AXNT20 KNHC 210006

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Mon Aug 20 2018

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 1800 UTC surface analysis and satellite imagery through 2330 UTC.


A far eastern Atlantic tropical wave has its axis extending from 06N35W to 18N33W, moving westward at 10-15 kt. No significant convection is noted.

A western Atlantic tropical wave has its axis extending from 05N54W to 19N52W, moving westward at 15 kt. No signficant convection is observed.

A western Caribbean Sea tropical wave has extends from 09N81W to 20N78W. No signficant convection.


The monsoon trough axis extends from western Africa at 12N17W to 08N40W, where scatterometer data indicates the intertropical tropical convergence zone continues to the coast of South America near 09N60W.



Weak ridging reaches across the northern Gulf of Mexico along roughly 27N, maintaining light to gentle breezes and 1 to 3 ft seas. Gentle to moderate easterly flow is noted elsewhere south of the ridge. Scattered to numderous showers and thunderstorms are active along the west coast of Yucatan, related to the normal evening trough that sets up in that region, but also largely enhanced by an upper low centered over the southwest Gulf.

Little change is expected in the pattern through Tue. By Wed, a cold front N of the area will transition to a stationary front along the northern gulf coast and then dissipate late at night. The remnants of the front will transition to a surface trough from the Florida Big Bend SW to the central basin, which is forecast to dissipate on Thu over the Tampa Bay adjacent waters. A surface ridge will then move eastward N of the area supporting northerly light to gentle winds across the basin through early Fri. Return flow will resume across the basin on Sat.


Fresh to strong winds and 7 to 9 ft seas are noted off the coast of Colombia, in the wake of the tropical wave over the western Caribbean. Moderate to fresh winds are noted elsewhere with 3 to 7 ft seas. No significant convection is noted.

The fresh to strong winds will prevail in the south- central Caribbean through Thu, increasing to near gale-force at night along the coast of Colombia. A tropical wave along 80W will continue west and move across Nicaragua and Honduras Tue through Thu. A second tropical wave will reach the east Caribbean on Tue while a third tropical wave is expected to approach the Lesser Antilles late on Thu. Heavy showers and tstms are forecast to develop in the SW basin Thu.


A surface trough is analyzed from near 30N73W to 22N75W, supported in part by an upper trough over the same area. A few showers and thunderstorms are noted near the northern end of the trough from 27N to 29N between 72W and 74W. A second surface trough is analyzed from near 32N45W to 26N65W. The subtropical ridge is displaces slightly north to along 31N.

The trough will continue to move west-northwest along the periphery of a surface ridge that dominates the remainder offshore waters then it will dissipate late Tue morning. A surface pre-frontal trough extends from 30N77W SW to Cape Canaveral, Florida to SW Florida generating scattered heavy showers and tstms N of 26N W of 78W. Similar precipitation is in the NE offshore waters from 25N-29N east of 67W associated with the tail of a surface trough located in the central Atlc. Showers off the NE coast of Florida will prevail for the next several days a weak cold front moves N of the area on Thu.

E of the lower Windward Islands, scattered moderate convection is seen within 45 nm either side of a line from 09.5N55W to 10N58W to 11N62W. A 1023 mb high is centered over the western Atlantic near 32N62W, with a ridge extending WSW to central Florida. A surface trough from 32N79W to just east of central Florida briefly interrupts the ridge. Scattered showers and thunderstorms are within 30 nm of the trough. This activity is likely to continue into tonight. A 1027 mb high is centered to the southwest of the Azores near 35N35W. It is allowing for ridging and generally fair weather to persist over the eastern Atlantic.

For additional information please visit http://www.hurricanes.gov/marine

$$ Christensen