Tropical Weather Discussion
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AXNT20 KNHC 190537

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
137 AM EDT Sat Aug 19 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
0530 UTC.


Tropical Storm Harvey is located near 13.7N 64.1W at 19/0300 UTC,
or about 243 nm south of St. Croix, moving west at 16 kt. Estimated
minimum central pressure is 1005 mb. Maximum sustained wind speed
is 35 kt with gusts to 45 kt. The low-level center of Harvey
remains near the eastern edge of a strong, but poorly organized,
convective area that covers the area from 11N-17N between 63W-
69W. Harvey will move through the eastern Caribbean tonight and
through the central Caribbean Sea Saturday. Interests in the
Caribbean Sea and the adjacent land areas of eastern Central
American and northern South America should monitor the progress of
Harvey. Locally heavy rains could occur tonight over portions of
the Windward Islands and the offshore islands of northern
Venezuela. Locally heavy rains could also occur over Aruba,
Bonaire, and Curacao on Saturday. See the latest NHC Intermediate
Public Advisory under AWIPS/WMO headers MIATCPAT4/WTNT34 KNHC, and
the full Forecast/Advisory under AWIPS/WMO headers
MIATCMAT4/WTNT24 KNHC for more details.


A tropical wave is in the east Atlantic with axis extending from
20N38W to a 1010 mb low pressure located near 13N39W to 10N39W.
Satellite imagery indicates a large cyclonic circulation in the
cloud field, but convection is limited in association with this
low. Saharan dust surrounds the wave/low. This system coincides
with a well defined 700 mb trough, and a high amplitude northward
bulge of moisture is noted on the TPW product. Environmental
conditions appear somewhat conducive for gradual development over
the next few days while the system moves west-northwestward to
northwestward at about 18 kt, but upper-level winds are forecast
to become unfavorable by the middle of next week. This system has
a low change of becoming a tropical cyclone within the next 48

A tropical wave extends from the northern Bahamas across eastern
Cuba and Jamaica to the southwest Caribbean, moving west at 15-20
kt. An area of moderate convection is along the wave`s axis from
20N-27N between 74W-80W. The wave shows up very well on the TPW
animation and 700 mb streamline analysis. Moisture associated with
this wave will continue spreading over the northern Bahamas and
central Cuba this morning, and across south Florida and western
Cuba by the afternoon and evening, increasing the likelihood of
showers and thunderstorms. There is a potential of locally heavy
rain and localized flooding with this activity.

The northern extend of a tropical wave is now over Mexico
generating some convective activity over the State of Veracruz.
For further information about this wave, please see the Tropical
Weather Discussion for the eastern Pacific Ocean.


The monsoon trough extends from the African coast near 13N17W to
13N30W to 09N44W. The ITCZ extends from 09N44W to 11N53W. Besides
the convection mentioned in the Tropical Wave and Special Features
sections, scattered moderate convection is from 07N-11N between



A weak surface ridge continues to dominate the Gulf waters,
anchored by a 1016 mb high centered near 29N93W. Mainly light to
gentle anticyclonic winds are prevailing across the basin. A
surface trough is analyzed from 30N85W to 27N87W. Scatterometer
and surface data indicate the wind shift associated with this
trough. A thermal trough will develop during the evening hours
over the Yucatan Peninsula before pushing offshore into the SW
Gulf each night. A surge of fresh winds will accompany this
trough. Little change in this weather pattern is expected through
early next week. In the upper levels, a large and well- defined
upper-level low is spinning over the Straits of Florida inducing
some shower and thunderstorm activity over the southeastern Gulf
and the Florida Peninsula. The upper-low will drift westward
across the eastern Gulf during the weekend.


A tropical wave is over eastern Cuba along 78W. Please, see the
Tropical Waves section above for details. Tropical Storm Harvey
will continue moving through the eastern Caribbean tonight and
through the central Caribbean Sea through the day. Please, see
Special Features section for more details. An upper-level low
spinning over the waters just north of western Cuba supports
scattered showers and thunderstorms across the northwest Caribbean
waters and the Yucatan Channel. Scattered showers and
thunderstorms are also noted over the southwest Caribbean
associated with the eastern extent of the Pacific`s monsoon trough
combined with a diffluent pattern aloft.


Daytime heating, local sea breezes and mountain upslope lifting
will combined with available moisture to produce isolated to
scattered showers and thunderstorms mainly during the afternoon
and evening hours through the weekend.


A pair of tropical waves are moving westward across the tropical
Atlantic while the northern portion of another tropical wave is
affecting the northern Bahamas. Please, see Special Features and
Tropical Wave sections above for details. The remainder of the
Atlantic is under the influence of a surface ridge, with a center
of 1025 mb located near 35N33W. A belt of fresh to locally strong
easterly winds is noted per scatterometer data roughly between
17N-23N due to the pressure gradient between the ridge and the
tropical waves and associated lows located between the coast of
Africa and the Lesser Antilles. 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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