Tropical Weather Discussion
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AXNT20 KNHC 211022

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
622 AM EDT Mon Aug 21 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.

Based on 0600 UTC surface analysis and satellite imagery through
1015 UTC.


A tropical wave extends along 80W S of 21N moving W at 15-20 kt.
The remnant circulation of Harvey is analyzed as a 1007 mb low
along the wave axis near 15N80W. Scattered moderate to isolated
strong convection is from 14N-21N between 78W-86W. Gradual
development of this system is still possible through Monday night
while it moves west-northwestward near the coast of Honduras. It
could become a tropical cyclone again before it reaches the coast
of Belize or the Yucatan Peninsula early Tuesday. The remnants are
expected to move into the Bay of Campeche on Wednesday, where
redevelopment appears more likely due to more favorable upper-
level winds. Interests in northern Nicaragua, Honduras, Belize,
and the Yucatan Peninsula should monitor the progress of this
system. There is a medium chance for this system to become a
tropical cyclone within 48 hours.


A tropical wave off the coast of W Africa extends from 21N22W to
10N22W, moving W at 15 kt. The Hovmoller Diagram shows the
westward propagation of the wave. In addition, this wave in a
moist area based on SSMI TPW imagery, and has a well pronounced
700 mb trough. Scattered moderate convection is from 10N-16N
between 20W-23W. A 1009 mb low is analyzed ahead of the wave near
14N27W. It is forecast to move westward in tandem with the wave
over the next 24-48 hours. Saharan dust is noted W of the wave

A tropical wave extends from 20N52W to 10N57W moving W at 15-20
kt. The wave is well depicted on the SSMI TPW animation and 700
mb streamline analysis. The northern portion of the wave has
fractured and is analyzed as a surface trough from 24N50W to
21N52W. No significant deep convection is associated with the
wave itself, however, scattered moderate to isolated strong
convection is associated with the surface trough from 20N-26N
between 48W-53W.

A tropical wave is over the Yucatan Peninsula, Guatemala, and the
Eastern Pacific, from 21N90W to 10N91W, moving W at 15-20 kt.
Subtle troughing is noted on 700 mb streamline analysis, and
abundant moisture is observed on the SSMI TPW animation. Scattered
moderate to Isolated strong convection is over the Eastern


The monsoon trough extends from the African coast near 18N16W to
14N27W to 09N30W to 06N40W. Besides the convection mentioned in
the tropical wave section, scattered moderate convection is from
09N-12N between 24W-29W, and from 05N-08N between 33W-38W.



Weak surface ridging is over the Gulf of Mexico with axis along
30N. 10-15 kt easterly surface flow is over the Gulf. A surface
trough is over the E Gulf from 28N85W to 25N85W. Scattered showers
are within 120 nm of the trough axis. In the upper levels, an
upper level low is centered over the E Gulf near 26N88W enhancing
the showers. Expect over the next 24 hours for surface ridging to
build over the Gulf. Also expect the upper level low to remain
quasi-stationary and continue to produce convection. Looking
ahead, the remnant low of Harvey, currently moving across the
Caribbean Sea is expected to reach Belize or the Yucatan Peninsula
on Tuesday, and then move into the Bay of Campeche by the middle
of the week, where redevelopment appears more likely.


The primary area of concern across the Caribbean Sea is the
surface low (remnants of Harvey) that is generating convection over
the central Caribbean. Please, see Special Features section for
more details. A tropical wave is over Central America, with axis
along 90W/91W. Please, see the Tropical Waves section for
details. A trough of low pressure located across the Atlantic
waters, north of Hispaniola, combined with abundant tropical
moisture supports the development of showers and strong
thunderstorms across parts of Hispaniola, and the S Bahamas. This
trough and associated moisture will continue to move WNW today.


Daytime heating, local sea breezes, and mountain upslope lifting
will combine with available moisture to produce scattered showers
and thunderstorms across the island mainly during the afternoon
and evening hours. A trough of low pressure, currently located
north of Hispaniola will bring increased moisture, cloudiness,
and precipitation to the island.


The trough of low pressure north of Hispaniola extends from
27N71W to 19N72W. This system continues to produce disorganized
showers and thunderstorms, with fresh to strong winds mainly on
its northeast side based on scatterometer data. Environmental
conditions are expected to be unfavorable for development of this
system during the next day or two, but they could become slightly
more conducive for development by midweek when the system is near
the northwestern Bahamas or Florida. This feature is expected to
move west-northwestward at 15-20 kt during the next few days. A
pair of tropical waves are between the coast of Africa and the
Lesser Antilles, and a another surface trough extends from 24N50W
to 21N52W. Please, see the Tropical Waves section for details.
The remainder of the Atlantic is under the influence of a ridge,
with a 1023 mb high located SW of Bermuda near 32N68W. This high
is forecast to remain quasi-stationary over the next 24 hours.
Another 1024 high pressure is center over the central Atlantic
near 32N48W.

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