[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 311808
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
107 PM EST SAT DEC 31 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 1200 UTC surface analysis and satellite imagery through
1715 UTC.

...SPECIAL FEATURES...

...Caribbean Sea Gale Warning...

The pressure gradient between high pressure over the southwest
North Atlantic and lower pressures of Colombia will result in
an area of gale force winds and seas of 10 to 13 FT over the
southwest Caribbean from 11N to 13N between 73W and 76W beginning
around 0000 UTC. Please refer to the HIGH SEAS FORECAST...MIAHSFAT2/FZNT02
KNHC...and the OFFSHORE FORECAST...MIAOFFNT3/FZNT23 KNHC...for
more details.

...THE MONSOON TROUGH/THE ITCZ...

The Monsoon Trough passes through the southernmost part of
Liberia, to 04N11W. The ITCZ continues from 04N11W to 02N25W
01N40W and 01S46W. Scattered moderate isolated strong convection
from 02N to 05N between 33W and 46W. Scattered moderate convection
elsewhere from 05N to the equator W of 28W.

...DISCUSSION...

...THE GULF OF MEXICO...

Broad mid- to upper level anticyclonic W to NW flow spans the
entire Gulf of Mexico with moderate to strong subsidence covering
the area S of 25N. Deep layered moisture was noted over the Gulf N
of 28N. A stationary front was forming along the Gulf coast from
near Pensacola Florida westward to the upper Texas coast with an
area of low pressure, 1012 MB developing off Corpus Christi as of
15 UTC. A cluster of 1025 MB surface high pressures off the
Carolinas has allowed S to SE return flow to increase over most of
the Gulf with several elevated platforms reporting winds of 25
KT. Enhanced low level convergence along the stationary front
on the Gulf coast was resulting in very heavy rainfall along the
Texas and southwest Louisiana coasts. Low pressure along the
Texas coast is forecast to track northeast to interior Mississippi
with fresh to locally strong southerly winds spreading across
the Gulf.

...THE CARIBBEAN SEA...

Broad anticyclonic flow covers most of the Caribbean W of 75W
which became more confluent and generally W to NW over the eastern
part of the basin. Strong deep layered subsidence was noted over
virtually the entire basin. Patches of scattered to broken low
level clouds and possible showers were noted in the area from 15N
to 18N between 70W and 82W, including Hispaniola and the Windward
Passage. An additional area of showers was noted over the Windward
and Leeward islands extending over the Virgin Islands.
Scatterometer data indicated moderate to fresh trade winds over
the NW and south-central portions of the basin. The area of
forecast gale force winds was missed by the scatterometer pass.
Little change is expected over the basin as gale force winds
intermittently pulse in the area from 11N to 13N between 73W and
76W. Refer to the special features section for additional
details.

...HISPANIOLA...

Upper level WNW winds and fairly deep layered subsidence was noted
over Hispaniola in water vapor imagery. The 12Z Santo Domingo
rawindsonde indicated a moist atmosphere up to 700 MB with
precipitable water values of 1.7 inches. This could result in
enhanced showers over the island later this afternoon despite
the drying aloft.

...THE ATLANTIC OCEAN...

A broad upper level trough was over the southwest N Atlantic
N of 25N between 55W and 70W was gradually lifting out to the NE
as ridging builds in behind it. Strong subsidence remained in the
wake of the trough N of 28N. This trough supports a cold front
extending through 32N56W to 23N66W, which became stationary and
extended through 22N70W to near the windward passage. Broken to
locally overcast low and mid clouds defined the front with
embedded showers. A cluster of 1025 MB high pressures extending
from S Carolina to 32N72W cover the NW portion of the discussion
area in the wake of the cold front.

A narrow upper level trough extends from a cyclonic circulation
near 31N43W through 23N43W to 18N41W. Associated mid and high
level clouds cover the Atlantic Ocean from 22N to 30N between 32W
and 45W. Further east, an upper level trough extends through
32N23W to 28N35W. A surface trough extends from a 1014 mb low
pressure center near 34N23W, through 30N20W and 25N22W. No
significant deep convective was noted. Surface anticyclonic flow
covers the Atlantic Ocean from 15N northward between 28W and 60W.
A 1025 mb high pressure center is near 31N45W.

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

$$
Cobb
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