[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210914
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Sat Aug 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 0600 UTC surface analysis and satellite imagery through
0740 UTC.

...SPECIAL FEATURES...

Hurricane Grace is centered near 20.5N 97.8W at 21/0900 UTC or
40 nm SW of Tuxpan Mexico moving W at 12 kt. Estimated minimum
central pressure is 970 mb. Maximum sustained wind speed is 95
kt with gusts to 115 kt. Peak seas are currently 30 ft. Numerous
moderate and scattered strong convection is noted within 150 nm
in the northeast semicircle and within 210 nm in the southwest
semicircle of Grace. An additional band of scattered moderate
convection is noted between 180 nm and 300 nm in the northeast
semicircle and between 240 nm and 360 nm in the southwest
semicircle, including along the Pacific coast of Mexico. Grace is
forecast to weaken to a tropical storm this afternoon, to a
tropical depression early Sun, and dissipate by Sun afternoon.
Please read the latest NHC Public Advisory at
https://www.nhc.noaa.gov/text/MIATCPAT2.shtml and Forecast/
Advisory at https://www.nhc.noaa.gov/text/MIATCMAT2.shtml for more
details.

Tropical Storm Henri is centered north of the area near 33.1N
73.2W at 21/0900 UTC or 170 nm SE of Cape Hatteras North Carolina
moving NNE at 10 kt. Estimated minimum central pressure is 996 mb.
Maximum sustained wind speed is 60 kt with gusts to 75 kt. Peak
seas are currently 28 ft, north of 31N. Numerous moderate and
isolated strong convection is noted within 270 nm in the southeast
semicircle and 30 nm in the northwest semicircle of Henri, with
similar convection from 33N to 35N between 71W and 74W. Henri is
forecast to strengthen to a hurricane well north of the area this
afternoon. 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 WAVES...

A tropical wave is in the Atlantic Ocean along 23W south of 23N,
moving W at around 15 kt. Scattered moderate convection is noted
from 10N to 14N and between 20W and 26W.

A tropical wave is in the Atlantic Ocean along 37W south of 21N,
moving W at around 15 kt. Scattered moderate convection is noted
from 04N to 11N and between 32W and 40W.

A tropical wave is in the Atlantic Ocean along 49W south of 21N,
moving W at 10 to 15 kt. Scattered moderate convection is noted
from 07N to 13N and between 43W and 55W.

A tropical wave is in the Carribbean Sea along 69W south of 21N,
extending from near the eastern Dominican Republic southward to
western Venezuela, moving W at around 15 kt. The tropical wave is
enhancing the formation of a few showers and isolated
thunderstorms over Venezuela.

A tropical wave is in the Carribbean Sea along 78W south of 20N,
extending from eastern Cuba and western Jamaica southward to
eastern Panama, moving W around 10 kt. Scattered moderate
convection is noted from 12N to 15N between 76W and 80W.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends from the coast of Africa near the
Mauritania-Senegal border near 16N16W to 13N30W to 11N53W. The
ITCZ then continues from 11N53W to the coast of northeast
Venezuela near 10N63W. Scattered moderate convection is present
from 03N to 15N between the coast of Africa and 20W, and from 14N
to 16N between 55W and 60W.

...GULF OF MEXICO...

Refer to the Special Features section above for details on
Hurricane Grace now inland over Mexico.

High pressure of 1015 mb is centered in the northeast Gulf near
28N86W with a ridge axis reaching west-northwest to the Texas-
Louisiana border, and east-southeast to near Tampa Bay, Florida.
Light to gentle anticyclonic winds are under the ridge across the
northeast Gulf, with moderate SE winds elsewhere in the northern
Gulf and southeast Gulf. Moderate to fresh E-SE winds are found in
the periphery of Grace in the central and southwest Gulf. Seas in
the area are in the 6 to 12 ft range.

For the forecast, Grace will move inland and weaken to a tropical
storm near 20.2N 99.6W this afternoon, and dissipate Sun morning.
High pressure will build in the wake of Grace and prevail through
early next week.

...CARIBBEAN SEA...

Convergence associated with distant Hurricane Grace over mainland
Mexico is supporting scattered moderate convection over the Gulf
of Honduras and adjacent land areas. Similar convection is noted
over the western Caribbean from 12N to 16N between 81W and 86W,
including over portions of Honduras and Nicaragua. Scattered
moderate convection is also noted south of Hispaniola from 15N to
17N and between 72W and 74W. The rest of the basin has isolated to
scattered showers on mainly moderate to fresh trades, except for
gentle to moderate trades in the southwest Caribbean south of 11N,
and also north of 18N and east of 85W. Seas of 3 to 5 ft dominate
the basin, locally to 6 ft in the Gulf of Honduras.

For the forecast, moderate to fresh trade winds will dominate,
except localized pulses of strong winds are possible in the Gulf
of Honduras through tonight. Early next week, fresh to strong
winds will develop over the central Caribbean.

...ATLANTIC OCEAN...

Refer to the Special Features section above for details on
Tropical Storm Henri. Also, please read the Tropical Waves and
Monsoon Trough/ITCZ sections for additional convection across the
Atlantic Basin.

The tropical Atlantic remains under the dominion of an expansive
Azores-Bermuda subtropical ridge from 30N to 32N where light to
gentle winds and 3 to 4 ft seas prevail. The reliable easterlies
are carrying an outbreak of dry and dusty Saharan air across the
basin, resulting in fairly tranquil weather conditions outside of
the deep tropics and the outer rainbands of Tropical Storm Henri.
Fresh to strong winds are in the periphery of Henri, roughly from
29N to 31N and between 69W and 75W, while tropical storm force
winds are now confined to north of 31N. Seas in the area are 6 to
12 ft. Moderate to fresh winds are found from north of the
convergence zone to 30N. Seas in this region are in the 4 to 7 ft
range. Gentle to moderate trades and seas of 4 to 6 ft are found
elsewhere in the basin.

For the forecast west of 55W, Henri will strengthen to a
hurricane well north of the area near 35.6N 72.3W this afternoon
while associated outer winds and seas diminish south of 31N at the
same time. Otherwise, moderate to fresh E to SE winds will
prevail E and across the Bahamas through Mon, except for fresh to
possibly locally strong winds at night north of Hispaniola and the
approaches to the Windward Passage. A tropical wave will move
across the area by mid-week with fresh to strong winds ahead of
it.

$$
Lewitsky
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