000 AXNT20 KNHC 211205 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 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 0600 UTC surface analysis and satellite imagery through 1100 UTC. ...SPECIAL FEATURES... Upper level cyclonic wind flow spans the Gulf of Mexico. A trough extends from the Florida Panhandle, beyond the Yucatan Channel, into the NW Caribbean Sea. This weather pattern is drawing deep tropical moisture northward, from the SW Caribbean Sea between 76W and 84W, and is supporting scattered to numerous moderate to strong rainshowers, from the SW Caribbean Sea, across Cuba, to Florida, and the Bahamas and the nearby Atlantic Ocean. This activity is expected to continue through at least Tuesday, with heavy rainfall and flooding. ...TROPICAL WAVES... A tropical wave is along 12N33W 07N34W 01N35W, moving W 10 to 15 knots. 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 tropical wave is just to the east of the Caribbean Sea, along 59W from 16N southward. 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. A surface ridge will remain in the northern Gulf Coast through Thursday night. The current eastern Gulf of Mexico surface trough will drift westward through at least Wednesday. It is possible that a low pressure center may develop along the trough, in the the NW Caribbean Sea, toward the end of the work-week. 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. Atlantic Ocean high pressure will maintain fresh to locally strong trades over the central Caribbean through Fri night. Strong winds and seas to 9 ft will affect the NW coast of Colombia. A western Caribbean Sea surface trough will drift westward across Central America through at least Thursday. It is possible that a low pressure center may develop along the trough, and move across Nicaragua and Honduras, emerging into the Gulf of Honduras by Thursday. The pressure gradient between the trough and the Atlantic Ocean high pressure will result in fresh to strong winds in the central Caribbean Sea, and in parts of the western Caribbean Sea. 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 chances for heavy rainfall in Florida, across the Bahamas, and in the western Atlantic Ocean will continue. An east-to-west oriented ridge will be along 30N through the middle of the week. The ridge will support fresh to locally strong E to SE winds mainly S of 26N, including the Old Bahama Channel, and the approaches to the Windward Passage through Tue night. Fresh to occasionally strong winds will prevail N of Hispaniola, mainly at night. A broad area of low pressure may develop over the NW Caribbean Sea and move northward across the eastern Gulf of Mexico. This will cause strong SE to S winds to develop over the waters W of 75W late Fri into Sat. For additional information please visit http://www.hurricanes.gov/marine $$ MT