[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 270630 CCA
TWDAT

Tropical Weather Discussion...Corrected
NWS National Hurricane Center Miami FL
205 AM EDT Mon Aug 27 2018

Corrected Tropical Waves section

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
0545 UTC.

...TROPICAL WAVES...Corrected

A far eastern Atlantic tropical is just west of the African coast
with its axis along 18W/19W from 04N to 20N, moving westward at
10-15 kt. The wave is embedded within the broad monsoonal trough
region of W Africa. Moisture and convection within this region of
the far eastern Atlantic has increased during the past few days
as observed on GOES-16 imagery. The latest satellite imagery
shows scattered moderate to strong convection just east of the
wave axis to along and just inland the coast of Africa from 07N
to 12N. This activity is holding together as it moves away from
the African coast. Similar convection is west of the wave axis
along and within 120 nm south of the monsoon trough between the
wave and 23W.

A central Atlantic tropical wave has its axis along 48/49W from
03N to 20N, moving westward at 15-20 kt. This wave is surrounded
by a rather stable and dry environment. Only isolated weak
showers and thunderstorms are seen within 150 nm west and within
120 nm east of the wave axis from 08N to 14N.

A tropical wave that was tracked across the central Atlantic
during the past few days appears to have become more defined at
the surface and low-levels near 59W, and will likely be added to
the 06Z analysis. The 700 mb model wind and streamline fields
support a tropical wave in this general area. Partial
scatterometer data from last night highlighted some evidence of
a northeast to southeast shift in wind direction across the wave
axis. Scattered showers and isolated thunderstorms are within 60
nm east of the wave axis from 14N to 18N.

A western Caribbean Sea tropical wave has its axis along 79W
south of 20N, moving westward at about 15 kt. The upper flow is
cyclonic north of 14N in association with an upper-level low
over east-central Cuba. The northern portion of the wave, being
the case that it is in the favorable location east of the upper
low, is helping to trigger off scattered moderate convection
within 120 nm west of the wave axis from 18N to 20N. This
activity is being further enhanced by an upper-low over east-
central Cuba. Isolated showers are possible within 120 nm on
either side of the wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis passes through the coastal sections of
Guinea-Bissau near 12N17W to 09N25W to 11N33W and to just east
of the tropical wave along 48W/49W. ITCZ from 6N50W to 05N53W.
Aside from convective activity associated with the far eastern
Atlantic tropical wave, scattered moderate isolated strong
convection is within 240 nm south of the trough axis between 23W
and 27W. Scattered moderate convection is within 180 nm south
and 60 nm north of the trough axis between 34W and 41W.

...DISCUSSION...

GULF OF MEXICO...

An upper-level trough extends from northeastern Florida to
29N83W, and continues as a shear axis to an upper-level low at
24N93W. At the surface, a westward moving trough extends from
2991W to 23N92W. Upper-level cyclonic wind flow covers nearly the
entire Gulf of Mexico east of 94W eastward. A second upper-level
low is noted at the coast of Mexico near 20N97W. With these
features in play along with a very moist and unstable atmosphere
in place, scattered shower and thunderstorm activity will continue
over much of the basin through the next couple of days.

A surface trough will develop during the evening hours in the
Yucatan Peninsula, before pushing offshore into the SW corner of
the Gulf of Mexico each night. This trough, in combination with
Sunday's daytime heating acting on ample instability in place,
triggered off scattered moderate isolated strong convection over
much of the Yucatan Peninsula. Over the past few hours this
activity has diminish some as it pushes off the west coast of the
Yucatan and to the eastern Bay of Campeche. Scattered showers and
isolated showers remain over sections of the Yucatan Peninsula.
A surge of moderate to fresh northeast to east winds will
accompany this trough. A weak surface ridge will remain over the
rest of basin, with its associated gradient supporting a mainly
gentle to moderate wind flow regime.

CARIBBEAN SEA...

An upper-level trough extends from a small upper-level low near
22N63W west-southwestward to Hispaniola, and continues to another
upper-level low over east-central Cuba. A trough extends from
this low southward to just south of Jamaica and to northwestern
Colombia. Plenty of atmospheric instability over the western half
of the Caribbean for these features to work with is bringing
scattered moderate convection in clusters over the waters just
south of Cuba to 19N between 81W and 85W. Isolated moderate
convection is seen elsewhere north of 13N west of 77W. Instability
from the upper-level low over Cuba earlier resulted in scattered
to numerous showers and thunderstorms over much of the central and
eastern sections of that island. This activity has decreased
during the past few hours, but is expected to quickly re-develop
today as daytime gets underway. The activity will gradually shift
from east to west as the upper low tracks further away to the
W.

The eastern segment of the eastern Pacific monsoon trough
stretches eastward into the far southwestern Caribbean to the
northwestern coast of Colombia. Scattered showers and thunderstorms
are south of 13N and west of 75W.

Fresh to strong winds, and building seas to 10 feet, will continue
in the south central Caribbean Sea through Wed. A tropical wave
will approach the waters east of the Lesser Antilles on Tue
accompanied by fresh easterly winds and wave heights expected
to max out around 8 ft. The wave will enter the eastern Caribbean
early on Wed, increasing the likelihood of scattered showers and
isolated thunderstorms over much of the Lesser Antilles.

ATLANTIC OCEAN...

Several small surface and upper-level feature are evident across
this area of the discussion domain.

The tail-end of an upper-level trough extends from within 180 nm
offshore the southeastern United States southwestward to NE
Florida. An upper-level low moving westward is near 28N71W, with
and inverted trough stretching southwestward to 25N74W and to an
upper-level low over east-central Cuba. Another inverted trough
extends from the upper low northeastward to north of the area at
32N70W. At the surface, a trough with good track history, is
analyzed from near 29N75W to the central Bahamas and to just north
of the coast of Cuba at 22N78W. Latest satellite imagery shows
scattered showers and thunderstorms moving westward over much of
the central Bahamas west through the Straits of Florida and to
southern Florida. The surface trough is forecast to move across the
area through Mon. Gentle to moderate winds will be associated
with this trough. A small upper-level low moving steadily
westward is seen in water vapor imagery to be near 22N63W, with a
trough extending westward to Hispaniola and to an upper-level low
over east-central Cuba. This upper low is showing a surface
signature identifies as a trough from 27N64W to near 22N66W.
Scattered moderate convection is noted within 180 nm west of the
trough from 24N to 27N. Isolated showers and thunderstorms are
elsewhere to the west of 60W.

An upper-level trough stretches from an upper-level low also
located well north of the area at 35N39W southwestward through
32N45W to 27.5N50W and to the upper-level low that is near 22N63W.
A pair of surface troughs are analyzed from near 32N43W to 29N50W,
and from near 32N50W to 29N56W to 31N51W. Scattered moderate
convection is within 75 nm southeast of the first trough. Isolated
showers and weak thunderstorms are along and within 30 to 60 nm of
the the second trough. Isolated showers are elsewhere to the
north of 24N between 45W and 60W.

Outside the above described features, surface high pressure is
present across the Atlantic, with the strongest high pressure
found north of 28N and east of 50W.

Water vapor imagery and the Total Precipitable Water (TPW)
animation reveal that atmospheric moisture is increasing over
much of the basin east of 52W.

East winds will pulse to fresh to strong at night just north of
Hispaniola through Tue. A weak surface ridge will remain over the
remainder of these waters, with its associated gradient supporting
gentle to moderate east to southeast winds west of about 50W.

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

$$
Aguirre
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