Tropical Weather Discussion
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AXNT20 KNHC 122341

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
741 PM EDT Sat Aug 12 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 1012 mb low is centered near 24N69W. Scattered moderate to
isolated strong convection is noted from 23N-27N between 67W-70W.
The low continues to show signs of organization. Conditions
remain conducive for development, and a tropical depression is
likely to form tonight or Sunday while the system moves
northwestward. The low is forecast to turn northward, then
northeastward away from the United States early next week. There
is a high chance for tropical cyclone formation during the next
48 hours.


A tropical wave is in the far eastern Atlantic west of the Cabo
Verde Islands moving west at about 20 kt. The wave axis extends
from 20N26W to an embedded 1011 mb low near 11N27W to 08N27W. The
wave shows up very well on the SSMI TPW animation and 700 mb
streamline analysis. Scattered moderate convection is noted where
the wave meets the monsoon trough from 08N-13N between 26W-33W.

A tropical wave in the central Atlantic extends from 20N46W to
09N47W. It is moving W at 15-20 kt. The wave coincides with a
well defined 700 mb trough, and a high amplitude northward bulge
of moisture is noted on the SSMI TPW product. African dust
surrounds the wave, which is limiting the associated convective
activity. Only isolated moderate convection is seen near the
southern end of the wave axis, from 08N-11N between 45W-50W.

A tropical wave in the western Caribbean extends from central Cuba
at 22N81W to 17N81W to an embedded 1009 mb low near 10N80W, moving
W at 20 kt. The wave is in a moist area as seen by SSMI TPW
imagery. A pronounced 700 mb trough is over the western
Caribbean. Scattered moderate convection is over Cuba from 21N-23N
between 78W-82W. Scattered moderate to isolated strong convection
is over the SW Caribbean from 10N-15N between 78W-83W.


The monsoon trough extends from the coast of African near 13N17W
to 12N20W to 11N32W to 08N46W. The Intertropical Convergence Zone
continues from 08N46W to the coast of South America near 08N59W.
Aside from convection associated with the tropical waves,
scattered moderate convection is noted from 09N-14N between
14W-22W. Isolated moderate convection is from 06N-10N between



A 1018 mb high is centered over the NE Gulf of Mexico near
27N88W. 5-10 kt anticyclonic surface winds are going around the
high. Clusters of scattered moderate convection are over most of
Florida. More scattered moderate convection is inland over
Louisiana, Mississippi, and S Alabama. Further S, scattered
moderate convection is over W Cuba, and the N Yucatan Peninsula.
In the upper levels, an upper level high is centered over SE
Louisiana near 30N90W. Expect over the next 24 hours for the
surface high to remain quasi-stationary. Expect convection to
persist over the N Gulf, especially during the afternoon and
evening hours.


A tropical wave is moving through the western Caribbean. See
Tropical Waves section for details. The tropical wave will
continue to propagate westward, moving west of the area late
Sunday night. Fresh to locally strong winds prevail over the
south central Caribbean, while gentle to moderate winds are
blowing elsewhere. These general conditions will persist through
the weekend. The eastern extent of the E Pacific monsoon trough
is producing scattered moderate convection over, Costa Rica, and
Panama. Further N, widely scattered moderate convection is over E
Cuba, Jamaica, Hispaniola, and Puerto Rico. Scattered moderate
convection is also inland over Guatemala, El Salvador, Honduras,
and Nicaragua. Of note in the upper levels, an upper level low is
centered over Jamaica near 18N77W enhancing convection. Expect
the tropical wave to move W with convection and showers. Also
expect convection to persist over the SW Caribbean.


Presently widely scattered moderate convection is over Hispaniola,
mostly due to an upper level trough. The upper level trough will
move W during the next 24 hours, thus a clearing trend is


Please see the special features and tropical wave sections above.
A weak surface trough persists across the central Atlantic and
extends from 31N50W to 27N56W. Isolated showers are within 60 nm
of the trough axis. The Bermuda- Azores high will strengthen over
the central Atlantic this weekend. The pressure gradient will
tighten between the area of high pressure and the tropical wave
currently over the eastern Atlantic this weekend. This will
freshen winds north of the tropical wave by Sunday as the wave
propagates westward. The Saharan Air Layer tracking product from
CIMSS indicates abundant african dust between the two tropical
waves currently located across the tropical Atlantic.

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