[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 160539 CCA
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
139 AM EDT Mon Sep 16 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 0000 UTC surface analysis and satellite imagery through
0510 UTC.

...SPECIAL FEATURES...

Humberto has strengthened to a hurricane near 29.4N 77.6W at
16/0300 UTC or 685 nm W of Bermuda moving NE at 3 kt. Estimated
minimum central pressure is 988 mb. Maximum sustained wind speed
is 65 kt with gusts to 80 kt. Numerous moderate to scattered
strong convection extends outward from the center 270 nm NE quad,
180 nm SE quad and 90 nm W semicircle. A rainband 150-210 nm S of
the center is producing strong convection over portions of the NW
Bahamas. Latest ASCAT pass from around 16/0256 UTC indicates all
tropical storm force winds on the west side are now to the east of
79.5W longitude. A slow NE motion is forecast to continue through
this morning, followed by a turn to the ENE with a gradual
increase in forward speed over the next 3 days. Please read the
latest NHC forecast/advisory under AWIPS/WMO headers
MIATCMAT4/WTNT24 KNHC, or at the website hurricanes.gov for more
details.

Showers and thunderstorms have increased overnight in
association with an area of low pressure along a tropical wave
in the central tropical Atlantic. The 1008 mb surface low is
centered near 09N41W along a wave that extends along 41W from
04N-16N. Environmental conditions are forecast to be conducive
for gradual development, and a tropical depression is likely to
form within the next two to three days while the system moves
slowly west-northwestward to northwestward.

...TROPICAL WAVES...

An eastern Atlantic tropical wave with axis along 26W from 04N-19N
is moving W around 15-20 kt. The wave shows up well in 700 mb
trough diagnostics and TPW imagery. Scattered moderate convection
is from 10N-15N between 26W-33W.

A central Atlantic tropical wave with axis along 41W from 04N-
16N, is moving W around 15 kt. A 1008 mb surface low is centered
along the wave axis near 09N41W. The wave is well depicted in
satellite imagery and TPW imagery. Scattered moderate convection
is noted from 08N-12N between 38W-47W. See section above for
more details.

An Atlantic tropical wave with axis along 57W from 07N-21N, is
moving W around 15-20 kt. This wave is well depicted in model
guidance and satellite imagery. Scattered moderate convection is
seen from 11N-19N between 55W-62W. The wave will bring enhanced
rain to the Lesser Antilles and eastern Caribbean today.

An eastern Caribbean tropical wave extends its axis along 66W from
20N southward, moving west around 15 kt. This wave is well
depicted in TPW imagery. Scattered moderate convection covers the
area from 15N-17N between 66W-70W.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from northern Mauritania near 21N17W
to 13N24W to 09N41W to 09N51W. The ITCZ continues from 09N51W to
10N56W. Aside from the convection already discussed in the
Tropical Waves section above, scattered moderate convection is
noted from 05N-14N between the coast of Africa and 20W.

GULF OF MEXICO...

The weather over the Gulf of Mexico is dominated by a large mid to
upper-level low that is centered over the western portion of the
basin. A W-E surface trough is analyzed along 25N between 84W-97W.
Scattered moderate convection is seen from 27N-29.5N between
90W-93W. The latest ASCAT pass shows fresh to strong E winds from
27N-29.5N between 89W-94W. Light winds are over the south-central
Gulf. A 1017 mb high is near 23.5N85W.

A broad area of disorganized showers and thunderstorms over the
central and eastern Gulf of Mexico is associated with an upper-level
low and a weak surface trough. Some slight development of this
system is possible during the next couple of days while it moves
westward over the western Gulf of Mexico. The system is forecast
to move inland along the northwestern Gulf coast by late today or
Tuesday, and further development is not expected after that time.
High pressure will gradually build over the Gulf Tue through Fri.

CARIBBEAN SEA...

Refer to the Tropical Waves section above for details on the
tropical waves moving through and approaching the basin.

Relatively dry air covers the central Caribbean. In the SW
Caribbean, the East Pacific monsoon trough is inducing scattered
moderate to strong convection from 10N-14N between 80W-84W. The
latest ASCAT pass depicts moderate to fresh trades in the south-
central Caribbean.

Moderate to fresh trade winds will dominate much of the basin. A
tropical wave moving across the eastern Caribbean will reach the
central Caribbean later today. Another tropical wave will
approach Barbados this morning and move across the eastern
Caribbean later today, and into the central Caribbean through mid
week, bringing widespread showers and thunderstorms, gusty winds
and building seas. Northerly swell from a large, gale force low
centered near 41N42W will reach the Atlantic passages into the
Caribbean Sea late today or tonight. By Wed, these swells will
begin to gradually subside.

ATLANTIC OCEAN...

Refer to the sections above for details on Hurricane Humberto and
the tropical waves moving across the basin.

A mid-latitude low currently centered near 41N42W extends its
cold front south entering the discussion area near 32N37W to
27N44W to 26N53W. The front becomes stationary from that point to
29N60W to Bermuda. A pre-frontal trough is analyzed from 31N34W to
25N43W with scattered showers. To the east, a 1029 mb surface
high centered well to the north remains in control over this
area.

Humberto will move to the ENE, passing just north of Bermuda
Thursday morning, while growing in size. Northerly swell from a
large, gale force low centered near 41N42W will reach the Atlantic
passages into the Caribbean Sea late today or tonight. By Wed,
these swells will begin to gradually subside.

$$
Hagen
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