Tropical Weather Discussion
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AXNT20 KNHC 201742

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1242 PM EST Sat Jan 20 2018

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 1200 UTC surface analysis and satellite imagery through
1745 UTC.


Broad strong high pressure over the SW N Atlc waters will continue
to move eastward while slightly strengthening the next two days.
This is currently supporting fresh to near gale-force winds in
the south-central Caribbean waters with the strongest winds being
along the coast of NW Colombia. The pressure gradient in this
region is expected to slightly increase tonight, thus leading to
the development of gale-force winds along Colombia. Gale winds are
expected to continue through Sunday morning, but remain in the
strong to near-gale range through Monday. See the latest NHC High
Seas Forecast under AWIPS/WMO headers MIAHSFEP2/FZPN03 KNHC for
more details.


The monsoon trough enters the Atlantic Ocean near 07N12W and
continues to 03N16W to 01N21W. The ITCZ begins near 01N21W and
continues along 01N40W to 01S50W. Scattered moderate rain showers
are from 01N to 06N between 10W-18W and within 175 nm either side
of the ITCZ.



A broad surface ridge extends from the SW N Atlc waters across
Florida, the SE CONUS, into the Gulf and into inland Mexico. This
setting is providing the basin with light to moderate return flow,
except for locally fresh wind off the coast of Texas. A middle to
upper level low centered between Louisiana and Mississippi extends
a trough S-SW across the basin. To the east, SW flow associated
with the NW periphery of a ridge centered in the south-central
Caribbean supports diffluent flow, which is supporting cloudiness
and possible isolated showers across the E Gulf, the Yucatan
Channel and the Florida Straits. A weakness in the ridge analyzed
as a surface trough along the SE coast of Florida into the
Straits of Florida may enhance the shower activity for the SE
Gulf. Otherwise, low level moisture convergence support isolated
showers over Louisiana adjacent waters as indicated by radar
imagery. The next cold front will come off the coast of Texas
Monday morning, extend from the Florida Big Bend SW to near
Tuxpan, Mexico Tuesday morning and then is expected to stall over
South Florida to the central Gulf waters Wednesday. Remnants of
the front will lift N late on Wed, with strong NE winds
developing across the NW Gulf waters.


A broad middle to upper level ridge centered over the south-
central waters covers the Caribbean. Diffluent flow in the western
periphery of this ridge along with moderate to high low level
moisture support scattered showers within 175 nm west of a surface
trough that extends along Nicaragua, Costa Rica and northern
Panama adjacent waters. Isolated showers are elsewhere west of
75W. The tail of a weakening stationary front extends across the
Windward Passage to near 18N80W supporting isolated showers in
that region and over portions of Hispaniola. Shallow moisture in
the trade winds may support scattered to isolated showers across
Puerto Rico and adjacent waters. Otherwise, strong high pressure
over SW N Atlc waters supports fresh to near-gale force winds in
the south-central basin, increasing to gale-force off the coast of
Colombia tonight through Sunday morning. See the Special Features
section for more details.


Partly cloudy skies prevail across the island as the tail of a
weakening stationary front extends across the Windward Passage
towards western Jamaica adjacent waters. Isolated showers are
occurring along the northern half of the Island. Similar weather
conditions are forecast through Sunday morning as the front
dissipates. Fresh northeasterly winds will continue across the
Windward Passage through tonight and then it will limit to the
Atlc approaches as the ridge slides towards the central Atlc


Strong high pressure covers the SW N Atlc waters being anchored by
a 1026 mb high near 29N72W. A weakness in the ridge is analyzed as
a surface trough along the SE Florida coast SW towards the Straits
of Florida. This surface feature in underneath diffluent flow
aloft between a trough over the Gulf and a broad ridge covering
the Caribbean Sea. This scenario support cloudiness and possible
isolated showers in the northern Bahamas, the Great Bahama Bank
and the straits. A broad middle to upper trough over the north-
central Atlc with base near 30N continue to support a cold front
that extends from 30N47W SW to 22N59W to 21N67W. From 21N67W, the
front transitions to a weakening stationary front that traverses
the Windward Passage. Scattered to isolated showers are N of 24N
between 40W and 55W. The remaining eastern Atlc is under the
influence of the Azores high that extends a ridge axis near 23N.
The front in the central Atlc will continue to weaken as it loses
support from aloft. A remnant surface trough is forecast in the
central waters by Monday morning. The next cold front will exit
the NE Florida coast Tuesday afternoon.

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