[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 311741
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
141 PM EDT Wed Jul 31 2019

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
1500 UTC.

...TROPICAL WAVES...

An Atlantic Ocean tropical wave is along 31W from 04N-18N, moving
W around 15 kt. Scattered moderate convection is noted close to
where the wave intersects the monsoon trough, from 06N-10N between
33W-36W, in an area where a recent scatterometer pass indicated a
small scale low pressure area may be forming along the monsoon
trough, part of a much broader gyre along the monsoon trough
between 25W and 40W. Looking ahead, upper- level winds are
forecast to gradually become more conducive for further
development as the wave moves westward, and a tropical depression
could form over the weekend several hundred miles east of the
Lesser Antilles.

An Atlantic Ocean tropical wave is along 48W/49W from 04N-25N,
moving W around 15 kt, and is very well defined on low level
precipitable water imagery. Recent scatterometer satellite passes
from around 13 UTC depicted the wave very well at the surface as
well. Despite abundant low level moisture, the wave is moving
through an area of fairly dry mid and upper levels, and no
significant convection is noted with this wave.

A Caribbean tropical wave extending from central Colombia through
western Haiti is moving west at 10 kt. A small area of showers and
thunderstorms is noted between Jamaica and western Cuba just west
of the wave axis, but otherwise no significant convection is
observed near the wave over the Caribbean. An earlier
scatterometer satellite pass showed a surge of moderate to fresh
trade winds in the wake of the tropical wave south of Hispaniola,
responsible for a line of clouds reaching from Jamaica to Costa
Rica on morning visible satellite imagery.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of Senegal near 14N16W
to 10N35W to 11N45W to 10N50W. The ITCZ continues from 10N50W to
the coast of Suriname near 05N55W. Scattered moderate convection
is evident at the mouth of the Gambia River off Senegal and
Gambia, and from 06N-10N between 33W-36W.

GULF OF MEXICO...

The main weather maker in the Gulf of Mexico currently is a broad
upper low pressure centered near 27N88W. Divergence aloft on the
southeast side of this upper cyclone is supporting clusters of
showers and thunderstorms over the southeast Gulf, Florida Keys
and parts of South Florida. Divergence aloft between the upper low
and a large upper anticyclone over New Mexico is enhancing showers
and thunderstorms off the coast of Texas as well. A few showers
and thunderstorms are also active over the warm Loop Current in
the central Gulf. Despite the thunderstorms, buoy and
scatterometer passes indicated overall winds remain light to
gentle. Buoys and altimeter passes show seas mainly 2 ft or less.

Looking ahead, weak high pressure ridging will remain over the
northern Gulf through the next few days providing for generally
a gentle to moderate wind flow and relatively low seas across
the area.

CARIBBEAN SEA...

See the Tropical Waves section above for information on the
tropical wave over Caribbean Sea between Colombia and Haiti.

Judging from surface based observations, buoys, scatterometer and
the way the low level cloud motion is on visible satellite
imagery, moderate E to SE winds dominate the eastern Caribbean
east of 70W. This is in an area where a tropical wave had been
entering, but the surface data and regional sounding data indicate
this feature may have lost a clear definition. However, low level
troughing is evident from the USVI and Puerto Rico into the
Atlantic, related to a sharp upper trough north of the area.
Numerous showers and thunderstorms remain active in this area
extending westward into Hispaniola, related to the divergence
aloft south of the upper trough axis. The pattern is fairly dry
over the eastern Caribbean, and no trade wind showers are noted on
regional mosaic radar imagery there. Satellite based lightning
data shows a few thunderstorms active over the southwest Caribbean
between Panama and Nicaragua, mainly due to trade wind convergence
associated with the approaching tropical wave. Seas are 2 to 3 ft
in the northwest Caribbean, 5 to 7 ft in the south central
Caribbean where trade winds are strong behind the tropical wave,
and 3 to 5 ft elsewhere.

For the forecast, the tropical wave over between Colombia and
Haiti will reach the far western Caribbean by early Sat. Another
tropical wave will move across the tropical Atlantic waters
through Fri enter into eastern Caribbean by late Sat, then reach
thecentral Caribbean Sun and Sun night. Scattered showers and
thunderstorms will be associated with these waves. In the wake of
these waves, trade winds will increase to strong speeds over the
south central Caribbean waters.

ATLANTIC OCEAN...

West of 50W, a string of upper lows interconnected by sharp upper
troughs reaches from 31N50W southwestward through the Turks and
Caicos and into central Cuba. Divergence aloft south of this axis
is supporting clusters of showers and thunderstorms mainly south
of 24N and west of 55W, with the heaviest activity over the Old
Bahama Channel, where the northern extent of a tropical wave is
present. A few thunderstorms are active over the Gulf Stream
Current off northeast Florida. Recent scatterometer also shows
fresh trad winds south of 24N with light to gentle breezes farther
north into the subtropical ridge. Seas are 4 to 6 ft south of 24N
and 2 to 4 ft north of 24N.

Looking ahead, the northern part of the tropical wave is moving
through the southeastern Bahamas will continue to move west-
northwestward across the central Bahamas through Thu, then
northwestward across the NW Bahamas Thu night and to southern and
central Florida Fri through through Sat night. Scattered to
numerous showers and thunderstorms, some with strong gusty winds
and heavy rainfall, will impact the waters between Florida, the
Bahamas and Cuba through Sat night. Otherwise, moderate breezes
will generally prevail across the area.

Farther east, a few thunderstorms are noted are noted north of 25N
between 45W and 50W, related to the upper low west of the area.
farther south into the tropics, scatterometer satellite passes
showed fresh trade winds following the well- defined tropical wave
along 48W/49W. A concurrent altimeter pass indicated 5 to 6 ft
seas in the area of fresh trade winds in the deep tropics as far
east as 35W. Fresh trade winds are also noted over the tropical
east Atlantic, north of the broad gyre along the monsoon trough
where it intersects the tropical wave along 31N. Seas east of 35W
are 5 to 7 ft throughout the eastern Atlantic east of 35W. Another
tropical wave may be starting to emerge into the eastern Atlantic
off Africa. Looking ahead, much will depend on the development
over the eastern Atlantic, particularly with the wave along 31W.
Please see the Tropical Weather Outlook on hurricanes.gov for more
information regarding these developments.

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

$$
Christensen
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