[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 031039
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
639 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 0600 UTC surface analysis and satellite imagery through
1130 UTC.

...TROPICAL WAVES...

A tropical wave has an axis extending from 16N33W to 04N34W and
is moving W around 10 kt. The wave coincides with a surge of
moisture as noted in the TPW product, but African dust surrounds
the northern side of the wave and is inhibiting convection there.
Scattered moderate convection is seen within the moister southern
portion of the wave from 01N to 08N between 30W and 36W.

A tropical wave extends from 19N52W to 05N53W. This feature is
moving W around 10 kt. The low level cloud field associated with
this wave exhibits an inverted-V signature. This wave shows up
well in the TPW animation where a pronounced bulge of moisture is
observed. This wave remains surrounded by Saharan dust which is
limiting convection in the vicinity of this wave. Only a small
cluster of moderate convection is noted E of the wave axis from
09N to 11N between 49W and 51W. Moisture associated with this wave
will begin reaching the Windward Islands early this afternoon and
bring a modest increase in chances for showers and thunderstorms
for this area during the next day or so.

A tropical wave has an axis extending from the eastern Cuba near
21N76W to the coast of Colombia 08N77W, moving westward at around
20 knots. The wave is well depicted in the moisture product. The
monsoon trough extends E over the SW Caribbean from Costa Rica to
northern Colombia near 10N74W. The tropical wave is interacting
with the trough to generate numerous moderate and isolated strong
convection from 11N to 13N between 81W and 84W. Scattered moderate
and isolated strong convection is found elsewhere within 120 nm
of a line from 08N75W to 14N83W. Model guidance indicates that the
abundant moisture associated with this wave will spread W from
the SW Caribbean over Nicaragua and Honduras this afternoon and
tonight.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean from the coast of
Senegal near 14N17W, then extends SW to 04N37W. The ITCZ continues
from 04N37W to 04N45W to the coast of French Guiana near 05N53W.
Aside from the convection associated with the tropical waves,
cloudiness and isolated moderate convection is observed within 150
nm of a line from 11N16W to 07N28W and within 120 nm of a line
from 03N38W to 07N46W.

...DISCUSSION...

GULF OF MEXICO...

A trough curves SSW from a weak 1014 mb surface low centered near
the mouth of the Mississippi to near 24N90W. Scattered moderate
convection is noted from 28N to 30N between 87W and 92W. This
system is forecast to weaken and slowly move W toward NE Texas
through Wed.

The remainder of the Gulf remains under the influence of a weak
ridging curving W over the basin from the Atlantic. The ridge is
manifested over the western Gulf in the form of two weak 1017 mb
high pressure centers located near 27N94W and near 23N97W. The
area of high pressure 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 the end of the week and generate moderate to fresh
nocturnal winds over the SW Gulf.

CARIBBEAN SEA...

A tropical wave is entering the western Caribbean. Please see the
Tropical Waves section for details. Satellite-derived wind data
from around 02Z this morning indicates moderate to fresh trades
over the central and eastern Caribbean, while surface observations
show winds are light over the western Caribbean. Winds are
forecast to increase across the central Caribbean beginning
tonight as high pressure to teh N builds. Marine guidance suggests
winds in the 25-30 kt range over the south-central Caribbean,
with seas building to between 10 and 12 ft by early Wed morning.
Near gale force NE winds will possible near the coast of Colombia
Thu night and Fri night.

Convection continues to flare up over the SW Caribbean mainly in
the vicinity of the monsoon trough. This pattern will remain in
place for the next several days, even after the tropical wave
departs.

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

$$
CAM/MT
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