000 AXNT20 KNHC 131800 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Wed Oct 13 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 1750 UTC. ...SPECIAL FEATURES... Atlantic Gale Warning: A 1000 mb low pressure is just N of the area near 31.5N 46.5W. An occluded front extends E from the low to another low of 1002 mb near 31.5N42W. A cold front extends W from the 1002 mb low to 29N49W to 31N55W. The morning ASCAT passes show gale force SW to W winds extending southward to 29N from the easternmost low. The ASCAT data also show near-gale force W to NW winds extending southward to 28N from the westernmost low. Scattered moderate isolated strong convection with this system is noted north of 25N between 35W-47W. Expect gale force SW to W winds north of 29N between 36W-47W through this evening at 14/0000 UTC. As the low moves eastward, expect the gales to move from west to east within this area. Seas of 11 to 13 ft are expected within the area of gale force winds. Please read the latest High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details. ...TROPICAL WAVES... An Atlantic tropical wave axis is along 30W from 03N-18N, moving W at 10-15 kt. Moderate westerly upper-level winds over the tropical wave, induced by an upper-level low near 24N23W, are pushing much of the convection east of the wave axis. Scattered moderate to isolated strong convection is observed from 09.5N to 13N between 23W-31W. Another Atlantic tropical wave axis is along 51W/52W from 04N-17N, moving W at 10-15 kt. Scattered to numerous moderate with embedded isolated strong convection is noted where the wave interacts with the ITCZ from 07N to 10.5N between 48W-54W. The northern portion of the wave is surrounded by dry Saharan air and a subsident mid-level ridge axis, suppressing the development of showers and thunderstorms. An eastern Caribbean tropical wave axis extends from 19N66W through Puerto Rico to Venezuela near 05N67W. The tropical wave is moving W at 10-15 kt. Isolated to scattered showers are seen between 60-120 nm E of the wave axis, mainly N of 15N. Otherwise, mid to upper-level ridging is providing subsidence, which is suppressing convection. The western Caribbean tropical wave that had been analyzed along 80W at 13/0600 UTC has been repositioned slightly to the east along 79W as of 1200 UTC, based on surface observations and total precipitable water imagery. The tropical wave is moving W at around 10 kt. No deep convection is noted in association with the wave as it moves into a dry airmass, except for isolated moderate showers along the wave south of 11N to Panama, near where the wave intersects the east Pacific monsoon trough. ...MONSOON TROUGH/ITCZ... A monsoon trough extends from the coast of Guinea-Bissau near 12N16W to 05N29W. The ITCZ is analyzed from 05N32W to 07N41W to 09N50W, then continues W of a tropical wave from 09N53W to 09N60W. Isolated moderate showers are along the monsoon trough east of 25W. Scattered moderate and isolated strong convection is noted along the ITCZ from 06.5N to 10.5N between 37W and 60W. ...GULF OF MEXICO... A weak ridge extends from northern Georgia to the south-central Gulf of Mexico and maintains tranquil weather conditions across most of the basin. The pressure gradient between the ridge and Tropical Storm Pamela over northern Mexico is resulting in fresh to locally strong SE to S winds in the west-central Gulf of Mexico, especially near the coast of southern Texas, where the latest ASCAT pass shows 20-25 kt winds. SSE winds of 23 kt and wave heights of 6 ft have recently been occurring at NOAA buoy 42020, located about 60 nm SE of Corpus Christi. Seas of 4 to 6 ft cover the western Gulf. Moderate E winds prevail east of 90W, with 2 to 3 ft seas. For the forecast, weak high pressure extending from the eastern U.S. southwestward to the central Gulf and will influence the Gulf waters during the next several days. Moderate to fresh southerly winds are expected over the western Gulf between the ridge and lower pressure over the Southern Plains and northern Mexico through Thu. Gentle to moderate breezes will persist elsewhere through Fri. A cold front will enter the NW Gulf Fri night with fresh to strong northerly winds following it. The front will reach from central Florida to the western Bay of Campeche Sun morning with moderate to fresh N-NE winds across most of the Gulf. ...CARIBBEAN SEA... An upper-level low is centered near the NW Bahamas near 25N75W. An upper-level trough extends SW from the upper-low to northern Central America. Strong upper-level diffluence to the east of the upper-trough is inducing numerous strong convection over the central Caribbean from 12N to 15.5N between 71.5W and 74W. Scattered moderate and isolated strong convection surrounds that area, from 09N to 18.5N between 70.5W and 77W. The morning ASCAT pass indicated a surface trough or possible outflow boundary within the convection, extending along 74W from 12N to 18N. Elsewhere, scattered showers and isolated tstorms over the NE Caribbean are associated with a tropical wave, described in the section above. The morning ASCAT pass shows gentle wind speeds over the western Caribbean, west of 77W, where seas are likely 1 to 3 ft. Mainly moderate wind speeds are elsewhere east of 77W, except for stronger winds likely within the strong thunderstorm activity. Seas are 3 to 5 ft east of 77W, except higher in the NE Caribbean passages, due to northerly swell from the Atlantic. However, this northerly swell will subside tonight. For the forecast, the vigorous upper-level trough extending from the Bahamas to the NW Caribbean will support active weather across the central Caribbean and extreme NE Caribbean through tonight behind two tropical waves. Developing low pressure NE of the southern Bahamas will drift E-NE tonight through the weekend. This will weaken the pressure gradient across the Caribbean basin, leading to tranquil marine conditions. ...ATLANTIC OCEAN... An upper-level low is centered near the NW Bahamas. A weak surface trough extends from 30N71W to 28N73W to 25N74W. A more potent surface trough extends from 27N67W to 1010 mb low pressure near 24.5N 70.5W to 21N71W. The morning ASCAT data shows fresh to strong winds within 180 nm in the NE semicircle of the low pressure center, while gentle to moderate wind speeds prevail elsewhere across the western Atlantic, west of 60W. Strong upper-level diffluence to the east of the upper-low is inducing scattered moderate and isolated strong convection from 21N-30N between 64W-71W. Scattered moderate showers and isolated tstorms are occurring within 60 nm either side of the western/weaker surface trough, mainly north of 26.5N. Seas of 4 to 6 ft prevail over the western Atlantic, except up to 8 ft in N swell to the NE of the Virgin Islands. The N swell across these waters will subside tonight. The 1010 mb low pressure near 24.5N 70.5W is forecast to drift northward through tonight, then accelerate eastward on Thursday. Development, if any, of this disturbance should be slow to occur during the next couple of days due to unfavorable upper-level winds, and there is a low chance of tropical cyclone formation during the next 48 hours. Regardless of development, this system will continue to produce very active weather and impact the regional waters through late Thu. Locally heavy rainfall is possible over portions of Hispaniola, the Turks and Caicos, and the southeastern Bahamas during the next day or two. Farther east, a surface ridge axis extends from 1020 mb high pressure near 31N20W to 21N42W to a 1016 mb high pressure near 25N59W. Fair weather and light to gentle anticyclonic winds are within 150 nm either side of the ridge axis. To the south, fresh trades are noted from 09N to 16N between 30W and 60W, where seas are mainly 7 to 8 ft. To the north of the ridge, strong to gale force winds and thunderstorms are occurring, especially from 24N-31N between 36W-47W, described above in the Special Features section. The Cumbre Vieja volcano, on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Significant volcanic ash is possible near the volcano. 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/ $$ Hagen