Tropical Weather Discussion
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AXNT20 KNHC 090510

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1210 AM EST Sat Dec 9 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 0000 UTC surface analysis and satellite imagery through
0415 UTC.

A 1007 mb low is centered NE of the Tampa Bay region near 28N84W
with the associated cold front extending S-SW to the coast of the
Yucatan peninsula near 22N88W to across northern Guatemala. Strong
high pressure is building in west of the front across the western
and central Gulf waters maintaining a strong pressure gradient
and resulting near gale to gale force NW to N winds generally S of
26N W of the front. As the front moves eastward...the near gale to
gale force conditions are expected to persist through late
Saturday. Looking the front enters the NW Caribbean Sea
and then begins to stall across the SW Caribbean waters...near
gale to gale force N winds are again forecast W of the front in
the offshore waters off the coast of Nicaragua. See the latest
NWS High Seas Forecast under AWIPS/WMO headers MIAHSFAT2/FZNT02
KNHC for more details.

The monsoon trough extends from the African coast near 10N14W to
06N23W. The Intertropical Convergence Zone axis extends from
06N23W to 03N30W to 03N40W. Widely scattered moderate convection
is from the Equator to 06N between the Prime Meridian and 11W.


The main feature across the basin is the Special Features 1007 mb
low and frontal system that extends across eastern Gulf this
evening. Aside from the near gale to gale force wind field...
scattered showers and tstms are occurring S of 30N W of the front
across the SE Gulf and Florida peninsula. The cold front is
expected to clear the basin by late Saturday with strong to near
gale NW winds continuing across the southeastern two-thirds...
gradually diminishing from the NW through Sunday. Thereafter...
gentle to moderate N winds will prevail as high pressure builds in
across the western waters early next week.

Divergent middle to upper level flow is noted over the western
Caribbean between the strong upper level troughing over the
western Gulf of Mexico and an upper level anticyclone centered
over northern Colombia. Increased moisture and cloudiness
continues to support widely scattered showers and isolated tstms
generally between 75W-85W this evening focused on a surface trough
analyzed from 10N81W to 17N80W. This area of troughing will linger
across the SW Caribbean until Saturday night and then likely merge
with the cold front that is expected to impact the NW and far
western waters Saturday and Saturday night. The front is forecast
to stall across the western Caribbean through Tuesday and
gradually weaken by mid-week. Farther east...a surface trough
extends from 13N59W near Barbados to 15N69W. Isolated showers are
occurring within 75 nm either side of the trough axis and will
remain embedded within fresh to strong trades on the southern
periphery of a ridge anchored across the central Atlc. The trades
will weaken gradually across the eastern Caribbean by Sunday as
the ridge weakens and retreats northward.

Fair weather conditions prevail across the island this evening as
a surface high centered in the central Atlc extends ridging
across the area. Isolated showers however are occurring across the
southern adjacent waters in association with a diffuse remnant
frontal boundary.

Southwesterly flow aloft is noted on water vapor imagery over the
SW North Atlc between a middle to upper level trough over the
eastern CONUS and Gulf of Mexico and an upper level ridge anchored
over the central and western Caribbean Sea. The troughing
supports the 1007 mb Special Features low and frontal boundary
centered in the vicinity of the Tampa Bay region...however a
stationary front meanders across the northern Florida peninsula
and into a 1008 mb low centered near 32N78W. Scattered showers and
tstms are occurring generally within 120 nm either side of the
front as the entire system moves rapidly off to the NE.
Otherwise...the remainder of the SW North Atlc waters are under
the influence of a surface ridge anchored by a 1026 mb high
centered near 30N57W. Lastly...water vapor imagery indicates a
cut-off middle to upper level low centered near 28N36W supporting
a nearly collocated 1013 mb low centered near 28N38W. A stationary
front extends from the low to 25N34W then to 18N37W becoming a
surface trough W-SW to 14N50W to 13N61W. Scattered showers and
tstms are occurring from 22N-31N between 28W-40W near the low
center...with isolated showers possible within 90 nm either side
of the surface trough axis. The low is forecast to gradually
weaken through late Saturday night and then drift westward as a
surface trough through Monday.

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