AXNT20 KNHC 221643
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Fri Oct 22 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
The axis of a tropical wave is along 44W, south of 17N and it is
moving W at 10-15 kt. Scattered moderate convection is observed
from 05N to 10N and between 39W and 50W.
The axis of a tropical wave is along 59W, south of 17N and it is
moving W at 10-15 kt. A broad surface curvature is evident on
visible satellite imagery. Scattered showers are noted from the
coasts of NE Venezuela and Guyana to 12N and between 55W and 63W.
The axis of a tropical wave is along 70W, south of 21N, extending
from the Dominican Republic to W Venezuela, and it is moving W at
10-15 kt. No deep convection is associated with this wave.
The axis of a tropical wave is along 78W, south of 21N, extending
from the E Cuba to Panama, and it is moving W at 10-15 kt.
Scattered moderate to isolated strong convection is found where
the wave interacts with the E Pacific monsoon trough, mainly from
the coast of Panama to 13N and between 75W to 83W.
The monsoon trough passes through the coast of The Gambia near
13N17W to 07N22W. The ITCZ continues from 07N22W to 07N33W and
07N44W. Another segment of the ITCZ continues from 07N46W to
04N51W. Scattered moderate convection is noted within 60 nm of the
ITCZ from 32W to 39W.
GULF OF MEXICO...
Scattered moderate to isolated strong convection is observed
across the southern portion of the Gulf of Mexico, extending from
SW Florida to the W Bay of Campeche, mainly as a result of
divergence aloft and a surface trough present along 94W, from 17N
to 23N. The rest of the Gulf, especially N of 25N, is under a dry
airmass that is suppressing the development of showers and
thunderstorms. A cold front drapes across the N Gulf, from the
Florida panhandle to SE Texas, but it is not producing any
significant convection. A weak pressure gradient results in
moderate or weaker winds across the basin. Seas S of 25N are 3-4
ft, with the highest seas occurring in the Florida Straits, and
1-3 ft elsewhere.
For the forecast, a cold front entering the northern Gulf of
Mexico will continue to press southward across the eastern Gulf
through Sat. The front is expected to stall later on Sat and will
linger through early next week. Moderate to fresh winds are
expected across the NW Gulf on Sat into Sun. Gentle to moderate
winds will prevail in the western through early next week.
Divergence aloft and a surface trough along the coast of the
Yucatan peninsula result in scattered moderate convection in the
Gulf of Honduras. The rest of the Caribbean Sea enjoys fairly
tranquil weather conditions due in part to the dry Saharan airmass
moving through the region. The modest pressure gradient between
the 1028 mb ridge over the NW Atlantic and lower pressures in
South America allow for fresh to locally strong trades E of 76W
according to the latest scatterometer satellite data and synoptic
observations. The strongest winds are found near the Lesser
Antilles. Moderate or weaker trades are prevalent in the remainder
of the Caribbean. Seas of 5-8 ft are occurring E of 75W and 2-5
ft elsewhere. A recent altimeter wave data show seas of 8 ft in
the SE Caribbean.
For the forecast, high pressure N of the area will support fresh
to locally strong trades E of the Windward Islands through the
weekend. Winds are expected to become moderate across the central
Caribbean early next week. Moderate to fresh winds are expected
over the south-central Caribbean with winds reaching locally
strong in the Venezuela basin through Sun. Gentle to moderate
tradewinds will prevail elsewhere.
A large area of showers and isolated thunderstorms is present over
the western tropical Atlantic. The combination of a surface
trough between Florida and the NW Bahamas and divergence aloft
results in scattered moderate convection from 22N to 27N and
between 73W and the coast of Florida. The storm activity is also
affecting a good portion of the Bahamas island chain. Farther
east, two other surface troughs, extending from 30N70W to 24N73W,
and 30N45W to 26N59W, are producing widely scattered showers and
isolated thunderstorms from 22N to 30N and between 47W and 71W.
Recent scatterometer satellite data show fresh winds in
association with the convection. The rest of the tropical Atlantic
enjoys fairly tranquil weather conditions. A weak surface trough
along 41W, from 20N to 24N, is only producing a few shallow
showers, but its signature was quite evident on scatterometer
An expansive 1028 mb subtropical ridge dominates the North
Atlantic and the pressure gradient between this feature and lower
pressures in South America result in fresh to strong trades from
06N to 19N and between 35W and the Lesser Antilles as observed on
recent satellite-derived wind data. Fresh NE winds are also
occurring E of 30W and from 20N to 30N. Seas of 7-10 ft are
found E of 60W, with the highest seas occurring E of the Lesser
Antilles and well W of the Canary Islands. Seas of 4-7 ft prevail
elsewhere in the basin.
The Cumbre Vieja volcano, on the island of La Palma in the
Canary Islands, has been erupting since 19 September 2021.
Marine and aviation interests should monitor this ongoing
situation by reading the Volcanic Ash Advisory issued by Meteo-
France, at http://vaac.meteo.fr/volcanoes/la-palma/.
For the forecast, high pressure will move east of the area tonight as a
weak cold front moves off the SE U.S. coast. The front will stall
near the northern Bahamas through early next week. Moderate to
locally fresh winds will develop north of the boundary Sat night
into Sun off the central Florida coast. Expect showers and
thunderstorms along this boundary.