[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181206
TWDAT

Tropical Weather Discussion...UPDATED
NWS National Hurricane Center
Miami FL 1205 UTC Sat Sep 18 2021

Updated to include the disturbance in the Eastern Atlantic in
the Special Features

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
1030 UTC.

...SPECIAL FEATURES...

Tropical Storm Odette is centered near 38.0N 69.3W at 18/0900
UTC or 200 nm S of Nantucket Massachusetts moving NE at 13 kt.
Estimated minimum central pressure is 1008 mb. Maximum sustained
wind speed is 40 kt with gusts to 50 kt. Seas are peaking at 12
to 13 ft near and up to 90 nm in a semicircle N of the center.
Odette remains highly sheared, with an exposed and elongated
center. Numerous moderate to isolated strong convection is noted
well NE of the center from 36N to 40N between 63W and 67W. Odette
is expected to continue a NE track with little change in speed
through Sunday. This will take Odette south of the northeast U.S.
and Atlantic Canada coasts over the weekend. Odette is forecast
to maintain its current intensity while transitioning into an
extra- tropical storm through tonight. Afterward, gradual
strengthening is likely and Odette will become a strong
extratropical storm on Sunday. Please read the latest NHC Public
Advisory at https://www.nhc.noaa.gov/text/MIATCPAT5.shtml for more
information. The Atlantic Offshore Waters Forecast issued by OPC
can be found at
https://www.ocean.weather.gov/offshore/indexphp?basin=atl&type=offshore#close

Atlantic gale warning: Low pressure near 14N49W centered in the
tropical Atlantic continues to become better organized. There
has been considerable easterly shear across this low, displacing
most of the convection toward the northern and western side.
However, as the low moves into a more favorable environment on
the southeast side of an upper low, the convection is increasing
and a band is forming on the north side of the. There is a high
chance this low will become a tropical depression in the next 48
hours. While a scatterometer pass from late yesterday evening
did not conclusively show this low was closed off, it did show
strong winds on its north side, between the low and high
pressure north of the area. These winds may increase as the low
deepens today, and a gale warning has been issued accordingly,
which may be changed to a tropical storm warning if the low
continues to be become better organized. The window for that to
happen is fairly small, as the low will enter a less favorable
environment relative to the upper trough heading into mid week
when the low reaches a position to the northeast of the Leeward
Islands. Regardless of development, increased winds, seas, and
convection is likely within 120 to 180 nm mainly on the north
side of the low over the next couple of days. Refer to the
latest NHC Tropical Weather Outlook at www.hurricanes.gov for
more details.

An Atlantic tropical wave is along 24W from 19N southward
through the Cabo Verde Islands and a 1008 mb low pressure near
09N25W. Scattered moderate to isolated strong convection is
found from 03N to 10N and between 21W and 34W. The associated
shower and thunderstorm activity has become a little better
organized since yesterday, and environmental conditions appear
conducive for further development during the next couple of
days. A tropical depression could form while the system moves
northwestward at about 10 mph to the west of the Cabo Verde
Islands before it reaches cooler waters and stronger upper-level
winds early next week. Refer to the latest NHC Tropical Weather
Outlook at www.hurricanes.gov for more details.

...TROPICAL WAVES...

Another Atlantic tropical wave is near 50W/51W from 19N southward
through a 1009 mb low pressure, and moving W near 15 kt.
Scattered moderate to isolated strong convection is present from
14N to 18N between 45W and 53W. See the Special Features section
above for potential development of this system.

A W Caribbean tropical wave is in the Gulf of Honduras along 87W
from 18N southward across Honduras, Nicaragua and Costa Rica to
the E Pacific Ocean, and moving W near 10 kt. No significant
showers or thunderstorms are noted in the Caribbean related to
this tropical wave.

...MONSOON TROUGH/ITCZ...

A monsoon trough extends across the African coast near the
Mauritania-Senegal border at 17N16W through the 1008 mb low
mentioned in the Tropical Waves section above to 12N37W. No ITCZ
is present based on the latest analysis. A few showers are
possibly ongoing off Dakar, Senegal. Elsewhere, no significant
convection is noted other that what is described in the Tropical
Wave section above.

The E end of the E Pacific monsoon trough is triggering scattered
showers and thunderstorms near the Panama-Colombia border.

...GULF OF MEXICO...

Scattered showers and a few thunderstorms are active over the loop
current in the central Gulf, on the southeast side of a short wave
trough digging through the northwest Gulf. Gentle to moderate
breezes and slight seas are noted across the basin.

For the forecast, weak high pressure will extend across the
eastern and central Gulf of Mexico through early next week. This
pattern will support continued gentle to moderate winds and mostly
slight seas across the Gulf through the next several days.
Looking ahead, a weak cold front may move into the northwest and
north- central Gulf by mid week.

...CARIBBEAN SEA...

The Atlantic ridge north of the basin is maintaining fresh to
strong trade winds over the south- central Caribbean, particularly
off Colombia. A recent altimeter satellite pass indicated seas to
8 ft about 120 nm northwest of Cartagena. Fresh to strong E winds
were noted in the Gulf of Honduras by an earlier scatterometer
satellite pass. Mostly moderate winds and sea persist elsewhere. A
few showers and thunderstorms are active off the southern
peninsula of Haiti, as well as from western Panama to southeast
Nicaragua.

For the forecast, the Atlantic ridge will shift westward through
Sun, as Tropical Storm Odette, off the middle Atlantic coast,
lifts northward. This will support fresh to strong winds over the
south- central Caribbean and Gulf of Honduras into early Sun. The
ridge will weaken starting Sun night as a tropical wave and area
of low pressure currently across the central Atlantic move to the
northeast of the Leeward Islands early Mon, then begin to move
more NW. There is a high chance this low pressure will form into a
tropical cyclone over the next several days. Regardless of
further development, expect increase winds, seas and thunderstorms
north through east of the Leewards early next week.

...ATLANTIC OCEAN...

Please see the Special Features section above for potential
tropical development in the Atlantic Basin. A mid to upper- level
trough near 29N50W continues to trigger scattered moderate
convection from 25N to 31N between 46W and 50W. Locally fresh
winds and seas up to 6 ft are possible near this convection. Refer
to the Tropical Waves and Monsoon Trough/ITCZ sections for
additional convection across the basin.

An expansive surface ridge extends southwestward from a 1026 mb
Azores high across S of Bermuda to Florida. This feature is
providing gentle to moderate winds with seas at 3 to 5 ft north
of 25N west of 35W. Other than the fresh winds and higher seas
mentioned near the 1008 mb low in the Special Features section,
gentle to moderate winds and seas of 3 to 5 ft are seen N of
between 10N and 26N between 50W and the S Florida Coast and the
Lesser Antilles. Moderate to locally fresh NE trades and seas at 6
to 8 ft are evident N of 27N between the African coast and 35W.
Gentle to locally moderate winds and seas of 4 to 6 ft prevail
across the rest of the basin.

For the forecast west of 65W, weak ridging through the N Bahamas
will support mostly light breezes and slight seas north of 22N
through early next week, and moderate trade winds and moderate
seas south of 22N at least through Sun. Meanwhile, an area of low
pressure currently well to the SE over the central tropical
Atlantic will approach the waters NE of the Leeward Islands Sun
and Mon, then begin to move more NW over open Atlantic waters.
There is a high chance this low pressure will form into a tropical
cyclone over the next several days. Regardless of further
development, expect increase winds, seas and thunderstorms N
through E of the Leewards Islands and NE of Puerto Rico early
next week.

$$
Christensen/Delgado
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