[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200015
TWDAT

Tropical Weather Discussion...UPDATED
NWS National Hurricane Center Miami FL
0015 UTC Fri Aug 20 2021

Updated to include the information from the Intermediate Advisory
on Tropical Storm Grace

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 1800 UTC surface analysis and satellite imagery through
2300 UTC.

...SPECIAL FEATURES...

Tropical Storm Grace has entered the E Bay of Campeche after
traversing the Yucatan Peninsula. As of 0000 UTC, the center of
Grace was located near 20.7N 91.0W or 55 nm NNW of Campeche,
Mexico moving W at 13 kt. Estimated minimum central pressure is
995 mb. Maximum sustained wind speed is 50 kt with gusts to 65
kt. Peak seas are currently 15 ft just N of the Yucatan
peninsula. An area of 12-14 ft seas is noted between Cozumel and
Cancun. Scattered moderate isolated strong convection is from
19N to 21N between 86W and 93W, including portions of the NW
Caribbean and the E and central Bay of Campeche. Convection
associated with an outer band of Grace is also affecting parts
of Belize. Gusty winds and heavy rain will continue over the
Yucatan peninsula through tonight. A general westward to west-
northwestward motion is expected tonight, followed by a general
westward to west-southwestward motion at a slower speed
beginning tomorrow. On the forecast track, Grace is expected to
move away from the coast of the Yucatan Peninsula this evening,
and continue moving across the southern Gulf of Mexico on
Friday.  Grace is expected to make a second landfall on the
mainland coast of Mexico late Friday or early Saturday. 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 near 29.7N 71.4W at 19/2100 UTC
or 390 nm SSE of Cape Hatteras North Carolina moving W at 9 kt.
Estimated minimum central pressure is 997 mb. Maximum sustained
wind speed is 55 kt with gusts to 65 kt. Peak seas are currently
25 ft. Numerous moderate isolated strong convection is within 90
nm SW and 30 nm NE semicircles of center. On the forecast track, the
center of Henri will remain well offshore of the east coast of the
United States over the next couple of days, but it is forecast to be
near southern New England on Sunday and Monday.  Little change in
strength is expected during the next 12 to 24 hours, but Henri
is forecast to intensify into a hurricane by Friday night with
additional strengthening expected this weekend. Swells generated by
Henri should continue to affect Bermuda during the next day or
so. Swells are expected to increase across much of the east coast
of the U.S. and Atlantic Canada later this week and this weekend.
These swells could cause life-threatening surf and rip current
conditions.

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 along 29W from 21N southward, moving W at 10-15
kt. Scattered moderate convection is noted mainly ahead of the
wave axis from 09N to 15N between 29W and 35W.

A tropical wave is along 39W/40W from 21N southward, moving W at
10-15 kt. Scattered moderate convection is on either side of the
wave axis from 06N to 12N between 35W and 45W.

A tropical wave is along 59W/60W from 21N southward, moving W at
around 15 kt. The wave is generating scattered showers and
thunderstorms mainly over the Windward Islands and the eastern
Caribbean E of 65W. Moisture associated with this wave will
continue to impact the eastern Caribbean and parts of the Lesser
Antilles tonight and Fri.

A tropical wave is along 72W extending from Hispaniola to western
Venezuela. It is moving W at around 10-15 kt. The wave is likely
enhancing some convective activity over western Venezuela, including
lake Maracaibo.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of Mauritania near 17N16W
to 13N29W to 09N46W. The ITCZ then extends from 09N46W to 09N57W.
In addition to the convection associated with the tropical waves,
scattered moderate convection is from 11N to 16N east of 20W.

...GULF OF MEXICO...

Refer to the Special Features section above for details on Tropical
Storm Grace.

The most recent scatterometer data show storm force winds just N
of the Yucatan peninsula to about 23N, with fresh to strong winds
associated with the cyclonic circulation of Grace roughly covering
the waters from 20N-25N between 88W-92W. Seas are 10-15 ft in
this area of high winds. Gentle to moderate return flow is noted
over the NW Gulf, with similar wind speeds elsewhere across the
remainder of the Gulf region under the influence of 1020 mb high
pressure located over the NE Gulf. Outside of the influence of
Grace, seas are in the 3-5 ft range, except 1-3 ft over the NE
Gulf.

For the forecast, conditions associated with Grace will affect
the Yucatan channel through tonight, and the region N of the
Yucatan Peninsula and the SW Gulf, including the Bay of
Campeche, through Sat. Winds and seas will gradually diminish
across the western Gulf late Sat into Sun. High pressure will
build in the wake of Grace and prevail through early next week.

...CARIBBEAN SEA...

Refer to the Special Features section above for details on
continuing impacts from Tropical Storm Grace over the NW
Caribbean. Fresh to strong SE winds are still affecting the
Caribbean waters W of 84W, with an area of 12-14 ft seas between
Cozumel and Cancun, and 8-12 ft N of 10N W of 84W, including the
Yucatan Channel.

In the E and Central Caribbean, moderate to fresh trades prevail
with 4-7 ft seas, except in the SW Caribbean where seas are 2-4
ft. Scattered to numerous showers and thunderstorms are noted
over Central America, particularly over Nicaragua. Similar
convective activity is seen over norther Colombia.

For the forecast, Grace will continue to move west of the area this
evening, with marine conditions gradually improving. Otherwise,
moderate to fresh trade winds will dominate elsewhere, except for
locally fresh to strong winds in the Gulf of Honduras tonight.

...ATLANTIC OCEAN...

Refer to the Special Features section above for details on Tropical
Storm Henri. Three tropical waves are moving westward between the
W coast of Africa and the Lesser Antilles. Please, see Tropical
Waves section for details.

E of Henri, the Atlantic forecast waters are dominated by a 1023
mb high pressure centered near new. Under the influence of this
system, mainly gentle to moderate ne-E winds are noted S of 30N
and E of 60W. Winds increase to moderate to fresh near the
northern end of the tropical wave located along 59W/60W, and N of
23N E of 18W to the W coast of Africa, including the Canary
Islands. Seas of 6-7 ft are related to these winds.

For the forecast, Henri will move N of area on Fri, and
strengthen to a hurricane near 31.9N 72.9W by Fri evening.
Otherwise, moderate to fresh E to SE winds will prevail E and
across the Bahamas Fri through Mon, except for fresh to locally
strong winds at night N of Hispaniola and the approaches to the
Windward Passage.

$$
GR/SDR
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