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000
AXPZ20 KNHC 280930
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Wed Sep 28 2016

Tropical weather discussion for the eastern Pacific Ocean from
the Equator to 32N, east of 140W. The following information is
based on satellite imagery, weather observations, radar, and
meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0930 UTC.

...SPECIAL FEATURES...

Hurricane Ulika is centered at 13.9N 139.0W, or about 1135 sm
ese of Hilo Hawaii at 09 UTC Sep 28, moving nne, or 030 degrees
at 6 kt. The estimated minimum central pressure is 992 mb. The
maximum sustained wind speed is 65 kt with gusts to 80 kt.
Currently, scattered strong convection is observed within 60 nm
of the center, with a area of scattered moderate convection
noted elsewhere within 180 nm over the se quadrant of the
center. Ulika is forecast to remain a hurricane for 24 hours,
then weaken to a tropical storm with the center moving w of 140W
late in a couple of days. Refer to the latest NHC forecast/
advisory under AWIPS/WMO headers WTPZ24KNHC/TCMEP4, or visit the
NHC website at http://hurricanes.gov for additional details.
After the center moves w of 140W, refer to the latest CPHC
forecast/advisory under AWIPS/WMO headers WTPA22 PHFO/TCMCP2, or
visit the CPHC website at http:www.prh.noaa.gov/cphc/ for
additional details.

Tropical Storm Roslyn is centered at 20.2N 115.5W, or about 405
sm wsw of the southern tip of the Baja California Peninsula at
09 UTC Sep 28, moving nne, or 025 degrees at 8 kt. The estimated
minimum central pressure is 1005 mb. Maximum sustained wind
speed is 35 kt with gusts to 40 kt. Currently, scattered
moderate convection is observed well ne of the center, within 90
nm either side of a line from 22N114W to 24N114W. Roslyn is
forecast to weaken to a tropical depression today, and further
weaken to a remnant low tonight, and gradually dissipate in
about 3 days. Refer to the latest NHC forecast/advisory under
AWIPS/WMO headers WTPZ23 KNHC/TCMEP3, or visit the NHC website
at http://hurricanes.gov for additional details.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends wnw off the Pacific coast of Costa
Rica at 09N84W to 11N105W to 05N118W where it loses identity.
Scatterometer winds indicate that the monsoon trough resumes
just sw of tropical cyclone Roslyn near 13N117W to 13N136W.
Isolated moderate and strong convection is noted within 150 nm
either side of a line from 04N77W to 09N102W to 07N118W, and
within 75 nm either side of a line from 12N126W to 15N132W.

Scattered moderate isolated strong convection is observed n of
11N between 93W and 98W to include the Gulf of Tehuantepec.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A sub-tropical ridge axis extends from nw to se across the
offshore zones w of the Baja Peninsula terminating near 24N110W.
Light to gentle n-ne winds are observed w of the Baja Peninsula.
Fresh to strong e to se winds,and combined seas of 7 to 11 ft
will expand n across the far offshore waters, generally from 11N
to 24N w of 115W today and tonight, as tropical cyclone Roslyn
continues north-northeastward, and later nw. The subtropical
ridge will rebuild from 29N120W to 22N106W on Fri with gentle n
flow returning, except becoming moderate along the Baja coast
during the overnight hours. The pressure gradient will tighten
this weekend, with moderate to fresh nw winds, and 5 to 8 ft
seas, w of Baja on Sun, and fresh to strong nw winds developing
Sun night.

Light to gentle nw winds are expected across the entire Gulf of
California late today, with little change expected through Thu.
Light and variable winds expected across the far northern
gulf waters beginning on Thu night.

Fresh drainage flow expected across the Gulf of Tehuantepec
tonight, increasing to fresh to strong flow on Thu, and then
pulsing through the upcoming weekend.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Light to gentle southerly winds are expected n of the monsoon
trough, while gentle to locally moderate s to sw flow is
expected s of the monsoon trough through the upcoming weekend.
Combined seas of 3 to 6 ft primarily in long-period sw swell is
expected this week.

REMAINDER OF THE AREA...

As tropical cyclone Ulika moves w of 140W and tropical cyclone
Roslyn dissipates, the pressure gradient will tighten around the
subtropical ridge, with fresh anticyclonic winds expected
between the monsoon trough/ITCZ and the ridge on Mon, with
combined seas of 6 to 7 ft. The gradient will then relax some by
the middle of next week.

$$
Nelson