[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251753
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Sun Jul 25 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
1730 UTC.

...SPECIAL FEATURES...

A 1011 mb low is centered near 29N78.5W. Earlier scatterometer satellite
data showed a broad and well defined cyclonic circulation, with
peak winds to 30 kt within 60 nm across the SE semicircle. Disorganized
shower and thunderstorm activity continues mainly to the east and
southeast of the center. Environmental conditions are expected to
be marginally conducive for development, and a tropical depression
could still form later today or early Monday while the system
drifts westward toward the east coast of Florida. Interests in
Florida should continue to monitor the progress of this system.
This system has a medium chance of development within 48 hours.
Please read the latest Tropical Weather Outlook at hurricanes.gov
for more information.

Heavy rainfall is expected to continue in Southern Central
America, particularly in Panama, Costa Rica and Southern
Nicaragua. High moisture content, persistent monsoon flow, and
favorable conditions aloft will continue to support scattered to
numerous strong convection capable of producing torrential rain
through Monday. Heavy rainfall in these areas could cause
significant flooding and mudslides.

...TROPICAL WAVES...

An Atlantic tropical wave is near 22W/23W from 20N southward,
moving westward at 10 kt. Scattered moderate convection is note
from 06N to 08N between 22W and 24W.

An Atlantic tropical wave 57W south of 12N moving west at 15-20
kt. There is reasonable evidence of this wave in Hovmoller
diagrams going back several days. Recent satellite- derived wind
data from the lower levels of the atmosphere hints the wave is
restricted to the deep tropics. Scattered moderate convection is
evident from 07N to 11N between 50W and 58W.

A Caribbean Sea tropical wave is along 72W from central Hispaniola
to northwest Venezuela, moving W at 10 kt. The tropical wave is
moving west of an upper level low centered off northern Haiti.
Dry, subsident air in the northerly flow on the west side of this
upper low is inhibiting any major convection near the tropical
wave.

A Caribbean Sea tropical wave is near 81W from 22N southward,
moving W at 10 to 15 kt. Convection associated with this wave is
confined to near the monsoon trough, S of 12N and is described
below.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean along the coast of
Senegal near 13N17W to 11N18W to 08N35W. The ITCZ continues from
08N35W to 08N52W. No significant convection is evident along
these features at this time.

...GULF OF MEXICO...

A surface trough extends from southwest Florida near Flamingo to
1012 mb low pressure near 25N85W to off southeast Louisiana near
29N90W. Farther west, 1018 mb high pressure is centered near
26N94W. A few showers are likely ongoing off Louisiana near the
trough, and farther south over the central Gulf along the loop
current. Light to gentle winds and slight seas prevail across the
Gulf.

For the forecast, showers and maybe a few thunderstorms will
continue south of the trough today. The high pressure will meander
and weaken through Mon as a low pressure currently located about
140 nm east of Daytona Beach, Florida, drifts westward toward the
east coast of Florida.

...CARIBBEAN SEA...

Refer to the Tropical Waves section above for more information on
convection across the Caribbean Basin.

Overall, a relatively benign pattern continues across the
Caribbean today. There are scattered showers and thunderstorms
over the far southwest Caribbean, south of 12N, from western
Colombia to Costa Rica, to include the coast of Panama, posing a
risk of flooding. A few showers and thunderstorms are starting to
develop over the higher terrain of central Hispaniola, enhanced by
an upper low centered the Turks/Caicos. But no significant
showers or thunderstorms are noted elsewhere. Light breezes and
slight seas are noted over the northwest Caribbean, and gentle to
moderate trade winds with 2 to 4 ft seas elsewhere. The trade wind
flow is lighter than usual, related in part to a relatively
weaker subtropical ridge north of the area.

For the forecast, the current pattern will continue, with
diminished tradewinds across the basin through Wed. Look for
scattered showers and tstms across the eastern Caribbean and
tropical Atlantic waters today associated with another tropical
wave.

ATLANTIC OCEAN...

See the Special Features section for more information on the low
east of Florida and the Tropical Waves section for information on
the wave off the African coast.

Clusters of showers and thunderstorms are noted over the Atlantic
north of Puerto Rico and east of the Bahamas, specifically from
20N to 25N between 62W and 68W. This activity is tied to upper
level divergence between an upper low over the Turks/Caicos
Islands and an upper trough in the northwest flow aloft farther to
the northeast over the central Atlantic. A weak surface trough is
analyzed in this area of convection, from 22N68W to 29N62W. Another
trough is analyzed farther east, from 22N to 28N between 45W and
50W. The troughs are south of a 1029 mb high pressure near 38N37W. Recent
scatterometer satellite passes indicated fresh E winds near
western trough. This is evidence of a broader area of fresh winds
from 18N to 25N between 55W and 70W between the trough and the
ridge, with seas estimated to be 5 to 7 ft. Similarly fresh winds
and 5 to 7 ft seas are likely between the eastern trough and the
ridge, from 25N to 30N between 35W and 50W. Aside from fresh to
strong winds near the Cape Verde Islands and off Morocco, this
pattern is support generally moderate trade winds and 4 to 6 ft
seas across the basin.

$$
Christensen
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