000 AXNT20 KNHC 120532 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 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 0000 UTC surface analysis and satellite imagery through 0505 UTC. ...TROPICAL WAVES... An Atlantic tropical wave has its axis along 20W, south of 17N and it is moving W at 10-15 kt. Scattered moderate to isolated strong convection is observed from 03N to 15N and between 15W and 29W due to the interaction between the wave and the monsoon trough. Another Atlantic tropical wave has its axis along 39W, south of 17N and it is moving W at 10-15 kt. Isolated showers are noted near the wave axis, mainly from 03N 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 58WW, south of 20N and it is moving W at 10-15 kt. A 1010 mb low pressure is centered along the tropical wave near 14N58W. 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 fresh to strong winds are occurring over the E semicircle. Seas of 6-9 ft are found within 90 nm of the center. The disturbance has a low chance of development over the next 48 hours and 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. Please visit hurricane.gov to read the latest Tropical Weather Outlook from the National Hurricane Center. A Caribbean tropical wave has its axis along 72W, 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 15N to 22N and between 65W to 72W, affecting Puerto Rico, Hispaniola and the SE Bahamas. A few showers and isolated thunderstorms are also noted along the southern portion of the wave, affecting W Venezuela. A recent scatterometer satellite pass show a well-defined surface curvature. 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 87W, south of 21N, extending southward through Honduras and W Nicaragua, 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 Senegal near 13N17W to 05N28W. A segment of the ITCZ continues from 05N28W to 06N38W. Another ITCZ segment extends from 06N40W to 08N58W. Scattered moderate convection is noted within 300 nm of the ITCZ, mainly to the north, between 41W to 53W. ...GULF OF MEXICO... A dry airmass dominates the Gulf of Mexico resulting in fairly tranquil weather conditions across the basin. A cold front reached the NW Gulf last night, but has recently retreated back into SE Texas as a warm front. A weak surface trough is noted from 29N92W to 27N97W, paralleling the NW Gulf coast, and it is producing a few shallow showers near the trough axis. Another 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... The interaction between a mid to upper level low near the Cay Sal Bank and a surface trough that extends from Florida into the NW Caribbean along 82W results in a few weakening showers between Cuba and the Cayman Islands. 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, the weather conditions over the NE Caribbean are expected to improve by early Tue morning as a tropical wave moves W and gradually weakens. Another tropical wave near 58W is expected to approach the central and northern Lesser Antilles early Tue and move across the Leeward Islands and Virgin Islands Tue afternoon through Tue night. Expect thunderstorms and strong gusty winds with the wave passage. Northerly swell spreading across the central Atlantic today will reach the regional Atlc waters and Caribbean passages early Tue and continue into early Wed morning. ...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 27N68W, resulting in scattered moderate to isolated strong convection from 20N to 28N and between 65W to 79W. Farther E, a surface trough enters the tropical Atlantic near 31N30W and extends to 26N43W. 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 near Florida will continue to linger in the area and weaken through Wed. This trough will continue to bring scattered showers and thunderstorms with it. Otherwise, Atlc high pres extends W-SW into the area along 30N. Farther south, low pressure is forecast to develop around mid-week near the SE Bahamas. Northerly swell across the central Atlc will reach waters E of 72W late tonight through Tue. $$ DELGADO