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Atlantic Tropical Weather Discussion

AXNT20 KNHC 270555

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0605 UTC Tue Jul 27 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 0000 UTC surface analysis and satellite imagery through
0545 UTC.


A tropical wave is in the E Atlantic extending from 04N to 20N
with axis near 28W, moving W at 10 kt. The wave is embedded
within the Saharan Air Layer, which is hindering convection at
this time.

A tropical wave is in the E Caribbean extending S of 15N with
axis near 64W, moving W at 10-15 kt. Strong vertical shear and
some low-level dry airmass are limiting convection to isolated
showers to S of 17W and E of 65W. 

A tropical wave is in the central Caribbean extending S of 20N
with axis near 77W, moving W at 10-15 kt. Upper-level divergence
is supporting scattered showers and isolated tstms over 
Hispaniola, Jamaica, and its adjacent waters. 

A tropical wave is in the W Caribbean extending S of 21N with
axis near 85W, moving W at 10-15 kt. Scattered to isolated
showers are over Nicaragua and Costa Rica adjacent waters.


The monsoon trough extends from the coast of Africa near 11N16W 
to 06N33W to 07N41W. The ITCZ continues from 07N41W to 08N59W. 
Scattered moderate isolated strong convection is from 03N to 10N
between 30W and 52W.


A weak pressure gradient across the basin supports light to
gentle variable winds across the gulf with seas in the 1 to 3 
ft range. A middle to upper-level low over the western basin
supports scattered to isolated showers over the NE Mexico
adjacent waters. Over the eastern half of the basin, a surface
trough pressure supports similar shower activity on the SE gulf
and Yucatan Peninsula. 

Weak high pressure persists across the northern Gulf along 29N 
while a trough extends from near Tampa Bay, Florida to 24N90W. 
Scattered showers and isolated thunderstorms will persist near 
and south of the trough axis through tonight as if drifts 
westward. Atlantic high pressure will begin to build 
westward into the Gulf region Wed and Thu. 


Three tropical waves are moving across the Caribbean supporting
some localized shower activity. Aside from showers, two of these
waves are supporting moderate to fresh trade winds across the 
eastern and central Caribbean with seas to 5 ft. See the 
tropical waves section for further details.

Gentle to moderate trade winds are expected through early Wed. 
The exception will be moderate to locally fresh winds 
near the coast of Colombia, and in the Gulf of Venezuela. Winds 
will increase across the E and central Caribbean Thu into Fri as 
the Atlantic ridge builds westward in the wake of a trough 
moving westward across the Atlantic waters north of the Greater 


A surface ridge dominates the subtropical Atlantic waters and
supports and provides mostly fair weather with gentle to moderate
winds and seas in the 3 to 5 ft range. A surface trough is 
analyzed near 23N54W to 16N54W. Scattered showers are noted in 
the vicinity of the trough. Otherwise, diffluent flow aloft 
supports scattered showers NE of the Bahamas.  

A weak Atlantic ridge extends from SE of Bermuda to near the NW 
Bahamas. 1012 mb low pressure is moving NW and inland across 
coastal Georgia. An elongated area of showers and thunderstorms 
spreading northward of 20N between 61W and 67W will persist 
north of 25N tonight through Tue then diminish Tue night. A 
broad inverted trough along 55W will enter the SE waters early 
Tue and move westward and across the Bahamas through Thu.