Tropical Weather Discussion

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Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Mon Oct 25 2021 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 31N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1625 UTC. ...TROPICAL WAVES... The axis of a tropical has been repositioned along 22W based on recent scatterometer satellite data and visible satellite imagery showing a sharp surface trough SE of the Cabo Verde Islands. The wave is south of 17N and it is moving W at around 10 kt. A few showers and isolated thunderstorms are noted within 200 nm on both sides of the wave axis. Fresh to strong trades are noted in recent satellite-derived data from 11N to 15N and between 18W and 24W. The axis of a tropical wave is along 64W, south of 19N and it is moving W at 10-15 kt. A recent scatterometer satellite pass indicate a broad surface curvature near the NE coast of Venezuela. Scattered moderate convection is observed from NE South America to 13N and between 56W and 66W. The axis of a tropical wave is along 77W, south of 18N, and it is moving W at 10-15 kt. Dry air is suppressing the shower and thunderstorm activity in the Caribbean Sea, but the wave is helping to induce scattered moderate convection in the Pacific coast of Colombia. ...MONSOON TROUGH/ITCZ... A monsoon trough exits across the coast of Senegal near 14N17W and continues to 08N23W. The ITCZ then extends from 08N23W to 06N37W and to the coast of NE Brazil near 03N51W. Scattered moderate convection is seen within 220 nm on both sides of the ITCZ between 27W and the coast of Brazil. Scattered moderate convection is also present within 150 nm on the south side of the monsoon trough E of 20W. ...GULF OF MEXICO... An upper level trough across the central United States and a developing low pressure off the Georgia coast are providing a favorable upper level pattern for scattered moderate to isolated strong convection to flare up in the SE Gulf of Mexico. Most of the convection is S of 25N and E of 86W, affecting portions of the Florida Keys and Florida Straits. A few showers are seen in the SW Gulf, mainly within 60 nm of the coast of Mexico. A surface trough is identified in the E Bay of Campeche and another one extends from SE Louisiana to the Big Bend region of Florida, but they are not producing any significant convection. Weak pressure gradient results in moderate or weaker anticyclonic winds prevailing across the basin. However, stronger winds are likely in the areas of showers and thunderstorms. Seas of 2-4 ft are present N of 20N and 1-3 ft elsewhere. For the forecast, a weak ridge along 25N will dominate the Gulf waters through Tue and produced gentle to moderate winds. Fresh to strong southerly winds will develop in the NW Gulf Tue night into Wed ahead of a cold front expected to push off the Texas coast on Wed. The front will move across the Gulf region through Thu night. Fresh to strong winds are expected ahead and behind the front, with building seas to 12 ft in the wake of the front. Gale force winds may also occur, mainly over the north-central and NE Gulf Wed night to Fri as the pressure gradient tightens across the area. ...CARIBBEAN SEA... Aside from the storm activity associated with the tropical waves moving across the Caribbean Sea discussed in the Tropical Waves section, only a few showers are noted near the coast of Panama and SE Costa Rica. A dry airmass dominates the rest of the basin, providing fairly tranquil weather conditions. A modest pressure gradient between the 1026 mb high pressure in the NW Atlantic and lower pressures in South America result in fresh to locally strong trades in the central and eastern Caribbean Sea, with the strongest winds occurring within 100 nm of NW Colombia and in the SE Caribbean based on the latest scatterometer satellite data. Seas of 5-8 ft are found in the central, southwest and eastern Caribbean Sea, with the highest seas occurring off the NW Colombian coast. Moderate to locally fresh, especially in the Gulf of Honduras, and seas of 2-5 ft are present elsewhere in the basin. For the forecast, a weak Atlc ridge prevails across the W Atlc this morning. The associated pres gradient across the Caribbean will support fresh to locally strong trades across the eastern Caribbean and tropical Atlc waters E of the Windward Islands through tonight. Winds are also expected to pulse fresh to strong in the south-central Caribbean, including the Gulf of Venezuela through tonight. A cold front will reach the NW Caribbean Thu night into Fri morning, with seas building to 8-9 ft in the Yucatan Channel later on Fri. ...ATLANTIC OCEAN... An intensifying low pressure system off the coast of Georgia and a surface trough extending SW to southern Florida are producing a large area of showers and thunderstorms, mainly W of 72W and N of Cuba, affecting the NW Bahamas. Recent scatterometer satellite data indicate that fresh to strong winds are occurring W of 70W and N of 26N. Elsewhere in the basin, a weak surface trough extends from 25N44W to 17N41W, but it is not producing any deep convection. Another weak surface trough peeks into the tropical Atlantic, entering the region near 31N53W to 29N54W. A few showers are seen near and east of the trough axis, mostly north of our area. An expansive 1031 mb Azores ridge patrols the rest of the tropical Atlantic, promoting fairly tranquil weather conditions. The pressure gradient between the high pressure system and lower pressures in South America result in fresh to strong trades from 05N to 19N and between 33W and the Lesser Antilles. Seas in this region are in the 7-10 ft range, with the highest seas occurring a couple of degrees east of the Windward Islands. Another area of fresh to strong NE winds is found in the E Atlantic from 15N to 22N and E of 30W. Seas of 3-6 ft are prevalent W of 60N and 5-8 ft are present elsewhere in the basin. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Ash cloud slowly drifting SW. Higher concentration over volcano and western vicinity. Marine and aviation interests should monitor this ongoing situation by reading the Volcanic Ash Advisory issued by Meteo- France, at http://vaac.meteo.fr/volcanoes/la-palma/. For the forecast W of 65W, weak ridge extends from the central Atlc westward to 75W this morning. 1013 low pres along the SE Georgia coast will move NE through Tue and then generally north- northeastward through the middle of the week. The associated cold front will move eastward across the northern forecast waters today with fresh to strong southerly winds and building seas expected ahead of the front. Another cold front will push off NE Florida coast on Tue, and bring more fresh to strong winds across the waters N of 27N. A third cold front is expected to sweep across the region Thu night through Fri night bringing another round of fresh to strong winds north of the Bahamas.