[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 031739
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
139 PM EDT Wed Oct 3 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...

Hurricane Leslie is centered near 29.5N 56.8W at 03/1500 UTC, or
445 nm ESE of Bermuda. Movement is stationary. Estimated minimum
central pressure is 975 mb. Maximum sustained wind speed is 70 kt
with gusts to 85 kt. Scattered to numerous moderate convection is
noted within 120 nm of the center. Little motion is expected for
the next several hours. A northward motion is forecast to begin
this evening, and this motion with an increase in forward speed
should continue through Friday night. A turn to the east is
expected this weekend. Some additional strengthening is forecast
during the next day or so, but a slow weakening trend is expected
to begin on Friday. See the latest NHC forecast/advisory under
AWIPS/WMO headers MIATCPAT3/WTNT33 KNHC for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave extends its axis along 22W
from 03N-15N, moving westward around 15 kt. Scattered moderate
convection is within 120 nm west and 90 nm east of the wave axis
from 09N-13N. Another area of scattered moderate convection with
this wave is within 120 nm west and 330 nm east of the wave axis
from 03N-07N. Total Precipitable Water imagery shows deep
moisture surrounding the wave. The wave has an associated 700 mb
trough, as shown by model analyses.

A central Atlantic tropical wave is along 40W from 05N-14N moving
westward around 15 kt. Scattered showers and thunderstorms are
occurring from 07N-12N between 36W-47W. The wave has an associated
700 mb trough, as shown by model analyses.

An eastern Caribbean tropical wave has its axis along 63W from
06N-18N, moving westward at 10-15 kt. A TPW animation shows a
slight moisture maximum associated with the wave. The wave is not
producing any significant convection. The wave is moving through
an area of mid-level ridging and sinking air in the eastern
Caribbean.

...MONSOON TROUGH/ITCZ...

The monsoon trough extends from the coast of west Africa near the
Senegal/Mauritania border near 16N16W to 09N20W to 07N25W to
09N40W. The ITCZ extends from 09N41W to 08N59W. Aside from the
convection mentioned in the tropical waves section above,
isolated showers are observed within 240 nm north of the ITCZ
between 48W-53W.

...DISCUSSION...

GULF OF MEXICO...

A surface trough is moving slowly westward over the northern Gulf,
and is analyzed from 30N86W to 26N85W at 1200 UTC. Scattered
showers and isolated thunderstorms are occurring within 60 nm of
the trough axis. Enhanced moisture associated with this trough is
seen on GOES-16 TPW imagery. Enhanced convection will continue
through today offshore the northern Gulf coast in association with
this trough. Another trough extends across the Bay of Campeche
along 94W from 19N-21N. Scattered showers and isolated
thunderstorms are over the Bay of Campeche south of 21N and west
of 94W. Surface ridging prevails across the northwest Gulf. Little
to no shower activity is observed north of 24N and west of 90W.

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 tropical wave is over the eastern Caribbean. Refer to the
Tropical Waves section above for details. A broad surface trough
over the western Caribbean is analyzed at 1500 UTC from 18N78W to
15N81W to 11N82W. The position of the trough is supported by a
recent ASCAT pass. This trough is associated with a broad area of
low pressure located over the southwestern Caribbean Sea.
Satellite imagery shows scattered moderate and isolated strong
convection from 12N-15N between 78W-83W. Isolated showers and
thunderstorms are elsewhere over the southwest Caribbean Sea south
of 17N and west of 77W. Some slow development of this system is
possible this weekend while the low drifts across the northwestern
Caribbean Sea. A mid to upper level trough extending over the
Bahamas and Greater Antilles will help advect moisture northward
as the week progresses. As a result, very heavy rainfall is likely
to spread over sections of Hispaniola and Jamaica later this week
and into the weekend.

Another area of convection that was generated yesterday closer to
the aforementioned trough axis has been drifting eastward and is
gradually weakening as it moves farther from the trough. This area
of scattered moderate convection is located from 13N-15N between
69W-72W. Upper-level diffluence in this area is becoming less
pronounced, so expect the convection in this area to become less
intense over the next 12 hours.

Large NNE swells generated from Leslie will continue to move
through the Atlantic passages into the Caribbean during the next
few days.

ATLANTIC OCEAN...

Two tropical waves over the tropical Atlantic between the west
coast of Africa and the Lesser Antilles are described in the
Tropical Waves section above. Hurricane Leslie is described in
the Special Features section above.

An area of upper-level diffluence just east of the central Bahamas
is causing scattered showers and thunderstorms from 25N-27N
between 71W-75W. This activity could continue in this area over
toward the central Bahamas through this evening.

An E-W surface trough is analyzed to the east of Hurricane Leslie along
30.5N between 36W-42W. Scattered moderate convection is seen from
27.5N-31N between 34W-45W. Another surface trough is analyzed
south of Hurricane Leslie from 25N56W to 21N62W to 20N67W.
Scattered showers are occurring between 100 nm to 300 nm southeast
of the trough axis from 17N-26N between 50W-60W. GOES-16 Total
Precipitable Water imagery indicates that an atmospheric river
has developed. Tropical moisture from the vicinity of 17N61W is
being transported northeastward to the vicinity of the surface
trough near 30N36W. The moisture is following the mid to upper
level flow in between the cyclonic flow associated with Leslie and
anticyclonic flow in the vicinity of 23N43W. The atmospheric
river is enhancing the aforementioned convection over the central
Atlantic

Surface ridging generally prevails over the eastern Atlantic,
leading to quiet weather from 19N-27N east of 40W.

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

$$
Hagen
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