000 AXNT20 KNHC 251805 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Wed Aug 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 1705 UTC. ...SPECIAL FEATURES... A robust tropical wave over the central Caribbean Sea is producing a large area of disorganized showers and thunderstorms, mainly south of 17N and between 71W to 78W. A broad area of low pressure is expected to form over the SW Caribbean Sea during the next day or so. A recent scatterometer satellite pass indicate fresh to strong trades over the NE quadrant of the disturbance. Environmental conditions are forecast to be conducive for development, and a tropical depression or tropical storm is likely to form late this week or over the weekend. The system is expected to move northwestward over the northwestern Caribbean Sea and near or across the Yucatan Peninsula of Mexico on Friday and into the Gulf of Mexico this weekend where conditions are expected to be favorable for additional development. This system has a medium chance of development within the next 48 hours. Refer to the National Hurricane Center Tropical Weather Outlook at www.hurricanes.gov and the High Seas Forecast at www.hurricanes.gov/marine for more details. A 1012 mb low pressure positioned near 26N54N and a surface trough that extends from 21N55W to a dissipating cold front near 33N49W results in a large area of showers and thunderstorms, especially to the NE and SW of the system. Most of the activity is concentrated from 23N to 34N and between 50W and 58W. Strong to near-gale SE winds are noted in the latest satellite derived wind data in the eastern quadrant of the disturbance. Seas of 8-12 ft are noted from 25N to 30N and between 50W to 53W. Only slow development of this system is expected during the next day or so due to unfavorable upper-level winds. Afterwards, environmental conditions are forecast to become more conducive for development, and a tropical depression is likely to form late this week or this weekend while the system turns eastward over the open central Atlantic. This system has a medium chance of development within the next 48 hours. Refer to the National Hurricane Center Tropical Weather Outlook at www.hurricanes.gov and the High Seas Forecast at www.hurricanes.gov/marine for more details. Heavy Rainfall in southern Central America: A broad area of low pressure is expected to form over the SW Caribbean Sea later this week, resulting in an increase in moisture and unstable conditions across southern Central America. Heavy rainfall is expected across eastern Nicaragua, Costa Rica, Panama, and NW Colombia through early in the weekend. The heaviest precipitation is forecast to affect southern Costa Rica and western Panama late this week. These rains could cause significant flooding and mudslides in some areas. Please, monitor the latest forecasts from your local or national meteorological service. ...TROPICAL WAVES... An Atlantic tropical wave has its axis along 34W, south of 19N, and it is moving W at 10 to 15 kt. A 1008 mb low pressure is along the wave axis near 11N34W. Scattered moderate to isolate strong convection is noted in the northern semicircle of the system from 12N to 16N and between 31W and 36W. Fresh to strong NE winds are noted north of broad center on a recent scatterometer satellite pass. Some development of this system is possible over the next several days over the eastern tropical Atlantic. Upper- level winds are forecast to become less conducive for development by this weekend. For more details, please see the latest Tropical Weather Outlook. Another Atlantic tropical wave has its axis along 54W, south of 19N, and it is moving W at around 15 kt. A few showers are noted within 200 nm E of the wave from 08N to 10N. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean through Senegal near 15N17W and continues to 14N29W and to 07N40W. The ITCZ then extends from 07N41W to 06N47W. Aside from convection noted in the tropical waves section, scattered moderate isolated strong convection is observed within 90-120 nm of the coast of Africa from 04N to 13N. This convective activity is likely ahead of the next tropical wave approaching the W coast of Africa. ...GULF OF MEXICO... Weak high pressure over the southern United States maintains mainly gentle to moderate easterlies across the Gulf of Mexico. However, moderate to locally fresh trades are noted in the Florida Straits and NE Gulf based on recent satellite derived wind data. Moisture in the N Gulf associated with a weak surface trough, extending from SW Alabama to 27N94W, is interacting with an upper level trough over the NW Bahamas, resulting in scattered showers north of 25N and from the W Florida coast to near the trough axis. Another weak surface trough is noted in the Bay of Campeche and a few showers are seen near the coast of Veracruz. The rest of the basin enjoys fairly tranquil weather conditions. Seas in the SE Gulf and Bay of Campeche are in the 2-4 ft range, while 1-2 ft are prevalent elsewhere in the region. For the forecast, a surface trough will move into the eastern Gulf tonight into Thu morning, bringing fresh NE to E winds. Otherwise, high pressure pressure will dominate the basin through Fri, producing mainly gentle to moderate E to SE winds. Fresh winds will pulse west of the Yucatan Peninsula tonight and again Thu night. A broad area of low pressure is expected to form over the southwestern Caribbean Sea over the next day or so. Environmental conditions are forecast to be conducive for development, and a tropical depression is likely to form late this week or this weekend while the system moves northwestward over the northwestern Caribbean Sea. The disturbance is expected to move near or across the Yucatan Peninsula of Mexico on Saturday, and move into the western Gulf of Mexico by Sunday where conditions could be favorable for additional development to occur. Expect a large increase in winds and seas Sun and Sun night over the central and western Gulf. ...CARIBBEAN SEA... The E Pacific monsoon trough enters the SW Caribbean Sea near the Nicaragua/Costa Rica border and continues to NW Colombia. The increase in moisture and instability in the region due to the interaction between the disturbance discussed in the Special Features and the monsoon trough is resulting in a large area of showers and thunderstorms, south of 13N, and from the SE coast of Nicaragua to NW Colombia. Generally tranquil weather conditions are observed in the NW and E Caribbean thanks to dry air. A recent scatterometer satellite pass depicted fresh to strong trade winds in the central and E Caribbean Sea, mainly between 65W and 75W. Seas in this area are 5-8 ft. Fresh to locally strong NE winds were also observed between coast of central Cuba and the Cayman Islands due to a surface trough that is mostly positioned over the central Bahamas, but the southern end extends to the NW Caribbean. Seas in the NW Caribbean and Gulf of Honduras are 3-6 ft. Moderate to locally fresh trades and 5-8 ft seas prevail in the SW Caribbean. For the forecast, fresh to locally strong trade winds will dominate most of the central Caribbean today. A broad area of low pressure is expected to form over the southwestern Caribbean Sea over the next day or so from a tropical wave currently located over the central Caribbean Sea along 74W. Environmental conditions are forecast to be conducive for development, and a tropical depression is likely to form late this week or this weekend while the system moves northwestward over the northwestern Caribbean Sea. The disturbance is expected to move near or across the Yucatan Peninsula of Mexico on Saturday, and move into the Gulf of Mexico by Sunday. Based on the forecast, winds and waves will likely increase between 78W and the Yucatan Peninsula Fri and Sat. ...ATLANTIC OCEAN... A sharp and convectively active surface trough extends from the Bahamas and E Cuba from 28N71W to 19N79W. This system is interacting with an upper level trough to generate scattered moderate to isolated strong convection mainly west of the trough axis to Florida and from 23N to 30N. A recent scatterometer satellite pass indicate strong to near-gale NE winds from the N coast of Cuba to 27N and between 72W to the SE coast of Florida. Seas of 4-7 ft are noted W of 53W. A region of moderate to fresh E winds is observed NW of the disturbance discussed in the Special Features, from 15N to 23N and between 28W and 44W. Similar winds are noted near the coast of Western Sahara. W of 53W, seas are 5-8 ft. For the forecast W of 65W: A surface trough located over the central and northwest Bahamas will move into the eastern Gulf of Mexico Thu morning. Fresh to strong NE winds are expected west of the trough axis, including the Florida Straits. Otherwise, high pressure located just N of the forecast region will dominate the SW N Atlantic through Sat. Fresh to locally strong winds are expected to pulse N of Hispaniola during the evening hours through Sat night. $$ DELGADO