[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 192309
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
609 PM EST Tue Dec 19 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
2315 UTC.

...SPECIAL FEATURES...

...Gale Warning in the Caribbean Sea...

Pulsing nocturnal easterly winds to gale-force are expected again
near the coast of Colombia during the overnight tonight and early
morning hours on Wednesday, particularly from 11N to 13N between
74W and 76W. Expect sea heights to range from 10 to 14 ft within
the area of gale force winds, with a larger area of 8-11 ft seas
extending into the west-central Caribbean. Wind will diminish
below gale-force by early Wednesday afternoon. Thereafter, strong
to near-gale force winds will persist in the area each night this
week. Please read the latest NHC High Seas Forecast under
AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.

...ITCZ/MONSOON TROUGH...

The monsoon trough enters the Atlantic Ocean through Sierra Leone
and continues to 04N28W. The ITCZ extends from 04N28W to northeast
Brazil near 02N51W. Scattered moderate isolated strong convection
is noted from 2N-4N between 6W-11W. Similar convection is near
3.5N14.5W. Scattered moderate convection within about 30 nm on
either side of the trough between 19W-23W, and within 60 nm N of
the ITCZ between 35W-38W.

...DISCUSSION...

...GULF OF MEXICO...

A ridge dominates the Gulf, anchored by a 1023 mb high centered
over the Florida Big Bend. Scatterometer and surface data depict
gentle to moderate anticyclonic flow across the basin. Patchy
dense fog will occur again tonight into the early morning hours
along the Gulf coast from the western Florida Panhandle all the
way westward to across most of the coast of Texas. The visibility
is expected to drop below one mile. Moist air, in a southerly wind
flow, will move across the cooler sea surface to generate this
dense fog over the bays and nearshore coastal waters. Dense fog
advisories are in effect. The high pressure will move eastward
over the next 24 hours. A weak cold front will reach the coast of
Texas Wed, and stall across the northern Gulf by Thursday, then
move north as a warm front late Thursday. A stronger cold front
will reach the NW Gulf on Friday, move SE and reach from the
western Florida Panhandle to the SW Gulf near Veracruz, Mexico by
late Saturday. Fresh southerly return flow is expected across the
western Gulf ahead of the front. Fresh to strong winds and
building seas will follow the front.

...CARIBBEAN SEA...

Please refer to the Special Features section for details about
the gale warning near the coast of Colombia. The most recent
scatterometer data indicated fresh to strong winds across the
basin roughly between 70W and 83W. An altimeter pass indicated
seas of up to 14 ft over the southwest Caribbean in association
with the strong trade winds. Fresh to strong NE to E winds are
expected in the lee of Cuba and across the Windward Passage
through Wed night. Patches of low-level moisture embedded in the
trade wind flow are moving across the area producing isolated to
scattered passing showers. Broad mid to upper-level anticyclonic
wind flow and strong subsidence dominates the entire Caribbean Sea
producing generally dry conditions. However, the trade winds will
continue to carry isolated to scattered showers.

...HISPANIOLA...

As previously mentioned, broad mid to upper-level anticyclonic
wind flow and strong subsidence dominates the entire Caribbean
Sea supporting mostly stable conditions. However, low-topped
trade wind showers will continue to affect Hispaniola from time
to time tonight and Wednesday.

...ATLANTIC OCEAN...

A deep layer trough in the eastern Atlantic is supporting a
stationary frontal boundary that extends from 31N39W to 21N60W.
This front will dissipate over the next 24 hours. Mainly low-
level clouds with isolated showers are along the front. A ridge
is noted in the wake on the front, with a 1023 mb high pressure
center located just E of the NW Bahamas near 26N75W. East of the
stationary front, the Azores high dominates the remainder of the
eastern Atlantic. A second cold front is approaching from the
north, and now crosses Bermuda to near 30.5N80W. The high pressure
is forecast to dissipate as the the second cold front reaches
from 31N58W to the NW Bahamas by Wednesday morning, then the front
will stall and begin to dissipate. Another cold front will reach
the waters E of northern Florida by Thursday morning and extend
from 31N58W to 27N65W to along 27N to near the NW Bahamas.
Moisture associated with this front may reach south Florida on
Friday.

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

$$
GR
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