000 AXNT20 KNHC 210513 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 113 AM EDT Mon May 21 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 0400 UTC. ...SPECIAL FEATURES... An upper-level trough extends across the eastern Gulf of Mexico and western Caribbean, with diffluent flow aloft prevailing across the Florida Peninsula, the western Atlantic, and Caribbean, to the east of the upper trough's axis. This pattern is drawing deep tropical moisture northward from the SW Caribbean between 76W and 84W and is supporting scattered to numerous moderate convection along this corridor. This activity is expected to continue through at least Tuesday, with heavy rainfall and flooding possible over the land areas affected. ...TROPICAL WAVES... An eastern central Atlantic tropical wave has an axis that extends from 13N31W to 00N33W, moving W at 10 to 15 kt. This wave is embedded in a sharp 700 mb trough. Although deep moisture accompanies the wave, subsidence from aloft is inhibiting convection except over the southern portion. Scattered moderate convection is from 00N to 04N between 29W and 35W. A central Atlantic tropical wave has an axis that extends from 17N56W to 05N57W, moving W at 5 to 10 kt. This wave continues to appear as a 700 mb trough and has a poleward surge in moisture associated with it. Scattered showers and isolated thunderstorms are within 300 nm of either side of the trough axis. This trough will enter the E Caribbean by Tuesday and then will become ill defined. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through coastal Africa near 11N15W to 05N20W. The ITCZ extends from 05N20W to 03N31W, then resumes west of a tropical wave from 01N35W to 00N51W. Besides the convection associated with the wave, isolated moderate convection is from 01N to 07N between 11W and 28W. ...DISCUSSION GULF OF MEXICO... An upper-level trough prevails across the eastern Gulf, with an axis along 85W. Diffluent flow aloft east of the trough is bringing tropical moisture over the far east Gulf and western Atlantic waters affecting the Florida Peninsula and Florida Straits/Keys. Please refer to the Special Features section above for more details. A surface trough is embedded underneath the upper trough, and as of 0300 UTC has an axis that extends from 30N84W to near 23N85W. A weak ridge axis extends across the remainder of the basin along 30N producing mainly gentle to moderate winds. A weakening line of thunderstorms has emerged within 120 nm E of the SE Texas coast as of 0300 UTC and will likely affect those waters until sunrise. The surface trough is expected move NW across the eastern Gulf through today. The upper-level trough over the eastern Gulf will remain nearly stationary through the first half of this week, supporting ongoing convection over the eastern Gulf. CARIBBEAN SEA... An upper-level trough extends over the eastern Gulf of Mexico and western Caribbean. A surface trough is over the western Caribbean and as of 0300 UTC had an axis extending from 21N85W to 11N83W. The combination of upper- level diffluence on the eastern side of the upper-level trough and convergence associated with the surface trough is supporting scattered to numerous moderate convection across the Caribbean waters between 78W and 84W. Broad high pressure over the subtropical Atlantic continues to support moderate to fresh tradewinds over most of the basin, except fresh to strong winds over the central Caribbean. Wave heights of 8 to 9 ft persist over the central Caribbean as confirmed by both satellite altimeters and current buoy data. Over the next day or so, the upper-level trough and surface trough will remain nearly stationary enhancing shower and thunderstorm activity over the western Caribbean. The surface ridging pattern over the Atlantic will persist, keeping a similar wind profile in place across the basin into the middle of this week. ATLANTIC OCEAN... Diffluent flow aloft to the east of an upper-level trough currently over the eastern Gulf of Mexico, combined with a surface trough extending just offshore of northern Florida is supporting scattered to numerous moderate convection across Florida, the Bahamas, and Atlantic waters mainly west of 76W. To the east, high pressure centered over the central Atlantic spans across the basin. Surface observations and latest scatterometer data indicate prevailing fresh to locally strong southeast winds over the Bahamas as well as within a few hundred miles north of Hispaniola and Cuba. A recent altimeter pass indicates wave heights of 8 to 9 ft over these waters as far N as 26N outside of the Bahamas. Moderate to fresh tradewinds are occurring elsewhere across the central and western Atlantic south of 27N. Gentle to moderate winds cover the central Atlantic north of 27N. Moderate to occasionally fresh northeast winds are occurring over the eastern Atlantic. The overall pattern will change little through the next 24 hours. Therefore, the chances for heavy rainfall over the Florida Peninsula, Bahamas, and western Atlantic will continue. For additional information please visit http://www.hurricanes.gov/marine $$ Latto