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Atlantic Tropical Weather Discussion



421 
AXNT20 KNHC 161804
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
204 PM EDT Mon Jul 16 2018

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 
1745 UTC.

...SPECIAL FEATURES...

SW Caribbean Sea gale warning: The synoptic pattern set-up with 
strong high pressure situated over the central Atlantic interacting
with broad low pressure over the SW Caribbean Seas and over 
northern S America will allow for the ongoing strong to near gale
force NE to E strong winds near the coast of Colombia from 11N to
13N between 74W and 76W to again reach minimal gale force 
Tue night and Wed night over the same area along with seas in the 
range of about 9-13 ft. Please read the High Seas Forecast, under
the AWIPS/WMO headers HSFAT2/FZNT02 KNHC, for more details.

...TROPICAL WAVES...

An eastern Atlantic tropical wave axis stretches from near 23N38W
to 15N40W and to 05N42W, moving westward at 15-20 kt. The 
wave is depicted on GOES-16 RGB imagery as having a rather broad 
inverted-V shape envelope of broken to overcast of mainly 
stratocumulus clouds covering over an area from 09N-23N between 
30W-50W. Scattered moderate convection is behind the wave along 
and within 60 nm either side of the ITCZ between 35W-40W.
Scattered showers and isolated thunderstorms are ahead of the 
wave from 06N-09N between the wave and 44W. The GOES-16 RGB 
images along with visible images of the far eastern Atlantic are 
depicting yet another massive plume of Saharan dry air and associated
dust following in behind the wave from 09N-27N east of 36W to 
well inland Africa, where even more intense Saharan dust is being
captured by the GOES-16 imagery behind and around another 
tropical wave. Visibilities within these areas of dust are 
expected to be sharply reduced.

An eastern Caribbean Sea tropical wave is tilted NE to SW with its 
axis reaching from Puerto Rico to just inland the coast of 
Venezuela at 11N69W, moving westward at about 20 kt. This wave 
continues to be impinged upon by Saharan dust as observed in 
GOES-16 satellite imagery. Scattered showers and isolated 
thunderstorms moving quickly west-northwestward are seen north of 
15N between 67W-72W, while isolated showers also moving quickly 
west-northwestward are seen north of 13N and east of 74W to 
vicinity of the Leeward Island and northern Windward Islands. This
wave will move across the rest of the eastern Caribbean Sea 
through by early Tue, then across the central Caribbean Sea 
through Wed night and the western Caribbean Seas Thu through Fri 
before moving inland Central America and the Yucatan Peninsula Fri
night. The Saharan dust in its wake will filter across the 
eastern Caribbean and much of the central Caribbean through Wed.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of southern Guinea
Africa to 07N17W and to 08N26W, where latest scatterometer data 
indicate that it transitions to the ITCZ and continues to 08N33W
to 06N41W and to near 05N51W. Aside from the convection near the
eastern Atlantic tropical wave, scattered moderate convection is 
within 60 nm north of the ITCZ between 44W-51W. Similar activity 
is to the NW of the ITCZ from 05N-07N between 51W-57W. 

...DISCUSSION...

GULF OF MEXICO...

A 1019 mb high centered over the central gulf waters near 26N91W,
and is the main feature that is influencing the synoptic pattern 
across the basin. Its associated gradient is allowing for 
generally light to moderate anticyclonic flow to exist over the 
gulf waters. Current NWS mosaic radar displays show scattered 
to numerous showers and thunderstorms rapidly increasing over the
far northern gulf north of 28N between 86W-90W. This activity is 
expected to remain active through at least the next couple of days
as upper-level disturbances move from E to W around the eastern 
periphery of an upper-level anticyclone centered over western 
Texas. Isolated showers and thunderstorms moving westward are 
present over much of the eastern gulf waters as well as over the 
eastern half of the central gulf. This activity should continue 
through tonight and into Tue. Expect high pressure to prevail 
across the northern waters through Thu. A surface trough will move
westward off the Yucatan Peninsula each evening through Thu, 
enhancing nocturnal winds over the eastern section of the SW Gulf.

CARIBBEAN SEA...

Please read the Special Features section for details about
pulsing gale force winds near the coast of Colombia. Aside from 
the tropical waves mentioned above, an upper level low is noted 
on water vapor imagery just to the south of the Yucatan Channel.
A rather dry and stable environment is only for isolated showers 
moving quickly with the trade wind flow to occur across much of 
the basin. Mainly fresh E winds will continue over the central 
Caribbean Sea through Thu, with the exception of strong NE-E winds
in the SW and S central sections of the Caribbean outside the 
near gale to minimal gale force wind area described above.

ATLANTIC OCEAN...

A weak surface trough extends from near 32N78W southwestward to
just east of NE Florida. Scattered showers and isolated
thunderstorms are seen north of 28N between 72W and 79W. Another
surface trough extends from near 32N60W to 29N67W and
northwestward to near 32N76W. Scattered moderate isolated strong 
convection is along and within 90-120 nm SE of this trough 
between 60W-64W while isolated showers and thunderstorms are along
and within 60 nm SE of the trough between 64W-75W. This trough 
will slowly weaken through Tue as the supporting upper trough 
lifts to the NE away from it. High pressure will build in the wake
of the trough. A large area of Saharan Air Layer (SAL) dust
that is currently over the central Atlantic from 08N-24N and 
between 45W-60W will continue to translate westward through the 
rest of the week. A weaker area of dust is visible from the SE 
Bahamas to 60W and from 09N-27N, also translating in westward 
motion.

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

$$
Aguirre