405 AXNT20 KNHC 090005 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 PM 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 1800 UTC surface analysis and satellite imagery through 2330 UTC. ...SPECIAL FEATURES... The center of Tropical Storm Florence at 08/2100 UTC is near 24.6N 54.7W. FLORENCE is moving W, or 270 degrees, 04 knots. The estimated minimum central pressure is 989 mb. The maximum sustained wind speeds are 60 knots with gusts to 75 knots. Scattered moderate to strong rainshowers are from 24N to 26N between 54W and 56W. Widely scattered moderate to isolated strong rainshowers are elsewhere from 21N to 27N between 50W and 58W. Florence is expected to move across the southwestern Atlantic Ocean between Bermuda and the Bahamas on Tuesday and Wednesday, and approach the southeastern U.S.A. coast on Thursday. Florence is expected to intensify to a hurricane on Sunday, and intensify more to a major hurricane by Tuesday. Please read the latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC for more details. The center of Tropical Storm Helene at 09/0000 UTC is near 13.6N 22.2W. HELENE is about 200 km to the SE of Praia in the Cabo Verde Islands. HELENE is moving W, or 275 degrees, 11 knots. The estimated minimum central pressure is 998 mb. The maximum sustained wind speeds are 50 knots with gusts to 60 kt. Scattered to numerous strong rainshowers are from 11N to 14N between 20W and 25W. Scattered moderate to isolated strong rainshowers are elsewhere from 10N to 16N between 20W and 25W. Please read the latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT3/WTNT33 KNHC for more details. The center of Tropical Depression Nine at 08/2100 is near 13.6N 34.9W. T.D. NINE is stationary at the moment. The estimated minimum central pressure is 1007 mb. The maximum sustained wind speeds are 30 knots with gusts to 40 knots. Scattered to numerous strong rainshowers are from 13N to 16N between 36W and 40W. 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. Please read the latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough is along 11N40W 08N49W. The ITCZ continues from 11N40W to 07N58W. Isolated moderate to locally strong rainshowers are elsewhere from 07N to 13N from 40W eastward. Rainshowers are possible elsewhere from 10N southward between 40W and 60W. ...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 is producing widely scattered moderate convection over the Straits of Florida from 23N-26N between 80W-85W. Upper level diffluence is also over the W Gulf producing widely scattered moderate convection from 22N-24N between 90W-94W. On the surface, a trough is over the Straits of Florida from 25N80W to 23N84W. Weak ridging from the Carolinas to the Texas coast will shift N over the SE United States. Gentle to moderate E to SE winds and modest seas will prevail through the middle of next week. The exception will be fresh winds pulsing off west of the Yucatan peninsula, mainly during the late evening. 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. Relatively weak surface ridging over the western Atlantic will maintain moderate to fresh trade winds over most of the region into Sun. Building surface high pressure over the eastern Gulf of Mexico will allow fresh to locally strong E to SE winds and building seas over portions of the NW Caribbean Sun through Tue. ATLANTIC OCEAN... Please read the SPECIAL FEATURES section for details about T.S. Florence, T.S. Helene, and T.D. Nine. An upper level low is centered over the W Atlantic near 30N71W. Widely scattered moderate convection is from 27N-35N between 59W- 69W. A surface trough is over the W Atlantic from 31N75W to S Florida near 26N81W. Widely scattered moderate convection is W of 75W. A 1012 mb low is centered over the W Atlantic near 32N68W. A surface trough extends S from the low to 28N72W. A 1021 mb high is centered over the central Atlantic near 35N38W. 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 $$ mrf/mt