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000
AXNT20 KNHC 191033
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
633 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 0600 UTC surface analysis and satellite imagery through
1030 UTC.

...SPECIAL FEATURES...

Tropical Storm Harvey is located near 13.8N 65.9W at 19/0900 UTC,
or about 243 nm south of St. Croix, moving west at 18 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 convective area that
covers the area from 10N-17N between 65W-71W. Harvey will continue
moving through the eastern and central through the day. 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 today. 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.

...TROPICAL WAVES...

A tropical wave is in the east Atlantic with axis extending from
20N39W to a 1010 mb low pressure located near 13N40W to 10N40W.
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 imagery. Environmental
conditions appear somewhat conducive for gradual development over
the next few days while the system moves west-northwestward to
northwestward at about 15-20 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 hours.

A tropical wave extends across the central Atlantic with axis from
22N57W to 11N57W, moving west at 10-15 kt. The wave shows up very
well on the TPW animation and 700 mb streamline analysis. At this
time, scattered showers are noted across the northern portion of
the wave mainly north of 18N between 53W-59W. Environmental
conditions are expected to be only marginally conducive for
development during the next few days. This system has a low change
of becoming a tropical cyclone within the next 48 hours.

A tropical wave extends from the northern Bahamas, across central Cuba
and west of Jamaica, then to the southwest Caribbean, moving west
at 10-15 kt. An area of moderate convection is along the wave`s
axis from 22N-28N 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 in 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.

...ITCZ/MONSOON TROUGH...

The monsoon trough extends from the African coast near 15N17W to
the low/wave near 14N40W. No significant convection is observed at
this time.

...DISCUSSION...

GULF OF MEXICO...

A weak surface ridge continues to dominate the Gulf waters,
anchored by a 1017 mb high centered near 28N88W. Mainly light to
gentle anticyclonic winds are prevailing across the basin. A
surface trough is analyzed from 30N84W to 28N86W. 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 activity over the southeastern Gulf and the Florida
Peninsula. The upper-low will drift westward across the eastern
Gulf during the weekend.

CARIBBEAN SEA...

A tropical wave is over eastern Cuba along 79W. Please, see the
Tropical Waves section above for details. Tropical Storm Harvey
will continue moving through the eastern and central Caribbean
through the day. Please, see the Special Features section for
more details. An upper-level low spinning over the waters just
north of western Cuba supports scattered showers across the
northwest Caribbean waters and the Yucatan Channel. Scattered
showers and thunderstorms are noted over the southwest Caribbean
mainly south of 10N associated with the eastern extent of the
Pacific`s monsoon trough combined with a diffluent pattern aloft.

...HISPANIOLA...

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

ATLANTIC OCEAN...

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 the 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 1026 mb located near 39N22W. 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 areas of low pressure 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.

For additional information please visit
http://www.hurricanes.gov/marine

$$

ERA