000 AXNT20 KNHC 121047 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Tue Oct 12 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 0600 UTC surface analysis and satellite imagery through 1030 UTC. ...TROPICAL WAVES... An Atlantic tropical wave has its axis along 22W, south of 16N and it is moving W at 10-15 kt. Scattered moderate to isolated strong convection is observed from 07N to 22N and between 21W and 23W. Another Atlantic tropical wave has its axis along 41W, south of 17N and it is moving W at 10-15 kt. Isolated showers are noted near the wave axis, mainly from 05N to 08N. The northern portion of the wave is surrounded by dry Saharan air, suppressing the development of showers and thunderstorms. A third Atlantic tropical wave has its axis along 60W, south of 19N and it is moving W at 10-15 kt. Strong westerly shear is displacing the convection to the E of the center, especially from 11N to 17N and between 53W and 59W. Satellite-derived wind data indicate that the tropical wave, located a little over 150 miles east of the Windward Islands, has become less defined overnight. While this system continues to produce showers and thunderstorms primarily east of its center, strong upper-level winds will likely prevent further development during the next couple of days. Regardless of development, the system could produce locally heavy rainfall and gusty winds across portions of the central and northern Lesser Antilles today. There is a low chance of development in the next 48 hours and 5 days. A Caribbean tropical wave has its axis along 73W, south of 21N and it is moving W at 15 kt. Divergence aloft is helping to enhance the scattered moderate to isolated strong convection seen on satellite imagery from 11N to 19N and between 71W to 75W, impacting Hispaniola and the SE Bahamas. Although environmental conditions are not forecast to be conducive for development of this system, a broad area of low pressure, however, is expected to form near the southeast Bahamas on Wednesday and drift generally eastward through the end of the week. Regardless of development, locally heavy rainfall is possible over portions of the Lesser Antilles, Puerto Rico, and Hispaniola during the next couple of days. This disturbance has a low chance of development over the next 48 hours. Please visit hurricane.gov to read the latest Tropical Weather Outlook from the National Hurricane Center. A second Caribbean tropical wave has its axis along 88W, south of 20N, extending southward through Honduras and El Salvador, and it is moving W at 15 kt. No deep convection is noted near the tropical wave. ...MONSOON TROUGH/ITCZ... A monsoon trough extends from the coast of Guinea-Bissau near 11N15W to 06N30W. The ITCZ continues from 06N30W to 06N40W, then resumes W of a tropical wave near 06N43W to 06N52W. Scattered moderate convection is noted from 03N to 08N between 17W and 29W and between 37W and 51W. ...GULF OF MEXICO... A dry airmass dominates the Gulf of Mexico resulting in fairly tranquil weather conditions across the basin. A surface trough cross the Florida peninsula into the NW Caribbean along 82W, but no deep convection is associated with this feature. A weak 1015 mb high pressure over the NE Gulf results in gentle to moderate anticyclonic winds prevailing across the basin. However, fresh NE-N winds are noted within 60 nm of the N and W coast of the Yucatan peninsula. For the forecast, a weak and narrow ridge extends from the eastern U.S. southwestward to the N 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 tonight through Thu. Gentle to moderate breezes will persist elsewhere through Fri. A cold front enter the NW Gulf Fri night. ...CARIBBEAN SEA... Outside of the active tropical wave described in the Tropical Waves section, the rest of the Caribbean Sea has fairly tranquil weather conditions. Fresh trades are noted over the E Caribbean and the Gulf of Honduras, mainly within 90 nm of the coast of Honduras. Moderate or weaker winds are present in the rest of the basin. Seas of 3-6 ft are found in the central, E and SW Caribbean, while 1-3 ft are prevalent elsewhere. For the forecast, a tropical wave near 60W is expected to approach the Lesser Antilles this morning and move near the Virgin Islands by tonight. Expect thunderstorms and strong gusty winds with the wave passage. Northerly swell will continue to impact the regional Atlc waters and Caribbean passages today through Wed. ...ATLANTIC OCEAN... A broad mid to upper level low near the Cay Sal Bank in the Bahamas is interacting with two surface troughs, one located in the NW Bahamas and another one extending from the SE Bahamas to near 26N70W, resulting in scattered moderate to isolated strong convection from 20N to 30N between 64W to 78W. Farther E, a surface trough enters the tropical Atlantic near 31N29W and extends to 24N42W. This feature is only generating a few showers near the trough axis. The rest of the basin enjoys fairly tranquil weather conditions under a dry environment. The pressure gradient between the 1022 mb high pressure over the N Atlantic and the lower pressures in the E Caribbean results in fresh SE winds from the E Greater Antilles to 28N and between 55W and 72W. Moderate to fresh trades are noted S of 20N and between the coast of Africa to the Lesser Antilles. Moderate or weaker winds are found in the remainder of the basin. A northerly swell results with seas of 8-11 ft is found N of 23N and between 30W and 63W, while seas of 5-8 ft prevail elsewhere in the tropical Atlantic. The Cumbre Vieja volcano, that is on the island of La Palma in the Canary Islands, has been erupting since 19 September 2021. Currently, significant volcanic ash is seen in the vicinity of the volcano spreading eastward. Marine and aviation interests should monitor this on-going situation, by reading the Volcanic Ash Advisory, that is issued by Meteo- France, at http://vaac.meteo.fr/volcanoes/la- palma/. For the forecast west of 65W, a surface trough stretching across Florida will continue to linger in the area and weaken through Wed. This will lead to scattered showers and thunderstorms off the Florida coast. Otherwise, Atlc high pres extends across into the area and will help maintain quiescent conditions through Fri. Farther south, low pressure is forecast to develop around mid- week near the SE Bahamas. Northerly swell across the central Atlc will continue across the waters E of 72W through tonight. $$ AReinhart