076 AXNT20 KNHC 070005 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 PM EDT Thu Sep 6 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 2345 UTC. ...SPECIAL FEATURES... Hurricane Florence is centered near 25.0N 49.6W at 06/2100 UTC, which is about 900 nm east-northeast of the northern Leeward Islands or 915 nm east-southeast of Bermuda. It is moving NW or 305 degrees at 9 kt. The estimated minimum central pressure is 989 mb. Maximum sustained winds have diminished to 70 kt with gusts to 85 kt. Latest satellite imagery shows that the cyclone has been undergoing southwesterly vertical upper-level shear as noted by its rather tilted NE to SW cloud/convection structure in its northeastern quadrant. The imagery also shows what appears to be the low- level center exposed on the southwest side of the cyclone's deep convection. The deep convection consists of the scattered moderate isolated strong type intensity from 25N to 27N between 45W and 48W. Similar convection is within 60 nm NE of the center. The latest NHC forecast calls for Florence to move northwestward through tonight before it turns toward to the west on Fri. It is forecast to weaken slightly through Fri, then strengthen late on Fri. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPAT1/WTNT31 KNHC for more details. A broad and elongated area of low pressure is centered several hundred miles west-southwest of the Cabo Verde Islands is denoted by a tropical wave with its axis along 32W/33W and extending from 04N to 20N. A 1008 mb low is on the wave axis near 14N32W. This system is moving westward at 10 to 15 kt. The associated shower and thunderstorm activity has not yet increased in organization. Latest satellite imagery shows scattered moderate isolated strong convection within 210 nm of the low in the NE quadrant, and within of the low in the W quadrant. Scattered moderate convection is within 30 nm of 15N33W. Environmental conditions are conducive for development, and a tropical depression is expected to form within the next day or two while the system moves slowly westward or west-northwestward across the tropical Atlantic. The chance of this system becoming a tropical cyclone during the next 48 hours remains high. Please read the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information. A tropical wave just inland along the coast of western Africa has its axis near 15W from 04N to 20N, with a 1008 mb low on the axis at 14N15W. This system is moving westward at 10 to 15 kt. Latest satellite long term animation indicates that this system is exhibiting signs of organization. Large clusters of scattered moderate to strong convection are observed in advance of this system from the coastal sections of Senegal to Sierra Leone, west to 18W and eastward to within 240 nm inland the coast of Africa. A tropical depression is likely to form over the weekend or early next week while the wave and associated low pressure moves westward or west-northwestward over the far eastern tropical Atlantic Ocean. The chance of this system becoming a tropical cyclone during the next 48 hours is in the medium range. Interests in the Cabo Verde Islands should monitor the progress of this system. Please read the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information. ...TROPICAL WAVES... A tropical wave has its axis along 80W south of 20N, moving westward at 10 to 15 kt. Scattered moderate convection is within 120 nm east of the wave from 13N to 15N, and from 18N to 20n within 120 nm east of the wave. Scattered showers and isolated thunderstorms are elsewhere within 120 nm either side of the wave. A tropical wave has its axis along 94W and south of 21N, and continues southward across southeastern Mexico and the Isthmus of Tehuantepec and further southward to the eastern Pacific near 04N. It is moving westward near 15 kt. Only isolated showers are seen within 60 nm of the wave axis. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the coastal sections of Senegal near 14N17W, to the 1008 mb low that is associated with the tropical wave along 32W/33W as discussed in the Special Features section. It continues from this low to 10N37W to 08N41W. The ITCZ extends from 08N41W to 08N50W to 08N59W. Aside from the convection described above associated with the two tropical waves along 32W/33W and the one inland the coast of Africa near 15W, only scattered moderate convection is seen within 60 nm south of the ITCZ between 46W and 54W. ...DISCUSSION... GULF OF MEXICO... Upper-level cyclonic flow is located over eastern Louisiana and Mississippi while upper-level anticyclonic flow is located over the west-central Gulf of Mexico. A moist and unstable atmosphere continues to support scattered moderate convection over the far NW Gulf northwest of a line from just west of Mobile to 28N91W to Brownsville. Scattered moderate convection has moved offshore the west Florida coast to the extreme eastern gulf waters from 24N to 29N east of 85W. Isolated showers are elsewhere across the Gulf. A weak surface ridge will build from the Carolinas to the coast of Texas in the wake of Gordon. Over the southeastern two-thirds of the Gulf of Mexico, gentle easterly winds will prevail through Fri. Thereafter, expect gentle to moderate easterly winds and modest seas into early next week. The exception will be fresh winds pulsing off the west coast of the Yucatan Peninsula, mainly during the late evening hours, due to a daily trough that sets up in the far southwestern Gulf of Mexico. CARIBBEAN SEA... Please see Tropical Waves section above for details regarding a tropical wave along 80W. Upper-level cyclonic flow covers the western Caribbean Sea west of a Hispaniola to Panama line, while upper level anticyclonic flow covers the eastern Caribbean. Aside from convection related to the tropical wave, isolated showers and thunderstorms are elsewhere west of 74W. A relatively weak surface ridge in the western Atlantic Ocean will maintain moderate to fresh trade winds in most of the region through late Sun. ATLANTIC OCEAN... Please read the Special Features section above for details about Hurricane Florence. Two areas of tropical development interest pertains to a broad area of low pressure in the eastern Atlantic near 14N32W, with a higher chance of development and a vigorous tropical wave and low pressure system nearing the coast of Africa, with a medium chance of development. A large upper-level low located over the Bahamas and Cuba is moving west-northwestward. Associated upper level cyclonic flow covers the Atlantic west of 67W from the Greater Antilles to 34N. A westward moving surface trough is analyzed from 31N75W to the NW Bahamas and to 23N80W. Another surface trough is analyzed from near 32N67W to 26N65W. Scattered to numerous moderate convection is from 22N- 29N between 72W-79W. Scattered moderate convection is also seen from 28N-32N between 61W-67W. A weak pressure pattern will maintain gentle to moderate easterly winds across the western Atlantic area through Sun night. Easterly swell from Hurricane Florence will move into the open waters east of the Bahamas starting this weekend. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre