[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 301045
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 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 1200 UTC surface analysis and satellite imagery through
1030 UTC.

...SPECIAL FEATURES...

Hurricane Sam was centered near 21.5N 59.1W at 30/0900 UTC or 300
nm NE of the Northern Leeward Islands moving NW at 10 kt.
Estimated minimum central pressure is 937 mb. Maximum sustained
wind speed is 125 kt with gusts to 150 kt. The well-defined eye is
30 nm in diameter. Numerous moderate scattered strong convection
is within 180 nm of the center in the E semicircle and 90 nm W
semicircle. Maximum significant wave height near the center is
estimated at 41 ft. NOAA buoy 41044, located near 21.6N 58.6W,
measured a significant wave height of 35 ft. The buoy was located
outside the northern eyewall, about 35-40 nm east of Sam's center
at the time of the observation. Sam will move northwest with an
increase in forward speed is expected through tonight. A turn
toward the north is anticipated by late Friday, and a
northeastward motion is forecast to begin on Saturday. On the
forecast track, the core of Sam will continue to pass well to the
northeast of the northern Leeward Islands this morning, and pass
to the east of Bermuda early Saturday. Some fluctuations in
intensity are expected during the next couple of days, but Sam is
forecast to remain a major hurricane through Saturday, with more
significant weakening anticipated later in the weekend. Swells
generated by Sam will impact the Northern Leeward Islands and the
Greater Antilles, including Puerto Rico, during the next few days.
Swells are expected to reach Bermuda and the Bahamas by Friday,
and then spread to the United States east coast by this weekend.
These swells could cause life-threatening surf and rip current
conditions. Please read the latest High Seas Forecast issued by
the National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest NHC
Forecast/Advisory and Public Advisory at www.hurricanes.gov for
more details.

Tropical Storm Victor was centered near 8.7N 27.3W at 30/0900 UTC
or 480 nm SSW of the Cabo Verde Islands moving WNW at 11 kt.
Estimated minimum central pressure is 1004 mb. Maximum sustained
wind speed is 40 kt with gusts to 50 kt. Numerous moderate to
scattered strong convection is within 210 nm of the center in the
W semicircle. Scattered moderate to isolated strong convection is
seen within 150 nm E semicircle. Maximum significant wave height
near the center is estimated to be near 16 ft. Victor will
continue moving WNW to NW through the weekend. Additional
strengthening is forecast, and Victor could become a hurricane on
Friday. A weakening trend is expected to begin over the weekend.
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 45W from 17N southward,
moving W near 10 kt. Scattered moderate showers and isolated
tstorms are found along and within 150 nm E of the wave axis from
05N-13N.

A western Caribbean tropical wave is near 85W from 18N
southward, moving W at 5 to 10 kt. No significant convection is
occurring with the wave at this time.

...MONSOON TROUGH/ITCZ...

A monsoon trough enters the Atlantic through the coast of
Mauritania near 19N16W to 11N23W. The monsoon trough resumes west
of T.S. Victor near 07N29W to 06N37W. The ITCZ extends from
06N47W to 08N55W. Scattered moderate convection is present from
05N-11N between 37W-51W.

GULF OF MEXICO...

Scattered moderate to strong convection is along the western
Gulf, off the Texas and Mexico coast from 21N to 29N and W of 93W.
This is being supported by ample upper-level diffluence in the
area. Conditions will be favorable for additional showers and
tstorms today over the northwest Gulf of Mexico. A 1017 mb
surface high pressure is located over the NE Gulf near 30N85W.
Gentle to moderate winds prevail across the basin. Seas are 2 to
4 ft over the western Gulf and 1 to 2 ft over the eastern Gulf.

For the forecast, weak high pressure will persist over the Gulf
through tonight, supporting gentle to moderate southerly winds
across the basin. A weak cold front will move southward over the
eastern Gulf Fri and dissipate over the southeast Gulf by Sat.
Stronger higher pressure will build across the region behind the
front, allowing winds and seas to increase 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...

Recent ASCAT wind data show gentle trades continuing over most
of the basin. Scattered showers and tstorms continue near Cuba
and Hispaniola as well as portions of the southeastern Caribbean,
including Barbados and St. Vincent. Gentle trades are noted across
the basin. Seas are 3 ft or less across most of the Caribbean
Sea, except in the northeast Caribbean passages, where swell from
Hurricane Sam will peak later today through tonight.

For the forecast, Hurricane Sam will move to 23.0N 60.2W this
afternoon, 25.6N 61.4W Fri morning, 28.4N 61.8W Fri afternoon,
31.1N 61.3W Sat morning, and move east of Bermuda near 33.5N 59.9W
Sat afternoon, and 35.5N 58.0W Sun morning. 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 become moderate to fresh across the
basin by the weekend.

ATLANTIC OCEAN...

Please read the Special Features section above for details on
Hurricane Sam and 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.
Marine and aviation interests should monitor this ongoing
situation by reading the latest 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 30/0900
UTC.

A surface trough extends from 30N63W to 23N69W. Mid to upper
level southwesterly winds are advecting moist air into the area,
essentially creating an atmospheric river of moisture, seen in
Total Precipitable Water imagery, just ahead of Hurricane Sam.
Scattered moderate showers and tstorms are near the trough axis,
especially within the area from 21N-28N between 65W-71W. A 1017
mb high pressure is located just east of Jacksonville, Florida
near 31N79W. Recent ASCAT data show mostly gentle wind speeds
covering the western Atlantic west of 65W. Seas are 2-4 ft west
of 70W, but 4-6 ft between 65W-70W due to easterly swell from
Hurricane Sam. The east Atlantic is being dominated by a 1033 mb
high pressure centered over the Azores. This is driving fresh to
strong trade winds east of 40W from 20N-30N. Seas are 8 to 11 ft
in the area.

For the forecast, Hurricane Sam will move to near 24N61W this
evening, near 27N62W Fri morning, near 30N62W Fri evening, near
32N61W Sat morning, and near 34N59W Sat evening. Expect rough
seas in the form of swell from Sam to impact the area northeast
of the Bahamas starting today. Swell up to 10 ft could reach as
far west as 70W, with 15 ft waves reaching 65W as Sam passes to
the east of 65W.  Meanwhile, a weak pressure pattern will
maintain light to gentle breezes and slight seas through today
west of 70W. A weak cold front will move from the Carolinas to
the central Bahamas Fri and and dissipate by Sat. Stronger high
pressure will build off the Carolinas this weekend, which will
bring moderate to occasionally fresh winds to the western
Atlantic through the weekend.

$$
AKR
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