 mb located just over the Azores extends a ridge across the forecast area. Three tropical waves are moving westward across the southern periphery of the ridge. The trough offshore northern and central Florida will be overtaken by the cold front later today. The front cold front will drop southward through early next week, reaching from 31N60W to 28N65W to 27N70W by early Sun morning. The high pressure ridge south of the boundaries will shift southward across the western Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ GR