[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171747
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
147 PM EDT Fri Aug 17 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
1745 UTC.

...SPECIAL FEATURES...

The center of Tropical Storm Ernesto at 17/1500 UTC is near 47.1N
32.9W or 605 nmi to the NNW of the Azores. Ernesto is moving NE
at 26 knots. The estimated minimum central pressure is 1005 mb.
The maximum sustained wind speeds are 40 knots with gusts to 50
knots. Scattered moderate convection is N of 44N between 26W and
34W. Ernesto is expected to become a post-tropical cyclone by
tonight and then become extratropical as it merges with a frontal
zone on Saturday. The post-tropical cyclone or its remnants will
move across Ireland and the United Kingdom Saturday night. Please
read the latest NHC forecast/advisory under AWIPS/WMO headers
MIATCPAT5/WTNT35 KNHC for more details.

...TROPICAL WAVES...

A tropical wave is in the E Atlc with axis extending from 06N-18N
along 30W, moving W at 10-15 kt. The wave is in a low deep layer
wind shear environment, however both CIRA LPW and GOES-16 water
vapor imagery at the lower levels show dry air affecting the wave.
These two factors are contributing to the lack of convection at
this time.

A tropical wave is in the central Atlc with axis extending from
05N-16N along 57W, moving W at 15-20 kt. The wave is in a low
deep layer wind shear environment, and CIRA LPW imagery shows
abundant low level moisture associated with it. However, some dry
air intrusion is noted in the NW wave environment shown both in
CIRA LPW and water vapor imagery at the lower levels. This dry air
limits the area of scattered moderate isolated strong convection
from 10N-15N between 54W-61W.

A tropical wave is in the central Caribbean with axis extending
from 10N-20N along 70W, moving W at 10-15 kt. The wave is in a
moderate deep layer wind shear environment. GOES-16 water vapor
imagery at the lower levels show very dry air over the central Caribbean.
This is limiting convection to isolated showers and tstms over
Dominican Republic adjacent waters.

A tropical wave is the SW Gulf of Mexico with axis S of 20N along
95W, moving W at 10-15 kt. GOES-16 water vapor imagery at the
lower levels show dry air over this region, which is hindering
convection in the Bay of Campeche at this time.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of W Africa near
10N15W to 07N20W to 07N28W. The ITCZ begins near 09N32W and
continues to 08N40W to 07N48W to 10N52W. Scattered moderate convection
is from 04N-10N E of 21W and from 05N-11N between 38W-46W. For
more information about convection, see the tropical waves section.

...DISCUSSION...

GULF OF MEXICO...

The Bermuda high extends a ridge axis SW across Florida and large
portions of the Gulf into eastern Mexico. The ridge is providing
return flow in the range of 5-10 kt across the region except in
the north-central Gulf where scattered heavy showers and tstms
enhance the winds to fresh. The area of convection is N of 25N
between 85W and 92W and is being supported by inflow of shallow
moisture from the Caribbean by southeasterly wind and middle
level diffluent flow. Otherwise, a tropical wave moving over the
EPAC waters south of southern Mexico reaches the Bay of Campeche,
however is not supporting convection at the time. Surface ridging
will prevail across the basin through early next week. Showers
over the NE basin 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, an upper level anticyclone
provides divergent flow aloft, which supports a broad area of
scattered showers and tstms from 12N-21N between 83W-90W. A
tropical wave is moving across the central basin, however low
level dry air suppress the development of deep convection at the
time. Scattered to isolated showers and tstms are occurring
across Hispaniola and adjacent waters being supported by shallow
moisture and middle level diffluence. Scattered showers and tstms
are in the eastern Caribbean associated with a tropical wave
approaching the Lesser Antilles. Otherwise, surface ridging
extending from the Atlantic to the northern half of the basin,
continues to support fresh to strong winds in the south-central
Caribbean. The center of high pressure SW of the Bahamas will
stall the next several days, which will allow the continuation of
these winds in the south-central basin. The axis of the tropical
wave supporting showers in the E Caribbean is forecast to move
across the Lesser Antilles Sat morning. Showers will prevail in
the E Caribbean through the weekend.

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 surface trough that extends from 31N55W SW to
26N61W to 24N72W. Scattered showers and tstms are within 105 nm
either side of the trough. Isolated showers are across the
Bahamas. A large area of disorganized showers and thunderstorms
is SE of the Windward Islands associated with a tropical wave.
Environmental conditions are becoming less conducive and
development of this system is not expected while it moves
westward. This system is forecast to move through the Windward
Islands on Saturday where it could bring locally heavy rainfall to
portions of the area this weekend. For further information
associated with the tropical waves, see section above.

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

$$
Ramos
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