[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 170005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Thu Aug 16 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
2330 UTC.

...SPECIAL FEATURES...

The center of Subtropical Storm Ernesto at 16/2100 UTC is near
43.0N 41.0W, or 1035 km/560 nmi to the ESE of Cape Race in
Newfoundland, and about 1305 km/705 nmi to the WNW of the Azores.
Ernesto is moving NE, or 045 degrees, 16 knots. The estimated
minimum central pressure is 1007 mb. The maximum sustained wind
speeds are 40 knots with gusts to 50 knots. Scattered moderate to
isolated strong rainshowers cover the waters from 41N to 44N
between 37W and 44W. Please read the latest NHC forecast/advisory
under AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more details.

...TROPICAL WAVES...

An Atlantic Ocean tropical wave is along 24W/25W from 17N
southward. Rainshowers are possible within 300 nm on either side
of the tropical wave. The wave is in a moderate deep layer wind
shear environment, and CIRA LPW imagery shows dry air affecting
the wave. These two factors are contributing to the lack of
convection at this time.

An Atlantic Ocean tropical wave is along 52W/53W from 18N
southward. The wave is in a low deep layer wind shear
environment, and CIRA LPW imagery shows abundant low level
moisture associated with it. Scattered to numerous strong
rainshowers are from 10N to 13N between 51W and 54W. Widely
scattered moderate to isolated strong rainshowers are elsewhere
from 07N to 14N between 48W and 60W.

A Caribbean Sea tropical wave is along 66W/67W from 20N southward.
The wave is in a moderate to strong deep layer wind shear
environment. GOES-16 water vapor imagery at the lower levels show
very dry air over this region of the Caribbean. Isolated moderate
rainshowers cover the Caribbean Sea from 18N southward between 60W
and 72W.

A tropical wave is moving across the Yucatan Peninsula, from 22N
southward. GOES-16 water vapor imagery at the lower levels shows
very dry air over this region. Upper level cyclonic wind flow
spans the Yucatan Peninsula and the SW corner of the Gulf of
Mexico. It is more likely that any nearby precipitation is more
related to the upper level cyclonic wind flow and not related to
the tropical wave. Scattered to numerous strong rainshowers cover
the western parts of the Yucatan Peninsula.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal sections of Guinea-
Bissau near 11N16W, to 09N23W, and 09N33W. The ITCZ continues from
09N33W to 12N42W, and 12N49W. Precipitation: Isolated moderate
rainshowers are elsewhere from 06N to 11N from 50W eastward.

...DISCUSSION...

GULF OF MEXICO...

The Bermuda high extends a ridge axis SW across Florida and large
portions of the Gulf to 96W, and weak winds in the range of 5-10
kt prevail in the region. Inflow of shallow moisture from the
Caribbean by southeasterly wind along with a middle level inverted
trough in the E basin support scattered showers and tstms N of
24N E of 90W. Winds in this region may be slightly higher in the
range of 15-20 kt enhanced by the convection. Otherwise, a surface
trough is in the W Bay of Campeche supporting scattered heavy
showers and tstms within 75 nm of the coast of Vera Cruz. A surface
ridge will prevail across the basin through early next week.
Rainshowers that are in the NE corner of the area are forecast to
continue through Sat night.

CARIBBEAN SEA...

CIRA LPW imagery shows abundant shallow moisture across most of
the Caribbean. In the western basin, diffluent flow aloft supports
a broad area of scattered showers and tstms from 11N-18N W of 76W.
A tropical wave is moving across the E basin, however both
Saharan Air Layer dry air and strong deep layer wind shear are
suppressing the development of convection at the time.

A ridge north of the area will maintain mainly fresh
to occasionally strong trade winds over the south-central
Caribbean and moderate to fresh trades elsewhere the next
several days. Winds along the coast of Colombia may reach near
gale-force at night the next two nights. A large area of showers
and thunderstorms associated with a tropical wave along 54W will
move west across the tropical N Atlantic tonight through Fri night,
reaching the eastern Caribbean Sat.

ATLANTIC OCEAN...

The Bermuda high and the Azores high covers most of the Atlc ocean
mainly supporting fair weather. A weakness in the ridge is
analyzed as a 1019 mb low centered near 32N55W from which a
surface trough extends SW to 24N63W. Scattered showers and tstms
are within 150 nm ahead of the low and trough N of 27N.

A large area of disorganized showers and thunderstorms is SE of
Lesser Antilles associated with a tropical wave. Some development
of this system is possible over the next couple of days while it
moves west-northwestward toward the Windward Islands. By late
Saturday, unfavorable environmental conditions should limit the
chances for additional development while the system moves over the
eastern Caribbean Sea. It is likely that this system may bring
locally heavy rainfall to portions of the Lesser Antilles on
Friday and Saturday.

A high pressure ridge along 30N will prevail across
the region through the weekend, supporting gentle to moderate
trade winds N of 22N and moderate to fresh trade winds S of 22N.
Winds may briefly pulse to strong along the N coast of Hispaniola
during the late afternoons.

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

$$
nr/mt
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