000 AXNT20 KNHC 151036 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 636 AM EDT Sat Jul 15 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 0600 UTC surface analysis and satellite imagery through 1045 UTC. ...TROPICAL WAVES... A central Atlantic tropical wave has its axis from 15N45W to 02N45W, moving westward 10-15 knots. The wave is surrounded by dry Saharan air as depicted in the latest METEOSAT-9 Saharan Air Layer imagery. Only convection noted within this wave is south of 10N to the ITCZ region between 43W-48W. A Caribbean tropical wave has its axis from 19N67W to 08N69W, moving westward at 20 kt over the past 24 hours. Satellite imagery shows a well-defined cloud structure to the wave, with a low-level vorticity maximum on the southern portion of the wave axis. Scattered moderate convection is north of 14N between 63W- 68W. This wave is forecast to move across the rest of the eastern Caribbean today and reach the central Caribbean by tonight. Increasing moisture along scattered showers and isolated thunderstorms will follow the wave. Some of the shower and thunderstorm activity may contain gusty winds. A central Caribbean tropical wave has its axis from 21N77W to 11N79W, moving westward at about 15-20 knots. The northern portion of the wave's axis just entered eastern Cuba. Subsidence aloft with dry air prevails in the wave's environment. Isolated showers and thunderstorms along the wave's axis north of 19N affecting eastern Cuba. The wave will move across the rest of the central Caribbean through the morning hours and the western portion of the basin tonight and through Sunday. The wave may acquire more moisture along with shower and thunderstorm activity as it moves through the western Caribbean. ...ITCZ/MONSOON TROUGH... The monsoon trough axis extends from 20N17W and continues to 11N26W to 09N44W. The ITCZ is west of a tropical wave from 07N48W to 06N56W. Aside from the convection related to the tropical wave along 46W, scattered moderate convection is within 180 nm north of the axis between 32W-43W and west of 46W. ...DISCUSSION... GULF OF MEXICO... A weak pressure pattern is present across the area. A very moist and unstable air mass in place over just about the entire Gulf, except over the Bay of Campeche where dry air is noted aloft. A surface trough is analyzed from near 29N84W to 27N88W. Isolated showers are occurring along the trough mainly north of 25N and east of 88W. Moisture guidance suggests that abundant moisture will continue over much of the Gulf through the weekend. With this scenario, showers and thunderstorms are expected through this period. CARIBBEAN SEA... A couple of tropical waves are moving through the Caribbean Sea. See the section above for details. Aside from the convection related to these waves, an area of scattered showers prevail over the southwest Caribbean south of 11N between 75W-83W due to the proximity of the monsoon trough. The pressure gradient through the basin remains fairly weak. Scatterometer data depicts gentle to moderate trades across the area. Expect a similar weather pattern to prevail through the next 24 hours. ...HISPANIOLA... Fair weather prevails across the island at this time. A tropical wave is approaching from the east. This wave will generate scattered convection today through Sunday. ATLANTIC OCEAN... A tropical wave is moving across the central Atlantic. See the section above for details. A surface trough was analyzed from 27N75W to 23N76W. Another trough is from 30N62W to 27N64W. These two features are the reflection of upper-level lows. The remainder of the basin is under the influence of a surface ridge, anchored by a stationary 1026 mb high centered near 35N48W. For additional information please visit http://www.hurricanes.gov/marine $$ ERA