[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211804
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 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 1200 UTC surface analysis and satellite imagery through
1630 UTC.

...SPECIAL FEATURES...

Grace, downgraded to a tropical storm is centered near 19.7N
98.9W at 21/1500 UTC or 20 nm NNE of Ciudad De, Mexico and moving
WSW at 11 kt. Estimated minimum central pressure is 990 mb.
Maximum sustained wind speed is 60 kt with gusts to 75 kt. Peak
seas are currently 14 ft near the Mexican coast. Numerous moderate
convection is noted over central Mexico and N of the Bay of
Campeche. Grace is being affected by the mountainous terrain
across central Mexico, and has lost most of the strong convection.
It is expected to weaken to a tropical depression tonight, and
then dissipate Sunday morning. 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.

Henri has strengthened into a hurricane earlier this morning and
is centered north of the area near 34.4N 72.5W at 21/1500 UTC or
155 nm ESE of Cape Hatteras, North Carolina and moving NNE at 12
kt. Estimated minimum central pressure is 991 mb. Maximum
sustained wind speed is 65 kt with gusts to 80 kt. Peak seas are
currently 34 ft, N of 31N and E of the Carolinas. Numerous
moderate and isolated strong convection is noted within 140 nm in
the east semicircle, and scattered moderate to isolated strong
convection is present within 240 nm in the southwest semicircle
of Henri. Henri is forecast to continue a NNE track with some
modest strengthening through tonight, then turn toward the NNW
with a gradual weakening trend on Sunday while approaching the
Northeast States. Rainfall of 5 to 7 inches are forecast for parts
of the NY-NJ-CT Tri-state area. 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...

An Atlantic tropical wave is along 25W from 22N southward and
moving W at 15 to 20 kt. Scattered moderate convection is noted
from 06N to 14N and between 18W and 26W.

Another Atlantic tropical wave is near 37W from 20N southward and
moving W at 10 to 15 kt. Scattered moderate convection is seen
from 05N to 13N and between 32W and 40W.

A third Atlantic tropical wave is along 50W from 21N southward to
near the N coast of Brazil, and moving W near 15 kt. Scattered
moderate convection is present from 07N to 14N and between 44W
and 53W.

A Caribbean tropical wave is near 70W from 21N southward across
Hispaniola to NW Venezuela, and moving W near 15 kt. Drier air at
the mid levels continue to hinder significant convection near
this wave.

Another Caribbean tropical wave is along 80W from 20N southward
across central Panama to the E Pacific Ocean, and moving W at 10
to 15 kt. Scattered moderate convection is found from the
Honduras-Nicaragua border eastward to near Jamaica.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends from the coast of Africa near the
Senegal-Gambia border at 14N16W to 13N30W to 11N42W. The ITCZ
then continues from 11N42W to 10N54W, N of Suriname. Scattered
moderate convection is evident from 03N to 17N between the African
coast and 18W, and farther W from 10N to 14N between 26W and 32W.
No significant convection is found near the ITCZ.

...GULF OF MEXICO...

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

A surface ridge extends east-southeastward from a 1015 mb high
near the Mississippi-Alabama border through S Florida. Modest
convergent winds along the N periphery of the high is coupling
with northerly wind shear aloft to trigger scattered showers and
isolated thunderstorms just S of Mobil, Alabama. Otherwise, light
to gentle SE to S winds and seas of 3 to 5 ft are evident over the
N and E Gulf. Moderate to fresh with locally strong ESE to SE
winds and seas at 6 to 10 ft are seen across the SW Gulf,
including the Bay of Campeche.

For the forecast, Tropical Storm Grace is inland over central
Mexico near 19.7N 98.9W 990 mb at 11 AM EDT or 15 UTC and moving
WSW at 11 kt. Maximum sustained winds are 60 kt with gusts to 75
kt. Grace will move farther inland to 19.4N 100.6W this evening,
weaken to a tropical depression over Michoacan, Mexico Sun
morning, then dissipate Sun evening. High pressure will build in
the wake of Grace and prevail through early next week.

...CARIBBEAN SEA...

Modest convergent trade winds are triggering isolated
thunderstorms near the Windward Islands. For additional
convection in the Caribbean Basin, refer to the Tropical Waves
section above.

Moderate to fresh NE to ENE trades and seas at 4 to 7 ft are
present across the E and central basin. Gentle to moderate trades
and seas of 4 to 5 ft prevail for the rest of the basin.

For the forecast, moderate to fresh trade winds will dominate
into next week. Localized pulses of strong winds are possible
offshore Colombia starting tonight and will develop over much of
the rest of the central Caribbean later on Sun.

...ATLANTIC OCEAN...

Refer to the Special Features section above for details on
Hurricane Henri N of the area. Convergent winds SW of Henri are
producing scattered showers and isolated thunderstorms off the
Georgia-N Florida coast, N of 30N between 76W and 79W. Please
read the Tropical Waves and Monsoon Trough/ITCZ sections for
additional convection across the Atlantic Basin.

The Atlantic ridge stretching from the 1023 mb Azores high across
Bermuda to S Florida continues to support light to gentle winds
and seas of 3 to 5 ft, N of 25N between 32W and 64W. N of 29N,
moderate to fresh SSE to SW winds and seas of 6 to 9 ft are seen
between 64W and 68W, and between 75W and 77W; strong to near-gale
S to SW winds and seas at 9 to 11 ft are found between 68W and
75W. Gentle to moderate NE trades and seas at 5 to 6 ft are
evident from 13N to 25N between 33W and Lesser Antilles/Bahamas,
and also near the Canaries Islands N of 20N between the NW African
coast and 33W. Gentle to moderate SE to SW winds and seas of 4 to
6 ft prevail for the remainder of the Atlantic Basin. Latest
visible satellite loop suggests the leading edge of Sahara Dust
to be near 38W.

For the forecast west of 55W, Hurricane Henri is now well north
of the area and will continue moving away from the region today,
with no further impacts expected. 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.

$$

Chan
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