000 AXNT20 KNHC 140516 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0605 UTC Wed Jul 14 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 0500 UTC. ...TROPICAL WAVES... Clusters of moderate to strong convection are approaching the west coast of Africa. The Hovmoller Diagram indicates the westward propagation of this convective activity, likely associated with the next tropical wave. Of note, on average, about 60 waves are generated over North Africa each year, but it appears that the number that is formed has no relationship to how much tropical cyclone activity there is over the Atlantic each year. While only 60% of the Atlantic tropical storms and minor hurricanes originate from easterly waves, nearly 85% of the intense (or major) hurricanes have their origins as easterly waves. A tropical is crossing just S of the Cabo Verde Islands. It axis is along 23W/24W, from 15N southward, moving westward from 10 to 15 kt. Scattered moderate convection is where the wave meets the monsoon trough, and mainly from 07N-11N between 21W-25W. A second tropical wave is along 53W/54W, from 15N southward, moving westward from 10 to 15 kt. Convection is limited near the wave axis. An active tropical wave is over the western Caribbean with axis along 85W. The wave extends from western Cuba southward across northern Central America. It is moving westward from 10 to 15 kt. The wave is generating scattered to numerous showers and thunderstorms over the NW Caribbean. Scattered showers and thunderstorms are noted over parts of the Yucatan peninsula and northern Central America. Upper diffluent is also helping to induce this convective activity. The wave will move across the Yucatan Peninsula into the SW Gulf of Mexico today and tonight. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean near the Guinea Bissau/Senegal border, and extends from 11N15W to 11N23W to 09N30W. The ITCZ continues from 09N30W to 08N40W to 09N51W. Scattered moderate isolated strong convection is noted from 05N- 09N between 26W-40W, and from 07N-10N between 40W-43W. GULF OF MEXICO... A ridge dominates the SE of United States and the Gulf waters, anchored by a 1027 mb high pressure located west Bermuda near 33N72W. This system is producing gentle to moderate NE to E winds across the Gulf region, with the exception of moderate to fresh easterly winds over the Florida Straits and SE Gulf waters. Moderate to fresh NE winds are also noted per scatterometer data just west of the Yucatan peninsula due to local effects associated with a thermal trough. Moisture, in the wake of the tropical wave located over the NW Caribbean, continues to enhance convection over South Florida and west-central Cuba. A short-wave trough over the SE Gulf is also helping to support this convective activity. Weather conditions are expected to improve in South Florida late Wed into Thu as the wave moves westward. For the forecast, a surface ridge just north of the area will maintain gentle to moderate E to SE winds and slight to moderate seas across much of the Gulf through Fri. A surface trough will develop each day over the Yucatan and shift westward into the SW Gulf. This will support fresh to occasionally strong winds off the northwest Yucatan Peninsula and eastern Bay of Campeche during the overnight hours through Thu night. Looking ahead, a trough will move through the southeast Gulf Fri and across the central Gulf Sat and Sun, bringing a slight increase in winds and seas to the Straits of Florida Fri night into Sat. CARIBBEAN SEA... An active tropical wave is over the NW Caribbean generating showers and thunderstorms. Please refer to the Tropical Waves section above for details. Elsewhere across the basin, patches of low level moisture embedded in the trade wind flow are noted, particularly over the eastern Caribbean. Satellite derived wind data show fresh to strong trades over the central Caribbean, and mainly moderate NE to E winds elsewhere. An altimeter pass indicates seas near 12 ft within the area of the strongest winds. For the forecast, high pressure centered north of the region will support strong to near-gale force tradewinds and rough seas over the central Caribbean today, including strong NE winds across the Windward Passage. Fresh to strong NE to E winds are expected in the Gulf of Honduras late today and tonight. Winds and seas will diminish through Fri, although fresh to strong winds will continue to pulse Thu and Fri in the Gulf of Venezuela and near the coast of NE Colombia. Looking ahead, tradewinds and related seas will slightly increase over the south-central Caribbean and around the Leeward Islands Sat into Sun as another tropical wave reaches the eastern Caribbean. ATLANTIC OCEAN... Two tropical waves are moving westward between the west coast of Africa and the Lesser Antilles. Please refer to the Tropical Waves section above for details. A diffluent pattern aloft supports scattered showers and thunderstorms over the NW Bahamas and the Straits of Florida. Farther east, an upper level low spinning near 26N58W continues to generate some shower activity with embedded thunderstorms. The surface reflection of this upper level low is analyzed as a trough that extends from 29N58W to 24N59W. The remainder of the Atlantic forecast waters are under the influence of the Atlantic ridge, with a 1031 mb high pressure located NE of the Azores. The ridge combined with lower pressures over west Africa is producing near gale force winds and moderate to rough seas between the Canary Islands. A recent scatterometer pass confirmed the presence of these winds. For the forecast W of 65W, a ridge extending just north of the area from roughly Bermuda to Georgia will maintain gentle to moderate E winds across the basin, with fresh winds pulsing off the coast of Hispaniola at night through Fri night. Looking ahead, winds and seas will build slightly Sat south of 22N and north of the Leeward Islands as a tropical wave approaches the region from the east. Expect fresh to strong winds to again pulse off Hispaniola during the upcoming weekend. $$ GR