Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 300243

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Sep 30 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.


Tropical Storm Ulika is just west of the discussion area near
17.5N 140.7W 1006 mb, or about 810 nm east of Hilo Hawaii, at
0300 UTC moving NW or 305 DEG at 9 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 90 nm to 150 nm to its northeast. Minimal tropical storm
winds are within 30 nm in the northeast quadrant, and 20 nm in the
southeast quadrant of the cyclone. Ulika is forecast to weaken to
a tropical depression on Friday as it continues to pull away from
the area. 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.


The monsoon trough axis extends from northwest Colombia to 
10N85W to 11N96W to 13N106W. It resumes at 13N112W to 09N122W to
weak low pressure at 13N134W 1011 mb. Scattered moderate
convection is within 60 nm north of the axis between 95W and 97W,
and within 120 nm south of the axis between 115W and 117W.



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 northwest and southwest
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 110W from 10N to
20N 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 17N to 20N between the trough and 112W. Scattered moderate
to isolated strong convection is noted from 17N to 20N east of 
the trough to 109W. 

Fresh to strong drainage flow will again occur 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 TO 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.


The pressure gradient will tighten around the subtropical ridge
over the next couple of days, 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.


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Page last modified: Friday, 30-Sep-2016 02:43:57 UTC