000 AXNT20 KNHC 200830 AAA TWDAT Tropical Weather Discussion...Updated NWS National Hurricane Center Miami FL 0830 UTC Sun Dec 20 2020 Updated to include Gulf of Mexico gale warning 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 0545 UTC. ...SPECIAL FEATURES... Gulf of Mexico Gale Warning: Near gale to gale force south to southwest winds are occurring over the NW Gulf within about 90 nm southeast of a 1014 mb low pressure system that is near 29N92W, with a trailing cold front that extends from it to 26N94W and to inland Mexico at 23N98W, and also within 60 nm southeast of the squall line segment that extends from near 27N91W to 26N93W. These conditions are forecast to diminish by early this afternoon as the low pressure reaches to just south of the western Florida panhandle, with the cold front extending fronm it to near 25N91W and to the SW Gulf. Please read the latest HIGH SEAS FORECAST- https://www.nhc.gov/text/MIAHSFAT2.shtml for more details. ...MONSOON TROUGH/ITCZ... The monsoon trough axis extends from the coastal sections of Sierra Leone near 09N13W to 06N17W, where latest scatterometer data indicates that is transitions to the ITCZ to 06N18W and continues to 05N30W to 05N40W and to the coast of Brazil near 04N51W. Scattered moderate to isolated strong convection is within 120 nm north of the ITCZ between 33W-38W and within 60 nm north and south of the ITCZ between 28W-33W. Scattered moderate convection is well to the south of the monsoon trough within 30 nm of line from 04N10W to 04N18W, and also within 180 nm north of the ITCZ between 38W-44W. GULF OF MEXICO... Please see SPECIAL FEATURES section above for details on an ongoing gale event over a section of the NW Gulf. A positively-tilted upper shortwave trough stretches from eastern Arkansas southwestward to eastern Texas. This feature is driving a a cold front that as of 03Z extends from a 1014 mb low at 29N92W, or about 60 nm southwest of Morgan City, Louisiana southwestward to 25N95W and to inland Mexico at 23N98W. A rather vigorous pre- frontal squall line is along a position from near Terrebonne Bay, Louisiana to 27N93W and to near 24N95W. Current NWS mosaic Doppler Radar imagery shows scattered moderate to isolated strong convection is along and within 60-90 nm east of the squall line north of 27N and also along and within 60 nm east of the squall line from 24N-27N. This activity is capable of producing strong gusty winds and numerous lightning strikes. East of both the cold front and squall line, high pressure ridging extends from a 1029 mb high pressure center that is located along the Delmarva Peninsula southwestward to the eastern Gulf. The gradient between the high pressure and lower pressure over the western Gulf near the squall line and cold front is allowing for generally gentle to moderate east to southeast winds over the area, with the exception of moderate to fresh southeast winds over the NW and north central Gulf waters as seen in the latest and current buoy observations as well in a partial ASCAT pass from last night. Stronger winds, up gale force and southerly in direction, were revealed in the 0244Z ASCAT to be associated with convection ahead of the front along and east of the squall line. Seas are in the range of 3-5 ft, except for higher seas of 4-6 ft in the NW Gulf. Seas near aforementioned convection may be tough. As for the forecast: The high pressure over the eastern Gulf will continue to shift eastward through Sun night in the response to eastward advancement of the low pressure and cold front. The front is forecast to reach from the central Gulf Coast to the western Bey of Campeche on Sun, and from southwest Florida to the Yucatan peninsula on Mon before exiting the southeastern Gulf early on Mon. Expect for the present ongoing shower and thunderstorm activity to gradually shift to the eastern Gulf today and tonight. Moderate to fresh southeast winds are expected in the NW Gulf on Wed. By Thu, a strong cold front is forecast to move across the basin, with the possibility of gale force northwest to north winds following in behind it over the SW and west-central Gulf waters. CARIBBEAN SEA... Latest scatterometer data revealed fresh to strong northeast to east winds over the south-central Caribbean. Fresh northeast winds are present south of Hispaniola and over the Windward Passage. These winds are the result of a tight gradient between high pressure that is located well north of the area along the U.S. Mid-Atlantic coast and lower pressure that is typically over NW Colombia and southwestern Caribbean Sea. These winds will continue into this morning as the high pressure remains in place. Winds are then forecast to diminish across the basin later on Sun as the high pressure shifts northeastward. Shallow low-level moisture in the form of scattered to broken low clouds is embedded in the trade wind flow, mainly north of about 14N. Isolated showers are possible with some of these clouds, except for scattered showers that are confined to the Gulf of Honduras, over the interior of Honduras and in some interior sections of Jamaica. An area of scattered to broken low and mid- level clouds is noted over the extreme southeastern Caribbean south of 13N and east of 64W. Surface observations from some of the Windward Islands indicate scattered light showers over and near that general area. Northeast winds over the Bahamas, and the Old Bahama Channel are also advecting patches of low-level moisture with possible isolated into eastern Cuba as well as sections of central Cuba. As for the forecast: A weakening stationary front over north- central Cuba will dissipate overnight tonight. The gradient associate to high pressure north of the area will support mostly fresh northeast trade winds across much of the area through Thu. Highest winds and seas will continue to be in the southern Caribbean, near the coast of Colombia, through Wed night. A cold front will slide southward into the northwestern Caribbean on Tue, stall across the region on Wed and dissipate by Thu. ATLANTIC OCEAN... A cold front extends from near 32N47W southwestward to 25N59W, where it transitions to a stationary front to 22N75W and dissipating to along the north-central coast of Cuba. A pretty extensive field of cold-air stratocumulus clouds is observed behind the frontal boundary, while broken low and mid-level clouds with mainly scattered showers are along and within 60 nm southeast and south of the frontal boundary, except for isolated, small and weak thunderstorms between 63W-67W. Mainly moderate northerly winds are noted in the wake of the front, with an area of fresh winds just to the north of the southeastern Bahamas as were detected by an ASCAT pass from last night. Strong high pressure is building in over the western Atlantic behind the front. A ridge prevails over the east Atlantic, anchored by a 1026 mb high pressure center located near 30N26W. Fresh trade winds are along the southern periphery of the ridge affecting the Cabo Verde Islands and regional waters were seen in a partial ASCAT pass from last night. As for the forecast: The aforementioned cold front will continue to push eastward and dissipate on Mon. The next cold front will move off the Florida coast on Mon, reach the southern Bahamas and southern Cuba by Tue, and continue moving eastward on Wed. Strong to near gale force winds are forecast to develop ahead and behind this next front off the Florida coast and north of the Bahamas on Mon through Tue. By the end of the week, a strong cold front will push off the northeast Florida coast enhancing winds and convection. $$ Aguirre