Atlantic Tropical Weather Discussion (Text)

AXNT20 KNHC 220000

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
759 PM EDT Tue Aug 21 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 
2345 UTC.


A tropical wave has moved off the African coast with axis along
22W between 06N-20N, moving westward at 10-15 kt. The wave is 
embedded within a very dry and stable environment inhibiting
convection at this time. 

A central Atlantic tropical wave has its axis extending along 40W
from 05N-18N, moving westward at 10-15 kt. This wave is also 
embedded within a very dry and stable environment caused by 
Saharan Air Layer outbreak migrating westward across the central 
and eastern Atlantic. Only isolated moderate convection is noted 
within 60 nm either side of the wave axis along 11N.

A tropical wave has been repositioned based on satellite imagery
and model data. The axis extends now along 60W between 09N-19N, 
moving westward near 15-20 kt. No significant convection is
observed with this wave at this time. 

A western Caribbean tropical wave has its axis extending along 
88W and south of 21N, moving westward at near 15 kt. Scattered
moderate convection is over Central America and Yucatan Peninsula
between 84W-92W. 


The monsoon trough axis extends from coast of Senegal near 14N17W
to 09N23W to 09N43W. No significant convection is noted with these
boundaries at this time. 



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. Latest NWS mosaic radar display shows isolated
showers and thunderstorms across much of the eastern part of the 
gulf, mainly due to a weak trough over that area. Scattered
showers and thunderstorms are observed over the far southwest 
section of the gulf in association with the Yucatan Peninsula 
trough that typically moves offshore across the southwestern gulf
late at night and into the morning hours, with the added factor 
of an upper-level low located just east of the coast of Mexico at 
22N97W. Expect for this convective activity to remain active 
through tonight. Otherwise, high pressure ridging will remain 
across the northern gulf waters, with the associated gradient 
producing gentle to moderate anticyclonic flow through Thu.


The pressure gradient across the area will maintain fresh to 
strong winds over the south central Caribbean off the coast of 
Colombia and across the Gulf of Venezuela through Thu. Moderate
to fresh trades will continue elsewhere through Thu. 

The tropical wave along 88W will move across the rest of the 
western Caribbean this evening before moving inland Central 
America. The tropical wave along 60W will enter the eastern
Caribbean through Wed night and enter the eastern part of the 
central Caribbean by Thu.


Over the western Atlantic, a surface trough is analyzed from near
30N74W to the central Bahamas. An upper-level trough extends from
an upper-level low at 31N66W to the central Bahamas, and to 
central Cuba as a shear axis. Another trough extends from 32N59W 
to 27N68W, and another one extends from near 32N45W to 28N50W. A 
small surface trough extends from near 31N54W to 28N56W. With
these features in place along with a moist and unstable
environment, the result is scattered shower and thunderstorm
activity over the waters north of 24N between 60W and 75W, with 
the most concentrated activity observed north of 27N and 
between 70W and 76W. Isolated showers and thunderstorms are 
elsewhere west of 58W. A 1025 mb high center is analyzed north of
these troughs at 33N58W, with a ridge extending westward to 
Bermuda, and southwestward from there to east-central Florida High
pressure ridging will continue over the basin through the next 
several days. The trough extending across the central Bahamas will
continue westward through this evening. The aforementioned shower
and thunderstorm activity is forecast to persist through Wed.

Over the eastern part of the basin, a 1026 mb high is centered 
near 34N42W, supporting generally moderate north to northeast 
winds north of 20N. Saharan dust and associated dry air, as also 
mentioned above under Tropical Waves, is noted mainly east of 
about 56W on GOES-16 Saharan Air Layer animation is inhibiting 
convection from developing across the eastern and central Atlantic

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Page last modified: Wednesday, 22-Aug-2018 00:00:16 UTC