Tropical Weather Discussion
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AXNT20 KNHC 211037

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
636 AM EDT Fri Apr 21 2017

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 0600 UTC surface analysis and satellite imagery through
1030 UTC.


The center of T.S. Arlene is located 40.0N 48.0W and is moving
west at 27 knots. The estimated minimum central pressure is 993
mb. The maximum sustained wind speeds is 45 knots with gusts to 55
knots. Scattered moderate convection is observed from 39N-42N
between 33W-49W. Please refer to the public advisory under the
WMO header WTNT31 KNHC and under the AWIPS header MIATCPAT1 for
more details.

A tight pressure gradient generated between a broad low pressure
system centered southwest of T.S. Arlene and a high pressure to
the west is supporting gale-force winds north of 30N between 49W-
54W. Seas in this area will range between 12 to 19 ft this
afternoon. These conditions will continue through the evening
hours. Please see the latest High Seas Forecast product under the
WMO header FZNT02 KNHC and under the AWIPS header MIAHSFAT2 for
further details.


The Monsoon Trough extends across the western Africa coast from
11N15W to 03N19W. The Intertropical Convergence Zone continues
from 03N19W to the coast of Brazil near 03S41W. Scattered moderate
convection prevails from 04N-10S and east of 30W.



A mid to upper-level low is centered northwest of the Yucatan
Peninsula near 23N91W. A diffluent flow aloft prevails to the east
of the low supporting scattered moderate convection from 20N-26N
between 80W-90W. A surface trough accompanies this convection,
extending from the western Caribbean across the Yucatan Channel to
24N85W. A surface ridge extends across the basin anchored by a
1021 mb high centered over the west Atlantic. A 1019 mb surface
high is centered over the Florida Panhandle near 30N85W.
Scatterometer data depicts gentle to moderate easterly winds
across the northern half of the basin while moderate to fresh
easterlies prevail south of 26N. Expect for the upper-level low to
dissipate in 24 hours. The surface trough is forecast to become a
center of low pressure this weekend over the southeast Gulf. The
low will move over northeast Gulf waters where it will dissipate
by Sunday.


The main feature in the basin is a surface trough that extends
from 24N84W to 16N87W. This elongated area of low pressure is
located under a broad area of mid to upper-level diffluent flow
that along with abundant moisture in the region supports scattered
to numerous showers mainly north of 20N west of 79W. This shower
activity will continue today as the trough moves slowly west
towards the Yucatan Peninsula. Latest scatterometer data depicts
fresh to locally strong easterly winds in the vicinity of the
trough. An area of fresh trades extends across the central
Caribbean north of 14N, including the Windward Passage. Moderate
trades dominate elsewhere.


Broken to overcast skies persist across the island with possible
isolated showers over the adjacent waters. These conditions are
expected to continue during the next two days.


T.S. Arlene is over central Atlantic waters north of the area.
Gale-force winds have developed south of a 990 mb surface low
located southwest of Arlene. See the Special Features section
above for further details. A surface ridge extends across the
western Atlantic anchored by a 1021 mb high centered near 31N70W.
To the east, a cold front enters the area from 31N41W to 25N45W to
22N54W. A surface trough, previously part of the front, extends
from 22N62W to 26N75W. No convection is associated with these
boundaries at this time. A surface ridge dominates the remainder
of the area, anchored by a 1018 mb high centered near 27N23W. T.S.
Arlene is forecast to dissipate in 24 hours. The area of gale-
force winds will dissipate in 24 hours.

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