Tropical Weather Discussion
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AXNT20 KNHC 222356

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
756 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.

Based on 1800 UTC surface analysis and satellite imagery through
2315 UTC.

A tropical wave extends from 25N89W to 16N90W moving NW at 10-15
kt. The remnant circulation of Harvey continues to be analyzed as
a 1010 mb low pressure along the wave axis, over the Yucatan
Peninsula near 20N90W, with scattered to numerous showers and
thunderstorms occuring from 20N-26N between 85W-91W, including the
Yucatan Channel where numerous showers and tstms are currently
noted. The low pressure area (remnants of Harvey) is forecast to
emerge off the coast of the Yucatan Peninsula tonight.
Environmental conditions are conducive for a tropical depression
or tropical storm to form on Wednesday or Thursday while the low
moves northwestward at about 10 mph across the western Gulf of
Mexico, possibly reaching the northwestern Gulf coast on Friday.
Regardless of development, this system is likely to slow down once
it reaches the coast, increasing the threat of a prolonged period
of heavy rainfall and flooding across portions of Texas,
southwestern Louisiana, and northeastern Mexico into early next
week. This system could also produce storm surge and tropical
storm or hurricane force winds along portions of the Texas coast
later this week, and interests from northeastern Mexico to
southwestern Louisiana should continue to monitor its progress.
A gale warning has been issued for the SW and west-central Gulf
beginning Wednesday morning. 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 23N29W to a 1011 mb low pressure
within the monsoon trough located near 14N34W moving W at 15-20
kt. Satellite imagery indicates a large area of cloudiness in
association with this wave, but convection is limited. A cyclonic
turning is seen near 18N33W. This wave remains in a very moist
area based on TPW imagery and has a well pronounced 700 mb trough.

A tropical wave is moving across the eastern Caribbean and extends
from 17N73W across Colombia to near 08N74W moving W at 20-25 kt.
An area of showers with embedded tstms is noted near the northern
end of the wave axis from 15N-17N between 70W-73W. The wave is
also enhancing some shower and tstm activity over northern Colombia.
The wave coincides with a 700 mb trough, and is well depicted in
the moisture product. This system will move across the central
Caribbean through mid week, and across the western Caribbean later
in the week.

The monsoon trough extends from the African coast near 14N17W to
17N25W, then resumes near 14N34W to 10N40W to 08N51W. The
Intertropical Convergence Zone axis continues from 08N51W to
10N57W. Scattered moderate isolated strong convection is from
09N-14N E of 20W. A large cluster of moderate to strong convection
is approaching the west coast of Africa likely associated with
the next tropical wave. Scattered moderate convection is within
about 150 nm SE of a line from 15N29W to 10N37W, and within 75 nm
south of trough axis between 45W-49W.


Attention remains focused on the remnant circulation of Harvey
currently located over the Yucatan Peninsula. Please, see Special
Features section for details. The large and well defined upper-
level low that was affecting the Gulf waters with showers and
tstms during the previous days has weakened some and now a large
anticyclonic circulation has developed over the eastern Gulf. The
upper-level low is still spinning over the NW Gulf near 27N93W
producing isolated showers and tstms. A 1020 mb high pressure
centered near Mobile, Alabama extends a ridge over the northern
Gulf producing mainly gentle winds.

A tropical wave is moving across the Caribbean Sea. Please, see
Tropical Waves section for details. The most recent scatterometer
data provide observations of fresh to locally strong SE winds
across the NW Caribbean mainly N of 20N W of 83W. Similar wind
speeds are noted over the central Caribbean. Strong trade winds
are forecast to pulse off the coasts of northeast Colombia and
northwest Venezuela in the wake of the tropical wave currently
located along 73W/74W. A surface trough over the Atlantic extends
to near Martinique in the Windward Islands producing isolated
showers. Moisture associated with this trough will affect mainly
the Leeward Islands later tonight and Wednesday, reaching the
UK/US Virgin Islands by Wednesday night. This will increase the
chance for showers with isolated tstms across the islands.

Scattered showers with embedded tstms are observed this evening
over Hispaniola, more concentrated over Haiti. Daytime heating,
local sea breezes and mountain upslope lifting will continue to
combine with available moisture to produce isolated to scattered
showers and thunderstorms mainly during the afternnon and evening

A trough of low pressure persists between the NW Bahamas and
Florida producing a large and disorganized area of showers and
thunderstorms. The trough extends from 29N79W across south Florida
to the Florida Keys. Any development of this system during the
next few days should be slow to occur while it drifts northward
over Florida and the adjacent waters. Environmental conditions
could become a little more conducive for tropical or subtropical
development by the weekend when the system begins to move
northeastward over the western Atlantic. Regardless of development,
very heavy rain and flooding is possible over portions of the
Florida peninsula during the next few days. Farther east, there
is another surface trough that extends 27N57W to 19N57W to near
Martinique in the Windward Islands. This trough is likely the
surface reflection of an upper- level low located near 27N58W. An
earlier scatterometer pass showed the wind shift associated with
this trough. The upper-level low is generating isolated showers
and tstms mainly from 22N-31N between 53W-60W. The remainder of
the Atlantic forecast area is under the influence of the
subtropical ridge.

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