[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 252300
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Sun Sep 26 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 1800 UTC surface analysis and satellite imagery through
2200 UTC.

...SPECIAL FEATURES...

Hurricane Sam is centered near 13.3N 48.5W at 2100 UTC, or 890 nm
ESE of the Northern Leeward Islands, moving WNW at 9 kt.
Estimated minimum central pressure is 943 mb. Maximum sustained
wind speed is 120 kt with gusts to 145 kt, making Sam a category 4
hurricane on the Saffir-Simpson scale. Peak seas are estimated
near 29 ft and are anticipated to reach near 34 ft by Monday.
Satellite imagery shows numerous moderate to strong convection
within 90 nm of Sam's center, with a well define eye 12-15 nm
wide. A slower motion to the west-northwest is expected during
the next couple of days before Sam begins to turn more northwest
and increase its forward speed. Additional strengthening is
expected to continue during the next 6-12 hours, then minor
fluctuations in intensity are likely as Sam goes through eye wall
replacement cycles over warm waters and light wind shear. 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.

Post-Tropical Cyclone Teresa is centered near 34.4N 64.3W at
2100 UTC, or about 130 nm N of Bermuda, drifting east at 4 kt.
Estimated minimum central pressure is 1010 mb. Maximum sustained
wind speed is 30 kt with gusts to 40 kt. Teresa remains a swirl of
low-level clouds and lacks any convection near the center, and has
thus lost all tropical or subtropical characteristic. A motion
toward the northeast is expected to continue through Sunday
morning before dissipating later on Sun. 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 been added to the 1800 UTC surface
analysis along 21W, south of 17N, and it is moving west around 10
kt. Scattered moderate isolated strong convection is seen from
03.5N to 15N between 18W and 26W. Dry Saharan air can be seen
moving off Africa with this wave from 14N to 24N extending from
the coast to 26W.

An Atlantic tropical wave has its axis near 32W, south of 17N,
and it is moving west around 10 kt. Widely scattered moderate
convection is noted from 04N-12N between 26W-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 to the north of 11N.

A Caribbean tropical wave has its axis near 67W, south of 20N,
and it is moving west around 15 kt. No significant deep
convection is noted over water in association with this wave.
However scattered moderate to strong convection is seen along the
wave axis over coastal Venezuela.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through coast of Senegal near 13.5N17W
to 07N33W. The ITCZ extends from 07N33W to 08N43W. Aside from
convection associated to the tropical waves and Sam described
above, scattered moderate isolated strong convection is noted
from 04N-09N from 36W to 48W.

GULF OF MEXICO...

A stationary front extends from the NE Gulf to the central Bay of
Campeche. Widely scattered moderate convection is noted within 60
nm either side of the front west of 83.5W. West of the front are
moderate or weaker N to NE winds. East of the front, E to SE winds
are gentle or weaker. Seas are 3-5 ft west of the front, and 1-2
ft east.

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 very modest north-south pressure gradient exists over the
Caribbean this afternoon between a broad 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 4-6 ft over the S central Caribbean and 2-4
ft elsewhere. Scattered moderate to strong convection is noted
from 10N-17N west of 80W.

Hurricane Sam will move to 13.7N 49.4W Sun morning, 14.3N 50.5W
Sun afternoon, 14.9N 51.6W Mon morning, 15.7N 52.7W Mon afternoon,
16.6N 53.9W Tue morning, and 17.4N 55.0W Tue afternoon. Sam will
change little in intensity as it moves near 19.5N 58.0W Wed
afternoon. Meanwhile, moderate trade winds will persist over much
of the Caribbean into early next week. Fresh winds will prevail
over the south-central Caribbean as high pressure builds east of
the Bahamas through Mon. Swell fro Sam will reach the Lesser
Antilles Tue morning.

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 along the
Florida coast. A pre-frontal trough extends from 27N76W to
26N80W. Widely scattered moderate convection is noted within 90 nm
SE of the front. Moderate N to NE winds prevail west of the front.
To the east a 1016 mb high is centered near 29N68W. To the east of
this, a trough, the remnants of Peter, extends from 28N63W to
22N68W. Fresh S to SW winds prevail within 180 nm east of the
trough. Scattered moderate to strong convection continues east of
the trough from 24N to 29N eastward to 58W. Farther east, a
dissipating frontal trough is noted from 31N33W to 26N40W to
31N54W. A 1009 mb low - the remnants of Rose - is located along
the trough at 28.5N34W. Scattered moderate isolated strong
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.

The stationary front across the NW waters will linger through
tonight, then push southeast as a weak cold front by Sun and
reach from 31N68W to 23N81W by Mon morning. The front will then
stall and dissipate by Tue. Farther east, Hurricane Sam will move
to 13.7N 49.4W Sun morning, 14.3N 50.5W Sun afternoon, 14.9N
51.6W Mon morning, 15.7N 52.7W Mon afternoon, 16.6N 53.9W Tue
morning, and 17.4N 55.0W Tue afternoon. Sam will change little in
intensity as it moves near 19.5N 58.0W Wed afternoon. Swell
associated with Sam will reach the Atlantic waters north of Puerto
Rico and the Virgin Islands Wed and the Bahamas and waters E of
75W on Thu.

$$
Stripling
This weather bulletin was brought to you by:
www.nashvilleweather.net