000 AXNT20 KNHC 271750 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1805 UTC Sun Jun 27 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 1700 UTC. ...SPECIAL FEATURES... Satellite imagery and nearby buoy and ship observations indicate that a small low pressure system has formed about 500 miles east-southeast of the Georgia-South Carolina border. Surface pressures have begun to fall across the area, and showers and thunderstorms have recently become better organized. Some additional development of this system will be possible later today, and especially on Monday when the system will move across the warmer waters of the Gulf Stream, and a tropical depression could form before the system makes landfall along the southern U.S. coast. The low is expected to move westward today, and then west-northwestward at about 15 mph on Monday, reaching the coast of the southeastern United States by late Monday. An Air Force Reserve Unit reconnaissance aircraft is scheduled to investigate the system Monday afternoon, if necessary. Latest Tropical Weather Outlook gives this system a medium chance of tropical cyclone formation through 48 hours. Please, read the latest Tropical Weather Outlook at www.hurricanes.gov, for more information. ...TROPICAL WAVES... A tropical wave has been added to the 1200 UTC analysis/surface map near the west coast of Africa based on satellite imagery, tropical wave diagnostics and the Hovmoler diagram that clearly shows the westward propagation of the wave. The wave is along 17W, from near Dakar, Senegal southward. Scattered moderate to isolated strong convection is noted on either side of the wave axis from 02N-12N between 12W-21W. A second tropical wave is along 33W, from 16N southward. A 1009 mb low pressure center is analyzed along the tropical wave, near 10N. Scattered moderate convection is within about 210 nm NW quadrant of the center. Some slow development of this system is possible through the middle of the week while it moves a little faster toward the west and then west-northwest at 15 to 20 kt. Fresh easterly winds are noted per scatterometer data within about 150 nm N semicircle of low. Please, read the latest Tropical Weather Outlook at www.hurricanes.gov, for more information. The tropical wave previously located along 48W is no longer discernible in satellite imagery or surface observations. As a result, it was dropped from the surface map at 1200 UTC. Dry air due to the Saharan dust is noted across the area. Another tropical wave is along 57W, from 18N southward, moving W at 10 to 15 knots. Convection is limited near the wave axis that is surrounding by African dust. A tropical wave is moving westward across the Caribbean Sea and extends from Hispaniola to western Venezuela. It axis is near 72W moving W at 10 kt. The wave is helping to induce some convective activity near Cabo Beata, Dominican Republic as well as over the Caribbean waters from 14N to 17N between 66W and 76W. A tropical wave has reached the Yucatan Peninsula and northern Central America. It axis is along 89W. Scattered showers and thunderstorms are flaring up near the northern end of the wave axis over the Yucatan Peninsula. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal plains of Guinea near 11N15W to a 1009 mb low pressure located near 10N33W to 07N39W. The ITCZ axis continues from 07N39W to 06N45W to 08N55W where a few showers are noted. The remainder of the convection is associated with the tropical waves. GULF OF MEXICO... An upper-level low is still spinning over the NW Gulf supporting scattered to numerous showers and thunderstorms, particularly on the east side of the low located near 27N95W. A surface trough, reflexion of this low, extends 27N91W to 24N96W. This trough over the northwest Gulf will move inland over Texas through late today, bringing scattered showers and thunderstorms as well as fresh SE winds along with it. Winds and seas could be higher near thunderstorms. Otherwise, a weak ridge dominates the eastern Gulf producing gentle to moderate SE winds. These winds will will persist through the middle of the week between a trough over the far southwest Gulf and the Atlantic ridge. CARIBBEAN SEA... Convection over the Caribbean is primarily associated with the tropical waves described above. The EPAC monsoon trough extends across Costa Rica and western Panama into northern Colombia. Scattered showers and thunderstorms are noted S of 10N E of 81W, including the Gulf of Uraba. A diffluent pattern aloft supports scattered showers and isolated thunderstorms across the central Caribbean, mainly from 13N to 16N between 79W and 82W. A relatively weak pressure gradient spans the Caribbean Sea with mainly gentle to moderate trades dominating. A surge in the trade wind flow is noted behind the tropical wave located near 72W. Fresh to locally strong easterly winds are occurring from 13N-16N between 65W-68W with seas of 5 to 7 ft. Elsewhere, seas are in the 3 to 5 ft range over the central Caribbean and Gulf of Honduras, and 1 to 3 ft across the remainder of the basin. The tropical wave currently along 72W will move westward across the basin through Mon. This pattern will support moderate to fresh trade winds over the south central Caribbean and off Honduras early this week, with gentle to moderate trade winds elsewhere. Then, winds will increase and seas will build slightly in most areas by the middle of this week as high pressure north of the Caribbean Sea extends into the basin in the wake of the above mentioned tropical wave. Another tropical wave may approach the Lesser Antilles late in the week. ATLANTIC OCEAN... Satellite imagery and nearby buoy and ship observations indicate that a small low pressure system has formed about 435 nm east- southeast of the Georgia-South Carolina border. Please, refer to the Special Features section for more details. An altimeter pass indicates seas of up to 11 ft within about 90 nm NE quadrant of the low located near 29N71W at 1200 UTC. A cold front is along 31N roughly between 40W and 52W. Scattered showers are along the frontal boundary. The remainder of the Atlantic forecast area is under the influence of a ridge anchored on a 1023 mb high pressure located W of the Madeira Islands near 32N20W. Fresh northerly winds are seen just off the coast of W Africa from 18N to 28N E of 20N, including the Canary Islands. Seas are in the 5 to 7 ft range within these winds. Similar sea heights are noted across the tropical Atlantic, mainly between 28W and 55W where moderate to locally fresh trades prevail. $$ GR