National Hurricane Center - Tropical Weather Discussion (Atlantic)
AXNT20 KNHC 180541
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
141 AM EDT Sat Aug 18 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 0000 UTC surface analysis and satellite imagery through
Tropical Storm Ernesto centered near 50.4N 25.6W at 18/0300 UTC
or 750 nm N of The Azores moving ENE at 30 kt. Estimated minimum
central pressure is 999 mb. Maximum sustained wind speed is 40
kt with gusts to 50 kt. Ernesto is expected to become post-tropical
overnight, and slight weakening is forecast to occur Saturday
while Ernesto merges with a frontal zone by Saturday night. On
this forecast track the post-tropical cyclone and its remnants
will move across Ireland and the United Kingdom Saturday night and
early Sunday. See latest NHC forecast/advisory under AWIPS/WMO
headers MIATCPAT5/WTNT35 KNHC for more details.
A tropical wave is in the E Atlc with axis extending from 04N-16N
along 35W, moving W at 20 kt. The wave is in a deep layer wind
shear environment. 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 E Caribbean with axis extending from
06N-18N along 60W, moving W at 20 kt. The wave is in a 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 as shown both in CIRA LPW,
and water vapor imagery at the lower levels. Widely scattered
moderate convection is from 10N-14N between 53W-61W.
A tropical wave is in the central Caribbean with axis extending
from 09N-18N along 76W, moving W at 20 kt. The wave is in a
moderate deep layer wind shear environment. GOES-16 water vapor
imagery at the lower levels shows very dry air over the central
Caribbean. This is limiting convection to isolated moderate
convection over E Cuba and W Hispaniola from 19N-23N between 72W-
The monsoon trough extends from the coast of W Africa near 13N17W
to 10N30W to 07N40W. The ITCZ begins near 07N40W and continues to
08N50W to 10N60W. Besides the convection mentioned in the
tropical wave section, scattered moderate to isolated strong
convection is over W Africa from 08N-14N between 04W-18W.
Scattered showers are within 120 nm of the remainder of the
monsoon trough and ITCZ.
GULF OF MEXICO...
A 1024 mb high is centered over the W Atlantic near 30N69W. A
ridge axis extends W from the high along 30N to E Texas. 10 kt SE
surface winds covers the Gulf of Mexico N of 24N. A surface trough
is over the Bay of Campeche from 22N90W to 16N93W. Scattwered
moderate convection is from 16N-19N between 92W-95W. In the upper
levels, an upper level high is centered over SE Louisiana near
30N90W. Upper level diffluence is over the Yucatan Channel
producing scattered showers.
Expect, a surface trough to develop along the Yucatan Peninsula
during the late afternoons, then drift westward across the
southwest gulf waters during the overnight hours accompanied by a
fresh east to southeast wind shift with the trough dissipating
along 96W during the late mornings. Otherwise, expect an east to
west ridge extends across the gulf waters along 30N accompanied
by gentle to moderate anticyclonic flow that is forecast to
increase to a fresh southerly breeze across the northwest gulf
waters on Sun evening, and continue through sunrise on Mon. The
ridge will then shift south and extend east to west across the
central waters during the middle of next week.
Two tropical waves are over the Caribbean Sea. See above. A
surface trough extends over the Gulf of Honduras near 18N86W to
the E Pacific near 10N86W. Scattered showers are within 120 nm of
the trough. Surface ridging extends from the Atlantic to the
northern half of the Caribbean. Fresh to strong winds are over the
south-central Caribbean. In the upper levels, an upper level low
is centered over central Cuba near 22N80W. Upper level diffluence
is over Jamaica and E Cuba enhancing convection.
Expect, strong nocturnal easterly trades along the northwest
coast of Colombia through the middle of next week. A tropical
wave along 76W will continue to move westward across the western
Caribbean during the weekend. A second tropical wave along 60W
will continue through the east Caribbean this weekend. A third
tropical wave in the central Atlantic will reach along 55W on Mon
night and reach the east Caribbean during the middle of next week
A tropical wave is over the Atlantic. See above. A 1024 mb high is
centered over the W Atlantic near 30N69W. A surface trough is over
the central Atlantic from 32N54W to 26N62W. Scattered showers are
within 90 nm of the trough. A 1028 mb high is centered over the
Azores near 38N29W.
Expect over the W Atlantic for fresh trades to be south of 23N,
except becoming locally strong along the north coast of Hispaniola
during the late afternoon into early evening hours. The surface
ridge axis will shift south to central Florida early next week.
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