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Atlantic Tropical Weather Discussion

AXNT20 KNHC 221757

Tropical Weather Discussion...UPDATED
NWS National Hurricane Center Miami FL
157 PM EDT Tue Aug 22 2017

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.

Updated to include Gale Warning conditions in Special Features

Based on 1200 UTC surface analysis and satellite imagery through 
1615 UTC.

A tropical wave extends from 14N89W to 24N88W moving NW at 10-15 
kt. The remnant circulation of Harvey continues to be analyzed as 
a 1010 mb low along the wave axis near 19N89W with scattered 
moderate convection occurring from 19N-24N between 84W-89W. Widely 
scattered moderate convection is elsewhere from 16N-27N between 
84W-92W. The low pressure area along the wave is forecast to
emerge off the coast of the Yucatan peninsula tonight with
environmental conditions favorable for development across the SW 
Gulf of Mexico through Thursday. Largest impacts at this point 
will be the expected rainfall and strong convection today across
the Yucatan peninsula and adjacent coastal waters through this
evening. By Thursday...regardless of tropical cyclone 
development...gale force winds are expected across portions of 
the Gulf of Mexico waters from 21N-25N between 90W-94W. See 
latest NWS High Seas Forecast under AWIPS/WMO headers 
MIAHSFAT2/FZNT02 KNHC and the Tropical Weather Outlook under 
AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details. 

A tropical wave extends from 15N31W to 24N27W moving W at 15-20 
kt. The wave coincides with an amplified 700 mb between 23W-37W 
with a maximum in 850 mb relative vorticity to the immediate west
of the wave axis that remains largely associated with a 1012 mb 
low centered near 15N32W. Scattered moderate convection is from 
11N-16N between 25W-31W.

A tropical wave extends from 08N72W to 17N72W moving W at 20-25 
kt. The wave has continued a westward motion after energy 
fractured to the N and is now associated with a surface trough
across the central Atlc waters. The wave is expected to move 
across the central Caribbean Sea and portions of Venezuela 
through tonight and across the SW Caribbean Sea on Wednesday.
Scattered moderate convection is from 14N-17N between 69W-74W.

The monsoon trough extends from the African coast near 14N17W to 
17N24W then resumes near 14N32W to 08N43W to 08N49W. The 
Intertropical Convergence Zone axis extends from 08N49W to 
10N57W. Scattered moderate and isolated strong convection is from
06N-14N between 12W-20W. Widely scattered moderate convection is
within 120 nm either side of a line from 11N31W to 06N39W to


An upper level low is centered over the western Gulf near 27N92W 
and continues to support isolated showers and tstms occurring 
primarily N of 23N between 87W-96W. Some of the convection within
the southeastern periphery of this area begins to fall under the
influence of a tropical wave and the remnant low of Harvey
mentioned in the Special Features section above. The northern
extent of the wave extends along 89W with the 1010 mb low centered
across the Yucatan peninsula near 19N89W. Scattered showers and
tstms are occurring S of 27N between 85W-91W in association with
the wave. Otherwise...ridging to the N remains anchored across 
the SE CONUS with a 1019 mb high centered across the Lower
Mississippi River valley. Light to moderate easterly winds prevail
mainly N of 22N. This overall synoptic pattern is expected to 
persist until tonight when the Special Features low pressure area 
emerges off the coast of the Yucatan peninsula and into the SW 
Gulf waters where environmental conditions are favorable for 
development of a tropical cyclone later this week.

The Special Features tropical wave is mentioned above...however
scattered showers and isolated tstms continue to impact the NW
Caribbean and portions of Central America as the low pressure area
analyzed along the wave axis moves NW into the Gulf of Mexico
waters by tonight. Low-level convergence is maximized along a line
from near 18N86W offshore of Honduras southward along coastal
Nicaragua to 11N84W. Another tropical wave is across the central
Caribbean and continues to support scattered showers and tstms
from 14N-17N between 69W-74W. The wave is expected to reach
Central America by Thursday. Otherwise...moderate to occasional 
fresh trades are expected through Thursday night.

A tropical wave continues to skirt south of the island this
afternoon with convection remaining generally S of 17N at this
time. Otherwise...skies are mostly clear with fair conditions
expected through Wednesday as dry air and subsidence prevails
aloft over the region.

The SW North Atlc is under the influence of a weak upper level 
low near 28N79W and an inverted upper level trough extending from
the low to 23N78W. The troughing supports a surface trough 
extending from the Florida Straits near 24N81W to 30N77W with 
scattered showers and isolated tstms occurring from 21N-31N 
between 73W-81W...including the Bahamas and the adjacent coastal
waters. Farther east...water vapor imagery indicates a middle to
upper level trough progressing over the central North Atlc waters
in the vicinity of 38N61W supporting a cold front extending from
33N60W to 32N65W then stationary to the W-NW to 33N70W. Scattered
showers and tstms are occurring N of 26N between 59W-66W and falls
on the northwestern periphery of an upper level low centered near
26N58W. While the upper level low is enhancing convection south of
the also supports a surface trough extending from 
15N59W to 22N57W to 27N59W within the eastern periphery of the 
upper level feature. Scattered showers and tstms are occurring
primarily E of the surface trough from 22N-30N between 51W-56W.
Finally...a dissipating cold front bridges the subtropical ridge
across the eastern Atlc with the front extending from 32N31W to
28N37W to 29N43W. Isolated showers are possible within 60 nm
either side of the front.

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