[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 301652
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1252 PM EDT Sat Jun 30 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
1715 UTC.

...TROPICAL WAVES...

A tropical wave that has emerged off the west coast of Africa is
along 15W from 03N-14N. Scattered moderate convection is noted on
either side of the wave's axis from 05N-10.5N E of 18W to the
coast of Africa. The Hovmoller Diagram shows the westward
propagation of the wave that also coincides with a moisture surge
in the TPW product.

A tropical wave has an axis extending from 04N27W to just W of
the Cabo Verde Islands near 16N26W moving W around 10 kt. This
wave is well defined in model diagnostics guidance and TPW
animation. Scattered moderate convection is noted near the
southern end of the wave from 03N to 06N between 22W and 26W. The
the wave is nearly surrounded by dry Saharan air.

A tropical wave has an axis extending N from 05N51W to 18N50W and
is moving westward around 15 knots. Scattered moderate convection
is present where the wave meets the ITCZ from 03N to 07N between
45W and 53W. Similar convection is noted near 10N50W. The wave
shows up well in model diagnostics guidance and TPW product.
African dust surrounds the wave, that also shows an inverted V
pattern on visible satellite imagery. A patch of moisture with
embedded showers is noted ahead of the wave approaching the
Windward Islands. Tropical moisture associated with this feature
will reach the waters E of the Windward Islands late today, and
move across the islands tonight into Sun, increasing the
likelihood of showers and isolated tstms.

A tropical wave has an axis extending N from NW Venezuela to the
eastern Dominican Republic near 19N70W. This system is moving W
between 10 and 15 kt and despite its longitude has dry Saharan
dust on both sides. As a result, there is no significant convection
currently associated with this wave. Some moisture on the SE side
of this wave could enhance convection over the basin this weekend
before the wave reaches Central America by Sun night.

Another tropical wave has an axis extending over Guatemala and El
Salvador into the eastern Pacific region. This wave is slowing
down and moving W at only around 5 kt. TPW satellite imagery and
model diagnostics show this wave to be poorly defined.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean from the coast of
Guinea near 10.5N15W and continues to 10N23W. The ITCZ stretches
from 10N23W to 05N40W to 06N50W. Aside from the convection
associated with the tropical waves, scattered moderate convection
is observed within about 150 nm N of the ITCZ axis between 34W and
39W.

...DISCUSSION...

GULF OF MEXICO...

As of 1500 UTC, a surface trough extends over the eastern Gulf
from 30N85W to 28N85W to 24N86W with a weak 1015 mb low off the
coast of Apalachicola. Abundant cloudiness with showers and tstms
is associated with the low/trough affecting mainly the waters N of
25N E of 87W. The low and associated trough will move little
today, then drift northwestward towards the SW Alabama and SE
Louisiana coasts Sun and Sun night while weakening. Scattered
showers and thunderstorms will continue over much of the NE Gulf
and then the north-central Gulf waters through at least Mon.

The remainder of the Gulf is under the influence of a weak high
pressure center of 1018 mb located over the north-central Gulf
near 26N90W. This system is producing light to gentle anticyclonic
flow and seas of 2-3 ft over the eastern half of the Gulf, and
gentle to moderate Se to S winds and seas of 3-5 ft over the
western half of the Gulf. Moderate to fresh return flow is
expected over the west-central and NW Gulf through the weekend.
This weak high pressure covering the central and western Gulf
will change little through Wed night. A surface trough will emerge
off the Yucatan Peninsula each evening through Wed, and act to
enhance nocturnal winds over the SW Gulf.

CARIBBEAN SEA...

A tropical wave is moving across the central Caribbean. Please,
see the Tropical Waves section for details. Recent scatterometer
data depicted fresh to strong winds across the south-central
Caribbean, while moderate to fresh trades are across the remainder
of the basin S of 18N E of 80W. Light to gentle winds are noted
over the NW Caribbean. A ridge will remain north and northeast of
the Caribbean and Tropical N Atlantic waters through the period.
Fresh to strong winds across the south- central Caribbean will
gradually diminish Sun through Tue before strengthening again Wed.

Convection continues to flare up over the SW Caribbean. A cluster
of moderate to strong convection has developed E of the coast of
Nicaragua from 10.5N-14N between 79W-83W. This cluster is in the
south side of an upper-level trough extending from an upper-level
low over eastern Cuba to NE Honduras. The upper- level low will
drift westward into the NW Caribbean over the weekend, and will
continue to enhance convection across the basin.

ATLANTIC OCEAN...

Three tropical waves are moving across the waters between the
coast of West Africa and the Lesser Antilles. Refer to the
Tropical Wave section above for details. A surface trough is over
the central Atlantic and extends from 32N50W to 25N53W. Light
winds are on either side of the trough axis based on scatterometer
data. This trough is a surface reflection of an upper-level low
spinning near 30N50W. Scattered showers are associated with this
trough.

A 1034 mb surface high located NW of the Azores near 45N38W is in
control of the remainder of the forecast area, extending a ridge
SW across the west-central Atlantic. Moderate to fresh winds are
around the southern periphery of the ridge W of 50W to the Lesser
Antilles. The ridge will weaken through Tue in response to the
development of broad low pressure system NE of the Bahamas. A
surface trough will develop from the low pressure and move
westward across the NW Bahamas Tue, and inland Florida Wed.
Scattered showers and thunderstorms are expected with the trough.
Otherwise, generally tranquil marine conditions are expected
across the region through the middle of next week.


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

$$
GR
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