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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 300002 CCA

Tropical Weather Discussion...Corrected
NWS National Hurricane Center Miami FL
2205 UTC Thu Sep 29 2016

Corrected header time

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 1800 UTC surface analysis and satellite imagery through
2145 UTC.


Tropical Storm Ulika is centered near 17.2N 140.2W 1006 mb, or
about 860 nm east of Hilo Hawaii, at 2100 UTC moving NW or 305
DEG at 7 kt. The maximum sustained wind speed is 35 kt with
gusts to 45 kt. Ulika remains under significant vertical
westerly shear attributed to an upper trough that is just to its
west. Abundant dry air aloft west of the trough is being
entrained into the cyclone as observed in water vapor imagery.
Latest satellite imagery shows diminishing scattered moderate
convection well removed from the cyclone between 60 nm to 120 nm
to its northeast. Minimal tropical storm winds are within 30 nm
in the east semicircle and 20 nm in the northwest quadrant of
the cyclone. Ulika continues to experience SW wind shear and is
forecast to weaken to a tropical depression late tonight west of
the area near 17.7N 141.W, and a post-tropical remnant low early
Friday afternoon near 18.3N 142.9W. Refer to the latest CPHC
forecast/advisory under AWIPS/WMO headers WTPA22 PHFO/TCMCP2, or
visit the CPHC website at for
additional details.


The monsoon trough axis extends from northwest Colombia to 
10N85W to 09N94W to 12N107W where it ends. It resumes at 
10N116W to 09N124W to 14N135W. Scattered moderate to isolated
strong convection is seen within 120 nm north of the axis
between 91W and 94W. Scattered moderate convection is within 
60 nm s of the axis between 103W and 108W.



Post-tropical remnant low of Roslyn is centered near 24.1N 115.6W
1014 mb moving N NW at 6 kt. Visible satellite imagery depicts the 
low as a cloud swirl consisting of mainly low clouds about 120 nm
in diameter. Associated winds continue to diminish with only 
20 to 25 kt with seas of 6 to 8 ft remaining within 30 nm of the
low in the northeast quadrant of the low. The low is forecast to
gradually dissipate through Friday afternoon.

Otherwise, a sub-tropical northwest to southeast oriented ridge
axis extends into the area from 32N136W to near 24N131W. High
pressure covers the area north of 22N west of 123W. Light to
gentle northerly winds are present west of the Baja California
Peninsula with seas of 4 to 5 ft in mixed NW and SW swell. The
ridge will strengthen and build southeastward through the next
48 hours. The associated gradient is expected to result in a
moderate to fresh northwest flow. Seas will build to 6 to 8 ft
over the far northern waters west of Baja California Norte on
Saturday evening, and continue into Sunday.

Light and variable winds are expected through the weekend across
the northern Gulf of California, and light to gentle nw-n flow
is expected elsewhere. Winds will increase through mid week as
the ridge builds into the region.

A high amplitude surface trough analyzed along 108W from 13N
to 22N is forecast to drift westward over the next couple of 
days. Deep convection continues to be very active in an inverted-v
shape pattern. The convection is of the scattered strong type 
intensity from 13N to 22N between the trough and 112W. Scattered 
moderate to isolated strong convection is noted from 14N to 18N 
between 102W and 106W. Scattered moderate convection is from
09N to 13N between 112W and 114W.

Fresh to strong drainage flow that occurred through the Gulf of
Tehuantepec in the overnight hours will again pulse up and down
through the weekend, peaking to the range of 25 to 30 kt with
seas of 8-10 ft late at night and through daybreak.


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 4 to 7 ft, primarily in long-period SW swell is
expected across the offshore waters through the upcoming weekend.


As tropical cyclone Ulika moves w of 140W tonight and the 
remnant low of Roslyn dissipates through Friday afternoon, the
pressure gradient will tighten around the subtropical ridge, with
moderate to fresh anticyclonic winds expected between the monsoon
trough/ITCZ and the ridge through Sunday, with combined seas
around the range of 5 to 7 ft.