964 AXNT20 KNHC 090529 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 129 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 0000 UTC surface analysis and satellite imagery through 0500 UTC. ...SPECIAL FEATURES... The center of Tropical Storm Florence at 09/0300 UTC is near 24.6N 55.2W. Florence is moving W, or 270 degrees, 05 knots. The estimated minimum central pressure is 989 mb. The maximum sustained wind speeds are 60 knots with gusts to 75 knots. 24-hour rainfall totals that are listed for the period that ended at 09/0000 UTC...according to the PAN AMERICAN TEMPERATURE AND PRECIPITATION TABLES...MIATPTPAN/SXCA01 KNHC...are 1.25 in Bermuda. Scattered moderate to strong rainshowers are within 30 nm of the center everywhere. Scattered moderate to isolated strong rainshowers are within 120 nm of the center in the NE quadrant, and within 150 nm of the center in the SW quadrant. The official forecast continues to call for a period of rapid intensification in about 12 to 24 hours. Florence is expected to reach major hurricane intensity between 36 and 48 hours, with additional strengthening after that. Florence is forecast to be an intense hurricane on days 3 through 5 as it moves across the warm waters of the southwestern Atlantic Ocean, between the Bahamas and Bermuda, and then as it heads toward the southeast U.S.A. coast. Public Advisories for Tropical Storm Isaac are issued under WMO header WTNT31 KNHC and under AWIPS header MIATCPAT1. Forecast/Advisories for Tropical Storm Isaac are issued under WMO header WTNT21 KNHC and under AWIPS header MIATCMAT1. The center of Tropical Storm Isaac at 09/0300 UTC is near 14.4N 37.5W. Isaac is moving W, or 270 degrees, 07 knots. The estimated minimum central pressure is 1002 mb. The maximum sustained wind speeds are 45 knots with gusts to 55 knots. Numerous strong rainshowers are within 150 nm of the center in the S semicircle, and within 60 nm of the center in the NE quadrant. 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. The center of Tropical Storm Helene at 09/0300 UTC is near 13.2N 22.8W. HELENE is about 250 km to the SE of the southernmost Cabo Verde Islands. HELENE is moving W, or 260 degrees, 11 knots. The estimated minimum central pressure is 999 mb. The maximum sustained wind speeds are 50 knots with gusts to 60 kt. Scattered to numerous strong rainshowers are within 240 nm of the center in the SE quadrant, and within 150 nm of the center in the SW quadrant. Public Advisories for Tropical Storm Isaac are issued under WMO header WTNT33 KNHC and under AWIPS header MIATCPAT3. Forecast/Advisories for Tropical Storm Isaac are issued under WMO header WTNT23 KNHC and under AWIPS header MIATCMAT3. ...TROPICAL WAVES... A tropical wave is along 81W/82W from Cuba and 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. It also has been interacting with an upper level cyclonic circulation center that is in the eastern Gulf of Mexico. Isolated moderate to locally strong rainshowers are from 13N northward from 76W westward. ...MONSOON TROUGH/ITCZ... The ITCZ is along 09N43W 09N50W 08N57W. Isolated moderate to locally strong rainshowers are elsewhere from 08N to 12N from 36W eastward. Rainshowers are possible elsewhere from 10N southward between 36W and 60W. ...DISCUSSION... GULF OF MEXICO... An upper level trough extends from a 24N87W cyclonic circulation center, to 20N99W, inland in Mexico. Upper level cyclonic wind flow covers the Gulf of Mexico and surrounding coastal plains. Isolated moderate rainshowers are from 90W eastward. Earlier scattered moderate to isolated strong rainshowers that were in the Yucatan Peninsula have dissipated/have been dissipating. 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... Upper level cyclonic wind flow covers the Caribbean Sea to the NW of the line that runs from SE Cuba to NE Nicaragua. Isolated moderate to locally strong rainshowers are from 13N northward from 76W westward. Tropical Storm Isaac near 14.4N 37.5W 1002 mb at 11 PM EDT moving W at 7 kt. Maximum sustained winds 45 kt gusts 55 kt. Isaac will move to 14.5N 40.9W Sun evening and strengthen to a hurricane near 14.5N 43.5W Mon morning. Isaac will continue W to 14.5N 46.1W Mon evening, and 14.5N 51.5W Tue evening. Isaac will change little in intensity as it approaches the Lesser Antilles near 14.6N 57.0W Wed evening, and continue into the eastern Caribbean near 15.0N 62.9W 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. An upper level cyclonic circulation center is near 30N70W. A 1014 mb low pressure center is near 31N68W.Upper level cyclonic wind flow also is from 27N northward from 75W westward. Isolated moderate rainshowers cover the Atlantic Ocean to the NW of the line that passes through 32N59W to 20N70W. Tropical Storm Florence near 24.6N 55.2W 989 mb at 11 PM EDT moving W at 5 kt. Maximum sustained winds 60 kt gusts 75 kt. Florence will strengthen to a hurricane near 24.5N 55.9W Sun morning, move to 24.8N 57.4W Sun afternoon, 25.2N 59.3W Mon morning, 25.8N 61.8W Mon afternoon, and 27.5N 67.5W Tue afternoon. Florence will change little in intensity as it moves across the north-central offshores near 30.0N 73.5W Wed afternoon, then continue to 33.8N 77.8W Thu afternoon. A weak pressure pattern across the SW N Atlc will maintain gentle to moderate mainly easterly winds elsewhere across the area through Monday. For additional information please visit http://www.hurricanes.gov/marine $$ MT