892 AXNT20 KNHC 101158 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 758 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 0600| UTC surface analysis and satellite imagery through 1145 UTC. ...SPECIAL FEATURES... Hurricane Florence is centered near 24.9N 58.9W at 10/0900 UTC or 545 nm SE of Bermuda and about 465 nm NNE of the northern Leeward Island moving WNW or 285 degrees at 8 kt The estimated minimum central pressure is 969 mb. The maximum sustained wind speeds have increased to 90 kt with gusts to 110 kt. Florence is rapidly strengthening. Latest satellite imagery shows an apparent 10 nm wide eye feature with Florence. Scattered moderate convection is within 90 nm of the eye in the NE quadrant, within 60 nm of the eye in the NW quadrant and within 30 nm in the semicircle. Scattered moderate isolated strong convection is elsewhere within 180 nm of the eye in the NE quadrant and within 150 nm of the eye in the SW quadrant. Scattered moderate convection is within 120 nm of the eye in the N and NW quadrants and within 60 nm of the eye in the S quadrants. Scattered moderate convection is seen well away from Florence from 21N to 24N between 56W and 63W, and from 24N to 27N between 61W and 64W. latest NHC advisory has Florence continuing to strengthen as it tracks in west-northwester motion during the next couple of days, before an expected turn to the northwest occurs Wed night or on Thu. 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. Hurricane Isaac is centered near 14.7N 42.7W at 10/0900 UTC, which is about 1070 nm E of the Windward Islands, moving or 275 degrees at 12 kt. The estimated minimum central pressure is 993 mb. The maximum sustained wind speeds are 65 kt with gusts to 80 kt. Issac has changed little during the past several hours. Isaac remains a small hurricane, with scattered moderate to numerous strong convection within about 75 nm of the center, except 60 nm in the N and S quadrants. Scattered moderate convection denotes an outer rainband within 30 nm of a line from 12.5N44W to 14N45W. Scattered moderate convection is within 30 nm of 13N46W and within 30 nm of 14N47W. Latest NHC advisory forecasts a westward motion, with a slight increase in forward speed the end of the week. 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. Hurricane Helene is centered near 14.3N 28.9W at 10/0900 UTC, which is about 265 nm W of the southernmost Cabo Verde Islands, It is moving WNW or 285 degrees at 15 kt. The estimated minimum central pressure is 984 mb. The maximum sustained wind speeds are 75 knots with gusts to 90 kt. Latest satellite imagery shows scattered moderate to numerous strong convection within 120 nm of the center in the NE, SE and S quadrants, and within 90 mm elsewhere of the center. Latest NHC advisory forecasts Helene to continue its present motion through the next couple of days, before a turn to the NW occurs on Wed. Scattered moderate convection is seen from 15N to 17N between 27W and 31W, and from 11N to 12.5N between 29W and 32W. 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... The northern portion of a tropical wave with is axis along 92W reaches northward to the eastern Bay of Campeche at 21N. Isolated weakening convection is seen over far eastern Mexico from 17N to 19N between 91W and 93W. Isolated showers and thunderstorms are over the Pacific waters near Guatemala and the Isthmus of the Gulf of Tehuantepec of southern Mexico between 92W 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 The gradient associated with a weak high pressure over the soutehastern United States will maintain light to moderate winds over the basin through Fri 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 mdoerate to strong convection is seen from 15N to 17N between 80W and 84W. Isolated showers and thunderstorms 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 24.9N 58.9W 969 mb at 5 am EDT this morning moving WNW at 8 kt. Maximum sustained winds 90 kt gusts 110 kt. Florence will move to near 25.4N 60.5W this afternoon, 26.1N 63.1W near tonight, 27.3N 66.2W near Tue afternoon, near 28.8N 69.3W Tue night, and 32.2N 74.8W Wed night. Florence is forecast to become a major hurricane this morning, and is expected to remain an extremely dangerous major hurricane through Thursday. Florence will continue to 34.5N 78.1W Thu night, and weaken to a tropical storm while moving inland to near 35.8N 79.6W Fri night. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre