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548
AXNT20 KNHC 162258
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
658 PM EDT Wed Aug 16 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
2215 UTC.

...SPECIAL FEATURES...
Hurricane Gert is centered near 38.7N 62.4W at 16/2100 UTC or
about 355 nm S of Halifax Nova Scotia and about 630 nm SW of Cape
Race Newfoundland moving NE at 27 kt. Estimated minimum central
pressure is 970 mb. Maximum sustained wind speed is 85 kt with
gusts to 105 kt. Scattered to numerous moderate convection is from
37N-42N between 58W-65W. Widely scattered moderate convection is
elsewhere from 35N-44N between 53W-66W. See latest NHC forecast/
advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more
details.

A tropical wave extends from 14N37W to 24N37W moving W at 10-15
kt. A 1009 mb low is centered at the southern extent of the wave
axis that coincides with maximum low to mid-level 700-800 mb
relative vorticity. Scattered moderate convection is from 14N-16N
between 38W-40W.

A 1009 mb low is centered near 14N49W moving W at 10-15 kt. This
low is also a focus of 850 mb relative vorticity on the southern
periphery of a mid-level ridge anchored over the central Atlc to
the N. Scattered moderate convection is from 12N-16N between
49W-54W.

...TROPICAL WAVES...
A tropical wave extends from 09N18W to 21N14W moving W at 10-15
kt. The wave coincides with broad 700 mb troughing between 13W-27W
that continues to emerge off the coast of West Africa this
evening. A pair of surface lows...one a 1008 mb low centered near
17N18W and the other a 1010 mb low centered at the southern extent
of the wave axis near 09N18W indicates the northern and southern
vortices respectively and the broad nature of spin in the local
environment surrounding the wave. Last evening...very strong and
intense convection was occurring...however this evening only
widely scattered moderate convection is noted from 06N-13N between
12W-22W.

A tropical wave extends from 10N64W to 22N60W moving W at 20-25
kt. The wave coincides with 700 mb troughing between 59W-70W that
continues to provide a favorable environment for scattered
moderate convection from 13N-22N between 58W-68W. This area of
convection also falls within the eastern periphery of an upper
level low noted on water vapor imagery centered near 20N72W.

A tropical wave extends from 10N84W to 21N83W moving W at 15-20
kt. The wave is noted on the southeastern periphery of a 700 mb
ridge anchored over the Gulf of Mexico near 27N87W. Widely
scattered moderate convection is from 09N-17N between 79W-87W.

...ITCZ/MONSOON TROUGH...
The monsoon trough extends from the African coast near 11N15W to
08N21W to 11N30W. To the west...the monsoon trough and ITCZ is
disrupted due to the tropical lows and tropical waves mentioned
above. Otherwise...scattered moderate convection is from 06N-10N
between 25W-31W...and from 06N-09N between 35W-50W.

...DISCUSSION...

GULF OF MEXICO...
Upper level divergent flow persists over the lower Mississippi
River valley this evening between a broad upper level low
centered in the western Gulf near 23N93W and an upper level
anticyclone centered near 31N81W. Scattered showers and tstms are
mainly occurring across inland portions of extreme eastern
Texas...Louisiana...and Mississippi...with only a few isolated
showers and tstms noted across the NW Gulf waters N of 26N W of
92W. This activity all lies on the northern side of a surface
ridge extending east to west along 27N/28N and anchored by a 1020
mb high centered near 28N87W. Mostly light to gentle anticyclonic
flow is E of 90W and gentle to moderate S-SE flow is W of 90W.
The high is expected to persist across the NE Gulf waters through
early Saturday. A surface trough will develop each evening across
the Yucatan peninsula shifting W into the Bay of Campeche during
the overnight hours. Locally higher winds can be expected in the
vicinity of the trough axis.

CARIBBEAN SEA...
A tropical wave is analyzed across the western Caribbean this
evening generating scattered showers and tstms across the Gulf of
Honduras region and inland portions of Central America. Overall
middle to upper level divergence is noted to the E of the wave
axis over the SW Caribbean producing widely scattered showers and
isolated tstms S of 13N between 72W-84W. Elsewhere...scattered
showers and tstms have likely peaked in intensity across Cuba and
continue moving offshore into the NW Caribbean waters. With the
loss of daytime heating and instability...this activity will
gradually decrease and then dissipate tonight. Farther east...
another tropical wave is impacting the eastern Caribbean with
scattered showers and tstms remaining E of 70W. Much of this
activity is being enhanced by an upper level low centered N of
Hispaniola near 20N72W. Otherwise...fresh to strong winds in the
south-central waters and in the vicinity of the tropical wave in
the eastern waters are expected through Thursday...with moderate
to fresh trades elsewhere.

...HISPANIOLA...
An upper level low is centered N of the island near 20N72W and
is providing overall dry conditions this evening...however a
tropical wave extends across the eastern Caribbean Sea and will
move across the island through Friday. Scattered showers and tstms
are expected to spread westward from the Mona Passage region
tonight to the Windward Passage region by Thursday night into
Friday.

ATLANTIC OCEAN...
Widely scattered showers and isolated tstms remain N of 27N
between 65W and 77W associated with frontal troughing extending SW
from Hurricane Gert centered N of the discussion area.
Otherwise...the remainder of the basin generally N of 23N is
under the influence of the Azores subtropical high which supports
fair weather. A 1025 mb high is centered S of the Azores near
35N27W and a 1025 mb high is centered near 32N43W.

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

$$
HUFFMAN