[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 021753
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
153 PM EDT Tue Oct 2 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
1715 UTC.

...SPECIAL FEATURES...

Tropical Storm Leslie is centered near 30.9N 56.1W at 1500 UTC,
or 450 nm E of Bermuda, moving SW at 7 kt. Estimated minimum
central pressure is 989 mb. Maximum sustained winds are 55 kt with
gusts to 65 kt. A recent ASCAT pass shows that the tropical storm
force winds are occurring north of 28N between 54W-59W. Scattered
moderate convection is within 150 nm of the center, with the
strongest convection in the northwest semicircle. A slow south-
southwestward or southward motion is expected through Wed. A turn
to the north is forecast to occur late Wed into Thu, followed by a
motion toward the north-northeast on Fri. Gradual strengthening is
expected during the next day or two, and Leslie is forecast to
become a hurricane tonight or on Wednesday. Public Advisories for
Leslie are under the WMO header WTNT33 KNHC, and the AWIPS header
MIATCPAT3. Forecast/Advisories for Leslie are under the WMO
header WTNT23 KNHC, and the AWIPS header MIATCMAT3.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave was added to the analysis
just off the coast of Africa along 16W from 03N-16N, moving
westward 10-15 kt. Scattered moderate convection is occurring
within 180 nm west and 210 nm east of the wave axis. The wave
coincides with a maximum in total column water vapor as depicted
in the GOES-16 TPW product. The wave has a 700 mb trough
associated with it, as shown by model analyses.

A central Atlantic tropical wave is along 48W from 03N-14N,
moving westward around 15 kt. Scattered showers are near 09N-11N
between 49W-52W and between 44W-46W. These showers appear to be
more related to the ITCZ than the wave.

A tropical wave is just east of the Lesser Antilles along 59W and
extends from Guyana to 18N, moving westward at 10 kt. A well-
defined 700 mb trough is shown in model analyses just east of
where the wave is analyzed. The wave has a well defined 700 mb
trough associated with it but lacks significant convection. A TPW
animation shows a moisture maximum is associated with this
tropical wave. Only a small area of isolated showers is seen east
of the wave axis from 09N-12N between 55W-58W. Otherwise, no
significant convection is noted.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of Senegal near 12N16W
to 09N23W to 09N36W. The ITCZ extends from 09N36W to 10N48W. The
ITCZ resumes west of the tropical wave along 48W and continues to
09N58W. Aside from the convection mentioned in the tropical waves
section above, scattered showers and isolated thunderstorms are
observed within 60 nm north and 120 nm south of the ITCZ between
36W-44W.

...DISCUSSION...

GULF OF MEXICO...

A weak surface trough is analyzed over the northeastern Gulf
along 85W from 25N-29N. The trough is producing scattered showers
and thunderstorms from 28N-29N west of 84W. This trough, along
with increasing moisture in the northeastern Gulf, could help to
enhance showers and thunderstorms over the northeast and north-
central Gulf for the remainder of this afternoon.

Expect ridging to prevail over the forecast area during the next
few days. A surface trough will develop each evening over the
Yucatan Peninsula. The trough will move into the SW Gulf
overnight, where it will dissipate each morning. Moderate to fresh
winds will accompany the trough.

CARIBBEAN SEA...

A broad surface trough along 79W is associated with a broad area
of low pressure located over the southwestern Caribbean Sea.
Satellite imagery shows numerous moderate with embedded scattered
strong convection east of the trough from 12N-17N and between
72W and 77W. Elsewhere east of the surface trough, scattered
moderate convection is present from 11N-18N between 71W and 78W.
Two small areas of scattered moderate convection are occurring
just offshore northeast Honduras and also just offshore east-
central Nicaragua. The persistent strong convection east of the
trough is being enhanced by an area of upper-level diffluence over
the same area. Some gradual development of the broad low pressure
area is possible late this week and this weekend while the low
drifts generally in a northward direction. A deepening mid to
upper level trough oriented E-W over the northern Caribbean and
Greater Antilles will help advect moisture northward as the week
progresses. As a result, heavy rain is likely to spread over
sections of Hispaniola and Jamaica later this week and into the
weekend.

Scattered showers and thunderstorms are occurring from 19N-21N
between 80W and 85W. Expect the activity in this area to remain
scattered and not very strong since upper-level troughing in the
area is weakening. Broad mid-level ridging is over the east-
central Caribbean with associated westerly upper level flow
leading to generally quiet weather conditions east of 71W.

Large NNE swell generated from Leslie will pass through the Atlantic
passages into the Caribbean.

ATLANTIC OCEAN...

The three tropical waves over the tropical Atlantic between Africa
and the Lesser Antilles are described in the Tropical Waves
section above. Tropical Storm Leslie is described in the Special
Features section above.

A broad mid to upper level trough over Leslie combined with an
area of upper-level diffluence to the southeast of Leslie
continues to enhance convection to the southeast of Leslie.
Scattered moderate convection is observed from 24N-29N between
42W-49W. A surface trough is analyzed extending from 28N54W to
20N63W. East of the trough axis, an area of scattered moderate
convection is noted from 20N-24N between 51W and 56W. Elsewhere
from 20N-26N, between 50W and the trough axis, scattered showers
and isolated thunderstorms are present. A shear line has developed
since this morning oriented east to west from 22N65W to 25N78W.
Scattered showers and thunderstorms are occurring within 60 nm of
the shear line. ASCAT and surface observations show NE 20-25 kt
winds along and north of the shear line.

The northeastern portion of the forecast area is under the
influence of a ridge, anchored by a 1018 mb surface high near
26N36W. Generally quiet weather prevails north of 20N and east of
40W.

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

$$
Hagen/Aguirre
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