000 AXNT20 KNHC 181806 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 206 PM EDT Sun Jun 18 2017 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... A tropical wave is in the central Atlantic associated with a 1009 mb low centered near 06N47W. Its axis extends from 10N46W to the low to 02N47W, moving W at 20 kt within the last 24 hours. The wave is in a region of favorable wind shear and is embedded in a moderate moist environment at the lower levels according to CIRA LPW imagery. However, Saharan dry air and dust continue to enter its environment, thus limiting the convection to scattered moderate from 06N to 10N between the wave axis and 52W. Upper level divergence support this convection. Some development of this system is possible during the next couple of days before environmental conditions become less favorable for tropical cyclone formation. This system is forecast to move to the west- northwest towards the Windward Islands and northeastern South America during the next two days. This system has a medium chance of becoming a tropical cyclone during the next two days. See the latest NHC Tropical Weather Outlook under AWISP/WMO headers MIATWOAT/ABNT20 KNHC for more details. A broad area of low pressure in the northwestern Caribbean Sea is centered by a 1006 mb low near 18N87W. This system is generating clusters of heavy showers with embedded tstms N of 13N W of 77W, including inland western Cuba. Gale force SE winds are N of 19N between 81W and 83W with seas of 9 to 11 ft. Fresh to near gale force winds are elsewhere N of 16N between 78W and 84W with seas to 10 ft. Gale conditions are forecast to continue through Monday morning. Gradual development of this system is expected while it moves slowly northwestward across the Yucatan Peninsula later today and over the southern or central Gulf of Mexico on Monday and Tuesday, where a tropical or subtropical cyclone is likely to form. Regardless of development, heavy rains are expected over portions of Central America, the Yucatan Peninsula, Jamaica, the Cayman Islands, and western Cuba during the next several days. The chance of formation into a tropical cyclone during the next two days is medium. Please read the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. ...TROPICAL WAVES... A tropical wave is in the E Atlc associated with a 1011 mb low near 08N21W. Its axis extends from 11N21W to the low to 02N21W. The wave is in a region of favorable wind shear and CIRA LPW show a moderate moist environment with some patches of dry associated with Saharan dry air and dust intrusion. Upper level divergence support scattered moderate convection from 08N to 12N between 20W and 25W. A tropical wave is in the central Atlc with axis extending from 10N33W to 02N34W, moving W at 20 kt within the last 24 hours. The wave is in a region of favorable wind shear. However, extensive intrusion of Saharan dry air and dust to its environment limit the convection to isolated showers within 120 nm either side of its axis from 05N to 08N. A tropical wave is in the W Atlc around 270 nm E of the Lesser Antilles. Its axis extends from 17N55W to 08N55W and has been moving W at 20 kt within the last 24 hours. The wave is in a region of unfavorable wind shear and its environment is being affected by extensive Saharan dry air intrusion. Shallow moisture and a middle level divergent environment ahead of the wave support scattered showers and tstms S of 16N between 57W and 65W. ...MONSOON TROUGH/ITCZ... The Monsoon Trough extends from the coast of west Africa near 10N14W to a 1011 mb low near 08N21W to 06N31W. The ITCZ extends from 04N36W to 05N43W, then resumes W of a tropical wave near 05N52W to 06N58W. Three tropical waves are embedded within the Monsoon trough/ITCZ. See tropical waves and special features sections for information about convection. ...DISCUSSION... GULF OF MEXICO... Broad surface high press covering great portions of the Atlc waters extends a ridge axis SW across the Florida peninsula to the NE Gulf, which continue to provide gentle to moderate SE flow across the basin, except for the SE gulf. Latest scatterometer data and surface observations show fresh to near gale force winds in the SE basin S of 24N E of 88W associated with a broad area of low pressure in the NW Caribbean with medium chances of becoming a tropical cyclone in the next two days as it moves slowly northwestward across the Yucatan Peninsula later today and over the southern or central Gulf of Mexico on Monday and Tuesday. Scattered showers associated with the rainbands of this systems are already affecting the Florida straits and the Yucatan channel. See the special features section and the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. CARIBBEAN SEA... The major concern in the basin is a broad area of low pressure in the NW Caribbean, which is generating numerous heavy showers and strong to gale force winds. Gradual development of this system is expected while it moves slowly northwestward across the Yucatan Peninsula later today and over the southern or central Gulf of Mexico on Monday and Tuesday, where a tropical or subtropical cyclone is likely to form. See the special features section and the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. Scattered heavy showers and tstms are in the SE basin ahead of a tropical wave with axis near 270 nm E of the Lesser Antilles. See tropical waves section for further details. Otherwise, a surface trough off the coast of Colombia is supporting scattered heavy showers and tstms S of 14N between 75W and 79W. ...HISPANIOLA... Isolated showers are across the island being influenced by the broad area of low pressure in the NW Caribbean. Showers are forecast to continue through later today. ATLANTIC OCEAN... Four tropical waves are moving westward between the coast of Africa and the Lesser Antilles. Please refer to the Tropical Waves section above for details. Otherwise, broad high pressure covers the Atlantic from the Azores to the Florida Peninsula, with a 1025 mb high pressure near 29N44W. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos