000 AXNT20 KNHC 121045 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Sun Sep 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 1020 UTC. ...SPECIAL FEATURES... Showers and thunderstorms over the Bay of Campeche and southern Gulf of Mexico have been increasing during the past several hours near and east of a surface trough of low pressure. A tropical depression is expected to form later today or tonight while the system moves northwestward and then northward near the coast of northeastern Mexico. Additional development is possible through the middle of next week if the system remains over water, and interests along the western and northwestern Gulf coast should monitor the progress of this disturbance. An Air Force Hurricane Hunter aircraft is scheduled to investigate the system this morning, and potential tropical cyclone advisories could be initiated later today. Regardless of development, the disturbance will continue to produce heavy rain across portions of southern Mexico today, including the western Yucatan Peninsula, which may lead to flash flooding and mudslides. By late today, heavy rain is expected to reach portions of the Texas and Louisiana coasts with a heavy rain threat continuing across those coasts through the middle of the week. Localized significant rainfall amounts are possible, potentially resulting in areas of flash, urban, and isolated river flooding. The chance of tropical cyclone formation within the next 48 hours is high. ...TROPICAL WAVES... An Atlantic tropical wave has an axis along 25W south of 21N, moving W at 15-20 kt. A 1010 mb low is analyzed along the wave near 17N25W. Scattered moderate to isolated strong convection is noted north of the low from 17N to 20N between 23W and 26W. The National Hurricane Center is tracking this disturbance for possible tropical development over the next few days. Currently, it has a low chance of development over the next 48 hours. An Atlantic tropical wave has an axis along 47W south of 22N, moving W at 15 kt. The wave is surrounded by dry Saharan air, which is inhibiting convection at this time. A Caribbean tropical wave has an axis along 68W south of 21N, moving W at 15-20 kt. This wave is moving in tandem with an upper level trough and is producing scattered moderate to isolated strong convection from 17N to 22N between 65W and 71W, impacting Hispaniola, Puerto Rico, and the Virgin Islands. A Caribbean tropical wave has an axis along 83W south of 15N, moving W at 10 kt. A few showers are noted near the wave axis, mainly north of Panama, but no significant convection is associated with this feature. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Mauritania near 20N16W to near a 1010 mb low near 17N25W to 12N31W to 06N38W. The ITCZ continues from 06N38W to 05N45W. Outside of the convection near the 1010 mb low, isolated convection is noted along the ITCZ from 05N to 07N between 39W and 43W. GULF OF MEXICO... See the Special Features section above for details on the disturbance over the Bay of Campeche. A trough stretches across the western Gulf from 27N93W to 18N93W. Scattered moderate to isolate strong convection is noted S of 27N between 89W and 98W and moving northward toward the Texas and Louisiana coast. Isolated thunderstorms are also moving across the Florida Panhandle. Overnight satellite data and surface observations show fresh to strong cyclonic winds W of 86W, with the strongest winds noted in the north-central Gulf and within 100 nm the coast of Veracruz, Mexico. Moderate to locally fresh easterlies are observed in the SE and NW Gulf, while gentle to moderate winds are present in the NE Gulf. Fresh to locally strong winds are occurring east of the trough in the Bay of Campeche. Seas of 4-7 ft prevail in the N Gulf, while 3-6 ft are present elsewhere in the basin, with the exception of 2-4 ft in the NE Gulf. For the forecast, please see the Special Features section above for more information about the potential for tropical cyclone development in the western Gulf. Elsewhere, quiescent conditions are expected to prevail across the central and eastern Gulf through midweek. CARIBBEAN SEA... Please see the Tropical Waves section above for details on the tropical waves along 66W and 82W. Scattered moderate convection is moving across the Greater Antilles N of 17N between 66W and 84W. Scattered moderate to isolated strong convection is noted in the SW Caribbean near the monsoon trough, S of 13N between 74W and 84W. Fresh to strong trade winds are continuing north of Colombia and the Gulf of Honduras, with moderate to locally fresh winds across the rest of the Caribbean. Seas of 5-8 ft are present in the central Caribbean and Gulf of Honduras and 2-5 ft are prevalent elsewhere. For the forecast, the fresh to strong winds occurring offshore Colombia and in the Gulf of Venezuela will diminish today. The fresh to strong winds in the Gulf of Honduras will pulse again this evening. By tonight and into Mon morning, moderate to locally fresh trades will prevail across the basin through Thu. ATLANTIC OCEAN... In the SW N Atlantic, a stationary front lingers from 31N67W to 29N78W. Scattered thunderstorms are noted along this boundary from 28N to 31N between 62W and 78W. A trough is analyzed east of the Lesser Antilles from 16N55W to 10N56W. Scattered moderate to isolated strong convection is noted from 12N to 23N between 55W and 62W. In the far eastern Atlantic, a cold front stretches from 31N20W to 30N38W. Scattered showers are along this boundary. High pressure extends across the basin anchored by a 1028 mb high near 35N45W. Moderate to locally fresh winds prevail across the basin S of 23N with light to gentle winds north of 23N. Seas are 4 to 7 ft with seas less than 3 ft near the Florida coast. For the forecast west of 60W, a frontal boundary will linger across the area through Mon which will bring showers and thunderstorms across the area. Otherwise, quiescent conditions will prevail through Wednesday. Meanwhile, an area of low pressure is expected to form north of the southeastern Bahamas in a few days resulting from the northern end of a tropical wave interacting with an upper- level trough. Gradual development of this system is possible, and a tropical depression could form by the middle of the week several hundred miles southeast of the Carolinas while it moves northwestward across the western Atlantic. This system has a low chance of formation in the next 48 hours and a medium chance through the next 5 days. $$ AReinhart