000 AXNT20 KNHC 031544 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 1144 AM EDT Thu Sep 3 2020 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 32N. The following information is based on satellite imagery, weather observations, radar and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1715 UTC. ...SPECIAL FEATURES... Tropical Storm Nana is centered near 16.4N 90.3W at 03/1500 UTC or 110 nm N of Guatemala City Guatemala moving W at 13 kt. Estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. On the forecast track, the center of Nana will move over northern Guatemala and southeastern Mexico today and tonight, then move over the Gulf of Tehuantepec on Friday. Continued rapid weakening is forecast, and Nana will likely become a remnant low on Friday. Nana is forecast to produce rainfall amounts of 3 to 6 inches, isolated totals of 8 inches over central and western Guatemala and the Mexican state of Chiapas. These rainfall amounts may produce life threatening flash floods and mudslides. Please consult products from your local weather office. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT1.shtml and Forecast/ Advisory at https://www.nhc.noaa.gov/text/MIATCMAT1.shtml for more details. Tropical Depression Omar is centered near 35.9N 61.1W at 03/1500 UTC or 290 nm NE of Bermuda moving E at 11 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. The center of Omar is currently exposed due to fairly strong WNW shear impacting the system. But a large area of strong thunderstorms is observed just to the east of the center. Omar is expected to gradually weaken over the next couple of days as it moves northeast. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPAT5.shtml and Forecast/ Advisory at https://www.nhc.noaa.gov/text/MIATCMAT5.shtml for more details. ...TROPICAL WAVES... A tropical wave that has emerged off the west coast of Africa is along 18N, from 18N southward. A 1008 mb low pressure is analyzed along the wave axis near 14N. The low pressure is well defined on visible satellite imagery, and scatterometer data show fresh SW winds on the SE quadrant of the low center. This system is producing a large area of scattered moderate convection from 10N- 15N between 16W-22W. This wave is merging with another disturbance located a couple of hundred miles south of the Cabo Verde Islands. Development of this system is likely to be slow during the next couple of days while it moves west-northwestward at about 15 mph, and a tropical depression is more likely to form early next week over the central tropical Atlantic where environmental conditions are forecast to be more favorable for development. The latest Tropical Weather Outlook states that this system has a high chance of tropical cyclone formation through 5 days. Refer to the latest Tropical Weather Outlook at www.hurricanes.gov for more details. A tropical wave is along 25W, from 18N southward, moving westward 10 to 15 knots. A 1008 mb low pressure is along the wave axis near 12N. Scattered moderate to isolated strong convection is observed mainly to the west of the low center from 11N-13N between 22W- 27W. There system has a low chance of tropical cyclone formation within the next 48 hours, but a high chance that a tropical depression will form through the next five days. Refer to the latest Tropical Weather Outlook at www.hurricanes.gov for more details. Another tropical wave is analyzed along 43W/44W S of 18N based on Tropical Wave Diagnostic. A swirl of low clouds is noted near the northern end of the wave axis. A tropical wave is along 57W from 19N southward. Visible satellite imagery shows a well defined inverted-V pattern associated with the wave. Some shower activity is noted near the wave axis but mainly from 12N-16N. Moisture related to this wave will spread over the Lesser Antilles tonight into Fri. A Caribbean tropical wave is along 61W from 20N southward, moving W 10 to 15 knots. Scattered moderate convection is active from 11N to 13N between 62W and 65W. A Caribbean Sea tropical wave is along 75W from 18N southward, moving W 10 to 15 knots. Scattered moderate to isolated strong convection is observed from 13N to 17N between 75W and 80W. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the southern coastal sections of Mauritania, to 13N25W, to 1008 mb low pressure near 13N36W to 13N55W. IN addition to the convection described in the Tropical Waves section, scattered moderate convection is evident south of the monsoon trough from 09N to 13N between 15W and 20W, and from 06N to 10N between 25W and 32W. Scattered moderate convection is also noted within 120 nm east of the low pressure near 13N36W. GULF OF MEXICO... A surface ridge extends westward across the northern Gulf coast from 1017 mb high pressure centered off Apalachicola Florida. E winds to 20 kt are active over the south central Gulf, between the high pressure and lower pressure farther south in the northwest Caribbean, on the northern periphery of Nana. Fresh NE winds are also noted off the west coast of the Yucatan peninsula, due to a short duration local effect common this time of the morning. Recent buoy observations along with a scatterometer pass from 04 UTC indicated moderate to occasionally fresh southerly flow elsewhere over the western and southern Gulf, with light to gentle breezes under the high pressure over the northeast Gulf. Buoy observations and altimeter data showed seas of 4 to 6 ft in south central Gulf, 1 to 3 ft in the northeast Gulf, and 3 to 5 ft elsewhere. A few showers are active over the south central Gulf as well this morning related in part to low level convergence in the easterly flow, but also due to divergent flow aloft over the area associated with a small upper low off Louisiana. The high pressure over the northeastern Gulf will dissipate through Fri ahead of a weak front moving into the northern Gulf Sat. The front will stall over the northern Gulf Sun, then slowly dissipate through early next week. Looking further ahead, another stronger front may enter the northwest Gulf by mid week. CARIBBEAN SEA... Please see the Special Features section above for information on T.S. Nana. A moist pattern prevails across the Caribbean in the wake of Nana. Satellite-derived precipitable water values show very high deep layer moisture over most of the basin. Clusters of showers and thunderstorms are observed in a large swath from the southern Windward Islands to almost northeast Nicaragua. under diffluent flow aloft. Showers and thunderstorms are also active west of Grand Cayman and south of western Cuba, on the east side of an upper trough. The track of Nana has temporarily interrupted the usual trade wind patterns in the Caribbean. This is leaving the normally rainy southwest Caribbean mostly rain free. Fresh trade winds and 4 to 6 ft seas are possible off southern Hispaniola, but elsewhere gentle to moderate winds are noted, with light and variable breezes in the southwest Caribbean. E swell in the northwest Caribbean will subside through the morning. The Caribbean will gradually revert back to its normal pattern over the next several days with moderate to fresh trade winds mainly over the central part of the basin. ATLANTIC OCEAN... A weak surface ridge extends east to west across the waters north of 27N. This is supporting moderate to fresh trade winds south of 22N, and lighter winds farther north into the ridge. Seas are generally 4 to 6 ft in open waters outside of the Bahamas. An upper level low centered north of the Leeward Islands is supporting a cluster of showers and thunderstorms about 150 nm northeast of the Virgin Islands. Subsident NE flow aloft between the upper low and and an upper anticyclone centered off the Carolinas is inhibiting significant convection elsewhere in the western Atlantic, west of 65W. The ridge will dissipate by Sun ahead of a weak frontal boundary entering the area from the north, but otherwise little change is expected into early next week W of 65W. Farther east, fresh SW winds and 6 to 8 ft seas are active south of the monsoon trough mainly east of 35W. As stated in the tropical waves section, this area may become active over the next several days, and there is a high chance a tropical depression will form in the eastern or central tropical Atlantic by early next week. $$ GR