TROPICAL WEATHER DISCUSSION BY NHC
093
AXNT20 KNHC 221805
TWDAT
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
205 PM EDT Wed Aug 22 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.
...TROPICAL WAVES...
A far eastern Atlantic tropical wave has its axis along 25W/26W
from 05N-20N, moving westward at 10-15 kt. The wave is embedded
within a very dry and stable environment inhibiting convection at
this time. Only isolated weak showers and thunderstorms are seen
within 120-180 nm east of the wave from 10N to 11N.
A central Atlantic tropical wave has its axis extending along 45W
from 05N-19N, moving westward at 10-15 kt. This wave is also
embedded within a very dry and stable environment caused by
Saharan Air Layer outbreak of the past several days that is
spreading westward across the central and eastern Atlantic.
Scattered moderate convection is within 120 nm east of the wave
from 08N to 10N. Isolated showers are within 180 nm east of
the wave from 14N to 19N.
An eastern Caribbean Sea tropical wave has its axis along 66W
south of 19N to well inland Venezuela. It is moving westward near
10-15 kt. Scattered showers and isolated thunderstorms are
increasing east of the wave from 21N to 16N.
A central Caribbean tropical wave has its axis along 76W/77W from
09N to 20N, moving westward near 15 kt. Previous deep convection
with this wave has dissipated. Only isolated showers and
thunderstorms are see within 120 nm east of the wave from 18N
to 20N.
The tropical wave previously along 92W has moved into the eastern
Pacific. Please refer to the eastern Pacific Tropical Weather
Discussion for details on this wave.
...MONSOON TROUGH/ITCZ...
The monsoon trough axis extends from the African coast near
14N16W to 10N23W to 09N35W to 09N44W. The ITCZ axis begins at
08N46W and continues to 10N55W to 10N61W. Scattered moderate
convection is within 120 nm north of the ITCZ axis between 45W
and 55W, and north of the monsoon trough within 30 nm of 11N39W.
...DISCUSSION...
GULF OF MEXICO...
High pressure of 1020 mb is analyzed near 26N94w as of 15Z, while
a surface trough extends from southeastern Georgia southwestward
to the northeastern gulf and continues to near 27N91W. The
nocturnal Yucatan Peninsula trough has moved across the
southwestern gulf during the late night and early morning hours,
and is analyzed from near 21N96W to 18N94W as of 15Z. The present
pressure gradient across the gulf generally supports light to
gentle winds throughout, except for gentle to moderate winds south
of 26N and relatively low seas of 1 to 3 ft. Scattered showers
and thunderstorms are observed over the far southwest section of
the gulf south of 21N and west of 94W in association with the
nocturnal trough that moved offshore the Yucatan Peninsula during
the overnight hours. Other scattered showers and thunderstorm
activity continues to increase over the north-central gulf in
association with the aforementioned surface trough, with further
support from an upper-level trough that is dropping southward
across the norther gulf section. The activity over the far
southwest is expected to weaken during the afternoon. It should
then re-develop tonight and Thu night as the surface trough
again moves across those same waters. The activity over the north-
central gulf should continue to increase through this afternoon
and into the evening hours. Otherwise, relatively weak high
pressure ridging will remain across the northern gulf waters, with
the associated gradient producing gentle to moderate anticyclonic
flow through Fri.
CARIBBEAN SEA...
Two tropical waves are moving across the basin. Refer to the
section above for details. An upper level trough extends from
eastern Cuba southwestward to just east of northeastern Honduras.
Water vapor imagery indicates plentiful deep layer moisture along
and to the northwest of this trough, and it is where isolated
showers and thunderstorms are occurring. Scattered moderate
isolated strong convection has increased over the far southwestern
Caribbean south of 11N between 77W and 82W mainly due to low-level
wind speed convergence, with the added factor of the eastern
segment of the eastern Pacific monsoon trough that stretches east-
northeastward to the far southwestern Caribbean along 09N and to
the typical climatological low found over northwestern Colombia
presently located just offshore that coast at 09N76W.
A slighter tighter pressure gradient behind the tropical wave
along 77W will help induce strong to near gale force northeast to
east trade winds over the south-central Caribbean waters off the
coast of Colombia and across the Gulf of Venezuela tonight. The
strong trades are forecast to reach northward to 15N. Moderate to
fresh trades will continue elsewhere through Fri as little overall
changes are expected with the present synoptic set-up through
Fri.
ATLANTIC OCEAN...
Two tropical waves are moving across the basin. Refer to the
section above for details. A surface trough is analyzed from
29N61W to 21N68W. A shear axis is evident by model and satellite
winds to be situated northwest of the trough from 32N65W to 25N70W
to east-central Cuba. Satellite imagery shows increasing scattered
showers and thunderstorms within 180 nm to the northwest of the
trough between 65W and 69W. Isolated showers and thunderstorms
are seen over the western portion of the basin west of about 75W.
This activity as well as that to the northwest of the surface
trough are expected to last through tonight and into Thu. Another
trough moving westward around 15 kt is along 52W from 17N to 30N.
No deep convection is noted with this trough, only isolated
showers within 120 nm east of the trough from 21N to 26N. A 1025
mb high center is analyzed north of 31N and extends a ridge across
the remainder of the basin. Saharan dust and associated dry air,
although not as dense as in previous days, is noted mainly east of
about 60W on GOES-16 GEO color dust imagery. The dust is keeping
convection rather limited, to non-existent, outside across the
eastern and central Atlantic waters, except as described above
near the the ITCZ region.
For additional information please visit
http://www.hurricanes.gov/marine
$$
Aguirre
https://www.nhc.noaa.gov/
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NHC is now also monitoring a future wave that is forecast to move
off the the African coast by tomorrow then track west over the
central Atlantic where conditions could become more favorable for
tropical cyclone formation by next week...RTW
