[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251708
TWDAT

Tropical Weather Discussion NWS National Hurricane Center Miami
FL 1805 UTC Sat Sep 25 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
1600 UTC.

...SPECIAL FEATURES...

Hurricane Sam is centered near 12.9N 47.6W at 25/1500 UTC or 950
nm ESE of the Northern Leeward Islands moving WNW at 9 kt.
Estimated minimum central pressure is 960 mb. Maximum sustained
wind speed is 105 kt with gusts to 130 kt. Peak seas are near 23
ft and are anticipated to reach near 35 ft by Monday. A slower
motion to the west-northwest is expected over the weekend,
followed by a turn to the northwest on Monday. Additional
strengthening is expected over the next day or so, and Sam is
forecast to become a category 4 hurricane by Sunday. Numerous
moderate and scattered strong convection is noted within 120 NM
of Sam's center. Please read the latest High Seas Forecast
issued by NHC at http://www.nhc.noaa.gov/text/MIAHSFAT2.shtml
and the latest NHC Public Advisory and Forecast/Advisory at
https://hurricanes.gov for more details.

Subtropical Depression Teresa is centered near 34.3N 65.0W at
25/1500 UTC or 120 nm N of Bermuda stationary. Estimated minimum
central pressure is 1009 mb. Maximum sustained wind speed is 30
kt with gusts to 40 kt. A motion toward the northeast is
expected to begin this afternoon and continue through Sunday
morning. Teresa is expected to become a remnant low by this
evening and dissipate on Sunday. Peak seas are near 13 ft and
are expected to diminish below 12 ft later today. There is no
significant deep convection occurring in association with Teresa
currently. Please read the latest High Seas Forecast issued by
OPC at
https://ocean.weather.gov/mobile/mobile_product.php?id=NFDHSFAT1
and the latest NHC Public Advisory and Forecast/Advisory at
https://hurricanes.gov for more details.

...TROPICAL WAVES...

An Atlantic tropical wave has its axis near 31W, south of 17N,
and it is moving west around 10 kt. Isolated moderate convection
is noted from 04N-10N between 24W-36W. Satellite imagery show
that the northern part of the wave remains embedded in dry
Saharan air, inhibiting the development of shower and
thunderstorm activity.

A Caribbean tropical wave has its axis near 65W, south of 20N,
and it is moving west around 10-15 kt. No significant deep
convection is noted in association with this wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through coast of Senegal near 12N17W
to 06N37W. The ITCZ extends from 08N40W to 07N59W to the coast
of Guyana. Aside from convection associated to the tropical
waves and Sam described above, scattered moderate and isolated
strong convection is noted from 10N-15N east of 23W.

GULF OF MEXICO...

As of 1500 UTC, a stationary front extends from the NE Gulf to
the Bay of Campeche. Scattered moderate convection is noted from
23N-27N between 85W-93W. West of the front are moderate or
weaker N to NE winds. East of the front, winds are gentle or
weaker. Seas are 3-4 ft west of the front, and 1-2 ft east.

For the forecast, the front will push southward on Sun and
dissipate by early next week. Moderate to locally fresh winds
prevail north of the front. Winds and seas will diminish across
basin through early next week as high pressure builds over the
northern Gulf.

CARIBBEAN SEA...

Refer to the section above for details on the tropical wave
moving across the easter Caribbean.

A modest north-south pressure gradient exists over the Caribbean
today between the 1009 mb Colombian Low and weak ridging north
of the Caribbean.  This is forcing fresh E trades over the S
central Caribbean and moderate or weaker trades elsewhere. Seas
are 5-6 ft over the S central Caribbean and 2-4 ft elsewhere.
Scattered moderate and isolated strong convection is noted from
10N-15N west of 80W.

For the forecast, Hurricane Sam near 12.9N 47.6W 960 mb at 11 AM
EDT moving WNW at 9 kt. Maximum sustained winds 105 kt gusts 130
kt. Sam will move to 13.3N 48.7W this evening, 13.7N 49.8W Sun
morning, 14.3N 50.8W Sun evening, 15.0N 51.9W Mon morning, 15.8N
53.0W Mon evening, and 16.6N 54.1W Tue morning. Additional
strengthening is expected over the next day or so. Meanwhile,
moderate trade winds will persist over much of the Caribbean
into early next week, while fresh winds prevail over the south-
central Caribbean as high pressure builds east of the Bahamas.

ATLANTIC OCEAN...

Please read the sections above for details on Hurricane Sam and
tropical waves moving across the basin.

The Cumbre Vieja volcano on the island of La Palma in the Canary
Islands has been erupting since 19/1410 UTC. Significant
volcanic ash mainly in the vicinity of the volcano.  Marine and
aviation interests should monitor this on-going situation by
reading Volcanic Ash Advisory issued by Meteo-France at
http://vaac.meteo.fr/volcanoes/la-palma/. The next advisory will
be issued no later than 25/2100 UTC.

A stationary front extends from 31N75W to 27N80W at the Florida
peninsula. A pre-frontal trough extends from 27N76W to 26N80W.
Isolated moderate convection is noted from 24N-30N between 73W-
80W. A surface trough extends from 27N63W to 23N68W. Scattered
moderate and isolated strong convection is noted from 24N-30N
between 58W-64W. Farther east, a dissipating cold front is noted
from 31N34W to 27N42W to 28N50W, where it transitions to a
dissipating stationary front to 31N54W. A 1010 mb low - the
remnants of Rose - is located just southeast of the cold front
at 28N34W. Scattered moderate convection is noted north of 25N
between 29W-34W. S winds just east of the low are fresh to
strong. Elsewhere across tropical N Atlantic (aside from near
Hurricane Sam), the winds are moderate or weaker.

For the forecast west of 65W, the stationary front will remain
stationary through early Sun, pushing south and eastward as a
weak cold front by Sun and reach from 31N69W to 24N80W by Mon
morning. The front will stall and dissipate by Wed. Farther
east, Hurricane Sam near 12.9N 47.6W 960 mb at 11 AM EDT moving
WNW at 9 kt. Maximum sustained winds 105 kt gusts 130 kt. Sam
will move to 13.3N 48.7W this evening, 13.7N 49.8W Sun morning,
14.3N 50.8W Sun evening, 15.0N 51.9W Mon morning, 15.8N 53.0W
Mon evening, and 16.6N 54.1W Tue morning. Additional
strengthening is expected over the next day or so, and will
reach near 18.4N 56.5W by early Wed.

$$
Landsea/A.Reinhart
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