AXNT20 KNHC 220520

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
120 AM EDT Sun Jul 22 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 0000 UTC surface analysis and satellite imagery through 0515 UTC.


A tropical wave is moving off the coast of Africa accompanied by thunderstorms. The wave's axis extends along 17N between 10N- 20N.

A tropical wave is in the east-central Atlantic with axis extending from 08N-22N along 38W, moving W at 15-20 kt. Saharan dry air and dust continue to prevail in the wave's environment as shown by CIRA LPW and GOES-16 RGB imagery. This is inhibiting large scale convection at this time.

A tropical wave is in the central Atlantic with axis extending from 09N-23N along 50W, moving W at 10-15 kt. The wave is moving across an extensive area of Saharan dry air, which is hindering convection at the time.

A low amplitude tropical wave is moving across eastern Colombia with axis extending from 00N-11N along 73W, moving W at 15-20 kt. Scattered moderate convection is observed across along the wave axis and between 69W-76W. The wave will lose some definition as it moves across the area today, but may emerge into the eastern Pacific off Colombia Mon.

A tropical wave is in the west Caribbean and reaching the EPAC waters with axis from 21N85W to 05N86W. The tropical wave is interacting with trade convergence to support scattered showers over Central America between 85W-93W.


The monsoon trough axis extends from the coast of Africa near 18N16W and continues to 08N30W. The ITCZ begins near 07N40W and continues to 06N55W. No significant convection is observed at this time with these features.



A surface ridge extends across the basin, anchored by a 1017 mb high centered near 24N87W. To the west, surface trough extends across the Bay of Campeche from 22N30W to 19N93W with scattered showers. A shortwave trough at mid/upper levels is supporting cloudiness and a few showers over the far east Gulf waters and Florida Peninsula. A pre-frontal trough extends across the Florida from 29N80W to 28N83W. Scatterometer data depicts light to gentle anticyclonic winds over most of the basin except north of 26N and east of 89W.

The weak trough across Central Florida will gradually settle southward over the next few days, bringing moderate west- southwesterly flow. The increasing westerly fetch will bring gradually higher seas in the offshore Gulf waters by early next week. Showers and thunderstorms will persist over the eastern Gulf today. A surface trough will move off the Yucatan Peninsula into the Bay of Campeche each evening, accompanied by fresh nocturnal winds and scattered showers.


A tropical wave is moving across the west Caribbean. Refer to the section above for details. A recent scatterometer pass depicted fresh to strong trade winds over the central Caribbean, reaching as far north as 17N between 73W-79W. Seas are estimated to be 07 to 11 ft in this area. Aside from the thunderstorms over the southwest Caribbean due to the monsoon trough over 10N, little to no shower or thunderstorm activity is noted due to the presence of Saharan dust and dry air, mainly impacting the eastern Caribbean.

For the forecast, high pressure north of the area will continue to support fresh to strong winds in the south-central Caribbean through tonight before winds diminish.


Mid to upper-level diffluent flow between a ridge in the west Atlantic and a trough along the eastern U.S. continue to support scattered showers over the west Atlantic mainly west of 70W. To the east, an upper-level low is reflected at the surface as a trough that extends from 31N55W to 23N56W. Two tropical waves extend across the basin. Refer to the section above for details. A broad high pressure prevails across the remainder of the basin centered near 40N43W.

For the forecast, high pressure ridge across the northern waters will remain in place through the weekend before lifting N Mon through Wed. Scattered showers and thunderstorms will persist N of 27N and E of 78W through early next week. Fair weather is elsewhere across the Atlantic, however hazy conditions are expected S of 26N as the extensive Saharan Air Layer outbreak moves across the Atlantic tropical waters.

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