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679
AXNT20 KNHC 140006
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
806 PM EDT Fri Jul 13 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.

…SPECIAL FEATURES…

…Gale Warning off the coast of Colombia in the Caribbean Sea…

Gale force NE-E winds are across the south-central Caribbean from
11N to 13N between 74W and 76W with associated sea heights ranging
from 10 to 14 feet. Minimal gale conditions are expected near the
coast of Colombia at night through Sun night. Please, see the
High Seas Forecast, under the AWIPS/WMO headers HSFAT2/FZNT02
KNHC, for more details.

…TROPICAL WAVES…

A tropical wave is off the coast of west Africa with axis
extending from 06N17W to 14N17W. Convection has reduced in the
last several hours to scattered moderate from 06N-17N east of
21W.

A tropical wave is in the central Atlc with axis extending from
09N42W to 20N42W. Isolated moderate convection is in the southern
wave environment near the ITCZ. The remainder wave environment
lacks convection partly due to the presence of Saharan dry air
and dust.

A tropical wave is moving across the Lesser Antilles with axis
extending from 10N61W to 18N61W. Scattered moderate convection
continues in the southern wave environment S of 13N between 60W-
65W. Light showers are occurring in the Leeward Islands. The wave
will move across the eastern Caribbean tonight through Sun.

A tropical wave is in the central Caribbean with axis extending
from 10N71W to 18N71W. No deep convection is associated with this
wave at the time partly due to remnant Saharan dry air in the
northern wave environment and strong deep layer wind shear.

…MONSOON TROUGH/ITCZ…

The monsoon trough extends from 10N14W to 09N27W. The ITCZ
extends from 09N27W to 10N41W to 09N43W to 10N59W. Aside from the
convection related to the tropical waves, scattered moderate
convection is from 05N- 09N between 45W-53W.

…DISCUSSION…

GULF OF MEXICO…

A ridge continues to dominate the Gulf waters, with two weak high
pressure centers of 1021 mb located across the northern Gulf.
Under the influence of this system, mainly light to gentle
anticyclonic flow will prevail across much of the Gulf region
this upcoming weekend, with seas generally under 5 ft. Gentle to
moderate SE-S winds are expected across the western Gulf on the
western periphery on the ridge. According to the GOES-16 RGB
Geocolor imagery, African dust has reached the SE Gulf, including
the Yucatan Channel.

A surface trough will move westward off the Yucatan Peninsula
each evening through Tue. It will enhance nocturnal winds and
seas over the SW Gulf. Marine guidance suggests fresh to locally
strong NE-E winds and seas of 4-5 ft in association with this
thermal trough. A tropical wave will move westward across the Bay
of Campeche and the Tehuantepec region today.

CARIBBEAN SEA…

Two tropical waves will continue to move across the basin. Refer
to the Tropical Waves section above for details.

A gale warning is in effect for the south-central Caribbean.
Refer to the Special Features section above for more information.

Saharan dust covers most of the Caribbean Sea, including the
Greater Antilles, where partly cloudy and hazy conditions prevail.

High pressure will build across the region behind each passing
tropical wave to freshen trade winds across the central Caribbean
waters. Winds will pulse to strong to near gale force each night
off the coast of Colombia through Tue, except to minimal gale
force tonight, Sat night and Sun night.

ATLANTIC OCEAN…

An area of low pressure, associated with the remnants of Beryl, is
located about 250 miles west-northwest of Bermuda. Although
upper-level winds are at best marginally conducive, this system has
become a little better organized today, and some additional
subtropical or tropical development is possible tonight and Saturday
while the low moves north-northeastward at about 10 mph. By Sunday,
the system should reach colder water north of the Gulf Stream, where
additional development is unlikely. The latest Tropical Weather
Outlook gives this system a low chance of tropical cyclone
formation during the next 48 hours. A weak low of 1014 mb is
analyzed on the 1200 UTC surface map near 33.2 69.6W. Visible
satellite imagery reveals that the low level center is totally
exposeure due to the strong wind aloft.

A surface trough extends from the aforementioned weak low to
the NW Bahamas. The trough will move little through Sun night while
weakening. Scattered showers and isolated thunderstorms can be
expected along and southeast of the trough. A recent scatterometer
pass clearly indicates the wind shift associated with this trough.

The remainder of the Atlantic forecast area is under the influence
of the Bermuda-Azores High, with a center of 1034 mb located WNW
of the Azores near 39N38W. The ridge extends SW into the NE
Caribbean and the SE Bahamas. High pressure building westward
from the central Atlantic through Tue will support fresh to
strong trade winds south of 23N W of 65W. Winds will pulse to
strong north of Hispaniola at night this weekend.

The Saharan Air Layer (SAL) from CIMSS, and GOES-16 RGB Geocolor
imagery, depict a large area of Afriai dust covering the
tropical Atlantic waters between the west coast of Africa and
the Lesser Antilles.

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

$$
GR/NR

AIRPRESS LOADED

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