178 AXNT20 KNHC 091211 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 811 AM EDT Sun Sep 9 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 55.8W at 09/0900 UTC or 660 nm SE of Bermuda moving W at 5 kt. Estimated minimum central pressure is 989 mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt. Florence will move over the southwestern Atlantic Ocean between Bermuda and the Bahamas Tuesday and Wednesday, and approach the southeastern U.S. coast on Thursday. Florence is expected to become a hurricane today and rapid intensification is likely to begin by tonight. Florence is forecast to become a major hurricane on Monday. Scattered moderate to isolated strong convection is from 22N-26N between 54W-58W. See latest NHC Public Advisories issued under WMO header WTNT31 KNHC and under AWIPS header MIATCPAT1. Forecast/Advisories are issued under WMO header WTNT21 KNHC and under AWIPS header MIATCMAT1. Tropical Storm Isaac is centered near 14.5N 38.1W at 09/0900 UTC or 1340 nm E of the Windward Islands moving W at 8 kt. Estimated minimum central pressure is 1001 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Strengthening is forecast during the next few days, and Isaac is expected to become a hurricane by Monday. Scattered moderate to isolated strong convection is from 11N-16N between 36W-42W. Public Advisories for Tropical Storm Isaac are issued under WMO header WTNT34 KNHC and under AWIPS header MIATCPAT4. Forecast/Advisories for Tropical Storm Isaac are issued under WMO header WTNT24 KNHC and under AWIPS header MIATCMAT4. Tropical Storm Helene is centered near 13.2N 24.0W at 09/0900 UTC or 100 nm SSE of the Southernmost Cabo Verde Islands moving W at 12 kt. Estimated minimum central pressure is 997 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. A Tropical Storm Warning is in effect for the Cabo Verde islands of Santiago, Fogo, and Brava. Additional strengthening is forecast during the next couple of days, and Helene is expected to become a hurricane later today. Scattered moderate to isolated strong convection is from 10N-17N between 19W-27W. Public Advisories for Tropical Storm Helene are issued under WMO header WTNT33 KNHC and under AWIPS header MIATCPAT3. Forecast/Advisories for Tropical Storm Helene are issued under WMO header WTNT23 KNHC and under AWIPS header MIATCMAT3. ...TROPICAL WAVES... A tropical wave is along 83W from W Cuba at 21N southward. This wave has a complex past history, and it is likely that it may have been related to T.S. Florence from several days ago. Scattered moderate to strong convection is from 13N-22N between 78W-85W. ...MONSOON TROUGH/ITCZ... The ITCZ is W of T.S. Isaac from 09N42W to the coast of South America near 08N59W. Scattered moderate convection is from 07N-09N between 30W-47W. ...DISCUSSION... GULF OF MEXICO... An upper level low is centered over the E Gulf of Mexico near 24N88W. Scattered showers are E of 89W. An upper level ridge is over the W Gulf W of 92W with northerly upper level flow. Scattered showers are along the Texas coast. At the surface, 5-10 southerly flow covers the Gulf. A weak surface ridge from the Carolinas to the Texas coast will shift northward in order to cover the SE United States. Gentle to moderate E to SE winds and modest seas will prevail through the middle of the next week. The exception will be fresh winds developing off the west coast of the Yucatan peninsula, mainly during the late evening. CARIBBEAN SEA... A large upper level high is centered over the central Caribbean near 16N75W. The tropical wave is main source of convection in the Caribbean. See above. Isaac is forecast to approach the Lesser Antilles Wed evening, and continue into the eastern Caribbean Thu. A relatively weak surface ridge in the western Atlantic Ocean will maintain moderate to fresh trade winds over most of rest of the region through Monday night. Building high pressure in the eastern Gulf of Mexico will allow fresh to locally strong E to SE winds and building seas in parts of the NW Caribbean Sea from Sunday through Tuesday. ATLANTIC OCEAN... Please read the SPECIAL FEATURES section for details about T.S. Florence, T.S. Isaac, and T.S. Helene. Isolated moderate convection is over the W Atlantic from 25N-30N between 74W-80W. A small upper level low is near 30N70W. A 1014 mb low pressure center is near 31N68W. A 1025 mb high is over the E Atlantic near 34N27W. For additional information please visit http://www.hurricanes.gov/marine $$ Formosa