[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 150544
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
144 AM EDT Sat Jul 15 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 0000 UTC surface analysis and satellite imagery through
0530 UTC.

...TROPICAL WAVES...

A central Atlantic tropical wave has its axis from 15N44W to
02N44W, moving westward 20 knots. The wave is surrounded by dry
Saharan air as depicted in the latest METEOSAT-9 Saharan Air Layer
imagery. Only convection noted with this wave is south of 10N to
the ITCZ region between 43W-48W.

A Caribbean tropical wave has its axis from 17N64W to 06N64W,
moving westward at 20 kt over the past 24 hours. The wave
exhibited a well pronounced northeast to southeast wind shift in
the upper air sounding from Trinidad this morning at 12Z. Satellite
imagery shows a well-defined cloud structure to the wave, with
a low-level vorticity maximum on the southern portion of the wave
axis. Scattered moderate convection is north of 13N between 63W-
67W. This wave is forecast to move across the rest of the eastern
Caribbean today and reach the central Caribbean by tonight.
Increasing moisture along scattered showers and isolated
thunderstorms will follow the wave. Some of the shower and
thunderstorm activity may contain gusty winds.

A central Caribbean tropical wave has its axis from 22N74W to
12N74W, moving westward at about 15 knots. The northern portion
of the wave axis is just west of Haiti. An upper-level low is
noted over the northern part of the wave, with an associated
trough extending from it over the remainder of the wave.
Subsidence aloft with dry air prevails in the wave's environment.
Isolated showers and thunderstorms are within 150 nm on both
sides of the waves axis and north of 19N affecting the Windward
Passage. The wave will move across the rest of the central
Caribbean through the morning hours and the western portion of the
basin tonight and through Sunday. The wave may acquire more
moisture along with shower and thunderstorm activity as it moves
through the western Caribbean.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough axis extends from 12N17W and continues to
11N21W where scatterometer data indicates the ITCZ then begins
and continues to 06N43W. The ITCZ then resumes west of a tropical
wave from 06N45W to 06N53W. Aside from the convection related to
the tropical wave along 45W, isolated moderate convection is
within 180 nm north of the axis between 37W-41W and west of 50W.

...DISCUSSION...

GULF OF MEXICO...

A weak pressure pattern is present across the area. A very moist
and unstable air mass in place over just about the entire Gulf,
except over the Bay of Campeche where dry air is noted aloft. A
surface trough is analyzed from near 26N87W to 22N85W. Isolated
showers are occurring along the northern portion of the trough.
Isolated showers and thunderstorms are south of 92W. Moisture
guidance suggests that abundant moisture will continue over much
of the Gulf through the weekend. With this scenario, showers and
thunderstorms are expected through this period.

CARIBBEAN SEA...

A couple of tropical waves are moving through the Caribbean Sea.
See the section above for details. Aside from the convection
related to the tropical waves, an area of isolated showers
prevails over the southwest Caribbean south of 12N between 75W-83W
due to the proximity of the monsoon trough. The pressure gradient
through the basin remains fairly weak. Scatterometer data depicts
gentle to moderate trades across the area. Expect a similar
weather pattern to prevail through the next 24 hours.

...HISPANIOLA...

A tropical wave has its axis extending across the Windward Passage
with scattered moderate convection. Fair weather prevails across
the island at this time. Moisture associated with the eastern
Caribbean tropical wave will begin to approach the eastern part
of the Hispaniola this afternoon, and spread across the remainder
of the island into Sunday. With this scenario expected, shower
and thunderstorm activity should become more widespread over
portions of the island as well as over the nearby waters.

ATLANTIC OCEAN...

A tropical wave is moving across the central Atlantic while the
northern portion of the wave that is currently over the western
Caribbean is affecting the southern Bahamas. See the section
above for details. A surface trough was analyzed from 29N73W to
25N74W. Another trough is from 30N61W to 25N62W. These two
features are the reflection of upper-level lows. The remainder of
the basin is under the influence of a surface ridge, anchored by
a stationary 1027 mb high centered near 35N48W.

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

$$

ERA
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