922 AXNT20 KNHC 102055 AAA TWDAT Tropical Weather Discussion...Updated NWS National Hurricane Center Miami FL 455 PM EDT Mon Sep 10 2018 Updated Atlantic Ocean and Gulf of Mexico sections 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 1200 UTC surface analysis and satellite imagery through 2030 UTC. ...SPECIAL FEATURES... Hurricane Florence is centered near 25.0 60.0W at 10/1500 UTC or 540 nm SE of Bermuda and about 1080 nm ESE of Cape Fear North Carolina moving W or 280 degrees at 12 kt The estimated minimum central pressure is 962 mb. The maximum sustained wind speeds have increased to 100 kt with gusts to 120 kt. Florence is continues to rapidly strengthening. Latest satellite imagery shows a very distinct eye feature, about 10 nm in diameter. The imagery shows scattered moderate convection within 90 nm NE of the eye in the NE quadrant, within 60 nm of the eye in the NW quadrant, within 60 nm of the eye in the SW quadrant and within 30 nm of the eye in the SE quadrant. 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 SE quadrant. Scattered moderate isolated strong convection is elsewhere within 120 nm of the eye in the W semicircle. Latest NHC advisory has Florence continuing to strengthen as it tracks in west- northwest motion during the next couple of days, before an expected turn to the northwest occurs on Wed night. 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 43.9W at 10/1500 UTC, which is about 1000 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. Latest satellite imagery shows that Issac's overall cloud pattern appears ragged. Isaac remains a small hurricane, with scattered moderate to numerous strong convection within 90 nm of the center in the N and SW, and within 60 nm of the center in the SE quadrant. Scattered moderate isolated strong convection is within 120 nm of center in the NE quadrant and within 60 nm of the center in the SE quadrant. An outer rainband is denoted by scattered moderate convection within 30 nm of a line from 12N46W to 14N45W. The latest NHC advisory forecasts a westward motion, with a slight increase in forward speed the through 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 14.6N 30.0W at 10/1500 UTC, which is about 330 nm W of the southernmost Cabo Verde Islands, and 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 late Tue, with a decrease in its forward motion, followed by a turn to the northwest and then to the north-northwest on Wed and Thu. Latest satellite imagery shows scattered moderate convection within 90 nm of the center in the SE quadrant and within 60 nm of the center in the SW quadrant. Scattered moderate convection is elsewhere within 270 nm of the center in the SW, within 210 nm of the center in the SE quadrant and within 120 nm of the center in the northern semicircle. 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 previous tropical wave that was along 92W has moved to over the far eastern Pacific, with its northern portion over southeastern Mexico. Scattered moderate is 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 analyzed over inland Africa. The ITCZ extends from 08N48W to 07N58W. Isolated moderate convection is within 60 nm N of the ITCZ between 54W and 58W. ...DISCUSSION... GULF OF MEXICO...Updated An upper-level trough extends from the NE corner of the Gulf of Mexico, to an elongated upper-level low at 25N88W and southwestward to the Yucatan Peninsula. Associated upper-level cyclonic flow covers the Gulf of Mexico east of about 94W, while upper-level anticyclonic flow is west of 94W. A surface trough is over the far western part of the gulf along a position from just northeast of Galveston to just northeast of Brownsville. Isolated showers and thunderstorms are noted over just about the entire basin, except for scattered moderate to isolated strong convection from 24N to 30N west of 94W due mainly to the combination of instability from an upper-level trough over central Texas and the surface trough both of which are acting on a very deep moisture laden atmosphere. Similar convection over the southeastern gulf waters are being sustained by upper-level divergence east of the upper low. This convection is rapidly increasing in coverage, and it is spreading northward across the southeastern gulf and over much of the Straits of Florida from the northwestern Caribbean Sea. Strong gusty winds can be expected with this activity. This area of convection is forecast to move slowly northwestward near the Yucatan Peninsula on Tue with limited development expected. Upper-level winds are forecast to become more conducive for development on Wed when the system moves over the southern Gulf of Mexico, and a tropical depression could form on Thu or Friday while the disturbance moves across the western Gulf of Mexico. Please refer to the latest Tropical Weather Outlook for the latest information on this system. The gradient associated with a weak high pressure over the southeastern 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 flow associated with the upper low over the Gulf of Mexico near 25N88W covers the northwestern Caribbean Sea as well as western and central Cuba. A weak surface trough is analyzed from near 21N82.5W to near just northeast of the northeastern coast of Honduras. Scattered moderate to strong convection increasing in coverage is observed to the north of 17N west of 79W to juts inland the coast of the Yucatan Peninsula. This activity is quickly lifting northward under moderate to strong upper-level southerly flow located to the east of the Gulf of Mexico upper-level low near 25N88W. Satellite imagery indicates that this activity is showing signs of organization, and it is forecast to move slowly northwestward near the Yucatan Peninsula on Tue with limited development expected. Upper-level winds are forecast to become more conducive for development on Wed when the system moves over the southern Gulf of Mexico. Isolated showers and thunderstorms are elsewhere west of 78W. A relatively weak surface ridge in the western Atlantic Ocean will maintain moderate to fresh trade winds over most of the region through Thu, except over the far eastern Caribbean where winds are expected to increase as Hurricane Isaac, near 14.6N 30.0W at 15 UTC, approaches that part of the Caribbean from the tropical Atlantic waters. Please refer to the latest advisory on Isaac for further details on its track and intensity. ATLANTIC OCEAN...Updated Please see the Special Features section for details pertaining to Hurricanes Florence, Isaac and Helene. A surface trough is analyzed from 32N61W to 29N65W. Upper-level cyclonic flow is present to the north of 27N between 67W and 74W attributed to an upper low moving westward near 29N74W. Broad anticyclonic is west of 74W due to the upper-level low in the Gulf of Mexico near 24N88W. Water vapor imagery shows mid to upper-level clouds streaming northeastward and eastward over the western half of the area. These clouds are originating from the deep convective activity that is occurring over the southeastern Gulf of Mexico as described above. Otherwise, isolated showers and thunderstorms are west of 65W. A weak 1017 mb high center is analyzed at 26N73W, with a ridge southwestward to the Straits of Florida. The associated weak gradeint is allowing for generally light to gentle winds to exist over the western half of the area. Expect for these conditions to continue through Wed, except in the northeastern section the the TAFB forecast offshore waters zones where Hurricane Florence is forecast to track across. Below is the latest forecast for Florence bases on the 15Z NHC advisory. Hurricane Florence near 25.0N 60.0W 962 mb at 11 AM EDT moving W at 11 kt. Maximum sustained winds 100 kt gusts 120 kt. Florence will move to near 25.5N 61.9W this evening, near 26.4N 64.7W Tue morning, near 27.8N 67.9W Tue evening, near 29.5N 71.0W Wed morning and north of the area near 33.0N 76.3W Thu morning. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre