Tropical Weather Discussion
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AXNT20 KNHC 112353

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
653 PM EST Mon Dec 11 2017

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 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through
2330 UTC.


A nearly stationary frontal boundary extends southwestward over
the western Atlc from 32N61W across eastern Cuba, Jamaica, to end
over the southwestern Caribbean Sea near 10N81W. A band of
cloudiness and showers is found along and up to 180 n mi west of
the front. The slow motion of the boundary is conducive to heavy
rainfall accumulations. 2.32 inches of rainfall has been observed
at Montego Bay, Jamaica during the 24 hours ending at 12 UTC this
morning. The pressure gradient between the front and high pressure
ridging southward along the coast of Nicaragua remains strong
enough to produce gale force winds to the west of the boundary
over the Caribbean Sea. The ridge has begun to weaken and winds
are expected to subside below gale force this evening. See the
latest NWS High Seas Forecast under AWIPS/WMO headers
MIAHSFAT2/FZNT02 KNHC for more details.

A strong cold front is pushing southward along the coast of
Morocco. Meteo France has posted a gale warning for the Agadir and
Tarfaya zones for N to NE winds increasing to gale force on
Tuesday, especially in gusts. Winds are expected to remain near
gale force over the Agadir, Tarfaya and Canarias forecast zones as
well as the southeastern portion of the Madeira forecast zone
until Wed, then subside by Wed evening.


The monsoon trough extends from Sierra Leone on the African coast
near 08N13W to 07N16W. The Intertropical Convergence Zone
continues from 07N16W to the coast of Brazil near 01S46W.
Isolated moderate convection is present from 03N to 05N between
37W and 40W.


Fair weather conditions continue across the entire Gulf of Mexico
due to a combination of strong surface high pressure centered
over Mexico ridging eastward over the Gulf and deep layer ridging
aloft. Surface winds are generally light to moderate over the
northern half of the Gulf and moderate to fresh over the southern
half. A weak cold front will introduce a reinforcing shot of cold
air into the Gulf on Tue. The coldest air will affect the
northeastern Gulf and bring a brief period of fresh to strong W to
NW winds to the northeastern waters. High pressure will rebuild
over the Gulf on Wed and Thu and maintain light to moderate winds
over the basin.


The main weather maker across the region is a nearly stationary
front that crosses the basin from the eastern tip of Cuba to
Jamaica to the coast of Panama near 10N81W. Please refer to the
Special Features section regarding the gale force winds over the
SW Caribbean. West of the front, northerly flow and scattered
showers are occurring between the front and the coast of Nicaragua
as well as the eastern third of Cuba. Moderate to fresh winds are
continuing along the coast of Colombia. Otherwise, generally
tranquil conditions exist to the east of the front, with light to
moderate trade winds and scattered shallow showers covering much
of the eastern and central Caribbean Sea. The front is forecast to
remain stationary while gradually weakening through mid-week.


Generally fair weather conditions prevail across the island this
evening as a frontal boundary remains nearly stationary just to
the west of the island across the Windward Passage and eastern
Cuba. The front is not expected to move much, so partly cloudy
skies and isolated showers are expected over the island during
the next day or two.


A mid-to upper-level trough is pivoting northeastward from the
western Atlantic into the central Atlantic. This will reduce
support for the boundary that remains nearly stationary over the
western Atlantic from 32N61W to the eastern tip of Cuba. A band
of clouds and showers is seen along and up to 240 n mi of the
front. Farther east, an upper-level trough extends SSW to the
coast of Guyana from a low centered near 24N49W. The accompanying
surface trough extends SSW from 28N51W to 16N57W. Scattered
moderate and isolated strong convection is tasking place from 15N
to 30N between 42W and 50W. The remainder of the basin remains
under a fairly quiet weather regime maintained by a strong
subtropical ridge supported by 1030 mb high pressure centered SW
of the Azores near 37N35W.

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