000 AXNT20 KNHC 111038 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1205 UTC Sat Sep 11 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 1000 UTC. ...SPECIAL FEATURES... Hurricane Larry is centered near 50.7N 51.7W at 11/0900 UTC or 250 nm NNE of Cape Race Newfoundland moving NNE at 42 kt. Estimated minimum central pressure is 966 mb. Maximum sustained wind speed is 65 kt with gusts to 80 kt. Most of the convection is over the northern semicircle with numerous moderate to isolated strong convection extending outward for 300 nm from the center. On the forecast track, Larry will continue to quickly move north-northeast today. Larry is forecast to transition into a post-tropical cyclone later today, and merge with a larger non-tropical low by tonight. Significant swells from Larry will continue affecting Bermuda, the east coast of the United States, and Atlantic Canada through tonight. These swells are likely to cause life-threatening surf and rip current conditions. Please read the latest High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. A tropical wave extends along 91W from the W Yucatan Peninsula southward through Guatemala. Disorganized showers and thunderstorms over portions of Central America, southeastern Mexico, and the adjacent waters of the northwestern Caribbean Sea and southern Gulf of Mexico are associated with this tropical wave interacting with an upper-level trough. Upper-level winds over the western Gulf of Mexico are expected to become more conducive for development over the weekend, and a tropical depression is likely to form on Sunday or Monday while the system moves northwestward and then northward near the coast of northeastern Mexico. Further development of this system will be possible through the middle of next week if it remains over water, and interests along the western and northwestern Gulf coast should monitor the progress of this system. Regardless of development, this disturbance is expected to produce heavy rain across portions of Central America and the Yucatan Peninsula today, which may lead to flash flooding and mudslides. By late this weekend, heavy rain will likely reach portions of the western Gulf coast, including coastal Texas and Louisiana through the middle of next week. Localized significant rainfall amounts will be possible, resulting in limited flash and urban flooding. This system has a high chance of formation in the next 48 hours. A tropical wave with an axis along 19W is producing a concentrated area of showers and thunderstorms between Senegal and the Cabo Verde Islands. Environmental conditions appear generally conducive for additional development, and a tropical depression is likely to form late this weekend or early next week while the system moves generally westward over the far eastern Atlantic near the Cabo Verde Islands. Interests in the Cabo Verde Islands should monitor the progress of this system. The disturbance has a medium chance of development over the next 48 hours. ...TROPICAL WAVES... An Atlantic tropical wave has an axis along 19W from 20N southward, moving W at 10-15 kt. Scattered moderate convection is noted from 12N to 16N between 17W and 23W. See the Special Features section for more information on this wave. An Atlantic tropical wave has an axis along 40W from 23N southward, moving W at 15 kt. The wave is surrounded by dry and dusty Saharan air which is inhibiting the development of convection. An Atlantic tropical wave has an axis along 59W from 22N southward, moving W at 15 kt. Satellite imagery shows broad surface curvature with this wave. Scattered moderate convection is noted from 16N to 21N between 56W and 62W. A Caribbean tropical wave has an axis along 77W from 16N southward, moving W at 10 kt. The interaction with this wave and the E Pacific monsoon trough is enhancing scattered moderate to isolated strong convection over the SW Caribbean. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coast of Mauritania near 19N16W to 11N28W to 06N34W. The ITCZ continues from 06N34W to 08N40W. Aside from the convection noted in the tropical waves section, scattered moderate convection is noted from 03N to 09N between 23W and 37W. GULF OF MEXICO... A complex weather pattern is allowing for a large area of disorganized showers and thunderstorms across the southern Gulf of Mexico, especially in the Bay of Campeche. A surface trough extends across the Bay of Campeche from 25N95W to 19N93W. Scattered moderate convection is noted S of 26N between 90W and 98W. In the northern Gulf of Mexico, a stationary front continues to linger from north of Tampa Bay, Florida near 28N93W to 28N94W. Scattered showers and thunderstorms are within 100 nm of the front. Overnight scatterometer satellite pass show fresh to locally strong E-NE winds within 160 nm of the Yucatan peninsula, with the strongest winds found in the E Bay of Campeche, S of 21N. Gentle to moderate winds are found in the rest of the basin. Seas of 2-4 ft are noted in the Bay of Campeche, SE and NW Gulf waters and 1-2 ft elsewhere in the Gulf. For the forecast, see the Special Features section above for information on the tropical wave that has potential to develop into a tropical cyclone over the southwest Gulf of Mexico Sunday or Monday. Expect an increase in winds and seas along these regions with this system. Meanwhile, a frontal boundary over the northern Gulf will prevail through Sun supporting showers and thunderstorms across the region. CARIBBEAN SEA... Please see the Special Features section above for details on the tropical wave over Yucatan and Guatemala that is inducing convection west of 85W. Scattered moderate to isolated strong convection is noted along the monsoon trough and tropical wave in the SW Caribbean S of 14N between 75W and 83W. Elsewhere, a complex of thunderstorms are moving near the Cayman Islands. Isolated thunderstorms continue to move across the waters near Hispaniola and Puerto Rico. Overnight scatterometer data depicted a large area of strong to locally near gale- force trades in the south-central Caribbean, especially within 190 nm of the NW coast of Colombia and the Gulf of Venezuela. Seas in the area are 6-9 ft. Moderate to fresh trades are noted in the north- central and E Caribbean and the Bay of Honduras with seas of 4-6 ft. Gentle to moderate trades and seas of 2-4 ft are found elsewhere in the basin. For the forecast, the Atlantic ridge will continue to build westward across the Caribbean, bringing an increase in the trade wind flow this weekend. Fresh to strong winds will occur offshore Colombia and in the Gulf of Venezuela, mainly at night through Sun. Fresh to strong winds are also likely in the late evening in the Gulf of Honduras through Sun. Scattered showers and thunderstorms across the NW Caribbean are expected to reduce in coverage later today. ATLANTIC OCEAN... Please see the Special Features section above for details on Hurricane Larry over the NW Atlantic. A cold front extends across the SW N Atlc from 31N69W to 29N76W with the rest of front stalled from 29N76W to the central Florida coast near 28N81W. Scattered showers and thunderstorms are noted within 80 nm of the front. A trough extends across the southern Bahamas from 25N73W to 20N73W. Isolated thunderstorms are north of Hispaniola and Puerto Rico from 19N to 22N between 66W and 71W. Otherwise, high pressure extends across the tropical Atlantic anchored by a 1025 mb high near 36N47W. A surface trough is analyzed from 17N50W to 09N51W with scattered moderate convection from 13N to 16N between 48W and 55W. Overnight scatterometer data depicted fresh to locally strong trades on the northern portion of the trough from 14N to 18N and between 45W and 53W. Moderate to fresh NE winds are noted E of 35W, from 19N to 27N. Gentle to moderate easterlies prevail in the rest of the basin. Seas of 4-7 ft is observed N of 14N and W of 35W, while seas of 5-8 ft is seen E of 35W. Seas of 3-6 ft are found elsewhere in the basin. For the forecast over the western Atlantic west of 65W, swells generated by Hurricane Larry will subside this morning. A frontal boundary will linger across the area through Mon which will bring showers and thunderstorms across the area through early next week. Otherwise, quiescent conditions will prevail through Tue. $$ AReinhart