Tropical Weather Discussion
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AXNT20 KNHC 221759

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1259 PM EST Mon Jan 22 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.


Gale Warning: The combination of central Atlantic high pressure
with lower pressures over the NW and central Caribbean Sea will
allow for of A tight pressure gradient will the present NE to E
trades in the SW Caribbean near the coast, and to within about
90 nm of the coast of Colombia, to increase to minimal gale
force beginning late tonight and into Tue morning before
subsiding back to strong winds in the late morning hours. Seas
are expected to building to the range of 10 to 13 ft with these
winds. These winds are expected to pulse back to gale force
again late Tue night into Wed morning. Model guidance indicates
that the pulsing of the strong trades to minimal gale force will
continue through the rest of the week as an area of strong high
pressure from the Gulf of Mexico surges southeastward across the
NW and central Caribbean behind a forecast cold front, with the
associated gradient fairly tight enough to induce these winds in
the upcoming days. Please see the latest NHC High Seas Forecast
under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.

Gale Warning: A gale warning is forecast to become in effect
early on Tue afternoon for the SW Gulf in the wake of the next
cold front that pushed off the coast of Texas this morning, and
is over the NW Gulf coast as of early this afternoon. The cold
front will reach from near SE Louisiana to near Tampico, Mexico
early this afternoon, from the Florida Big Bend to the eastern
Bay of Campeche tonight, from the Straits of Florida to the
Yucatan Peninsula to Veracruz, Mexico on Tue night, then move to
the SE of the area on Wed. Minimal gale force NW to N winds of
25 to 35 kt are forecast for the extreme SW Gulf near the coast
of Veracruz beginning early on Tue afternoon, then diminish to
strong winds late on Tue night. The gale force winds are expected
to return briefly to the same area on Wed night, then diminish
significantly on Thu. Please see the latest NHC High Seas Forecast
under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.


The Monsoon Trough axis extends from far western Africa to the
Atlantic Ocean near 06N09W and continues to 01N19W. The ITCZ
begins near 01N19W and extends to 02N32W to coast of S America
at 01N49W. Scattered moderate isolated strong convection is
within 120 nm N of the ITCZ between 33W-35W. Scattered moderate
convection is elsewhere within 180 nm N of the axis between 33W-
35W, and within 30 nm either side of a line from 02N25W to



A cold front moved off the Texas coast early this morning, and
as of 15Z extends along a position from just E of Lake Charles,
Louisiana to 28N94.5W to Brownsville, Texas. The cold front is
quickly catching up to a pre-frontal squall line that is about
30 nm to its east. Latest mosaic NWS doppler radar imagery shows
scattered showers and isolated thunderstorms along the squall
line. A batch of scattered showers and thunderstorms is
increasing out ahead of the squall line while moving east-
northeastward within 30 nm either side of a line from 30N89W to
28N91W to 26N92W. Behind the front, conditions rapidly dry out
as the leading edge of strong high pressure center over the
western United States is nosing eastward on the heals of the
front. The cold front will reach from near SE Louisiana to near
Tampico, Mexico by early this afternoon, and rapidly reach the
far SE Gulf waters on Tue night, and move to SE of the area on
Wed. The gradient associated with the aforementioned strong high
pressure will support fresh to strong northerly winds over much
of the Gulf through Wed, outside the gale warning portion of the
far SW Gulf as described above under Special Features.


Isolated showers and thunderstorms are seen over portions of the
NW Caribbean assisted by diffluence aloft. Fresh to strong winds
were noted in the latest scatterometer data over much of the
central Caribbean, with the strongest winds confined to along
and near the coast of Colombia. Moderate to locally fresh trades
are noted elsewhere across the basin. The pressure gradient
provided by high pressure N of the area should allow for fresh
to strong NE to E trades to occur W of about 70W elsewhere of
the gale force winds as described above under Special Features
through late Wed night. Strong NE winds are expected through the
Windward Passage after Wed. A cold front that is moving across the
western and central Gulf of Mexico will enter the NW Caribbean
Wed night, followed by increasing strong NE winds and with seas
building to around 10 ft.


Ridging dominates the western Atlantic anchored by a 1025 mb
high pressure center analyzed at 31N60W, with a ridge extending
westward to 31N71W and to the far NE Gulf of Mexico. A large
surface trough extends from near 29N72W to 26N75W to just N of
eastern Cuba at 22N77W. A rather robust mid/upper level trough
is evident on water vapor imagery to extend from a cyclonic
circulation near 33N64W through 32N65W to 26N68W and to eastern
Cuba. Upper-level dynamics related to a jet stream branch that
to the E of the trough is tapping abundant available deep layer
moisture between 64W and 70W resulting in scattered showers and
isolated thunderstorms northward of Hispaniola to 25N, and also
from 20N to 26N between 65W and 70W. Isolated showers and
thunderstorms are elsewhere N of 19N between 60W and 70W, along
with patches of rain. The cyclonic circulation near 33N64W is
forecast to dive southeastward to the central Atlantic near
24N46W by Wednesday, with the mid/upper trough sharpening in
the process. Expect favorable dynamics in play to allow for the
present shower and thunderstorm activity and rain patches to
expand eastward through Wed ahead of the trough as it reaches from
the cyclonic circulation southwestward to near 10N50W at that
time. The 1025 mb high is forecast to slide eastward to just SE of
Bermuda by early on Tue in response to a cold front that
approaches the SE United States. The cold front will move off the
NE Florida coast on Tue afternoon. The front will reach from near
31N73W to the Straits of Florida on Wed morning, and from Bermuda
to central Cuba on Thu morning. Strong NE winds under high
pressure will follow in behind the front. Scattered to numerous
showers and thunderstorms with gusty winds will precede the

To the E, another upper level cyclonic circulation is near
27N42W with a trough stretching to 22N36W and to near 17N30W. At
the surface, a stationary front is located over the E central
Atlantic from near 32N38W to 26N43W to 24N46W where it becomes
fractured to 22N59W. A surface trough is to the SE of the front
from 26N42W to 20N43W. Divergence aloft E of the upper level
cyclonic circulation is helping to trigger off scattered showers
and thunderstorms from 24N to 28N between 37W and 40W. Isolated
showers and thunderstorms are elsewhere N of 23N between 35W and
41W. The upper level cyclonic circulation is forecast to lift
out to the NE through Wed night and weaken while its related
trough dampens out. Isolated showers are near and within about
60 nm N of the fractured frontal boundary. A low-level
disturbance is clearly observed on visible satellite imagery to
be located near 21N63W. It is moving rapidly westward while
weakening. Isolated showers are within 60-90 nm of the

A 1034 mb high pressure system to the NE of discussion is at
38N14W. It extends a ridge southwestward to 32N27W and to near
26N38W. The high will remain nearly stationary over the next 24
hours, then begin to slowly shift southward and weaken

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