[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202315
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Wed Jul 21 2021

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 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through
2100 UTC.

...SPECIAL FEATURES...

Caribbean Gale Warning: The pressure gradient between the Atlantic
ridge and the Colombian/Panamanian low will support gale force
winds off the coast of the Colombia and in the Gulf of Venezuela
tonight, and again Wed night. Seas are forecast to build up to
12-14 ft with the strongest winds across the south-central Caribbean.
For more information, please see the High Seas Forecast issued
by the National Hurricane Center at
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml

...TROPICAL WAVES...

An Atlantic tropical wave extends its axis along 27W and south
of 21N, moving west at 10 to 15 kt. Scattered moderate convection
is noted where the wave meets the monsoon trough from 07N to 11N
between 26W and 31W.

A second tropical wave extends it axis along 48W from 20N southward,
moving westward at 10 to 15 kt. Subsidence and dry air associated
with the Saharan Air Layer surrounds the wave.

A third tropical wave is along 87W and south of 18N crossing
northern central America. This tropical wave is moving west at
10 to 15 kt. The wave is helping to induce scattered showers
and thunderstorms over parts of Belize, northern Guatemala and
the Yucatan Peninsula.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean through Senegal and
extends from 13N17W to 10N30W to 09N45W. The ITCZ extends from
07N50W to the coast of Guyana near 07N58W. Scattered moderate
to isolated strong convection is noted from 05N to 10N between
13W and 21W.

GULF OF MEXICO...

A surface trough is over the NW Gulf and extends from SE Louisiana
to south Texas. Scattered to numerous showers and thunderstorms
are noted ahead of the trough axis. Moderate to fresh winds are
behind the trough. Showers and thunderstorms are also noted over
most of Florida. The remainder of the Gulf is under the influence
of the Atlantic ridge that extends westward across Florida into
the eastern Gulf producing light to gentle anticyclonic flow.
Seas are in the 1-3 ft range across the entire basin, however
winds and seas could be higher near thunderstorms.

For the forecast, a ridge will continue to dominate the Gulf
waters producing gentle to moderate winds the rest of the work-
week. The exception will be moderate to fresh NE-E winds to the
west of the Yucatan Peninsula Wed night through Fri night due to
local effects induced by a thermal trough.

CARIBBEAN SEA...

A Gale Warning is in effect for the south-central Caribbean.
Please, see the Special Features section for details.

The most recent scatterometer data depict fresh to strong trades
prevailing across most of the central Caribbean with seas of 8-10
ft. Buoy 42058 is reporting combined seas of 9 ft. Elsewhere in
the basin, moderate to fresh trades prevail with 5-8 ft seas,
except in the NW Caribbean where trades are gentle to moderate
with 2-4 ft seas.

For the forecast, the aerial extent and strength of the trades
will increase beginning tonight. Fresh to strong winds will
reach as far north as Hispaniola adjacent waters. Fresh NE winds
are expected in the Windward Passage through Thu night. Fresh to
strong winds are forecast to pulse in the Gulf of Honduras Wed
night and Thu night with seas building to 6-7 ft.

Under the influence of this trade wind surge propagating across
the Caribbean, conditions appear fairly favorable for heavy
rainfall amounts over southern Central America over the next few
days. The onset of the activity is expected late on Wed, and
will likely peak Thu through Sat. In fact, the GFS model suggests
abundant tropical moisture in a NE winds flow from Nicaragua to
Panama and western Colombia late on Wed.

A pair of tropical waves are between the west coast of Africa and
the Lesser Antilles. Please refer to the Tropical Wave section
above for details.

A 1026 mb high pressure located E of Bermuda near 32N53W extends
a ridge across the Bahamas and Florida into the eastern gulf Of
Mexico. Scattered moderate convection is noted E of Florida and N
of the NW Bahamas ahead of a frontal boundary that crosses the SE
of United States. Mainly patches of low level clouds are seen over
the remainder of the ocean. Another high pressure center is located
just N of the Madeira Islands. Fresh to strong northerly winds
are noted per scatterometer data near the coast of Morocco where
seas are in the 6-8 ft range. Moderate to fresh N to NE winds are
seen across the Canary islands, and from 20N-30N E of of 30N.
Seas are generally in the 5-7 ft range within these winds.
Similar wave heights are also noted between 50W and the Lesser
Antilles.

For the forecast W of 65W, high pressure will be in control of
the weather pattern across the region. Fresh to strong easterly
winds will pulse just off north of Hispaniola, including the
approach to the Windward passage in the late afternoon and
evening hours for the next several days.

$$
GR
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