[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211633
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1233 PM EDT Thu Jun 21 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...

There are four tropical waves between the west coast of Africa
and the Lesser Antilles.

A tropical wave is along 25W from 03N-12N, moving W at 20 kt. The
Hovmoller Diagram shows the westward propagation of the wave,
that coincides with a modest surge of moistened air based on the
TPW product. Abundant cloudiness surrounds the wave's axis but
convection is limited.

A tropical wave is along 34W from 3N-11N, moving W at 20 kt. This
wave shows up well as a low amplitude moisture surge on the TPW
animation. Scattered showers are noted where the wave meets the
ITCZ.

A tropical wave is along 43W from 3N-11N, moving W at about 15
knots. The wave is well depicted in the moisture product, and
model diagnostics guidance. Scattered moderate convection is
noted on either side of the wave's axis from 6N-8N between 40W-
46W.

Another tropical wave is along 60W from 6N-17N, moving W at about
10 knots. The wave coincides with a high amplitude northward bulge
of moisture, and is also well depicted in model diagnostics
guidance. Scattered moderate convection is already affecting
Trinidad and Tobago as well as Barbados where showers and some
tstms have been reported. Moisture associated with this feature
will continue to affect the Windward Islands today. The wave will
then move across the eastern Caribbean this afternoon through Fri
night. The associated moisture is forecast by the GFS computer
model to spread out reaching the Leeward Islands later today and
tonight, and Puerto Rico on Fri, then Dominican Republic Fri night
into Sat.

A tropical wave is moving across the Caribbean Sea. Its axis is
along 73W, and extends from Hispaniola to northern Colombia.
The wave is interacting with an upper-level trough that crosses
eastern Cuba. Lingering moisture from this tropical wave will
continue to support scattered showers and isolated thunderstorms
across Hispaniola today. Moisture and instability related to this
wave will also affect the Windward Passage and eastern Cuba today.
Currently, scattered showers and tstms are noted in the Windward
Passage, across the waters between eastern Cuba and Jamaica, and
E of Jamaica. This wave is forecast to move across Jamaica tonight,
entering the western Caribbean Fri.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal sections of Guinea
near 10N13W to 06N29W. The ITCZ continues from 06N29W to 06N30W
05N40W to 05N50W to 06N57W. Outside of the convection associated
with the tropical waves, isolated moderate convection is from 3N-
7N between 24W-35W. Scattered moderate convection is from 6N-8N
between 55W-58W.

...DISCUSSION...

GULF OF MEXICO...

A 1007 mb low pressure centered along the Texas/NE Mexico border
near 27N99W continues to produce a large area of showers with
embedded tstms over the western Gulf coast and NE Mexico,
particularly over the states of Nuevo Leon and Tamaulipas, where
heavy rain has been reported. This slow moving system will
continue to generate rounds of rainfall across the western Gulf
coast from Texas to western Louisiana today. Flooding of low lying
and poor drainage areas will be possible. Winds and seas in the
NW Gulf will diminish further today as the low weakens.

A 1016 mb high pressure is analyzed over the SE Gulf near 24N86W,
A broad ridge will persist over this area, and support light
winds and seas less than 3 ft east of 88W through the upcoming
weekend.

A surface trough will develop in the Yucatan Peninsula each
afternoon, then move westward across the SW Gulf during the
overnight hours, accompanied by fresh to occasionally strong east
to southeast winds.

CARIBBEAN SEA...

A tropical wave is moving across the central Caribbean. Another
tropical wave has reached the Windward Islands. Wind observations
from these islands clearly show the wind shift associated with
the wave's axis. Please, see Tropical Waves section for details.
Expect increasing showers and isolated thunderstorms in
association with the passage of these tropical waves.

High pressure N of area is forecast to strengthen over the next
couple of days while moving westward. As a result, the trade
winds over the south-central Caribbean will strengthen and expand
in areal coverage across the basin through early next week. Winds
could reach near gale force along the coast of Colombia by Sun
night. Fresh to strong winds will affect the Gulf of Honduras
each night tonight through Mon night.

An upper-level trough extends from a cyclonic circulation located
over the western Atlantic near 27N65W to another cyclonic circulation
over the NW Caribbean and the Yucatan Peninsula. A diffluent pattern
aloft between this trough and an anticyclonic circulation over the
south-central Caribbean is helping to support scattered showers
and tstms across the Caribbean waters from 15N-20N between the
tropical wave along 73W and 85W. Lightning density indicates
frequent lightning with some of the observed convection. As of
1500 UTC, a trough, surface reflection of the upper-level low is
analyzed over the NW Caribbean extending from 20N85W to the Gulf
of Honduras.

ATLANTIC OCEAN...

An upper-level trough extends from a cyclonic circulation centered
near 27N65W to eastern Cuba. Scattered showers and tstms are
noted on the SE semicircle of the low affecting mainly the waters
from 24N-29N between 60W and 70W. A diffluent pattern aloft
between the aforementioned upper-level trough and an anticyclonic
circulation located E of the Lesser Antilles is helping to induce
this convective activity. Lightning data also indicate frequent
lightning with some of the perceived convection.

High pressure of 1029 mb centered near 33N34W extends a ridge
across the forecast area. Fresh trades are noted along the
southern periphery of the ridge, but mainly between 40W-70W. This
high pressure will slowly shift westward through Sat night, then
remain nearly stationary near 30N55W through Tue. The tightening
pressure gradient that results over the central Atlantic will
support fresh trade winds S of 23N and west of 50W. This will
cause seas to build to 6-7 ft in the waters E of the Bahamas this
weekend.

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

$$
GR
This weather bulletin was brought to you by:
www.nashvilleweather.net