[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201806
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
206 PM EDT Mon Aug 20 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 extending from
05N34W to 13N34W to 19N32W, moving westward at 10-15 kt. Isolated
moderate convection is from 05N to 17N. Scattered moderate
convection is within 120 nm west of the wave axis from 05N to 06N.
Isolated showers and thunderstorms are within 180 nm east of the
wave axis from 05N to 08N.

A central Atlantic tropical wave has its axis extending from
05N52W to 13N52W to 18N51W, moving westward at 15 kt. Scattered
moderate convection is within 60 nm east of the wave axis from
09N to 10N. Isolated showers and thunderstorms are within 60 nm of
the axis from 12N to 16N.

A western Caribbean Sea tropical wave has its axis extending from
southern Costa Rica northward to 15N78W and to eastern Cuba near
20N76W. It is moving westward at 10-15 kt. Isolated moderate
convection is within 60 nm east of the wave from 20N-21N.

The northern portion of an eastern Pacific tropical wave extends
along 94W northward to the Bay of Campeche to 19N. It is moving
westward near 20 kt. Only isolated showers are noted within 60 nm
of the wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from western Africa at 13N17W to
10N28W to 09N40W, where scatterometer data indicates the ITCZ
axis begins and extends to just east to the east of the central
Atlantic tropical wave. It resumes at 09N52W to just inland the
coast of S America at 07N59W. Scattered moderate convection is
within 120 nm south of the axis between 21W and 25W and also
between 27W and 29W.

...DISCUSSION...

GULF OF MEXICO...

A 1023 mb high is centered over the western Atlantic at 32N62W,
with a ridge axis extending WSW from the high to central Florida
and to the eastern gulf waters. The associated gradient is
allowing for generally moderate southerly flow to persist over
much of the gulf, except for lighter SW to W flow, in the 5-10 kt
range over the far northeastern gulf waters. Widely scattered
moderate convection is over the N Florida Peninsula N of 27N. The
northern portion of a tropical wave is over the Bay of Campeche.
No deep convection is occurring with this wave. See above for
details. Scattered moderate to isolated strong convection is from
15N to 21N between 92W and 95W. A small upper-level low is
centered over the Yucatan Channel near 22N86W enhancing the
convection over western Cuba and the NW Caribbean Sea.

Expect, a surface high to develop over the Gulf near 27N91W on
Tue. This high will meander over the western gulf waters through
Thu. A weak trough will stall over the eastern Gulf waters, then
drifts west and dissipates on Fri.

CARIBBEAN SEA...

A tropical wave is over the western section of the central
Caribbean. See above for details. A surface trough is evident
along a position from 19N69W to near 14N72W. Latest satellite
imagery shows an area of scattered showers and isolated
thunderstorms within 60 nm east of the trough from 15N to 16N.
This activity is being further aided by an upper-level
disturbance that is quickly moving westward in moderate to strong
east winds that are located to the south of an upper anticyclone
centered just north of the Dominican Republic. Otherwise, the
pressure gradient associated with surface ridging that extends
from the Atlantic to the northern half of the basin supports fresh
to strong winds in the south-central Caribbean.

Expect scattered shower showers and convection to persist over the
southwestern Caribbean through at least Wed. Also expect strong to near
gale force nocturnal easterly trades along the northwestern coast
of Colombia and across the Gulf of Venezuela through the middle
of the week.

ATLANTIC OCEAN...

A surface trough is analyzed from near 32N51W to 28N60W to near
27N65W. A second surface trough is analyzed from near 32N45W to
27N50W and to near 23N56W. Meanwhile, an elongated upper-level low
is near 32N62W. The present factors of a very moist and unstable
atmosphere and upper divergence to the east and southeast of the
low along with the presence of the first surface trough is leading
to scattered moderate convection from 26N to 29N between 62W and
65W. Isolated showers and thunderstorms are seen within 60 nm
south of the first trough between 57W and 62W. Yet a third surface
trough is analyzed along a position from near 28N69W to the
southeastern Bahamas near 22N74W. A shortwave trough passing just
to its NNE is providing additional atmospheric lift leading to
clusters of weakening scattered moderate convection from 25N to
29N and between 71W and 73W. Isolated showers and thunderstorms
are elsewhere within 90 nm of the surface trough from 22N to 25N.
The third trough is forecast to move westward across the Bahamas
through Tue, then weaken by Tue night and into Wed. An upper-
level anticyclone is identified to be just north of the Dominican
Republic near 21N70W. Its associated subsidence is suppressing
deep convection from developing in that general area.

E of the lower Windward Islands, scattered moderate convection is seen
within 45 nm either side of a line from 09.5N55W to 10N58W to
11N62W. A 1023 mb high is centered over the western Atlantic near
32N62W, with a ridge extending WSW to central Florida. A surface
trough from 32N79W to just east of central Florida briefly
interrupts the ridge. Scattered showers and thunderstorms are
within 30 nm of the trough. This activity is likely to continue
into tonight. A 1027 mb high is centered to the southwest of the
Azores near 35N35W. It is allowing for ridging and generally fair
weather to persist over the eastern Atlantic.

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

$$
Aguirre
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