Tropical Weather Discussion
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621
AXNT20 KNHC 091108
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
608 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 0600 UTC surface analysis and satellite imagery through
0945 UTC.

...SPECIAL FEATURES...
A cold front extends from the Tampa Bay region near 28N83W S-SW
to the coast of the Yucatan peninsula near 21N87W and across to
peninsula to near 18N93W. 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 ahead...as the
front enters the NW Caribbean Sea and then begins to stall across
the SW Caribbean waters...near gale to gale force gusts are
expected off the coast of the Yucatan peninsula and Belize and
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.

...ITCZ/MONSOON TROUGH...
The monsoon trough extends from the African coast near 09N13W to
06N19W. The Intertropical Convergence Zone axis extends from
06N19W to the Equator near 44W. Widely scattered moderate
convection is from the Equator to 05N between the Prime Meridian
and 15W.

...DISCUSSION...

GULF OF MEXICO...
The main feature across the basin is the Special Features cold
front extending across eastern Gulf and central Florida peninsula
this morning. Aside from the near gale to gale force wind field...
scattered showers and tstms are occurring generally within 150 nm
E 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 to SE through Sunday.
Thereafter...gentle to moderate N winds will prevail as high
pressure builds in across the western waters early next week.

CARIBBEAN SEA...
Divergent middle to upper level flow is noted over the western
Caribbean between the strong upper level troughing over the
northwestern 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 W of 76W this morning focused on a pre-frontal surface
trough analyzed from 16N87W to 23N85W. This area of troughing
will linger across the western 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...isolated
showers are possible E of 74W 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.

...HISPANIOLA...
Fair weather conditions prevail across the island this morning 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
boundary.

ATLANTIC OCEAN...
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 Special Features cold front which extends from a 1005
mb low centered off the coast of the Carolinas near 33N77W. The
front extends SW to the Florida peninsula near 29N81W. Scattered
showers and tstms are occurring generally within 120-150 nm E 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 31N56W. Lastly...water vapor imagery indicates a
cut-off middle to upper level low centered near 27N37W supporting
a nearly collocated 1012 mb low centered near 26N37W. A
surface trough extends from the low to 26N34W to 23N34W to 15N40W.
Scattered showers and tstms are occurring from 20N-31N between
27W-39W near and E of the low center. The low is forecast to
gradually weaken through late Saturday night and then drift
westward as a surface trough across the central Atlc through
Monday.

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

$$
HUFFMAN




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