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Atlantic Tropical Weather Discussion (Text)



928 
AXNT20 KNHC 171206
TWDAT 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
806 AM 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 0600 UTC surface analysis and satellite imagery through 
1145 UTC.

...SPECIAL FEATURES...

The center of Tropical Storm Ernesto at 17/0900 UTC is near 45.6N
36.4W or 620 nmi to the NW of the Azores. Ernesto is moving NE at 
22 knots. The estimated minimum central pressure is 1006 mb. The 
maximum sustained wind speeds are 40 knots with gusts to 50 knots.
Scattered moderate convection is from 44N to 48N between 30W and 
37W. Ernesto is expected to become a post-tropical cyclone by
tonight and then become extratropical as it merges with a frontal
zone on Saturday. Ernesto will approach Ireland and the United 
Kingdom on Saturday. 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 05N-17N
along 29W, moving W at 10-15 kt. The wave is in a moderate deep 
layer wind shear environment, and 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
06N-20N along 54W, 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
has acted to reduced the convection to scattered moderate isolated
strong from 10N-15N between 50W-60W.

A tropical wave is in the central Caribbean with axis extending 
from 11N-20N along 70W, moving W at 10-15 kt. 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. This is limiting convection to
isolated showers and tstms over Hispaniola adjacent waters. 

A tropical wave is the SW Gulf of Mexico with axis S of 21N along
92W, moving W at 10-15 kt. Both CIRA LPW and GOES-16 water vapor 
imagery at the lower levels show dry air over this region, which 
is limiting convection to isolated showers in the Bay of Campeche.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of W Africa near 
11N16W to 08N21W to 07N30W. The ITCZ begins near 07N30W and 
continues to 06N40W to 06N50W. Scattered moderate isolated strong
convection is from 04N-07N E of 20W. For more information about 
convection, see the tropical waves section.


...DISCUSSION...

GULF OF MEXICO...

Upper level cyclonic wind flow covers the SW corner of the Gulf of
Mexico from 23N southward from the Yucatan Channel westward.
Warming cloud top temperatures and weakening convective 
precipitation, and lingering widely scattered moderate to isolated
strong rainshowers are in the Gulf of Mexico and the coastal 
plains of the western part of the Yucatan Peninsula from 21N 
southward between land and 93W.

A surface ridge extends from a 1025 mb high pressure center that
is near 31N69W, across Florida just to the north of Lake
Okeechobee, into the east central Gulf of Mexico, to the coast of
Mexico along 20N in the SW corner of the Gulf of Mexico.

Isolated moderate to locally strong rainshowers are in the waters
from 23N northward from 90W eastward.

An east-to-west oriented surface ridge extends across the Gulf 
waters along 28N. The ridge is accompanied by gentle to moderate 
anticyclonic wind flow, that is expected to increase to a fresh 
southerly breeze across the northwest waters, from Sunday night 
through early Monday. A surface trough will develop along the 
Yucatan Peninsula during the late afternoons, then drift westward 
across the SW Gulf waters during the overnight hours. The trough
will be accompanied by a fresh east-to-southeast wind shift, with
the trough dissipating along 96W during the late mornings.

CARIBBEAN SEA...

Isolated moderate to locally strong rainshowers cover the NW
corner of the Caribbean Sea, from 14N northward from 79W westward.
Upper level anticyclonic wind flow covers the Caribbean Sea from
the Windward Passage westward.

Nocturnal near gale force easterly trade winds are expected along
the northwest coast of Colombia overnight, and then again on 
Friday night. A tropical wave along 68W will continue westward 
across the central Caribbean tonight, and pass through the western
Caribbean waters during the upcoming weekend. A second tropical 
wave will reach along 55W on Friday, and pass through the eastern 
Caribbean Sea on Saturday and Sunday. The tropical wave will be 
accompanied by locally strong rainshowers through early Saturday.

ATLANTIC OCEAN...

An upper level trough passes through 32N37W, to 27N44W, to an 
Atlantic Ocean cyclonic circulation center that is near 25N53W. A 
surface trough is along 32N55W 28N57W 25N60W. Isolated moderate to
locally strong rainshowers are from 30N northward between 44W and
57W. Rainshowers are possible elsewhere from 20N northward 
between 30W and 60W. Surface anticyclonic wind flow is on either
side of the 32N55W-to-25N60W surface trough.

Broad upper level cyclonic wind flow, and isolated moderate 
rainshowers, cover the Atlantic Ocean from the Greater Antilles 
northward from 60W westward. A few individual cyclonic circulation
centers near 27N63W, and near 21N70W.

An east to west ridge extends from 30N65W to 28N81W. Light 
southerly winds are to the north of the ridge. Fresh trade winds
are to the south 23N, except becoming locally strong along the 
north coast of Hispaniola during the late afternoon into early 
evening hours.

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

$$
MT/NR


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Page last modified: Friday, 17-Aug-2018 12:06:18 UTC