[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181104
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Wed Aug 18 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
1045 UTC.

...SPECIAL FEATURES...

Tropical Storm Grace is centered near 18.8N 80.9W at 18/0900 UTC
or 55 nm south-southeast of Grand Cayman. Grace is moving W at 12
kt and the estimated minimum central pressure is 1000 mb. Maximum
sustained wind speed is 55 kt with gusts to 65 kt. Satellite
imagery shows numerous moderate convection within 150 nm NE
quadrant...120 nm S semicircle and 75 nm in the NW quadrant.
Peak seas near the center are currently in the 17-20 ft range. A
general westward to west- northwestward motion is expected for the
next several days. On the forecast track, the center of Grace
will continue to move ear or over the Cayman Islands later this
morning. Grace will approach the Yucatan peninsula of Mexico
tonight or early Thu. Grace is forecast to strengthen into a
hurricane by tonight, with some additional strengthening possible
prior to the center reaching the eastern Yucatan Peninsula.
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 30.1N 65.7W at 18/0900 UTC
or 140 nm south-southwest of Bermuda. Henri is moving W at 7 kt
and the estimated minimum central pressure is 998 mb. Maximum
sustained wind speed is 55 kt with gusts to 65 kt. Henri remains
a small tropical storm. Satellite imagery shows numerous moderate
convection within 60 nm E semicircle and 30 nm W semicircle.
Scattered moderate to isolated strong convection is within 60 nm
of 29N67W. Peak seas near the center are currently in the 12-16 ft
range. A gradual turn to the west-northwest and northwest by late
Thu is expected, followed by a turn to the northwest on Fri.
Little change in strength if forecast through Thu. However, Henri
could still become a hurricane by the weekend. 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 far eastern Atlantic tropical wave has its axis along 26W from
03N to 20N. It is moving westward at around 10 kt. Scattered
moderate convection is seen within 240 nm east of the wave axis
from 06N to 10N and within 300 nm west of the wave axis from
06N to 10N.

A central Atlantic wave has its axis along 46W from 03N to 21N.
It is moving westward at 15 kt. No significant convection is
noted with this wave.

A tropical wave is entering the far eastern Caribbean along
62W. It is moving westward at 15 kt. Scattered moderate
convection is 120 nm either side of the wave from 09N to 11N.

The earlier analyzed western Caribbean tropical wave has moved
well inland Central, with its southern portion over the eastern
Pacific. Please refer to the eastern Pacific Tropical Weather
Discussion for details on this wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from Mauritania near 17N16W to
15N25W, to 12N34W and to 08N44W. The ITCZ then extends from
08N44W to 98N60W. Aside from the convection associated with the
tropical waves along 26W, scattered moderate to isolated strong
convection is seen south of the monsoon trough from 64N to 14N
east of 22W to inland the coast of Africa.

...GULF OF MEXICO...

Fairly tranquil weather conditions prevail across the Gulf of
Mexico. Moderate to fresh northeast to east winds are over
the SE Gulf waters off the NW coast of Cuba to the Florida
Straits, and N and W of the Yucatan peninsula. Gentle to moderate
anticyclonic winds elsewhere in the basin. Seas are 2-4 ft in the
Gulf.

For the forecast, Tropical Storm Grace over the northwest
Caribbean Sea near 18.8N 80.9W 998 mb at 5 AM EDT moving W at 14
kt. Maximum sustained winds 55 kt gusts 65 kt. Grace will move to
19.3N 83.2W this afternoon, strengthen to a hurricane near 19.9N
86.4W late tonight with maximum sustained winds 75 kt guts 90 kt,
and weaken to a tropical storm inland the northern Yucatan
Peninsula Thu afternoon with maximum sustained winds 50 kt gusts
60 kt Grace will re-strengthen to a hurricane near 20.7N 93.4W Fri
afternoon with maximum sustained winds 65 kt gusts 80 kt, reach
to near 20.7N 96.8W late Fri night and move inland late Sat night.
Winds and seas will begin to increase across the southeastern
Gulf ahead of Grace today. These conditions will shift to west of
90W Thu through late Fri night.

...CARIBBEAN SEA...

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

Scattered moderate to isolated strong convection is noted within
100 miles of the NW coast of Colombia and between the Cayman
islands and W Cuba. Outside of the wind field of Tropical Storm
Grace, recent scatterometer satellite data show strong to near
gale-force trade in the south-central Caribbean Sea, especially
within 90 nm of the NW coast of Colombia and the Gulf of
Venezuela. Fresh to strong trades are noted in the rest of the
central and E Caribbean. Gentle to moderate trades are found in
the rest of the basin. Seas are 5-7 ft in the central and E
Caribbean. Seas are 3-5 ft in the NW Caribbean and 1-3 ft in the
remainder of the basin.

For the forecast, Tropical Storm Grace near 18.8N 80.9W 998 mb at
5 AM EDT moving W at 14 kt. Maximum sustained winds 55 kt gusts
65 kt. Grace will move to 19.3N 83.2W this afternoon, strengthen
to a hurricane near 19.9N 86.4W late tonight with maximum
sustained winds 75 kt guts 90 kt, and weaken to a tropical
storm inland the northern Yucatan Peninsula Thu afternoon.
Elsewhere, fresh to strong trades will be over the central
Caribbean through early Thu.

...ATLANTIC OCEAN...

Please refer to the sections above for details on Tropical Storm
Henri and on the tropical waves moving across the basin.

An expansive 1026 mb Azores ridge dominates the tropical
Atlantic, resulting in fairly tranquil weather conditions. The
strong high pressure system and lower pressures over NW Africa
result in a tight pressure gradient over the NE Atlantic. Strong
to near gale- force N-NE winds are found surrounding the Canary
Islands and off the coasts of Morrocco and Western Sahara. Seas in
this area are in the 6-9 ft range. Overnight scatterometer
satellite data detected fresh to locally strong NE winds from 19N
to 30N and between 27w and 47W, and seas are in the 3-6 ft range.
Moderate to fresh E winds are found south of 19N between 40W to
the Lesser Antilles, and north of the Greater Antilles to 22N.
Gentle to moderate anticyclonic winds and seas of 1-3 ft are
prevalent in the rest of the basin.

For the forecast west of 65W, Tropical Storm Henri near 30.1N
65.7W 998 mb at 5 AM EDT moving W at 7 kt. Maximum sustained winds
55 kt gusts 65 kt. Henri will move to 29.9N 66.9W this afternoon
with maximum sustained winds 60 kt gusts 75 kt and maintain
intensity as it reaches near 29.8N 68.7W late tonight, to near
29.8N 70.6W Thu afternoon, to near 30.4N 71.8W late Thu night,
then strengthen to a hurricane near 31.4N 72.3W Fri afternoon with
maximum sustained winds 65 kt gusts 80 kt and to north of the
area near 33.0N 71.9W. Fresh east to southeast winds over the far
southwest part of the area will shift W to the Straits of Florida
tonight. Otherwise, high pressure will persist across the forecast
waters through the period.

$$
Aguirre
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