[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181725
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1225 PM EST FRI NOV 18 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...

Gulf of Mexico Gale Warning: A strong cold front will enter the
northwest Gulf of Mexico this evening, and cross the central Gulf
on Saturday, then extend from the Straits of Florida to the SW
Gulf near 21N95W to the central Bay of Campeche early Sunday
morning. Strong NE winds are expected over the northern Gulf in
the wake of the front with building seas up to 9-10 ft. Strong
high pressure of 1038 mb behind the front will extend a ridge
across eastern Mexico and the western Gulf. This will support
northerly gale force winds beginning early Saturday just N of
Tampico, and spreading southward toward the area of Veracruz by
Saturday evening. Computer model indicates building seas of 11-12
ft within the area of gale force winds. 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 11N15W to 8N18W where it transitions to the ITCZ
and continues along 9N25W to 10N32W to 7N50W to the coast of
Guyana near 8N59W. Scattered moderate to isolated strong convection
covers the area from 6N-10N between 19W-28W. Scattered moderate
convection is from 7N-10N between 30W-40W.

...DISCUSSION...

...GULF OF MEXICO...

A gale warning is already in effect for the west and SW Gulf in
association with a strong cold front. Please, see Special Features
section for details. A relatively dry and stable airmass remains
in place over the Gulf of Mexico. Currently, Doppler Radar shows
scattered showers and isolated thunderstorms over the NW Gulf
under a southerly return flow. Isolated showers are noted moving
westward across the Straits of Florida. A 1023 mb high pressure
located over the State of Georgia extends a ridge across most of
the Gulf region. This will support moderate to locally fresh E-SE
wind flow across the area the rest of today.

...CARIBBEAN SEA...

A stationary front extends from the west Atlantic across Hispaniola
into the Caribbean Sea to near the Honduras/Nicaragua border.
Fresh to strong NE winds are noted per scatterometer data behind
the front, including the Windward Passage and in the lee of Cuba.
The front is generating scattered showers and thunderstorms over
the area from 15N-18N between 79W-82W. The front is forecast to
remain nearly stationary over Hispaniola over the weekend while
gradually dissipate over the Caribbean Sea. South of the front, a
broad area of low pressure persists. At 1200 UTC, a 1006 mb low
pressure is analyzed near 11N82W. This system continues to produce
disorganized cloudiness and showers over the southwestern
Caribbean Sea, and winds remains light in the area. Upper-level
winds have become less conducive for tropical cyclone formation,
and during the next couple of days any development should be slow
to occur. After that time, environmental conditions are expected
to be more conducive for gradual development, and a tropical
depression could form early next week while the low moves slowly
and erratically. A cluster of moderate to isolated strong
convection is noted within about 120 nm NW quadrant of low, over
the Atlantic coast of Nicaragua from 12N-14N. A surface trough
extends along 69W N of 14N to NE Dominican Republic. Clusters of
moderate to isolated strong convection are associated with this
trough affecting parts of Puerto Rico, the Mona Passage and
eastern Dominican Republic. The San Juan Doppler Radar now
indicates that the stronger shower and thunderstorm activity is
more concentrated across the Caribbean waters. The trough will
drift westward. The combination of the stationary front and the
trough will provide all the ingredients necessary to maintain a
very unstable atmosphere with scattered to numerous showers and
isolated to scattered thunderstorms over parts of Puerto Rico and
Hispaniola during the weekend. 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...

As previously mentioned, atmospheric conditions across Hispaniola
are forecast to remain very moist and unstable during the weekend
with the potential to produce scattered to numerous showers and
isolated to scattered thunderstorms. Upper diffluence is also
helping to induce convection across the island. Please, see the
Caribbean Sea section for more details.

...ATLANTIC OCEAN...

An upper-level trough over the west Atlantic supports a cold
front that enters the forecast region near 31N59W, then continues
SW to near 23N64W where it becomes stationary, extending over
Hispaniola and the Caribbean Sea. A 150nm-wide band of cloudiness
with embedded showers and isolated thunderstorms is associated
with the front, forecast to reach from 31N56W to northern
Hispaniola by early Saturday morning, and from 31N54W to NE
Dominican Republic by early Sunday morning. A pre-frontal surface
trough extends from 23N64W to the north-central coast of Puerto
Rico, generating scattered showers and isolated thunderstorms. A
large surface ridge dominates the remainder of the east and
central Atlantic anchored by a 1030 mb high pressure located NW of
the Azores near 40N36W. A surface trough, reflection of an upper-
level low, persists across the Atlantic and stretches from 27N32W
to 22N34W. Some shower activity is associated with this trough. A
strong cold front will move off the northeast Florida coast
Saturday night and extend from 31N68W to northern Bahamas on
Sunday. Fresh to strong NW winds will follow the front Saturday
night and early Sunday.

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

$$
GR
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