[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 102359
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
659 PM EST SAT DEC 10 2016

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...

...Gulf of Mexico Gale Warning...

A strong area of high pressure is building southward across
eastern Mexico and extends over much of the northern Gulf. The
pressure gradient is strong enough to support gale force winds
mainly south of 22N and west of 94W, with seas ranging between
10-16 FT. The ridge is forecast to shift eastward tonight with
winds dropping below gale force. Please read the High Seas
Forecast product under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for
more details.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough extends across the African Continent reaching
the Atlantic Ocean near 05N11W. The ITCZ begins from 05N11W and
extends through 03N25W to 05N40W. A surface trough is embedded
within the ITCZ extending from 10N30W to 04N30W. Scattered
moderate convection is observed within 90-120 nm north of the
ITCZ between 30W and 45W. Scattered moderate isolated strong
convection was noted from 03N to 06N between 05W and 12W.

...DISCUSSION...

GULF OF MEXICO...

The main concern across the basin is the Gale Warning over Bay of
Campeche. Please refer to the special features section above for
details. A surface ridge extends across the northern Gulf and
inland Mexico anchored by a pair of 1030 mb high pressures centered
just W of Victoria, TX and NW of Tampico, Mexico. Surface
observations indicated a surface trough along the coast from
Corpus Christi, TX to just E of Matamoros, Mexico. Another surface
trough over the Bay of Campeche extends from 24N94W to 19N93W
with scattered showers noted 60 NM either side of the trough. A
stationary front extends across the Yucatan channel. Broken top
overcast low and mid level cloudiness with embedded showers was
noted within 150 NM north of this front affecting portions of
South Florida and the Keys, as well as the northern portion of the
Yucatan Peninsula. A 1606 UTC ASCAT scatterometer pass indicated
20-25 KT winds over the Gulf south of 27N...with isolated 30 KT
winds within 120 NM of 22N91W. Water vapor imagery indicated
mainly zonal WSW flow across the Gulf with deep layered
subsidence noted N of 26N. This area of subsidence was slipping
slowly southward. Winds across the Gulf are forecast to decrease
overnight and veer more to the ESE by late SUN as the frontal
system dissipates over the far NW Caribbean.

CARIBBEAN SEA...

The strongest front thus far this season has slipped into the
Yucatan Channel with mainly low and middle level cloudiness and
isolated showers extending from western Cuba to the Yucatan
peninsula and Belize. Water vapor imagery depicted anticyclonic
flow over most of the basin west of 68W with the center of the
anticyclone near 15N76W. Subsidence N of 17N resulted in fair
skies over most of Cuba, Jamaica and Hispaniola. Over the
central portion of the basin, a surface trough extends from
17N76W to a 1009 mb surface low near 10N80W, or just N of Panama.
An expanding area of showers and thunderstorms were noted from 10N
to 16N between 75W and the coast of Central America. An earlier
1430 UTC ASCAT pass showed 20 to locally 25 KT winds over the
central basin S of 17N and S of 14N east of 70W. Additionally the
data indicated the closed circulation of the 1009 MB low itself.
Trade winds will increase somewhat to 25-30 KT over the south-
central Caribbean tonight into SUN with seas building to 12 FT.
The stationary front over the Yucatan Channel is expected to
dissipate by SUN afternoon.

...HISPANIOLA...

Multilayered cloudiness with embedded showers and an isolated
thunderstorm over the Mona Passage was associated with the
northern extension of the surface trough crossing the western
Caribbean. The 12Z rawindsondes from Santo Domingo and San Juan
showed a weaker than normal trade wind inversion with precipitable
water values of 1.5 inches. This supports the increased shower
activity in the area. Conditions should continue into SUN as an
inverted surface trough north of Puerto Rico moves W across the
area.

ATLANTIC OCEAN...

A cold front extends across the western Atlantic from 32N50W
through 27N65W which becomes stationary near 26N73W then
continues through the central Bahamas to the Florida Straits.
An inverted trough extends north of Puerto Rico from 24N66W to
19N67W with isolated showers. A surface ridge extends across the
remainder of the basin anchored by a weak 1021 mb surface high
centered near 27N45W and a 1026 mb high near 37N24W. The cold
front in the west-central Atlantic is expected to continue moving
east on SUN. As the surface ridge behind this cold front begins to
shift eastward into the Atlantic overnight and into Saturday,
increasing northeasterly winds and building seas are expected
behind the front. Little change is expected elsewhere.

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

$$
Cobb
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