[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231140
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
740 AM EDT Sun Aug 23 2020

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
1130 UTC.

...SPECIAL FEATURES...

Tropical Storm Laura is centered near 18.8N 70.9W or about 80 nm
east of Port Au Prince Haiti or about 95 nm southeast of Cap
Haitien, Haiti at 23/0900 UTC. Laura is moving WNW, or 285
degrees at 16 knots. The estimated minimum central pressure is
1005 mb. The maximum sustained wind speeds are 40 knots with gusts
to 50 knots. Satellite imagery shows a quite impressive large and
symmetrical cloud pattern with Laura that consists of numerous
moderate to strong type convection within 180 nm of the center in
the SW quadrant, within 150 nm of the center in the SE quadrant
and within 90 nm of the center in the N semicircle. Scattered
moderate to isolated strong convection is within 30 nm of line
from 18N74W to 19N75W. This observed convection acquired very
cold cloud top temperatures during the night while the center
remains over land. Laura is forecast to maintain its current
motion during the next few days. On the present forecast track,
the center of Laura will move across Hispaniola today, be near or
over Cuba tonight and Mon, and over the southeastern Gulf of
Mexico Mon night and Tue. Swells generated by Laura are affecting
portions of the Virgin Islands, Puerto Rico, and Hispaniola. These
swells are expected to spread across Cuba, much of the Bahamas,
and the Florida Keys during the next few days. Please consult
products from your local weather office. Please read the latest
NHC Public Advisory at
https://www.nhc.noaa.gov/text/MIATCPAT3.shtml and Forecast/
Advisory at https://www.nhc.noaa.gov/text/MIATCMAT3.shtml for more
details.

Tropical Storm Marco is centered near 23.7N 87.0W or about 160 nm
NW of the western tip of Cuba or 340 nm south-southeast of the
mouth of the Mississippi River at 23/0900 UTC. Marco is moving
NNW, or 335 degrees at 11 kt. The estimated minimum central
pressure is 994 mb. The maximum sustained wind speeds are 55 knots
with gusts to 65 knots. Numerous moderate to strong convection in
a CDO pattern is seen within 150 nm of the center in the NE
quadrant and in an outer wide band from 22N to 24N between 85W-
87W. Scattered moderate to isolated strong convection is within 30
nm of line from 24N83W to 26N85W and to 26N86W. Marco is forecast
to continue moving north-northwestward across the central Gulf of
Mexico today and will approach southeastern Louisiana on today. A
gradual turn toward the west with a decrease in forward speed is
expected after Marco moves inland on Mon and on Tue. Marco is
expected to produce rainfall accumulations of 2 to 4 inches with
isolated maximum amounts of 6 inches across the Central U.S. Gulf
coast through Tue. This rainfall may result in isolated areas of
flash and urban flooding along the Central U.S. Gulf Coast. Please
read the latest NHC Public Advisory at
https://www.nhc.noaa.gov/text/MIATCPAT4.shtml and
Forecast/Advisory at
https://www.nhc.noaa.gov/text/MIATCMAT4.shtml, for more details.

..TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 32W from
02N to 21N, moving westward at 10-15 knots. A rather dry and
stable environment surrounds this wave. Weak small isolated
showers and thunderstorms are within 60 nm of the wave axis from
05N to 09N.

A short-amplitude Caribbean tropical wave has its axis along 71W
south of 15N, moving westward at about 10 kt. Only isolated
showers and thunderstorms are noted near this wave.

A western Caribbean tropical has its axis along 79W south of 19N.
It is moving westward at 15 knots. The monsoon trough is along
11N73W in NE Colombia near the border with Venezuela, to 12N80W,
to 13N85W in Nicaragua, and westward, through Honduras, El
Salvador, and Guatemala, into the eastern Pacific Ocean. Scattered
showers and isolated thunderstorms are south of the monsoon
trough.

The previous tropical wave that was along 91W south of 17N is now
being described in the Eastern Pacific Tropical Weather
Discussion.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis passes through the coastal sections of
Mauritania near 18N16W to 18N20W to 16N22W to 11N24W to 11N35W
and to 09N50W, where latest scatterometer data indicates that it
transitions to the ITCZ and extends to near the coast of Venezuela
at 10N61W. Scattered moderate convection is along and within 60
nm south of the ITCZ west of 58W. Otherwise, the ITCZ is devoid of
deep convection for the time being.

GULF OF MEXICO...

Please see the Special Features section above for details on
Tropical Storm Marco.

Other than Tropical Storm Marco, relatively weak high pressure is
present over the basin. Scattered moderate to isolated strong
convection is seen along the coast and inland Mexico from 91W-96W.
Similar activity is over just about the entire eastern Gulf waters
east of 87W and to the south of Marco over the Yucatan Channel.
Isolated showers and thunderstorms are north of 24N and west of
87W.

Tropical Storm Marco centered near 23.7N 87.0W 994 mb at 5 AM EDT
is moving NNW at 11 kt. Maximum sustained winds 60 kt gusts 75
kt. Marco will intensify to a hurricane near 25.3N 87.6W this
afternoon with maximum sustained winds 65 kt gusts to 80 kt, reach
to near 27.3N 88.6W late tonight. Marco will maintain intensity
as it reaches to near 29.0N 89.7W Mon afternoon and move inland
and weaken to a tropical depression near 30.5N 93.1W Tue afternoon
and move inland to near 31.0N 95.0W early on Wed and dissipate
early on Thu.

Tropical Storm Laura currently over Hispaniola will move across
western Cuba Mon afternoon, then begin to gradually intensify as
it moves over the southeastern Gulf of Mexico near 23.5N 84.2W
late Mon night. Laura is forecast to reach near 24.9N 87.0W Tue
afternoon with maximum sustained winds 60 kt gusts 75 kt, to near
26.4N 89.4W late Tue night with maximum sustained winds 75 kt
gusts 90 kt and move inland near 29.9N 92.5W by late Wed night
with maximum sustained winds 85 kt gusts 105 kt. Atlantic high
pressure will build westward over the eastern Gulf in the wake of
Laura.

CARIBBEAN SEA...

Please see the Special Features section above for details on
Tropical Storm Laura.

A rather light gradient exists across the basin away from the
strong southerly winds that extend within 180 nm south of
Hispaniola in association with Tropical Storm Laura. The monsoon
trough axis is along 11N73W in northeastern Colombia near the
border with Venezuela to 12N80W to 13N85W in Nicaragua and
westward across Honduras, El Salvador, and Guatemala and into the
eastern Pacific Ocean. Outside convection related to the two
tropical wave described above, scattered moderate convection
is increasing over the Gulf of Honduras. Isolated showers and
thunderstorms are elsewhere east of 76W and south of 15N west of
15N west of 76W.

Tropical Storm Marco centered near  23.7N 87.0W 994 mb at 5 AM
EDT is moving NNW at 11 kt. Maximum sustained winds 60 kt gusts 75
kt. Marco will intensify to a hurricane near 25.3N 87.6W this
afternoon with maximum sustained winds 65 kt gusts to 80 kt, reach
to near 27.3N 88.6W late tonight.

Tropical Storm Laura centered near 18.8N 70.9W 1005 mb at 5 AM
EDT is moving WNW at 16 kt. Maximum sustained winds 40 kt gusts 50
kt. Laura will maintain intensity as it reaches the Windward
Passage near 19.8N 73.7W this afternoon, inland eastern Cuba near
20.9N 77.5W late tonight, inland western Cuba to near 22.2N 81.1W
Mon afternoon, then begin to gradually intensify as it moves over
the southeastern Gulf of Mexico near 23.5N 84.2W late Mon night
with maximum sustained winds 45 kt gusts 55 kt.

ATLANTIC OCEAN...

Please see the Special Features section above for details on
Tropical Storm Laura.

An upper-level cyclonic circulation center is within 850 nm to
900 nm to the east-northeast of Tropical Storm Laura. This
feature has acquired more convection during the overnight hours.
It is noted as a clustering of scattered moderate type convection
from 21N to 25N between 54W-57W. A surface trough may be forming
from this feature. Scattered showers and isolated thunderstorms
are to the northwest of the upper-level cyclonic circulation from
25N to 29N and between 55W-60W. To the east of the upper-level
cyclonic circulation, a 60 nm wide line of scattered showers and
thunderstorms that extends from 18N48W to 24N49W marks the leading
edge of an easterly surge. This feature was also hinted at by an
overnight ASCAT pass.

Scattered showers and thunderstorms are to the northwest of Laura
south of 25N between 72W-76W, including the areas of the southeastern
and central Bahamas. This activity is quickly moving westward.

Relatively weak high pressure is present over the area allowing
for gentle to moderate winds, with the exception of fresh to
strong winds south of 26N and between 65W-67W that are due to the
tighter gradient found between Laura and the broad Atlantic ridge
that stretches from well northeast of the area to near 28N50W and
northwestward to over the southeastern U.S.

Tropical Storm Laura centered near 18.8N 70.9W 1005 mb at 5 AM
EDT is moving WNW at 16 kt. Maximum sustained winds 40 kt gusts 50
kt. Laura will maintain intensity as it moves inland over Haiti
to the Windward Passage near 19.8N 73.7W this afternoon, inland
eastern Cuba near 20.9N 77.5W late tonight, inland western Cuba to
near 22.2N 81.1W Mon afternoon, then begin to gradually intensify
as it moves over the southeastern Gulf of Mexico near 23.5N 84.2W
late Mon night. Otherwise, the relatively weak high pressure in
place will remain through the next few days.

$$
Aguirre
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