Tropical Weather Discussion
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AXNT20 KNHC 190003

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
703 PM EST Sat Nov 18 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
2345 UTC.


A cold front will reach the NW Gulf of Mexico tonight and will
move across the remainder of the Gulf through Monday. Strong high
pressure building behind the front will generate gale force winds
over the SW Gulf waters S of 25N to the west of the front beginning
1200 UTC Sunday and persisting through Sunday night. See the
latest high seas forecast under AWIPS/WMO headers HSFAT2/FZNT02
for more details.


The monsoon trough extends from the African coast near 08N13W to
05N21W. The Intertropical Convergence Zone axis extends from
05N21W to 06N40W to 06N57W. Scattered moderate convection is from
03N to 06N between 16W and 35W.



A broad ridge extends from the SW N Atlc across the Florida
Peninsula and into the Gulf approximately to 93W. The ridge
supports light to gentle SSW winds E of 93W and SSW moderate flow
westward ahead of the next cold front that is coming off the Texas
and Louisiana coasts tonight. CIRA LPW and GOES-16 water vapor
imagery continue to show deep layered dry air basin-wide, which is
supporting clear skies. The cold front will sweep across the Gulf
through Monday. Gale force winds are forecast over a portion of
the SW Gulf Sunday behind the front. Please refer to the special
features section for more details.


The base of a middle to upper level trough extending from the W
Atlc reaches the NW Caribbean where it support a weak surface
trough from the NE Yucatan Peninsula near 20N87W to the Gulf of
Honduras near 15N83W. Shallow moisture in this region of the basin
support isolated showers 90 nm either side of the trough axis.
Latest scatterometer data showed a low center just N of the Mona
Passage from which a surface trough extends SW to 15N71W. In the
south-central basin, a 1008 mb low is off the coast of Colombia
near 11N74W from which a surface trough extends northward to
southern Hispaniola. This elongated area of low pressure prevails
underneath an upper level ridge that supports diffluent flow and
thus scattered showers and tstms across the NE Caribbean,
including Puerto Rico and the Virgin Islands. Isolated showers are
between 68W and 74W, including Hispaniola and the Mona Passage. High
pressure over the western Atlantic is supporting moderate to
fresh NE winds over the northwestern Caribbean. Mainly light to
gentle winds cover the remainder of the Caribbean. The area of low
pressure in the southern basin will stall through early morning
morning while it weakens to a surface trough that will move
westward through the middle of the week.


Isolated showers are across the island tonight being supported by
an elongated area of low pressure focused on a 1008 mb low just N
of the Mona Passage with associated surface trough extending SW to
southern Hispaniola adjacent waters. Showers will continue through
Monday as the area of low pressure drifts NE over the Atlc waters.


A broad ridge over portions of the NW Atlc waters extends SW
across the SW N Atlc supporting fair weather and NE to E moderate
to fresh winds. Over the central Atlc forecast waters a stationary
front extends from 30N40W to a 1008 mb low near 27N50W. A surface
trough then extends from the low SW to another 1008 mb low
pressure center located just N of the Mona Passage. These
features are supporting a large area of showers N of 22N between
37W and 56W and S of 23N between 55W and 69W. High pressure of
1019 mb centered near 26N25W dominates the eastern Atlantic. Over
the next 24 hours the lows will move NE with convection spreading
east. SW winds will increase to 20 to 25 kt N of 30N east of 70W
Sunday as a cold front approaches the region.

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