Atlantic Tropical Weather Discussion (Text)

AXNT20 KNHC 210532

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
132 AM 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 0000 UTC surface analysis and satellite imagery through 
0500 UTC.


An eastern Atlantic tropical wave has its axis extending from 
05N36W to 18N34W, moving westward at 10-15 kt. Scattered moderate
convection is noted from 08N to 10N between 25W and 32W.

A tropical wave was reanalyzed to be in the eastern Caribbean
along 63W to 18N, moving westward at 15 to 20 kt. The position 
was based to a large extent on sounding data from sites in the 
Lesser Antilles. No significant convection is observed.

A western Caribbean tropical wave extends south of 20N along
roughly 82W, moving west at 10-15 kt. No significant convection 
is observed.


The monsoon trough axis extends from coast of Senegal near 14N16W
to 10N20W, then to 08N40W. The intertropical convergence zone
continues westward to the mouth of the Orinoco River near 09N61W.
No significant convection is noted.



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. A few showers are ongoing over the east central Gulf
off Tampa Bay related to weak trough extending over the area. Scattered
to numerous showers and thunderstorms are active along the coast 
of Mexico in the far southwest Gulf, related to the normal 
evening/overnight trough that sets up off Yucatan and moves 
westward, but also largely enhanced by an upper low centered over 
the southwest Gulf.

The Yucatan surface trough will persist each afternoon, then 
drift westward across the southwest gulf waters during the 
overnight hours accompanied by a fresh east to southeast wind 
shift with the trough dissipating along 96W during the late 
mornings. Otherwise, the east to west ridge will persist across 
the northern Gulf waters between 26N and 27N overnight accompanied
by gentle to moderate anticyclonic flow. A surface high will 
develop along the ridge near 27N93W on Tue, and meander over the 
western gulf waters through late Thu, as a weak trough moves 
southeast into the northeastern gulf waters where it will stall on
Thu, and then drift west and dissipate on Fri with anticyclonic 
flow across the gulf waters late in the week.


A scatterometer satellite pass from 0240 UTC indicated fresh to 
strong winds over the south central Caribbean off the coast of 
Colombia. A concurrent altimeter satellite pass showed seas 
reaching 6 to 8 ft, but this likely missed the main area of seas 
closer to 9 ft, off the coast of Barranquilla. Moderate to fresh 
winds are noted elsewhere with 3 to 6 ft seas. No significant 
convection is noted. 

The strong nocturnal easterly trades will pulse along the 
northwest coast of Colombia and across the Gulf of Venezuela 
through early Thu. The tropical wave along 83W will continue west
and pass through the western Caribbean tonight. The second 
tropical wave along 63W will pass through the central Caribbean 
during mid week. A third tropical wave in the central Atlantic 
along 35W will reach along 55W on Thu.


Over the western Atlantic, a surface trough is analyzed from near
30N73W to 23N76W in the central Bahamas, supported in part by an 
upper trough over the same area. The surface trough was well 
defined in a pair of recent scatterometer satellite passes. A few 
showers and thunderstorms are noted near the northern end of the 
trough from 26N to 31N between 72W and 75W. A recent scatterometer
satellite pass also showed another surface trough from 31N53W to 
25N45W, but with no significant convection noted. The subtropical
ridge is displaced slightly north to along 31N, north of the 

The east to west ridge will meander from near new to Port 
Canaveral Florida for the next several days. The trough extending
across the central Bahamas will continue westward through late
today. Gentle to locally moderate southerly winds are expected 
north of ridge, a gentle northeast to east to southeast wind shift
is forecast along the trough, and moderate to fresh trades are 
expected south of 23N, except becoming locally strong along the 
north coast of Hispaniola during the late afternoon into early 
evening hour on Tue. 

Farther east, 1026 mb ridging is centered near 34N39W, supporting
generally moderate N to NE winds north of 20N with 3 to 5 ft seas
across the eastern Atlantic south of 32N. Moderate Saharan dust is
noted mainly east of 50W in this broad area of NE winds. The dry
conditions are inhibiting convective development across the

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Page last modified: Tuesday, 21-Aug-2018 05:32:29 UTC