[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 270903
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
403 AM EST Sat Jan 27 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 0600 UTC surface analysis and satellite imagery through
1145 UTC.

...SPECIAL FEATURES...

Atlantic and Gulf of Mexico Gale Warning: The pressure gradient
has significantly tightened between a cold front that extends from
32N49W to 27N54W to 24N63W where it becomes a weakening cold front
to 23N65W, then and a dissipating stationary front to 22.5N74W
and very strong high pressure of 1040 mb centered N of the area
at 36N73W. This tight pressure gradient has induced a large area
of near gale to minimal gale force NE to E winds over the waters
between the front and the Bahamas S of about 27N. Seas are in the
range of 12 to 16 ft with these winds, and are forecast to build
slightly higher today through Sun. As of late Fri night, a new
gale warning was issued for frequent gusts for the waters W of
the Bahamas including the Straits of Florida and far eastern Gulf
of Mexico near 83W. Ascat and ship data from late last night
indicated that winds over the affected gale winds waters had
increased to near gale force with frequent gusts. Seas associated
with these gale force winds are in the 10 to 15 ft range. Strong
NE to E winds are elsewhere W of the front, including through the
Atlantic passages in the Bahamas. The latest model guidance
indicates that these winds will be slow in diminishing, and as per
the latest issued forecasts, these winds are forecast to lessen
to just below gale force on Sun afternoon over the waters E of the
Bahamas to the frontal system mentioned above. The gale force
winds W of the Bahamas that include the Straits of Florida and far
eastern Gulf of Mexico are forecast to diminish late on Sat to
strong NE to E winds. Seas will still be on the high range
possibly reaching up to 14 ft at that time. By late Sun, these
winds and seas diminished considerably. Please see the latest NHC
High Seas Forecast under AWIPS/WMO headers Misfit/FZNT02 KNHC for
more details on this event.

Caribbean Gale Warning: The combination of very strong high
pressure centered E of the mid-Atlantic states and lower pressure
over South America is bringing minimal gale force NE to E winds
near the coast of Colombia. These conditions will persist late at
night into the early morning hours through Mon. Please see the
latest NHC High Seas Forecast under AWIPS/WMO headers
MIAHSFAT2/FZNT02 KNHC for more details on this event.

Far E Atlantic Gale Warning: Another very strong high pressure
system, this one of 1041 mb is centered NE of the Azores near
40N21W. The tight pressure gradient to its SE and S is allowing
for NE gale force winds that reach to strong gale force over Meteo
France marine zones of Agadir, Tarfaya and to near gale force NE
winds over Canarias except for strong gale force winds over the
eastern portion of that zone. NE winds are reaching near gale
force at times over zone Cap Blanc. These conditions are expected
through Sat evening. With the tight gradient not expected to
slacken in the short term, the gale conditions for Agadir, Tarfaya
and the near gale to gale for Canarias are forecast to continue
through Sun night. Please refer to Meteo France Weather Bulletins
for more information.

...MONSOON TROUGH/ITCZ...

The Monsoon Trough axis extends from the coast of Africa at
06N10W to 05N14W where the latest scatterometer data indicates
the ITCZ begins and continues to 02N23W to 01N30W to just below
the Equator at 34W. Scattered strong convection is within 120 nm
S and 60 N of the axis between 32W-34W, and W of the axis S of 01N
between 34W-40W. Scattered moderate isolated strong convection is
within 120 nm S and 180 N of the axis between 12W-19W, and also
between 22W-29W. Scattered moderate convection is within 150 nm S
and 120 N of the axis between 25W- 28W. Scattered moderate
convection is within 120 nm either side of the axis between 10W-
12W.

...DISCUSSION...

GULF OF MEXICO...
Please see the SPECIAL FEATURES section above for details about
regarding the gale conditions in the far SE Gulf.

Strong surface high pressure centered near the northeastern
United States is supporting a large area of strong E winds over
much of the eastern and central Gulf of Mexico. The exception is
in the far SE Gulf and Straits of Florida where strong E winds are
gusting frequently to gale force. These winds are forecast to
diminish late on as the strong ridging over the eastern Gulf
begins to weaken some. A surface trough has become evident over
the far NW portion from 28N95W to 26N95.5W in response to an
upper shortwave trough that is beginning to swing northeastward
around the base of a longwave trough that is moving through the
central U.S. Scattered showers and isolated thunderstorms along
with patches of rain have increased over much of the gulf during
the overnight hours. This activity is quickly moving east-
northeastward. Scattered showers and isolated thunderstorms have
recently developed over the SW Gulf just to the E of a surface
trough that extends from 21N96W to 19N92W. Strong winds are
expected to continue over the eastern Gulf today. A rather
progressive upper level pattern will bring surface low pressure
southeastward towards the area of southeastern Louisiana or
southwestern Mississippi early tonight, with a trailing cold
front across the NW Gulf waters. The low is forecast to
rapidly move across the NE Gulf on Sun while pushing the
cold front across the eastern gulf waters through early on Mon.
Expect widespread rain along with scattered showers and isolated
thunderstorms with system.

CARIBBEAN SEA...
Please see the SPECIAL FEATURES section above for details about
regarding the gale conditions near the coast of Colombia.

The Ascat pass from late last night clearly revealed an impressive
swath of strong to near gale force NE winds to the lee of Cuba.
Fresh to strong trades are occurring elsewhere across the basin,
except for the gale force winds near the coast of Colombia
as described above under SPECIAL FEATURES. Latest satellite
imagery shows scattered showers and isolated thunderstorm
over the far western Caribbean Sea close to the coasts of
Honduras including the Gulf of Honduras. Similar activity is over
the waters between Jamaica and 82W. Isolated showers and
thunderstorms are noted over the Yucatan Peninsula, northern and
eastern Honduras and eastern Nicaragua. Since the surface pattern
is expected to change very little through Sun, strong trade wind
flow is forecast to continue during the next couple of days.
Expect increasing low-level moisture along with scattered showers
to impact the NE Caribbean and islands in that location including
Puerto Rico through Sun night as a decaying frontal boundary over
the central Atlantic drops southward towards the NE Caribbean and
strong to near gale force NE winds advect the associated moisture
and shower activity towards that section of the Caribbean.

ATLANTIC OCEAN...
Please see the SPECIAL FEATURES section above for details about
the gale conditions over portions of the waters between the
Bahamas and a central Atlantic cold front.

A cold front enters the discussion area through 32N49W to 27N54W
to 24N63W where it becomes a weakening cold front to 23N65W, then
and a dissipating stationary front to 22.5N74W. Meanwhile, very
strong high pressure of 1040 mb is centered within about 110 nm E
of the northern coast of N Carolina. The resultant tight gradient
has increased the NE to E winds between the front and the Bahamas
to the ranges of near gale to minimal gale force and along with
large seas. These conditions are expected to continue into early
Sun afternoon. Scattered showers are within 60 nm either side of
the front. The stationary portion of the front is forecast to
continue to weaken through the weekend. The frontal remnants will
drift southward towards the NE Caribbean Sea islands, most likely
as a shearline. Precipitable water GFS model guidance indicates
that moisture and precipitation will increase for the NE Caribbean
islands through the weekend. before diminishing late Sun.

Farther east, a 1041 mb high pressure system centered near 40N21W
dominates the area E of the cold front maintaining rather stable
weather over much of the central and eastern sections of the area,
except for the far eastern portion S of 24N and E of 40W where
abundant mid and upper level clouds are streaming eastward towards
Africa ahead of a mid to upper level trough located N of 15N
between 30W and 40W.

For additional information please visit http://www.hurricanes.gov/marine

$$
Aguirre
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