000 AXNT20 KNHC 210551 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Mon Dec 21 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 0000 UTC surface analysis and satellite imagery through 0530 UTC. ...SPECIAL FEATURES... Atlantic Gale Warning: A cold front is west of the area over the Gulf of Mexico and as of 03Z it extends from a 1013 mb low pressure over Apalachee Bay southwestward to 24N87W and to near 19N94W. The low is forecast to strengthen as it moves northeastward into the western Atlantic. Fresh to strong winds are expected on either side of the front early this morning. Winds ahead of the front will reach gale force north of 28N and within about 90 nm east of the front by early this afternoon. Seas are expected to build up to 12-13 ft within the area of gale force winds. The low pressure will move well north of the area later today as the cold front progresses quickly eastward across the western Atlantic. By around 03Z tonight, winds will diminish below gale force ahead of the front expected to reach from near Bermuda to central Cuba at that time. Please read the latest High Seas Forecast at https://www.nhc.gov/text/MIAHSFAT2.shtml for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the border of Sierra Leone and Guinea near 09N13W to 08N17W, where a Sun evening ASCAT indicated that it transitions to the ITCZ to 05N30W and to 05N40W and to the coast of Brazil near 03N51W. Scattered moderate to isolated strong convection is within 60 nm either side of the ITCZ between 21W-28W. Scattered moderate convection is within 120 nm north and 60 nm south of the ITCZ between 32W-39W and also well south of the ITCZ within 30 nm of a line from 03N14W to 03N19W. GULF OF MEXICO... As mentioned above under SPECIAL FEATURES, as of 03Z a cold front extends southwestward from a 1013 mb low pressure that over Apalachee Bay southwestward to 24N87W and to near 19N94W. A pre- frontal trough extends from near Venice, Florida to near 25N85W. NWS Doppler Radar and satellite imagery show scattered showers and a few thunderstorms are seen within 60 nm southeast of the trough east of the trough. A 1021 mb high center is analyzed over the far NW Gulf near 28N96W. Latest ASCAT data shows fresh northwest winds behind the front to near 90W and fresh to strong northwest to north winds along and just offshore Veracruz, Mexico. Moderate to fresh winds are west of 90W, except for light to gentle winds west of 93W. Cold-air stratocumulus clouds are in the wake of the front east of 93W. Low-level scattered to broken clouds continue to be banked up along the Sierra Madre Mountains of Mexico. As for the forecast: The cold front will exit the southeastern Gulf this morning followed by fresh northwest to north winds. High pressure centered over the NW Gulf will shift eastward to northeast of the Gulf by late Tue allowing for southerly flow fresh winds to develop over western Gulf and gentle to moderate east winds to exist across the rest of the Gulf. A strong cold front is forecast to move across the area on Thu followed by possible gale force winds in the SW Gulf. CARIBBEAN SEA... ASCAT data from last night shows fresh to strong trade winds over the south-central Caribbean and in the Gulf of Venezuela. Fresh northeast winds are present south of Hispaniola. These winds are the result of the pressure gradient between high pressure located over the western Atlantic and lower pressure associated with the Colombian/Panamaniam low. These winds will persist over the south- central Caribbean during most of the forecast period. Patches of low-level moisture, embedded in the trade wind flow, are noted moving westward across the basin mainly north of about 14N. Isolated to scattered passing showers are possible with some of these clouds. Northeast winds over the southeastern Bahamas continue to advect small patches of low-level moisture, with possible isolated showers, toward the coast of eastern Cuba. As for the forecast: The cold front that is presently moving across the eastern and central Gulf of Mexico is forecast to reach the Yucatan Channel and western Cuba this morning. It is forecast to extend from central Cuba to northern Belize by tonight, then gradually weaken from eastern Cuba to the Gulf of Honduras on Tue. Another and stronger cold front is expected to reach the Yucatan Channel and western Cuba by Thu night. Fresh to strong northerly winds will follow this front. ATLANTIC OCEAN... A cold front is forecast to bring strong to gale force winds across the western Atlantic on Mon. Please see the Special Features section for more details on this upcoming event. Fresh to strong southerly winds in advance of this upcoming cold front are already present over the waters east of NE Florida to near 75W. Scattered showers and thunderstorms are moving northeastward over these waters. Farther east, a cold front enters the central part of the area near 32N35W and extends to 27N46W, where it becomes stationary to 24N57W and dissipating stationary to near 22N69W. Pockets of low-level moisture, with possible isolated to scattered showers, are observed to be along and within 120 nm north of the frontal boundary, except within 30-60 nm either side of the boundary between 55W-59W. Scattered to broken low clouds, with isolated showers, are over and near the Bahamas. Latest buoy and ASCAT data indicates mainly moderate to locally fresh winds northeast to east winds north of the stationary front to near 29N and between 47W- 57W. Gentle to moderate northeast to east winds are elsewhere north of the stationary frontal boundary. A ridge prevails over the east Atlantic, anchored by a 1029 mb high pressure center analyzed over the Madeira Islands. The gradient between it and lower pressure to its south is allowing for generally fresh trade winds to exist from about 13N-24N and east of 35W to include the area of the Cabo Verde Islands and surrounding waters. As for the forecast: The stationary frontal boundary will weaken and dissipate by this evening. A cold front is forecast to move off the Florida coast today, extend from the southeastern Bahamas to southern Cuba by Tue, and continue moving eastward on Wed. Gale force winds will develop ahead of the front off the Florida coast and north of the Bahamas today. Fresh to strong winds are expected behind the front. By the end of the week, a strong cold front will push off the northeast Florida coast enhancing winds and convection. $$ Aguirre