Tropical Weather Discussion
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AXNT20 KNHC 201040

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
640 AM EDT Sun Aug 20 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
1030 UTC.


A tropical wave extends its axis from 20N45W to 10N46W, moving
west at 15-20 kt. Satellite imagery indicates a large area of
cloudiness but convection is limited in association with this
wave due to Saharan dust intrusion. This system coincides with a
well defined 700 mb trough, and a high amplitude northward bulge
of moisture is noted on the TPW product.

A tropical wave was introduced to this map over the eastern
Caribbean, after analyzing upper-air soundings across the islands
and model guidance. The wave`s axis extends from 19N65W to 10N64W,
moving west at 10-15 kt. Scattered showers are noted over the
northern portion of the wave mainly north of 16N between 62W-66W
affecting the Leeward Islands, the U.S. Virgin Islands, and Puerto

A tropical wave extends across the central Caribbean with axis
extending from 19N72W to a 1008 mb surface low near 14N72W to
11N73W. This system was previously T.S Harvey. Scattered moderate
convection has developed during the past few hours near the low
center mainly from 12N-17N between 73W-77W. A fast westward
motion is expected to continue with this system for the next
couple of days as the wave moves along the southern periphery of
the subtropical ridge.

A tropical wave is over the western Caribbean with axis extending
from western Cuba along 84W to near 10N84W, moving west at 10-15
kt. The wave shows up very well on the TPW animation and 700 mb
streamline analysis. Energy from the wave has fractured to the
northeast and is analyzed as a surface trough currently located
over the Florida Peninsula. The wave is enhancing showers near
Honduras, Belize and adjacent waters.


The monsoon trough extends from the African coast near 15N17W to a
1008 mb low near 13N20W to 11N41W. The Intertropical Convergence
Zone extends from 11N51W to 09N61W. Scattered moderate convection
is observed within 100 nm on either side of the monsoon trough.



A large and well defined upper-level low centered over the
southeast Gulf near 25N85W continues to generate scattered
showers over the Florida Straits. The western half of the Gulf is
under the influence of a surface ridge, anchored by a 1016 mb
high pressure centered near 29N90W. Isolated showers and light to
gentle anticyclonic winds prevail west of 90W. The upper-low will
drift westward reaching the central Gulf by Monday. This system
will continue to enhance showers and thunderstorms across the Gulf
waters today.


Three tropical waves are moving across the basin. Refer to the
section above for details. Moisture associated with these tropical
waves will continue to affect the area increasing the likelihood
of showers and thunderstorms today. Scatterometer data depicts
moderate trades across the basin, with the strongest winds
remaining east of 70W.


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 through the weekend.


As previously mentioned, the northern part of the tropical wave
currently moving across the western Caribbean is analyzed as a
trough currently extending across southeast Florida. This trough
is generating scattered showers and thunderstorms west of 76W, and
will continue to move westward through the day. Another surface
trough is analyzed northeast of the Leeward Islands extending from
25N65W to 20N65W. This trough continues to produce disorganized
showers and thunderstorms from 19N-25N between 61W-66W. Environmental
conditions are not expected to be conducive for development of
this system during the next couple of days while it moves west-
northwestward at 15 to 20 kt. An area of fresh to strong winds is
noted per scatterometer data on the northern side of this trough.
The remainder of the Atlantic is under the influence of a surface
ridge, anchored by a 1023 mb high centered near 32N39W. Fresh to
strong northerly winds are also noted between the coast of Africa
and the Madeira/Canary Islands. These winds are the result of the
pressure gradient between the Atlantic ridge and lower pressures
over west Africa.

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