[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 302357
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
757 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 1800 UTC surface analysis and satellite imagery through
2345 UTC.

...TROPICAL WAVES...

A tropical wave that has emerged off the west coast of Africa is
along 15W from 04N-13N. Scattered moderate convection is noted on
either side of the wave's axis from 05N-14N and E of 22W 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 along 32W from 04N-18N,
moving W at 10 kt. This wave is well defined in model diagnostics
guidance and TPW animation. No significant convection is related
to this wave at this time, as it is surrounded by dry Saharan air.

A tropical wave has an axis extending along 52W from 05N-19N,
moving westward at around 15 knots. Scattered showers are present
where the wave meets the ITCZ near 03N. 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 tonight, and move across the
islands through Sun, increasing the likelihood of showers and
isolated tstms.

A tropical wave has an axis extending N from northeast Colombia
to western Hispaniola. This wave is moving W between 10 and 15 kt
and has dry Saharan dust in its environment. As a result, there
is no significant convection currently associated with it. 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 the Yucatan
Peninsula 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 11N15W and continues to 10N23W. The ITCZ stretches
from 10N23W to 06N31W, then resumes west of a tropical wave from
06N33W to 06N51W, then from 06N53W to 07N59W. 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...

A surface trough extends over the northeastern Gulf from a 1014 mb
low near 30N84W to 24N86W. Abundant cloudiness with showers and
tstms is associated with the low/trough affecting mainly the
waters N of 24N E of 89W. 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 28N91W. 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 45N36W 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.

GOES-16 RGB Geocolor clearly shows an extensive area of African
dust that extends from the west coast of Africa to the eastern
Caribbean. The Saharan dust occasionally obscures sky conditions
of the Caribbean islands. The dust turns skies hazy, reducing
visibility and can result in poor air quality. Saharan dust blows
across the Atlantic a few times during the summer, sometimes
reaching S Florida. Today, the Geocolor imagery indicates a patch
of African dust over the western Gulf of Mexico associated with
the Saharan dust outbreak from last week.

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

$$

GR/ERA
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