000 AXNT20 KNHC 141028 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 628 AM EDT Mon Aug 14 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 1030 UTC. ...SPECIAL FEATURES... Tropical Storm Gert is centered near 29.7N 72.2W at 14/0900 UTC, moving toward the north-northwest, or 345 degrees, at 8 kt. Estimated minimum central pressure is 1009 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Numerous moderate and scattered strong convection is noted within 90 nm southeast and 30 nm northwest semicircles of Gert. Scattered moderate isolated strong convection is noted elsewhere within 210 nm southeast and 60 nm northwest semicircles of Gert. The system is expected to remain east of the United States, taking a turn toward the north today, followed by a turn toward the north- northeast tonight. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. ...TROPICAL WAVES... The axis of a tropical wave is near 24W from 05N to 21N, with low pressure centered along the wave axis near 13N24W, moving W at 15 kt. Environmental conditions are expected to become more conducive for development of this low later this week, and there is a medium chance for tropical cyclone formation within 5 days. Scattered showers are noted from 10N to 16N between 20W and 27W. The axis of a tropical wave is near 39W from 06N to 21N, moving W at 20 kt. This wave is very evident in low-mid level satellite cloud wind vectors. Scattered showers are within 90 nm of the wave axis south of 13N. The axis of a tropical wave is near 57W from 07N to 21N, moving W at 15-20 kt. There is limited convection associated with this wave, with isolated showers noted near the southern end of the wave axis, from 08N- 11N between 55W- 58W. The axis of a tropical wave has moved west of the Caribbean waters, and is currently moving across the Yucatan Peninsula. This wave is helping produce active convection over the western Caribbean as well as the Yucatan Peninsula, Belize, Guatemala, Honduras, and Nicaragua. ...ITCZ/MONSOON TROUGH... The monsoon trough extends from the coast of Africa near 19N16W to 14N22W to 09N47W. The Intertropical Convergence Zone continues from 09N47W to 08N57W. Aside from the convection associated with the tropical waves, scattered moderate isolated strong convection is noted from 06N- 14N between 27W- 36W, and from 05N- 12N between 40W- 47W. ...DISCUSSION... GULF OF MEXICO... A ridge of high pressure prevails over the Gulf of Mexico, except for a thermally induced trough which has moved off the Yucatan Peninsula into the southwest Gulf. Latest surface observations indicate with light to gentle anticyclonic flow covering much of the Gulf waters, with two exceptions. The first is an area of moderate to fresh winds west of the trough in the southwest Gulf. The second is over the far western Gulf where moderate to fresh winds prevail due to a tighter pressure gradient between the ridge and a trough of low pressure over Mexico. The ridge will remain across the Gulf waters the next several days with these general conditions prevailing. A thermal trough will develop each evening over the Yucatan Peninsula, shifting westward into the southwest Gulf during the overnight hours, and dissipating over this area each morning. Locally higher winds can be expected west of the trough axis. CARIBBEAN SEA... The western Atlantic ridge has started to build westward south of T.S. Gert, which has tightened the pressure gradient over the area. Latest surface observations indicate fresh to strong winds over the south central Caribbean, moderate to fresh winds over the north central Caribbean, moderate winds over the eastern Caribbean, and gentle to moderate winds over the western Caribbean. The ridge will continue to build as Gert moves further north. This will bring an increase in coverage of fresh winds across the north central and eastern Caribbean through midweek. ...HISPANIOLA... Expect daytime heating, local sea breezes and mountain upslope lifting to produce scattered showers and thunderstorms during the afternoon and evening hours across the island the next couple of days. ATLANTIC OCEAN... Please see the Special Features section above for more on Tropical Storm Gert, and the Tropical Wave section above for more on the tropical waves propagating across the tropical Atlantic waters. Outside of these areas, the forecast area is under the influence of the subtropical high. This high pressure area has started to build westward into the southwest north Atlantic waters in the wake of T.S. Gert as the system moves northward. Moderate to fresh winds prevail over the eastern waters between the two easternmost tropical waves and the subtropical high, with gentle to moderate winds elsewhere. The area of fresh winds will spread westward along with the tropical waves the next couple of days. For additional information please visit http://www.hurricanes.gov/marine $$ AL