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Atlantic Tropical Weather Discussion

AXNT20 KNHC 192357

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
757 PM EDT Thu Jul 19 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 1800 UTC surface analysis and satellite imagery through 
2315 UTC.


A tropical wave is off the coast of west Africa from 06N to 18N 
along 19W, moving W at 10-15 kt. The wave is being engulfed by 
Saharan dry air and dust and is mainly in a strong deep layer wind
shear environment. However, shallow moisture and upper level 
diffluence is supporting scattered moderate convection from 06N to
13N E of 24W.

A tropical wave is in the central Atlantic with axis extending 
from 18N34W to 04N34W, moving W at 15 kt. The wave is moving 
across an extensive Saharan Air Layer Outbreak with dry air and 
dust hindering convection.

A low amplitude tropical wave is over the central Atlantic with 
axis extending from 12N52W to 02N53W, moving W at 15 kt. Scattered
moderate comvection is within 180 nm of the wave axis. 

A tropical wave is in the E Caribbean with axis S of 20N along
70W, moving W at 20 kt. The wave is in a strong deep layer wind 
shear environment. However, abundant shallow moisture and upper 
level diffluence in the NE Caribbean support scattered showers and
tstms N of 13N between 66W and 73W. 


The monsoon trough axis extends from W Africa near 15N17W to 
08N26W to 07N40W, where the ITCZ begins and continues to South 
America near 05N55W. Scattered moderate convection is from 06N to
10N between 24W and 30W, and from 04N to 08N between 46W and 50W.



The Azores high continues to extend a ridge axis SW across the
southern half of the Florida Peninsula to the central Gulf of
Mexico. This is supporting maily light to gentle winds over the
Gulf S of 27N. In the NE Gulf, a surface trough continues to 
generate scattered moderate convection and isolated tstms. The
trough is being supported by upper level level diffluent flow. 
The Bay of Campeche has shallow moisture as depicted by  low 
level water vapor imagery. The remainder of the Gulf is under dry
stable air which supports fair weather. The trough is forecast to
dissipate late Friday night and convection associated with it 
will cease by early Sat. However, an upper level trough will 
extend from the SE CONUS into the E Gulf, and will support the 
development of showers for the remainder of the weekend. In
addition, a surface trough will move westward off the Yucatan 
Peninsula each night, enhancing nocturnal winds over the eastern 
half of the Bay of Campeche.


A tropical wave is over the E Caribbean. See above. Upper level 
diffluent flow over Puerto Rico and eastern Hispaniola along with 
abundant shallow moisture supports this wave. The remainder of the 
basin is under dry, stable, air as indicated by the low level 
water vapor imagery of GOES-16. RGB imagery from GOES-16 also
shows a thin layer of Saharan Dust moving across the central and 
western portions of the basin. These factors along with strong 
deep layer wind shear contribute to a lack of convection 
elsewhere. The wave will cross Hispaniola tonight and continue to 
bring showers at the island and adjacent waters through early 
Friday. The convection will then shift to the SW basin during the 
weekend as the wave continues to move westward. Otherwise, fresh 
to strong winds will prevail in the central basin through the 
weekend as the Azores high remains nearly-stationary. Near gale 
force winds will be likely along the coast of Colombia. 


The base of an upper level trough is over the W Atlantic at 30N. 
This upper trough supports a cold front N of the area. Diffluent 
flow between the trough and a middle to upper level anticyclone 
over the Bahamas support scattered showers and tstms N of 28N W of
69W. Isolated showers are also across Andros Island and adjacent 
waters. A tropical wave over E Hispaniola supports scattered 
showers and tstms S of 22N between 61W and 70W. The remainder of
the Atlantic N of 18N is under the influence of the Azores high 
supporting fair weather conditions. No major changes expected 
during the next two days.

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