000 AXNT20 KNHC 131759 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sun Dec 13 2020 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 1745 UTC. ...SPECIAL FEATURES... Gulf of Mexico Gale Warning: A strong cold front will move into the NW Gulf tonight. Behind this front, strong cold air advection will induce northwest to north gale force winds to 35 kt over the NW Gulf overnight tonight along with seas building to 11 ft. This same surge of cold air will also bring similar northerly gale force winds, but slightly stronger, up to 40 kt, over sections of the western and SW Gulf Mon through Mon evening, with strong north winds elsewhere over the western Gulf. Seas are forecast to reach 11 ft in the SW Gulf. Winds and seas will decrease Tue as high pressure moves over the area. Please read the latest High Seas Forecast at https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the coast of Sierra Leone near 08N13W to 06N21W, where latest scatterometer data indicates that it transitions to the ITCZ to 06N21W to 04N38W to 03N51W. Scattered moderate to isolated strong convection is within 90 nm either side of the ITCZ between 37W-39W. Scattered moderate convection is seen within 180 nm south of the trough axis between east of 20W to just inland the coast of Africa. GULF OF MEXICO... Please see the Special Features section for details on a forecast Gulf of Mexico gale warning. As of 15Z, a cold front extends from the Florida panhandle near Panama City southwest to 29N87W, where it becomes stationary to 29N90W. From there it transitions to a warm front northwestward to along and just inland the Louisiana coast to inland northeastern Texas. An area of scattered showers and thunderstorms moving northeastward extends from inland Texas near Corpus Christi northeastward to the Louisiana border and offshore for about 60 nm. Isolated showers, mostly light, are along and near the stationary and cold fronts. Moist southerly flow resulting in patches of low clouds and stratus are over the rest of the Gulf. Isolated showers are possible with some of these cloud patches. Otherwise, a 1020 mb high center is analyzed over north-central Florida, with a a ridge extending west-southwestward to near 25N90W. As for the forecast: The warm front will continue to lift northward today, with fresh southerly winds developing in its wake. A more significant cold front will move into the Gulf tonight, then move across much of the basin Mon into Tue. Strong N winds will spill behind the front and gales will develop over portions of the western and southwestern Gulf Mon and Mon evening. Wind and seas decrease Tue as high pressures builds in. The next front will move into the western Gulf Tue night and across the Gulf by Thu. Northerly gales will briefly occur offshore Veracruz, Mexico Wed afternoon. CARIBBEAN SEA... Upper-level ridging covers the western Caribbean and Central America. Water vapor imagery depicts moderate subsidence inducing dry sinking air and rather stable atmospheric condition across these sections of the sea. An upper-level trough axis extends from near 30N58W to the eastern part of the Caribbean. At the surface, a trough has moved to just inland the northeastern part of the Yucatan Peninsula. Latest satellite imagery shows patches of low- level moisture in the form of scattered to broken clouds moving westward in the trade wind flow across the basin. Isolated showers are possible with some of these clouds. Latest partial ASCAT data reveals generally moderate to fresh trades over the central part of the sea, with the exception of fresh to strong trades south of about 14N between 74W-79W and to near the coast of Colombia. Gentle to moderate trades are elsewhere across the sea. Seas are in the range of 4-7 ft, except for higher seas in the range of 6-9 ft in the south-central section of the sea, where the fresh to strong winds are occurring. As for the forecast: The fresh to strong trades in south-central Caribbean will pulse nightly through Mon along the Colombian coast. High pressure will weaken across the western Atlantic early Mon through Wed allowing for weaker winds across the entire basin. A weakening cold front will move slowly southeastward across the Yucatan Channel and western Cuba late on Thu. ATLANTIC OCEAN... A cold front is analyzed from near 32N25W to 29N35W, then weakening stationary to 27N49W. The boundary then transitions to a shearline to near 24N59W. ASCAT data from this morning revealed a large area of fresh to strong northeast to east winds north of stationary front and shearline to 30N and between 45W-58W. Mainly fresh northeast to east winds are east of 45W north of the stationary and cold fronts. A surface trough is along a position from near 24N57W to 18N59W. This feature lies to southeast of a rather robust upper-level trough that stretches from near 32N54W southwestward to 24N60W and to the eastern Caribbean Sea. Upper-level divergence southeast of this feature is helping to promote an increasing area of rain with embedded scattered moderate convection over the area from 20N-29N and between 50W- 59W. Weak low pressure is forecast to develop along the surface trough near 24N by early Tue. Elsewhere across the eastern waters, moderate to large northwest swell remains in the waters roughly north of 20N and east of 67W, where seas are in the 8-12 ft. This area of swell is forecast to gradually shrink into the early part of the week as it shifts to the south and southeastward. A surface trough east of northern Florida extends from 32N79W to 29N80W. Light northwest winds are west of the trough. Isolated showers are near this trough. The morning ASCAT data showed moderate to fresh northeast to east winds between 58W-68W, gentle to moderate winds between 68W-75W and light to gentle winds west of 75W. A 1032 mb high center is analyzed north of the area at 35N52W, with a ridge extending west-southwestward to just east of the trough that is east of northern Florida. High pressure covers the discussion area outside the aforementioned described features. As for the forecast: The high pressure ridging east of northern Florida will shift eastward through Mon in response to the next cold front that will move over the northwest waters Mon afternoon. The front is forecast to reach a position from near Bermuda to Palm Beach, Florida, Tue morning before is becomes stationary. Strong southwest winds will develop Mon offshore the northern Florida coast ahead of the front. The next front will move off the northern Florida coast Wed night and reach from near 32N69W to central Florida Thu evening. $$ Aguirre