009 AXNT20 KNHC 051250 AAA TWDAT Tropical Weather Discussion...UPDATED NWS National Hurricane Center Miami FL 805 AM EDT Wed Sep 5 2018 UPDATED FOR T.D. GORDON AND HURRICANE FLORENCE INFORMATION 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 1230 UTC. ...SPECIAL FEATURES... Tropical Storm GORDON has weakened to a Tropical Depression, after making landfall, and moving inland more and more. The center of Tropical Depression GORDON, at 05/1200 UTC, is in central Mississippi, near 32.0N 89.9W, or 22 nm/40 km to the SSE of Jackson in Mississippi. GORDON is moving NW, or 325 degrees, 12 knots. The estimated minimum central pressure is 1002 mb. The maximum sustained wind speeds are 30 knots with gusts to 40 knots. The threat continues for heavy rain and flooding. Scattered moderate to isolated strong rainshowers cover the U.S.A. and the waters of the Gulf of Mexico from 28N northward, across the Florida Panhandle to northern Alabama between 84W and western Georgia and 91W in western Mississippi. Public Advisories for GORDON are issued under the WMO/AWIPS headers WTNT32 KNHC/MIATCPAT2. Forecast advisories for GORDON are issued under WMO/AWIPS headers WTNT22 KNHC/MIATCMAT2. The center of Hurricane FLORENCE, at 05/0900 UTC, is near 21.4N 44.8W. FLORENCE is moving NW, or 305 degrees, 11 knots. The estimated minimum central pressure is 976 mb. The maximum sustained wind speeds are 90 knots with gusts to 110 knots. Scattered to numerous strong rainshowers are within 90 nm of the center in the W semicircle, and within 60 nm of the center in the E semicircle. Scattered moderate to isolated strong rainshowers are elsewhere within 120 nm of the center in all directions. Isolated moderate rainshowers are in the remainder of the area from 20N to 24N between 42W and 49W. Public Advisories for FLORENCE are issued under WMO/AWIPS headers WTNT31 KNHC/ MIATCPAT1. Forecast Advisories for FLORENCE are issued under WMO/AWIPS headers WTNT21 KNHC/MIATCMAT1. A tropical wave is along 26W/27W from 20N southward. A 1007 mb low pressure center is along the wave near 11N. Environmental conditions are forecast to be conducive for additional development. A tropical depression is expected to form by the end of the week, as the system moves WNW, across the tropical Atlantic Ocean. Widely scattered moderate to isolated strong rainshowers are within 90 nm on either side of the line that runs from 07N33W to 12N29W to 16N26W. This system has a medium chance of becoming a tropical cyclone during the next 48 hours. Please read the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information. ...TROPICAL WAVES... A Caribbean Sea tropical wave is along 80W/81W from Cuba southward. The wave is moving through the area of an upper level NE-to-SW oriented cyclonic shear axis. Isolated moderate to locally strong rainshowers are in the NW corner of the Caribbean SEA. A tropical wave is along 97W/98W from 21N southward into the eastern Pacific Ocean. The tropical wave just has moved through the SW corner of the Gulf of Mexico. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of Senegal near 16N17W, to the 1007 mb low pressure center that is part of the SPECIAL FEATURES section with the 26W/27W tropical wave, to 08N32W, to 08N36W. The ITCZ is along 09N48W 06N57W. Widely scattered moderate to isolated strong rainshowers are from 05N to 12N between land and 21W. Isolated moderate rainshowers are from 05N to 10N between 40W and 60W, and from 05N southward between 27W and 44W. ...DISCUSSION... GULF OF MEXICO... Please read the SPECIAL FEATURES section for details about Tropical Storm Gordon. An upper-level inverted trough is to the west of Gordon, from southeastern Louisiana to an upper-level cyclonic circulation just northwest of the Yucatan Peninsula near 22N91W and to the eastern Bay of Campeche. An upper-level ridge extends from southwestern Louisiana to inland northeastern Mexico. Aside from convection associated with Tropical Storm Gordon, the availability of ample moisture along with the presence of the upper trough and low is allowing for the atmosphere to be unstable over much of the western and central gulf waters. As a result, scattered showers and isolated thunderstorms are seen west of 90W, with the most of the activity mainly occurring to the west of 94W. Isolated showers and thunderstorms are elsewhere over the remainder of the gulf. The shower and thunderstorm activity should remain quite active through this evening. Tropical Storm Gordon is now inland over southeast Mississippi. Winds and seas over the northern Gulf between Apalachicola and the mouth of the Mississippi River will be subsiding through early morning. Weak ridging will build from the Carolinas to the coast of Texas in the wake of Gordon, supporting gentle to moderate easterly winds and modest seas into early next week. The exception will be fresh winds pulsing off the west of coast of the Yucatan peninsula, mainly during the late evening, due to a daily trough that sets up over the southwest Gulf. CARIBBEAN SEA... An upper-level cyclonic shear axis is noted on water vapor imagery extending in NE to SW fashion from an elongated cyclonic circulation well north of the Caribbean southwestward to central Hispaniola, to near 15N76W and to central Panama. This feature is interacting with the tropical wave along 77W/78W initiating deep convection just south of central Cuba as described above under the Tropical Waves section. Otherwise, isolated showers and thunderstorms are over the remainder of the Caribbean west of 79W, while isolated showers are east of 79W. The easternmost sector of the eastern Pacific monsoon stretches along 09N/10N to across northern Panama, to the far SW Caribbean, and to northwestern Colombia. Widely scattered showers and isolated thunderstorms are seen from 09N-10N east of 81W to inland northwestern Colombia. The tropical wave along 77W/78W will move across the rest of the central Caribbean through this morning, then across the western Caribbean later on Wed and through Fri. The gradient associated with a relatively weak surface ridge, that is to the north of the region, will maintain moderate to fresh trade winds mostly everywhere, through the next several days. A relatively weak surface ridge in the western Atlantic Ocean will maintain moderate to fresh trade winds in most of the region through late Sunday. ATLANTIC OCEAN... Please read the SPECIAL FEATURES section for details about Hurricane Florence. A second area of interest pertains to a new area of broad low pressure, in the far eastern Atlantic Ocean, with a medium chance of tropical cyclone formation during the next 48 hours. An elongated upper-level cyclonic circulation is near 26N66W, with a trough extending southwestward to Hispaniola. Upper-level cyclonic wind flow covers the area north of 19N between 57W and 77W. At the surface, a trough is analyzed from near 21N63W to 31N60W. Scattered showers and thunderstorms are noted north of 22N between 61W and 70W. Isolated showers and weak isolated thunderstorms are elsewhere west of 59W. Strong high pressure to the north and northeast of Hurricane Florence is suppressing the atmosphere environment, maintaining it pretty stable over the eastern Atlantic, except near the broad area of low pressure as described above. A weak pressure pattern will maintain gentle to moderate easterly winds across the area through Sunday night. Easterly swell from Hurricane Florence will move into the open waters that are to the east of the Bahamas, from late tonight through Sunday. For additional information please visit http://www.hurricanes.gov/marine $$ ja/mt