[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 241746
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Tue Aug 24 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 1200 UTC surface analysis and satellite imagery through
1745 UTC.

...SPECIAL FEATURE...

Heavy Rainfall in southern Central America: A broad area of low
pressure is expected to form over the SW Caribbean Sea later this
week, resulting in an increase in moisture and unstable
conditions across southern Central America. Heavy rainfall is
expected across SE Nicaragua, Costa Rica, Panama, and NW Colombia
through early in the weekend. The heaviest precipitation is
forecast to affect southern Costa Rica and western Panama late
this week. These rains could cause significant flooding and
mudslides in some areas.

...TROPICAL WAVES...

An Atlantic tropical wave has its axis along 27W, south of 19N,
and it is moving W at 10 to 15 kt. A 1008 mb low pressure is
along the wave axis near 09N. A recent scatterometer satellite
pass show a broad circulation with fresh to locally strong N-NW
breezes between 27W and 32W and from 08N to 12N. The wave is
producing a large area of showers and thunderstorms, mainly to the
W of the wave axis to 31W, and from 05N to 11N. The NHC is
tracking this disturbance for possible tropical development over
the next 5 days. For more details, please see the latest Tropical
Weather Outlook.

Another Atlantic tropical wave has its axis along 46W, south of
18N, and it is moving W at 10 to 15 kt. A recent scatterometer
satellite pass reveals a sharp trough with gentle cyclonic winds.
This wave is not producing any deep convection.

A weak tropical wave was previously analyzed approaching the
Lesser Antilles, but it appears to have dissipated based Total
Precipitable Water analysis and wave diagnostics.

A Caribbean tropical wave has its axis along 67W, south of 20N,
and it is moving W at 10 to 15 kt. A recent scatterometer
satellite pass indicates that it has a broad curvature with fresh
to strong trades covering most of the central and eastern
Caribbean. This system is also producing a large area of showers
and thunderstorms, especially from 10N to 15N, affecting the ABC
islands and NW Venezuela, and between 62W and 74W. The NHC is
also tracking this disturbance for possible tropical development
over the next 5 days. For more details, please see the latest
Tropical Weather Outlook.

A second Caribbean tropical wave has its axis along 87W, south of
20N, and it is moving W at 10 to 15 kt. The wave extends from the
Gulf of Honduras, across Central America, to the Eastern Pacific.
The wave is not producing any deep convection on the Caribbean
side.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean through the coast of
Mauritania near 20N16W, passing near the Cabo Verde Islands, and
continues westward to 06N29W to 11N42W and to 08N49W. The ITCZ
then extends from 08N50W to 12N60W. Most of the convective
activity across the region is related to the tropical waves.

...GULF OF MEXICO...

High pressure continues to dominate the weather conditions across
the Gulf of Mexico. A surface trough in the northern Gulf extends
from 30N85W in the Florida Panhandle to 29N92W. A few showers are
noted along the weak trough. The other cluster of scattered
moderate convection is seen in the SW Bay of Campeche, mainly
within 70 nm of the coast of Veracruz, in association with the
northernly end of a tropical wave along 96W. A recent
scatterometer satellite pass observed fresh to locally strong N-NE
winds with these storms. Gentle to moderate anticyclonic winds
prevail across the rest of the Gulf. Seas of 2-4 ft are present
in the Bay of Campeche and the Florida Straits, while 1-2 ft is
prevalent elsewhere.

For the forecast, high pressure will dominate the basin through
Fri producing mainly gentle to moderate E to SE winds. Fresh winds
will pulse west of the Yucatan Peninsula tonight and again Wed
night. An area of low pressure is expected to form in the western
Caribbean late this week, and this system could approach the
Yucatan Peninsula or Belize by Sat. There is a medium chance of
tropical cyclone formation within the next 5 days. An increasing
pressure gradient between high pressure over the Gulf waters and
the possible tropical system over the western Caribbean will
result in fresh to strong easterly winds over the SE and south-
central Gulf during the upcoming weekend.

...CARIBBEAN SEA...

Two tropical waves are moving westward across the Caribbean Sea.
Please, see the Tropical Waves section for details.

Scattered moderate to isolated strong convection is noted in the
SW Caribbean Sea from the coast of Nicaragua to northern Panama.
Satellite imagery suggest that confluent winds, abundant moisture
and the presence of the eastern portion of the East Pacific
monsoon trough is resulting in the large area of convection. As
mentioned in the tropical wave section, fresh to strong trades are
prevalent across the central and eastern Caribbean, including the
entrance to the Windward Passage. Moderate to fresh winds are
present in the rest of the basin. Seas are 6-9 ft in the central
and eastern Caribbean, with the highest seas occurring off the NW
coast of Colombia. The rest of the Caribbean is observing seas of
3-6 ft.

For the forecast, fresh to locally strong trade winds will dominate
most of east and central Caribbean through midweek with seas in
the 7 to 8 ft range. Fresh to locally strong winds are also
expected in the Windward passage and in the lee of Cuba through
tonight. A tropical wave over the eastern Caribbean Sea along 67W
is expected to form a broad area of low pressure over the
southwestern Caribbean later this week. Conditions are forecast
to be conducive for development, and a tropical depression could
form late this week or this weekend while the system moves
northwestward over the northwestern Caribbean Sea, toward the
Yucatan Peninsula or Belize by Sat.

...ATLANTIC OCEAN...

Two tropical waves are moving westward between the W coast of
Africa and the Lesser Antilles. Please, see the Tropical Waves
section for details.

A broad subtropical ridge maintains dominance of the tropical
Atlantic. A 1009 mb low pressure is located near 22N46W is moving
NW at 10 to 15 kt. The system is producing a small area of showers
and thunderstorms near the center. A recent scatterometer
satellite pass show strong to near gale-force winds over the
northern and eastern semicircle, extending up to 200 nm from the
center. Seas in the area are in the 6-9 ft range. The NHC is
tracking this disturbance for possible tropical development over
the next 5 days. For more details, please see the latest Tropical
Weather Outlook. Northwest of the low, a weak surface trough
extends from a weakening stationary front north of the area to
24N54W. Scattered moderate showers are noted SE of the trough from
24N to 29N.

The combination of a surface trough NE of the Bahamas and an upper
level low is causing a large area of scattered moderate
convection from 24N to 29N and between 67W and 73W. The storms
produced an expansive outflow boundary that moved across the SE
Bahamas, eastern Cuba and Hispaniola, but it has dissipated as of
1725 UTC. The recent scatterometer satellite pass captured a broad
area of strong to near gale-force N-NE winds from the coasts of
Hispaniola and eastern Cuba to 25N and betwen 67W to 77W. The
strongest winds were near the northern coast of Hispaniola and
likely generated by the outflow boundary. Seas W of 60W are in the
4-8 ft range. Also, a weak trough over the SE United States is
generating some showers off NE Florida, mainly north of 28N and
between 77W and 80W. The rest of basin enjoys fairly tranquil
weather conditions.

The pressure gradient between the subtropical ridge and lower
pressure associated with the disturbance in the eastern Atlantic
is causing fresh to strong NE winds from 15N to 27N and between
the coast of Africa to 33W. Seas in this region are in the 5-8 ft
range. Gentle to moderate winds and 3-6 ft seas prevail in the
rest of the basin.

For the forecast W of 65W: A surface trough east of the Bahamas
will move westward, bringing strong NE to E winds over the
central Bahamas tonight. By Thu morning, the surface trough will
extend from 30N78W to the western tip of Cuba, bringing fresh to
strong E winds to the east of northern Florida before the trough
weakens by late Thu. Otherwise, a 1021 mb high pressure located
near Bermuda will dominate the remainder of the forecast region
through at least Wed. Fresh to locally strong winds are expected N
of Hispaniola including the approaches to the Windward Passage
through tonight. Fresh to locally strong winds will continue to
pulse north of Hispaniola during the evening hours through Sat
night. Expect increasing winds across the waters between Cuba and
the Bahamas by the end of the week as a tropical system develops
over the NW Caribbean.

$$
DELGADO
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