[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 030520
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
120 AM EDT Tue Jul 3 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 0000 UTC surface analysis and satellite imagery through
0515 UTC.

...TROPICAL WAVES...

A tropical wave has an axis extending from 17N31W to 03N32W and
is moving W at around 10 kt. The wave coincides with a surge of
moisture as noted in the TPW product. African dust surrounds the
wave. A patch of low level moisture is noted in association with
this wave N of 10N while scattered moderate convection is seen
where the wave meets the monsoon trough, mainly from 03N to 08N
between 27W and 32W.

A tropical wave extends from 19N51W to 05N52W. This feature is
moving W at around 10 kt. The cloud field associated with this
wave shows an inverted-V signature. This wave shows up well in the
TPW animation where a high amplitude N bulge of moisture is
observed. At this time, the wave is surrounded by Saharan dust
which is limiting convection in the vicinity of this wave. Only a
small cluster of moderate convection is noted along the wave's
axis near 12N. Moisture associated with this wave will reach the
Windward Islands early this afternoon bringing scattered showers
and isolated thunderstorms.

A tropical wave is moving across the central Caribbean. Its axis
extends from the Windward Passage near 19N74W to the coast of
Colombia 10N76W, moving westward at around 20 knots. The wave is
well depicted in the moisture product. Clusters of moderate to
strong convection are at the base of this wave over Colombia. The
GFS model indicates abundant moisture associated with this wave
over the SW Caribbean today, spreading over Nicaragua and Honduras
this afternoon and tonight.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean through the coastal
section of Senegal, then continues SW to near 10N23W to 05N38W.
The ITCZ extends from 05N38W to 04N45W to 06N52W. Aside from the
convection associated with the tropical waves, scattered moderate
convection is from 04N-08N between 36W-42W, and from 07N-10N
between 44W-49W.

...DISCUSSION...

GULF OF MEXICO...

As of 0300 UTC, a trough extends from a weak surface low of 1015
mb located near 30N88W to 24N90W. Scattered to numerous showers
and thunderstorms can be expected near this system as it continues
to interact with tropical moisture. The low is forecast to slowly
move W toward NE Texas through Wed.

The remainder of the Gulf remains under the influence of a weak
ridge extending W from the Atlantic. A 1017 mb high pressure
center located near 26N91W is within the ridge. This system is
producing mainly light to gentle anticyclonic flow and seas of
1-3 ft across much of the Gulf waters. This pattern will change
little through mid-week. A surface trough will emerge off the
Yucatan Peninsula each evening through Thu, enhancing 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. A recent ASCAT pass
provides observations of fresh trades over the south-central
Caribbean, with moderate to locally fresh winds elsewhere S of
18N E of 80W. Light to gentle winds are noted over the NW
Caribbean. Winds are forecast to increase across the central
Caribbean beginning tonight. Marine guidance suggests winds in the
25-30 kt range over the south-central Caribbean, with building
seas to 10-12 ft by early Wed morning. Near gale force NE winds
are possible near the coast of Colombia Wed night and Thu night.

Convection continues to intermittently flare up over the SW Caribbean
mainly in the vicinity of the monsoon trough, which is just north
of Panama along 09N-10N. This pattern will remain in place for the
next several days. Lightning density indicates frequent lightning
with much of the observed convection.

ATLANTIC OCEAN...

Two tropical waves are moving across the waters between the coast
of West Africa and the Lesser Antilles. Please refer to the
Tropical Waves section above for details.

An upper-level low is spinning NE of the Bahamas near 29N71W. A
surface low and associated trough, reflection of this system
aloft, is analyzed on the 0000 UTC surface map. The trough extends
from 31N66W to a 1014 mb weak low pressure located near 27N70W to
24N78W. A recent scatterometer pass clearly shows the wind shift
related to the trough axis particularly between 65W-70W. This
system has weakened the Atlantic ridge over the western Atlantic.
The low will move SW towards the Bahamas. The ridge will rebuild
and strengthen Wed through Sat night as the low weakens into a
trough and tracks across the NW Bahamas and over Florida by Wed.
An increase in moisture is likely along and behind the trough,
increasing the likelihood of showers and tstms over the Florida
Peninsula. As the ridge builds westward, winds N of Hispaniola
will pulse to strong speeds each day during the late afternoon and
evening hours beginning on Wed.

Farther E, another trough is analyzed from 33N49W to 28N51W. This
trough is also associated with an upper-level low that is helping
to induce scattered showers with embedded tstms from 30N-33N
between 46W-53W. Surface high pressure of 1033 mb located NW of
the Azores extends a ridge across the remainder of the central and
eastern Atlantic forecast waters. Moderate to fresh trade winds
are noted along the southern periphery of the ridge.

GOES-16 RGB Geocolor imagery continues to show an extensive area
of African dust that primarily extends from the west coast of
Africa to the northeastern Caribbean. The Saharan Layer (SAL) from
CIMSS also confirms the presence of this African dust outbreak.

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

$$
GR
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