Atlantic Tropical Weather Discussion (Text)

AXNT20 KNHC 301113

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Fri Jul 30 2021

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 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through 
1100 UTC.


A far eastern Atlantic tropical wave has its axis along 32W/33W 
from 03N to 15N, moving westward at 10-15 kt. Scattered moderate 
convection is within 120 nm either side of the wave from 06N to 

A central Atlantic tropical wave has its axis extending from 
20N59W to 13N57W and to inland Guyana. It is moving westward 
around 20 kt. Scattered showers moving quickly westward trail
the wave from 10N to 12N between 49W and 56W. 

A western Caribbean Sea tropical wave has its axis along 81W 
south of 21N. It is moving westward near 16 kt. Scattered 
moderate convection exists near the northern part of the wave 
from 18N to 21N between 79W-81W. Scattered showers and isolated 
thunderstorms are within 120 nm east of the wave from 17N to 18N 
and within 60 nm west of the wave from 16N to 20N.


The monsoon trough axis extends off the coast of Senegal near 
14N17W to 09N30W and to 06N42W. At this time, there is no 
coherent ITCZ west of the monsoon trough. Scattered moderate 
convection is within 240 nm south of the trough between 19W-25W
and within 120 nm south of the trough between 27W-38W.


High pressure ridging extends across the Gulf of Mexico, 
anchored by a 1017 mb high near 27N89W. A trough is over the 
western Gulf waters along a position from 28N95W to 24N96W and to 
20N95W. Another trough is over the far NE Gulf from 30N85W to 
27N83W. Clusters of scattered moderate to isolated strong 
convection are over the SW Gulf southwest of a line from 21N97W
to 18N93W. An area of increasing scattered moderate convection is
over the northeastern Gulf from 28N to 30N between 85W and 88W. 
Partial overnight ASCAT data passes along with recent buoy 
observations reveal light to gentle winds across the basin. Seas 
throughout are in the range of 2-3 ft, with the exception of 
higher seas, in the 3-5 ft range, over the SW Gulf and eastern 
Bay of Campeche.

For the forecast, the trough across the western Gulf will drift
west and gradually dissipate through this afternoon. Atlantic 
high pressure extends westward across the basin, with a weak 1017
mb high centered near 26N89W. The high will drift westward and 
dominate the Gulf region during the upcoming weekend, then
re-establish itself over the eastern Gulf by early next week. 


Numerous moderate to strong convection continues over far SW part 
of the basin south of 12N between 75W-80W, including to just
inland the coast of Colombia. This activity is being sustained 
by instability created by the eastern segment of the Pacific
monsoon trough that reaches to that part of the Caribbean Sea.
Additionally, low-level speed convergence found there is also 
contributing to the longevity of this convection. Scattered
showers and thunderstorms are confined to the waters from 
16N to 20N west of 82W, including the Gulf of Honduras. This 
activity has increased during the past few hours. Upper-level
divergence east of a small upper-level low noted on water vapor 
to be just east of Cozumel, Mexico is helping to keep this 
convection active. Overnight ASCAT data passes depict fresh to 
strong winds north of Colombia and moderate to fresh winds across 
the central and eastern Caribbean. Gentle to moderate winds are 
noted across the western Caribbean. Seas are in the range of 6-8 
ft in the central Caribbean and around 3-5 ft elsewhere. 

For the forecast, fresh to strong trades over the central 
Caribbean will continue through early Mon, then diminish to fresh
speeds through Tue night as Atlantic high pressure weakens.


Atlantic high pressure ridging extends west-southwest from a 1026
mb high near 30N52W to South Florida. Overnight ASCAT data helped
with the location of the ridge. An elongated northeast to 
southwest oriented upper-level low is identified on water vapor 
imagery at 25N70W. Scattered showers and isolated thunderstorms 
are south of 22N to just inland the Dominican Republic between 
68W-70W. Isolated showers and thunderstorms are observed elsewhere
over the southwestern north Atlantic along with light to gentle 
winds near the ridge axis and moderate to fresh winds south of 
24N. Seas are in the 3-5 ft. In the central Atlantic, a trough 
extends from near 22N42W to 30N45W with no significant 
convection noted. Otherwise, the aforementioned high pressure 
ridge also extends across this area. Light to gentle winds are 
near the ridge axis here as well, while moderate to fresh east 
winds are south of 24N. Seas are in the 3-6 ft range as detected 
by a couple of recent altimeter data passes. The high pressure 
dominates the eastern Atlantic. Moderate to fresh north to 
northeast winds are noted especially off the coast of Morocco, 
with seas of 4-6 ft. Atmospheric conditions are very dry and 
stable over the eastern Atlantic. It is also where Saharan dust is
quite prevalent per latest GOES-16 GeoColor images. The dust also
reaches westward to the central tropical Atlantic waters south of
about 25N. 

For the forecast west of 65W, high pressure ridging near 27N 
will change little into early next week. Expect fresh to locally 
strong east winds during the late afternoons and at night just 
off the northern coast of Hispaniola, including approaches to 
the Windward Passage through early next week. Moderate to fresh 
south to southwest winds are expected across the far northwest 
waters Sun night through Mon night.


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Page last modified: Friday, 30-Jul-2021 11:14:10 UTC