[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161737
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
137 PM EDT Sun Sep 16 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
1730 UTC.

...SPECIAL FEATURES...

Post-Tropical Cyclone Helene is centered near 43.8N 25.7W at
16/1500 UTC or 350 nm N of the Azores moving NE at 25 kt.
Estimated minimum central pressure is 989 mb. Maximum sustained
wind speed is 45 kt with gusts to 55 kt. See latest NHC
forecast/advisory under AWIPS/WMO headers MIATCPAT3/WTNT33 KNHC
for more details. On the current forecast track, Helene should
move away from the Azores overnight and then approach Ireland and
the United Kingdom tonight and Mon. See the latest NHC
forecast/advisory under AWIPS/WMO headers MIATCPAT3/WTNT33 KNHC
for more details.

Tropical Depression Joyce is centered near 34.7N 34.3W at 16/1500
UTC or 400 nm WSW of the Azores moving ENE at 16 kt. Estimated
minimum central pressure is 1005 mb. Maximum sustained wind
speed is 30 kt with gusts to 40 kt. Scattered moderate convection
is noted to the northeast of the center from 35N to 38N between
30W and 33W. Joyce is forecast to continue on its current motion
over the next day or so, with a decrease in forward speed. After
that time, Joyce should turn east-southeast away from the Azores.
See the latest NHC forecast/advisory under AWIPS/WMO headers
MIATCPAT5/WTNT35 KNHC for more details.

...TROPICAL WAVES...

A central Atlantic tropical wave has its axis extending along 39W
between 05N and 20N, moving westward at 10-15 kt. The wave is
supported by broad troughing at the 700 mb level, but is
surrounded by a rather dry environment from dust that moved off
the coast of Africa a few days ago. The dust is spreading westward
across the eastern Atlantic. These dry conditions are inhibiting
convection from developing along or near the wave. Only scattered
showers are along the wave's axis from 06N to 08N.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from well inland Africa southwestward
to the coastline near 13N16W and continues to 11N19W. The ITCZ
extends from 11N19W to 06N33W, then resumes west of the tropical
wave near 06N41W to 05N53W. Aside from the activity associated
with the tropical wave described above, scattered showers are
within 90 nm on either side of the ITCZ.

...DISCUSSION...

GULF OF MEXICO...

An upper-level low located north of the Yucatan Peninsula near
24N91W. A diffluent flow aloft prevails across the western portion
of the basin supporting scattered moderate convection west of 96W
affecting northeast Mexico and adjacent waters. At the surface,
high is centered near 28N94W. A ridge prevails across the basin. A
surface trough extends southwest from Florence to the Florida
Panhandle and the far northeast Gulf waters. Scatterometer data
depicts light to gentle anticyclonic flow across the basin. A
similar weather pattern will continue through the next 24 hours.

CARIBBEAN SEA...

A surface trough extends across the central Caribbean from 20N73W
to 13N75W. Abundant moisture prevails in this area supporting
scattered moderate convection between 69W-76W. THis activity is
affecting Hispaniola, Windward Passage and east Cuba. Diffluence
aloft prevails across the east Caribbean enhancing scattered
showers east of 69W affecting Puerto Rico and the Lesser Antilles.
Over the far southwest Caribbean, the eastern extent of the
eastern Pacific monsoon trough is bringing scattered showers over
the waters south of 12N from northwestern Colombia westward to
76W. Scatterometer data depicts gentle trades west of the trough,
while gentle to moderate trades are elsewhere east of the trough.
The central Atlantic tropical wave will move across the tropical
waters east of the Windward Islands by Tue, accompanied by fresh
winds and building seas.

ATLANTIC OCEAN...

Please refer to the Special Features section above, for details
on Post-Tropical Cyclone Helene and Tropical Storm Joyce.

A broad deep-layer trough extends across the central Atlantic
from a large and elongated upper-level low that is north of the
area near 35N52W southwestward to 20N69W. Plenty of instability
exists with this trough as it acts on a very moist atmosphere.
The trough is forecast to move westward during the next few days.

At the surface, a 1012 mb low is near 25N63W, with a trough from
28N60W to 24N66W. To the east, another trough extends from 27N55W
to 22N60W. Scattered moderate convection is noted with these
features between 52W-66W. Surface ridging prevails across the
remainder of the basin, anchored by a 1021 mb high centered near
27N29W.

An area of African dust is over the eastern Atlantic from 10N to
25N east of 37W, and is gradually migrating westward.

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

$$

ERA
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