[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 040000
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
700 PM EST TUE JAN 3 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.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough extends to the coast of Liberia and Sierra
Leone and becomes ill defined over the tropical eastern Atlantic
Ocean. The ITCZ is analyzed 03N20W through 02N35W to the northeast
coast of Brazil near 01S45W. No significant convection was
associated with the ITCZ.

...DISCUSSION...

GULF OF MEXICO...

Broad mid-to upper level ridge characterized by NW flow
dominated the entire Gulf of Mexico and was anchored by an
anticyclone over Mexico and the Ithsmus of Tehuantepec. Strong
subsidence prevailed over the southwestern half of the basin with
mid to upper level moisture noted over the remainder of the basin.
At the surface, a dissipating cold front extended from Cedar Key,
Florida to 26N89W which transitioned to a dissipating stationary
front to 24N96W as of 2100 UTC. A weak 1016 MB high pressure was
noted near 25N84W and another high pressure area, 1015 MB was
noted just off the SE Texas coast. The weak pressure gradient was
characterized by light but shifting winds over the Gulf with
scattered to locally broken low clouds in the vicinity of the
front. A stronger cold front currently located over Texas and NW
Louisiana is forecast to sweep rapidly southeast into the far NW
Gulf overnight tonight and extend from the Florida Big Bend to
extreme NE Mexico by midday Wed with an increase in NW to N
winds.

CARIBBEAN SEA...

Water vapor imagery shows strong subsidence in mostly moderate to
strong west to northwesterly flow over the entire Caribbean basin.
This flow was being induced by general troughiness over the basin.
At the surface, the pressure gradient generated by the
interaction of a ridge north of the Caribbean and lower pressures
prevailing north of South America is supporting fresh to strong
easterly winds over the central sections of the basin. A 1432 UTC
ASCAT pass showed an area of 20-25 KT winds over the basin from
11N to 17N between 67W and 80W. Little change in the overall
pattern is expected over the next 24 hours.

HISPANIOLA...

Water vapor imagery indicated a shortwave trough just to the
N of Hispaniola with moderate to strong westerly flow over the
Island. Broken to overcast mid and upper clouds were spreading
over the area with an isolated thunderstorm over the interior.
The 12Z rawindsonde from Santo Domingo showed a modest trade
wind inversion with precipitable water values of 1.25 inches.
NW winds at 200-250 MB were close to 80 KT. The shortwave trough
is expected to pass to the N of the island Wed with some drying
aloft.

ATLANTIC OCEAN...

A broad middle/upper level trough covers the central and east
central Atlantic north of 20N between 35W and 70W. A strong upper
level jet originates near 7N60W and extends through 12N50W to
21N35W to the African coast at 26N with satellite derived winds
indicating speeds of 100 to 120 KT. Broad ridging aloft covers
the eastern Atlantic. At the surface, a ridge prevails across the
western Atlantic W of 50W. A frontal system was analyzed as a
weakening stationary front from 29N23W through 24N35W to 22N47W.
A reinforcing cold front entered the area and extended through
32N35W to 28N50W. Scattered showers are observed along and within
90 NM east of this cold front.

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

$$
Cobb
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