[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 191737
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1237 PM EST SAT NOV 19 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...

An area of low pressure of 1006 mb remains over the SW Caribbean
located near 11N81.5W. Showers and thunderstorms have increased
and become better organized this morning in association with this
system. A cluster of moderate to strong convection is noted within
90 nm SE and 30 nm NW semicircles of low center. Scattered moderate
isolated strong convection is observed elsewhere from 10N to 13N
between 79W and 83W. In addition, scatterometer data and surface
observations indicate that the circulation has become a little
better defined, with fresh to strong winds, mainly in the northern
semicircle of the low due to the pressure gradient between the
low and high pressure to the N. Although environmental conditions
are only marginally conducive for additional development, only a
small increase in the organization of the low could result in the
formation of a tropical depression. This system is expected to
move slowly and erratically during the next few days. The latest
Tropical Weather Outlook gives this system a medium change of
tropical cyclone formation during the next 48 hours.

Gulf of Mexico Gale Warning: A strong cold front is moving across
the Gulf waters. At 1500 UTC, the front extends from the Florida
Panhandle to 25N95W to near Poza Rica, Mexico. Frequent gusts to
gale force are noted behind the front based on surface and buoy
observations. Strong northerly winds are expected over the
northern Gulf in the wake of the front today with building seas up
to 9-10 ft. A sharp ridge is currently building across eastern
Mexico and the western Gulf anchored by a 1039 mb high pressure
over NE Mexico. This will support northerly gale force winds near
Tampico early this afternoon, and spreading southward toward the
area of Veracruz by this evening. Computer model indicates
building seas of 11-12 ft within the area of gale force winds. The
front is forecast to cross the basin today, reaching from the
Straits of Florida to the SW Gulf by Sunday morning. Winds are
expected to diminish below gale force across the SW Gulf on
Sunday. Please refer to the High Seas Forecast product under
AWIPS/WMO headers HSFAT2/AXNT20 KNHC for more details.

...ITCZ/MONSOON TROUGH...

The monsoon trough extends across Africa into the east Tropical
Atlantic near 7N12W to 6N15W where it transitions to the ITCZ and
continues along 5N25W to 9N36W to 7N50W to the coast of Guyana
near 7N59W. Scattered moderate convection is within 90 nm S of
the ITCZ axis between 35W and 39W. No significant convection
elsewhere.

...DISCUSSION...

...GULF OF MEXICO...

A gale warning remains in effect for the west-central and SW Gulf
in association with a strong cold front currently moving across
the area. Please, see Special Features section for details. The
remainder of the Gulf region is under the influence of a ridge.
The pressure gradient between the ridge and a developing low
pressure area over the SW Caribbean is producing an increase in
winds over the SE Gulf, where scatterometer data indicate fresh
NE winds. Doppler Radar shows isolated showers moving westward
across the Straits of Florida. The cold front is forecast to move
across South Florida on Sunday morning. The frontal passage will
be mainly dry, followed by gusty northerly wind and chilly
temperatures on Monday morning.

...CARIBBEAN SEA...

A stationary front extends from the central Atlantic across
Hispaniola into the Caribbean Sea to the coast of Nicaragua near
14N83W. Fresh to strong NE winds are noted per scatterometer data
behind the front, including the Windward Passage and in the lee of
Cuba, particularly N of 18N E of 85W. Winds have also increased S
of Dominican Republic. Scattered showers and thunderstorms are
noted along the frontal boundary, mainly from 15N-17N between
72W-75W, and within about 30 nm either side of the front between
77W-79W. Additional shower and thunderstorm activity is noted
between the front and the developing low pressure over the SW
Caribbean, especially W of 80W to the coast of Nicaragua. Please,
see Special Features section for details on the evolution of the
low pressure. The front is forecast to remain nearly stationary
over Hispaniola on Sunday while gradually dissipate over the
Caribbean Sea. A diffluent pattern aloft is also helping to induce
some shower activity with isolated thunderstorm across the east
and central Caribbean. A ridge from the Atlantic and low-topped
trade wind showers are expected over the Lesser Antilles. A cold
front will move into the NW Caribbean on Sunday followed by fresh
to strong NE winds.

...HISPANIOLA...

Atmospheric conditions across Hispaniola remain very moist and
unstable due to the presence of a frontal boundary. This weather
pattern will persist on Sunday with additional showers and
thunderstorms and the potential for locally heavy rain and flash
flooding.

...ATLANTIC OCEAN...

A cold front, associated with an occluded low pressure system, enters
the forecast region near 31N55W, then continues SW to near 23N61W
where it becomes stationary, extending over Hispaniola and the
Caribbean Sea. A recent Ascat pass indicates fresh to strong
southerly winds just ahead of the front. Scattered showers are
also ahead of the front, but mainly N of 24N. The front will
remain nearly stationary through Monday while gradually weakening.
At the same time, another cold front will move off the NE Florida
coast tonight. This front will extend from 31N68W to the Northern
Bahamas on Sunday, and from 27N65W to the Southern Bahamas on
Monday. Fresh to strong NW winds will follow the second front
tonight and early Sunday. A ridge dominates the remainder of the
east and central Atlantic anchored by a 1029 mb high pressure
located W of the Azores near 38N36W. A surface trough, reflection
of an upper-level low, persists across the Atlantic and stretches
from 26N36W to 22N38W. Some shower activity persists in association
with this trough. Fresh to locally strong easterly winds are
between the trough and high pressure to the N, particularly N of
27N.

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

$$
GR
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