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Atlantic Tropical Weather Discussion

AXNT20 KNHC 091021

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Sun May 9 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 
1000 UTC.


The monsoon trough enter the Atlantic ocean through northern 
Guinea near 11N15W, then continues SW to near 02N28W. The ITCZ 
extends from 02N28W to 01N33W to 02N40W to 00N50W. A cluster of 
moderate to isolated strong convection is noted near the W coast 
of Africa covering the waters from 05N-09N between 11W-14W. 
Similar convection can be found from 00N-04N between 23W-28W, and 
from 02N-04N between 40W-52W.


A ridge dominates most of Gulf waters anchored on a 1021 mb high 
pressure located east of NE Florida. A surface trough has developed
near the NW Yucatan peninsula. Under this pattern, mainly moderate
to fresh SE return flow prevails over the west-central and NW 
Gulf. Moderate to fresh NE winds are near and ahead of the surface
trough, and mainly gentle winds are noted over the eastern Gulf. 
Scatterometer data also suggest the presence of another trough 
just W of Florida along 82W/83W. Moderate to fresh SE winds are 
observed on the E side of the trough affecting the waters from the
Florida Keys northward to about 26N. Seas are generally 4-6 ft W 
of 90W, and 2-4 ft E of 90W, except 1-2 ft in the NE part of the 
Gulf. A few clouds are noted, particularly across the western 
Gulf in a moist SE flow.

The pressure gradient between the ridge across the Gulf region 
and lower pressures over Texas and NE Mexico will support fresh 
to locally strong SE return flow across the NW Gulf today. A 
surface trough will develop over the Yucatan Peninsula each 
evening, shift westward into the SW Gulf waters each night, and 
dissipate over the SW Gulf each morning. Moderate to fresh 
easterly winds will be associated with this trough. Light hazy 
conditions due to agricultural fires in southeastern Mexico are 
likely across much of the Gulf today. A stationary front will 
linger across the northern Gulf coast Tue and Wed with showers 
occurring along the boundary. Building high pressure across the SE
CONUS will push the front across the Gulf on Thu.


The most recent scatterometer data provide observations of fresh
to strong trade winds across parts of the east and south-central
Caribbean, mainly from 11N to 14N between 66W and 76W. The aerial
extent and strength of the trades will increase tonight and Mon as
high pressure builds N of the basin. During this period, winds of
20-30 kt are expected with building seas of 8-11 ft. A recent 
altimeter pass shows seas to 8 ft near the coast of Colombia.
Winds will also pulse fresh to strong nightly in the Gulf of 
Honduras through Thu night

Abundant cloudiness, with embedded showers, is affecting the 
eastern Caribbean and the Lesser Antilles. Scattered showers and 
thunderstorms are noted over southern Haiti. Elsewhere, shallow 
moisture embedded in the trade wind flow will continue to move 
across the region producing isolated to scattered passing showers.
A diffluent pattern aloft, ahead of a deepening mid to upper-level
trough over the central Caribbean is helping to induce the clouds
and shower activity over the eastern Caribbean. A good amount of 
moisture will persist over this region today and Mon, and will 
reach Puerto Rico and the US/UK Virgins Islands later today, 
increasing the likelihood of showers. Moisture will spread over 
Hispaniola later on Mon. 


West of 60W: A cold front stretches from 31N62W to 27N68W where 
it becomes stationary to the NW Bahamas and the Straits of 
Florida. A few showers are along the frontal boundary, especially 
between Andros Island and the Florida Keys. A 1021 mb surface high
pressure over the western Atlantic waters near NE Florida extends
a narrow ridge eastward over the waters to the north of the NW 
Bahamas, producing light to gentle anticyclonic wind flow.

The stationary part of the front will weaken today as the cold 
front continues to move across the Atlantic before it dissipates 
by Mon evening. Another cold front will clip the northern forecast
waters on Wed, and stall on Thu. Then, the front will move southward
across the region as a low develops along the frontal boundary, 
and moves NE.

East of 60W: The remainder of the Atlantic forecast waters is 
under the influence of a ridge. A mid to upper-level low is 
centered near 25N45W generating some shower activity from 22N to 
28N between 38W-45W. A surface trough extends from 29N27W to 
27N35W to 28N44W. Satellite derived wind data show moderate to 
fresh trade winds across the southern periphery of the ridge, 
mainly from 10N-24N E of 35W toward the W coast of Africa, and 
from 03N- 20N W of 35W. Patches of low level clouds are seen 
across the tropical Atlantic.