330 AXNT20 KNHC 080550 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 205 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 0000 UTC surface analysis and satellite imagery through 0530 UTC. ...SPECIAL FEATURES... Tropical Storm Florence is centered near 24.8N 53.2W at 0300 UTC or 680 nm NE of the northern Leeward Islands, moving W at 6 kt. Estimated minimum central pressure is 999 mb. Maximum sustained winds are 50 kt with gusts to 60 kt. Scattered moderate isolated strong convection is within 120 nm northwest of the partially exposed center. Florence is expected to move west and intensify to a minimal hurricane this weekend, and threaten the U.S. east coast next week. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more details. Tropical Storm Helene, upgraded from a depression, is centered near 13.6N 18.5W at 0300 UTC or 350 nm E of the southern Cabo Verde Islands, moving W at 10 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained winds are 35 kt with gusts to 45 kt. Scattered moderate isolated strong convection is noted within 150 nm W of the center. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. Tropical Depression Nine is centered near 13.9N 34.9W at 0300 UTC or 1520 nm E of the Windward Islands, and stationary. Estimated minimum central pressure is 1007 mb. Maximum sustained winds are 30 kt with gusts to 40 kt. Scattered moderate isolated strong convection noted within 120 nm NW of the exposed center. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from 14N17W through T.S. Helene to 14N27W. The ITCZ extends west of T.D. Nine from 09N44W to 07N58W. Aside from the convection related to tropical cyclones, scattered moderate convection is from 08N to 11N between 23W and 40W. ...DISCUSSION... GULF OF MEXICO... Upper-level cyclonic flow located over the northeastern Gulf and strong northeast upper-level winds over the north-central Gulf along the western periphery of the large upper low over the NW Bahamas. A moist and unstable atmosphere is allowing scattered showers to develop over portions of the eastern Gulf east of 87W. Expect this activity to persist through the late morning. Weak 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 anticyclone is centered over the central Caribbean near 15N73W. Scattered moderate isolated strong convection is noted southwest of the upper anticyclone, roughly south of 14N and west of 73W. A relatively weak 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. A large upper-level low centered over the NW Bahamas extends a trough southwestward across western Cuba. Associated upper-level cyclonic flow covers the Atlantic west of 70W. A surface trough analyzed from western Cuba across the Bahamas to 31N72W is enhancing widely scattered shower activity west 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 $$ Mundell