Tropical Weather Discussion
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AXNT20 KNHC 210542

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
142 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 0000 UTC surface analysis and satellite imagery through
0515 UTC.


A tropical wave extends along 78W S of 21N moving W at 15-20 kt.
The remnant circulation of Harvey is analyzed as a 1007 mb low
pressure along the wave axis near 15N78W. Scattered showers are
within 120 nm of the wave axis. Gradual development of this
system is still possible through Monday night while it moves
west-northwestward near the coast of Honduras, and 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 off the coast of W Africa extends from 21N21W to
10N21W, 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 TPW imagery and has a well pronounced 700 mb
trough. Scattered moderate convection is noted where the wave
meets the monsoon trough from 10N-14N between 20W-24W. A 1010 mb
low is analyzed ahead of the wave near 14N25W, and 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 environment.

A tropical wave extends from 19N51W to 10N55W moving W at 15-20
kt. The wave is well depicted on the TPW animation and 700 mb
streamline analysis. The northern portion of the wave has
fractured and is analyzed as a surface trough extending from
24N50W to 20N51W. No significant deep convection is associated
with the wave itself, however, scattered moderate convection is
associated with the surface trough from 20N-24N between 47W-52W.

A tropical wave is over the Yucatan Peninsula, Belize, Honduras,
El Salvador, and the Eastern Pacific, from 21N88W to 10N89W,
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 strong convection is over El


The monsoon trough extends from the African coast near 17N16W to
14N25W to 06N38W. Besides the convection mentioned in the tropical
wave section, scattered moderate convection is from 05N-08N
between 33W-37W.



Weak surface ridging is over the Gulf of Mexico with axis along
30N. 10-15 kt easterly surface flow is over the Gulf. In the upper
levels, an upper level low is centered over the E Gulf near
26N88W. Widely scattered moderate convection is over the E Gulf
and N Florida from 25N-31N between 83W-88W. 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 low
pressure (remnants of Harvey) that is generating scattered showers
over the central Caribbean. Please, see Special Features section
for more details. A tropical wave is exiting the area, with axis
along 88W/89W. 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 Puerto Rico and Hispaniola. This
trough and associated moisture will move away from Puerto Rico on
Monday, but will continue to enhance the showers and thunderstorms
over Hispaniola.


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
27N70W to 20N70W. 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 20N51W. 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 1026 high pressure is center over the central Atlantic
near 31N46W.

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