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Atlantic Tropical Weather Discussion

AXNT20 KNHC 231026

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Fri Jul 23 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 
0930 UTC.


Caribbean Gale Warning: The pressure gradient between the broad
Atlantic ridge and the Colombian/Panamanian low will support gale 
force winds along the coastal waters of Colombia through 1200 
UTC, with seas building to 9 to 12 ft. The strongest winds are 
expected within 90 nm of the Colombian coast, mainly between 
Barranquilla and Santa Marta. Strong to near gale force winds will
also impact most of the south-central Caribbean through this
morning as well, before winds begin to gradually diminish during
the next 24 hours. For more information, please see the High Seas
Forecast issued by the National Hurricane Center at

Heavy Rainfall in Southern Central America: High moisture levels,
persistent strong trade wind flow, and favorable conditions aloft
will together support heavy rainfall for much of southern Central
America through early next week. The heaviest rain is expected 
over the Caribbean coast of Costa Rica and southeast Nicaragua. 
These rains could cause significant flooding and mudslides in 
some areas. Currently, scattered moderate convection is noted 
along the Caribbean coast from SE Nicaragua through western 


An Atlantic tropical wave is analyzed along 54W, south of 19N, 
moving W near 15 to 20 kt. Scattered moderate convection is 
evident along the ITCZ south of 12N between 40W and 53W. A broad
area of Saharan Air accompanies this wave, extending from 12N to
24N from 60W to beyond 40W. 

Another tropical wave is over the eastern Caribbean along 67W, 
south of 20N, moving W at near 15 kt. Scattered moderate 
convection is evident behind the wave across the SE Caribbean
south of 12N, associated with the ITCZ.

A third tropical wave is analyzed along 80W, from 13N to 25N, 
moving at 10 to 15 kt. No significant cloudiness or convection is
associated with this wave.


The monsoon trough enters the Atlantic Ocean near Guinea-Bissau 
near 11.5N16W and extends SW to 10N20W to 12N31W. The ITCZ 
continues from 12N31W to 12N50W. Scattered moderate isolated 
strong convection is noted within 240 nm south of these features 
between 30W and 50W.


1022 mb high pressure near 27N90W is the dominant feature over 
the Gulf of Mexico. This is supporting moderate E to SE winds 
across the west-central Gulf and Bay of Campeche, where seas are 
2 to 4 ft, and light to gentle breezes elsewhere with seas 2 ft or
less. Dry and generally stable conditions aloft dominate most of
the basin this morning. A cluster of scattered showers and 
thunderstorms across SW Florida has drifted west into the 
offshore waters north of Key West and diminished significantly
during the past few hours.

The Bermuda High extends across Florida to the second 1022 mb 
high across the N central Gulf of Mexico. This high pressure ridge
will drift westward over the weekend and become separated from the
Bermuda high, as low pressure meanders offshore of the Atlantic 
waters of Florida. This will maintain generally tranquil marine 
conditions across the Gulf through early next week.


A Gale Warning is in effect for the south-central Caribbean.
Please see the Special Features section for more details. 

Fresh to strong trades prevail across most of the central 
Caribbean to 80W, including the Windward Passage, and the Gulf of
Honduras, with fresh trades in the eastern Caribbean. Gentle to 
moderate winds are found elsewhere. Seas are 7-11 ft in the 
central Caribbean and 5-7 ft elsewhere, except for 2-4 ft south of
Cuba. Fresh to strong easterly trades are building in across the
NE Caribbean behind the tropical wave along 67W, and will bring
scattered afternoon convection to the area today.

High pressure centered across the central Atlantic extends W-SW 
to central Florida and is combining with low pressure over N 
Colombia to support fresh to strong E winds over the central 
Caribbean. Gale force winds north of Colombia will end early this 
morning. The pressure gradient south of the ridge will support fresh
to strong winds across the central Caribbean today. The ridge will
weaken west of 75W this afternoon through early next week as a
weak frontal system and low pressure move offshore of Georgia and
Florida and meander through the weekend, weakening the pressure
gradient across the basin.


A few clusters of showers and thunderstorms are noted between 28N
and 31N, from the Florida coast to 75W, to the south of a frontal
boundary sinking southward toward these northern waters. A broad 
surface ridge extends from 1027 mb high pressure near 34N41W to 
central Florida. Fresh to strong E winds are active along the 
north coast of Hispaniola to 21N. Elsewhere moderate to fresh E 
winds persist south of the ridge, south of 23N over the tropical 
Atlantic, where seas are 6 to 8 ft in easterly swell. Gentle 
winds and slight seas persist along and north of the ridge axis, 
with 3 to 5 ft seas. Farther east, strong to near gale force winds
are east of 20W, surrounding the Canary Islands. Moderate to 
fresh NE winds are noted elsewhere east of 35W, with 5 to 7 ft 

Moderate to fresh trades will prevail south of 25N through Sun as
the ridge generally remains in place. Low pressure along a 
frontal boundary just north of the area will sink southward today
through the weekend off the Georgia and NE Florida coasts. 
Environmental conditions are forecast to be marginally conducive 
for some gradual development over the weekend and into early next 
week while the system drifts slowly offshore of the southeastern 
United States. Regardless of development, showers and thunderstorms
and moderate to fresh winds can be expected over the weekend off 
the Florida coast as the ridge remains in place. A large tropical
wave approaching the Lesser Antilles will move into the E
Caribbean and adjacent Atlantic waters tonight through the weekend
to bring fresh E to SE winds and seas of 5-8 ft.