[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 292322
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Thu Sep 30 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
2300 UTC.

...SPECIAL FEATURES...

Hurricane Sam is centered near 20.2N 57.6W at 29/2100 UTC or 330
nm ENE of the Northern Leeward Islands moving NW at 8 kt.
Estimated minimum central pressure is 945 mb. Maximum sustained
wind speed is 115 kt with gusts to 140 kt. Seas are peaking to
41 ft. Numerous strong convection is within 90 nm of the center
in the NE semicircle and within 50 nm of the center in the SW
semicircle. Scattered moderate convection is noted farther N
from 21N to 22N between 55W and 58W, and farther SE from 18N to
21N between 54W and 56W. Swells generated by Sam will continue
to impact the Leeward Islands for the next few days, and reach
Puerto Rico and the Virgin Islands early Thu morning. These
swells are expected to reach Bermuda and the Bahamas in a day or
two, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. On the forecast track, Sam will continue to
pass well to the east-northeast of the northern Leeward Islands
through tonight. Please read the latest NHC Public Advisory at
https://www.nhc.noaa.gov/text/MIATCPAT3.shtml, Forecast/
Advisory at https://www.nhc.noaa.gov/text/MIATCMAT3.shtml, and
the NHC High Seas Forecast at www.hurricanes.gov for more
details.

Newly formed Tropical Storm Victor is centered near 8.3N 25.5W
at 29/2100 UTC or 470 nm S of the Cabo Verde Islands moving WNW
at 11 kt. Estimated minimum central pressure is 1005 mb. Maximum
sustained wind speed is 35 kt with gusts to 45 kt. Seas are
peaking at 12 to 15 ft near the center. Numerous moderate to
isolated strong convection is evident up to 200 nm in a NW
semicircle from the center. Scattered moderate convection is seen
up to 190 nm in a SE semicircle from the center. Victor will
continue on a WNW course for the next several days with a slight
increase in forward speed on Thu afternoon, staying away from the
Cabo Verde Islands. Steady strengthening is forecast, and Victor
is expected to become a hurricane in a day or two. Please read
the latest High Seas Forecast issued by Meteo-France at website
https://www.weather.gmdss.org/II.html and the latest NHC
Forecast/Advisory and Public Advisory at www.hurricanes.gov for
more details.

...TROPICAL WAVES...

An Atlantic tropical wave is along 43W from 17N southward and
moving W near 10 to 15 kt. Scattered showers are found from 06N
to 10N between 40W and 43W.

A western Caribbean tropical wave is near 83W from 18N southward
across W Panama into the E Pacific Ocean, and moving W at 5 to
10 kt. Scattered moderate convection is present over the SW
corner of the Caribbean Basin mainly south of 14N and west of
80W.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic through the coast of
Mauritania near 18N16W to a 1009 mb low near 18N17W to 09N24W to
1009 mb low pres near 07N34W to 06N40W. The ITCZ extends from
07N45W to 08N55W. Scattered moderate to isolated strong
convection is present from 02N-11N between 20W-41W.

...GULF OF MEXICO...

A surface trough extends across the northern portion of the basin
from 30N85W to 27N97W. Scattered moderate convection is noted
along the trough mainly west of 87W. Moderate to locally fresh
winds and seas up to 5 ft are possible near these showers and
thunderstorms. Otherwise, a broad surface ridge extending
southwestward from N Florida to central Mexico should sustain
light to gentle winds and seas at 1 to 3 ft across the E and
central Gulf. Moderate SE to S winds and seas of 2 to 4 ft
prevail across the rest of the Gulf, including the Yucatan
Channel.

For the forecast, weak high pressure will persist over the Gulf
through Thu night, supporting moderate southerly winds across the
western Gulf with mostly gentle winds in the eastern Gulf. A
weak cold front will move southward over the eastern Gulf Fri,
then stall and dissipate over the southeast Gulf through late
Sat. Stronger higher pressure will increase across the region
behind the front, allowing winds and seas to build over mainly
the southeast Gulf. Seas may build to 7 ft over the Straits of
Florida by Sat night. Light to gentle breezes and slight seas
will follow over most of the Gulf through early next week.

...CARIBBEAN SEA...

Light easterly trade winds allow island heating to generate
isolated thunderstorms over Cuba and Hispaniola. Farther S,
convergent trades are causing scattered showers and thunderstorms
near the Colombia-Venezuela border and adjacent waters, and also
over NE Venezuela and nearby waters. Refer to the Tropical Waves
section above for additional convection in the basin. Light to
gentle trades and seas of 2 to 3 prevail across the entire
Caribbean Basin.

For the forecast, Hurricane Sam will move to 21.2N 58.9W Thu
morning, 23.1N 60.4W Thu afternoon, then continue north of the
region to southeast of Bermuda by Sat then into the north central
Atlantic. Swells generated by Sam are forecast to continue over
Atlantic waters from off the northern Leeward Islands to north of
the Mona Passage through Fri. Meanwhile, gentle trades will
prevail over the Caribbean through Fri. Winds are expected to
increase moderate to fresh across the basin by the weekend.

...ATLANTIC OCEAN...

Please read the Special Features section above for details on
Hurricane Sam and newly formed Tropical Storm Victor.

The Cumbre Vieja volcano on the island of La Palma in the Canary
Islands near 28.6N 17.8W has been erupting since September 19th.
High concentration of volcanic ash is found near the volcano up
to 9,000 m ASL. Marine and aviation interests should monitor
this ongoing situation by reading Volcanic Ash Advisory issued by
Meteo-France at http://vaac.meteo.fr/volcanoes /la- palma/ for
details. The next advisory will be issued no later than 30/0300
UTC.

A surface trough meanders east-northeastward from 31N58W to
23N78W. Light to gentle with locally moderate winds and seas of
2 to 4 ft are evident N of 24N between 33W and the Georgia-
Florida coast. Fresh to strong with locally near-gale NE trades
and seas at 8 to 12 ft exist N of 19N between the NW African
coast and 33W. Outside the influence of Hurricane Sam, gentle to
moderate trades and seas of 4 to 6 ft are found from the Equator
to 24N between 35W and the Lesser Antilles. Outside the influence
of Tropical Storm Victor, gentle to moderate monsoonal winds and
seas at 5 to 7 ft prevail across the rest of the basin.

For the forecast, Hurricane Sam was near 20.2N 57.6W 945 mb at
2100 UTC, moving NW at 8 kt. Maximum sustained are winds
115 kt, with gusts to 140 kt. Sam will move to 21.2N 58.9W Thu
morning, 23.1N 60.4W Thu afternoon, 25.6N 61.4W Fri morning,
28.3N 61.9W Fri afternoon, and 31.0N 61.3W Sat morning. Sam will
change little in intensity as it moves into the north central
Atlantic early next week. In addition to hurricane conditions
northeast of the Leeward Islands through Thu, expect rough seas
in the form of swell from Sam to impact the area northeast of
the Bahamas starting Thu. Meanwhile, a weak pressure pattern will
maintain light to gentle breezes and slight seas through Thu. A
weak cold front will move from the Carolinas to the central
Bahamas by Fri and and dissipate by Sat. Stronger high pressure
will build in to the area, which will bring moderate to
occasionally fresh winds through the weekend.

$$
ERA
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