638 AXNT20 KNHC 081154 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 754 AM EDT Sat Sep 8 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 1115 UTC. ...SPECIAL FEATURES... Tropical Storm Florence is centered near 24.5N 54.2W at 08/0900 UTC or 730 nm SE of Bermuda moving W at 8 kt. Estimated minimum central pressure is 997 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Scattered moderate convection is from 23N-28N between 51W-56W. Florence is expected to move west and intensify to a minimal hurricane Sunday, and threaten the U.S. east coast next week. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC for more details. Tropical Storm Helene is centered near 13.7N 19.6W at 08/0900 UTC or 290 nm ESE of the Southernmost Cabo Verde Islands moving W at 11 kt. Estimated minimum central pressure is 1001 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. A Tropical Storm Warning is in effect for the Cape Verde Islands of Santiago, Fogo, and Brava. Additional strengthening is forecast for the next couple of days and Helene is expected to become a hurricane Sunday. Scattered moderate to isolated strong convection is from 11N-15N between 18W-25W. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT3/WTNT33 KNHC for more details. Tropical Depression Nine is centered near 14.3N 35.4W at 08/0900 UTC or 1490 nm E of the Windward Islands moving WNW at 4 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Gradual strengthening is forecast during the next few days, and the depression is expected to become a tropical storm later today and a hurricane by early next week. Scattered moderate to strong convection is from 13N-17N between 34W-39W. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough extends west of T.D. Nine from 12N38W to 08N48W. The ITCZ extends from 08N48W to the coast of South America near 07N58W. Aside from the convection related to tropical cyclones, scattered moderate convection is from 07N-10N between 31W-44W. ...DISCUSSION... GULF OF MEXICO... An upper level low is centered over the SE Gulf of Mexico near 25N86W. A moist and unstable atmosphere over the SE Gulf and Florida allowing scattered showers to develop over The Straits of Florida. Weak surface ridging from the Carolinas to the Texas coast will shift northward through Sat, supporting gentle to moderate easterly winds and modest seas into early next week. Fresh NE winds will pulse at times west of the Yucatan peninsula, mainly during the late evening, the next few days due to a thermal trough over the peninsula that moves west over the Bay of Campeche at night. CARIBBEAN SEA... An upper-level trough axis stretches from western Cuba to northeastern Honduras, and a broad upper level high is centered over the central Caribbean near 14N74W. Scattered moderate isolated strong convection is noted west of the upper level high, roughly south of 16N and west of 74W. A relatively weak surface pressure gradient north of the area in the western Atlantic Ocean will maintain moderate to locally fresh trade winds across most of the region through Sun. High pressure in the eastern Gulf of Mexico will strengthen E to SE winds and increase seas over the NW Caribbean Sun night and Mon. ATLANTIC OCEAN... Please see the Special Features section above for details about T.S. Florence, T.S. Helene, and T.D. Nine. An upper level low is centered over the NW Atlantic near 30N71W. Scattered showers are from 26N-29N between 68W-72W. A surface trough is over the NW Atlantic from 31N75W to S Florida near 26N81W. Widely scattered moderate convection is W of 75W. A weak pressure pattern will support gentle to moderate easterly winds across the western Atlantic into early next week. Tropical Storm Florence is forecast by the latest NHC advisory to move across the northeastern TAFB offshore waters zones Mon through Tue. Easterly swell well in advance of Florence will propagate through the open waters east of the Bahamas this weekend. For additional information please visit http://www.hurricanes.gov/marine $$ Formosa