422 AXNT20 KNHC 100531 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 131 AM EDT Mon Sep 10 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 0515 UTC. ...SPECIAL FEATURES... The center of Hurricane Florence at 10/0300 UTC is near 24.6N 57.7W. Florence is moving W, or 280 degrees, 06 knots. The estimated minimum central pressure is 974 mb. The maximum sustained wind speeds are 80 knots with gusts to 100 knots. Scattered moderate to strong rainshowers are within 30 nm of the center everywhere. Numerous strong rainshowers are within 90 nm of the center in the NW semicircle. Scattered moderate to isolated strong rainshowers are elsewhere from 21N to 28N between 54W and 62W. Public Advisories for FLORENCE are issued under WMO header WTNT31 KNHC and under AWIPS header MIATCPAT1. Forecast/Advisories for FLORENCE are issued under WMO header WTNT21 KNHC and under AWIPS header MIATCMAT1. The center of Hurricane Isaac at 10/0300 UTC is near 14.5N 41.6W. Isaac is moving W, or 275 degrees, 12 knots. The estimated minimum central pressure is 993 mb. The maximum sustained wind speeds are 65 knots with gusts to 80 knots. Numerous strong rainshowers are within 75 nm of the center in the W semicircle, and within 45 nm of the center in the E semicircle. Scattered moderate to strong rainshowers are from 12N to 14N between 41W and 44W. Anyone who is in the area of the Lesser Antilles should monitor the progress of Hurricane Isaac. Public Advisories for ISAAC are issued under WMO header WTNT34 KNHC and under AWIPS header MIATCPAT4. Forecast/Advisories for ISAAC are issued under WMO header WTNT24 KNHC and under AWIPS header MIATCMAT4. The center of Hurricane Helene at 10/0300 UTC is near 13.9N 27.2W. Helene is moving WNW, or 285 degrees, 11 knots. The estimated minimum central pressure is 984 mb. The maximum sustained wind speeds are 75 knots with gusts to 90 kt. Numerous strong rainshowers are within 135 nm of the center in the NW quadrant and in the SW quadrant. Widely scattered moderate to isolated strong rainshowers are elsewhere from 09N to 17N between 22W and 31W. Public Advisories for HELENE are issued under WMO header WTNT33 KNHC and under AWIPS header MIATCPAT3. Forecast/Advisories for HELENE are issued under WMO header WTNT23 KNHC and under AWIPS header MIATCMAT3. ...TROPICAL WAVES... A tropical wave is along 90W/91W from 21N southward, along the western side of the Yucatan Peninsula of Mexico, into the eastern Pacific Ocean. Isolated moderate to locally strong rainshowers are inland in Mexico, in the Isthmus of Tehuantepec of southern Mexico, between 90W and 95W. ...MONSOON TROUGH/ITCZ... The monsoon trough is inland in Africa. The ITCZ is along 08N48W 06N54W 07N58W. Isolated moderate to locally strong rainshowers are elsewhere from 10N southward from 20W eastward, and to the south of Hurricane Isaac and Hurricane Helene from 06N to 10N between 34W and 45W. Rainshowers are possible elsewhere from 10N southward from 60W eastward. ...DISCUSSION... GULF OF MEXICO... An upper level trough extends from the NE corner of the Gulf of Mexico, to a 26N87W cyclonic circulation center, into the SW corner of the Gulf of Mexico, just to the north of the Isthmus of Tehuantepec of southern Mexico. Upper level cyclonic wind flow covers the Gulf of Mexico and surrounding coastal plains to the east of the line that runs from coastal Alabama, to 26N92W, to the coast of Mexico near 20N92W. Isolated moderate rainshowers are in the area of upper level cyclonic wind flow. f A weak surface ridge in the SE U.S.A. generally will maintain light to moderate wind speeds in the basin through Friday night. A surface trough will move westward, off the coast of the Yucatan Peninsula each evening, and it will dissipate in the SW Gulf of Mexico each morning. The trough will be accompanied by moderate to fresh winds. CARIBBEAN SEA... Upper level cyclonic wind flow covers the Caribbean Sea to the NW of the line that runs from NW Cuba to the Gulf of Honduras. Scattered strong rainshowers are from 15N to 17N between 80W and 84W. Isolated moderate rainshowers are elsewhere to the NW of the line that runs from the Mona Passage to the east central coast of Nicaragua. The monsoon trough is along 09N74W in northern Colombia, beyond 10N in NW Costa Rica. Scattered strong rainshowers in clusters are from 09N to 11N between Colombia and 77W. Newly upgraded Hurricane Isaac near 14.5N 41.6W 997 mb at 11 PM EDT moving W at 12 kt. Maximum sustained winds 65 kt gusts 80 kt. Isaac will move to 14.9N 46.3W on Monday evening, to 14.9N 48.0W on Tuesday morning, to 15.0N 52.0W on Tuesday evening, and to 15.2N 57.3W on Wednesday evening. Isaac will weaken to a tropical storm near 15.5N 63.5W on Thursday evening, and continue to weaken as it moves to the central Caribbean Sea near 15.5N 70.0W on Friday. A relatively weak surface ridge in the western Atlantic Ocean will maintain moderate to fresh trade winds in most of the region through Monday night. ATLANTIC OCEAN... Please read the SPECIAL FEATURES section for details about Hurricane Florence, Hurricane Isaac, and Hurricane Helene. An upper level cyclonic circulation center is near 29N70W. A surface trough is along 36N61W 34N62W 31N64W. Upper level cyclonic wind flow also is from 30N northward from 77W westward. Isolated moderate rainshowers are from 26N northward from 69W westward. Hurricane Florence near 24.6N 57.7W 974 mb at 11 PM EDT moving W at 6 kt. Maximum sustained winds 80 kt gusts 100 kt. Florence will move to 24.9N 59.1W Monday morning, 25.6N 61.5W Monday evening, 26.5N 64.4W Tuesday morning, 27.8N 67.6W Tuesday evening, and 31.2N 73.6W Wednesday evening. Florence is forecast to strengthen rapidly into a major hurricane by Monday night, and it is expected to remain an extremely dangerous major hurricane through Thursday. Florence will continue to 34.0N 77.5W on Thursday evening, and weaken to a tropical storm while moving inland near 35.2N 79.0W on Friday evening. For additional information please visit http://www.hurricanes.gov/marine $$ MT