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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 271600

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1219 UTC Tue Sep 27 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 1200 UTC surface analysis and satellite imagery through
1430 UTC.


Tropical Storm Roslyn is centered at 18.3N 117.3W at 27/1500Z, or
about 500 nm WSW of the southern tip of the Baja California
Peninsula, moving NE, or 045 degrees at 6 kt. The estimated
minimum central pressure is 1003 mb. Maximum sustained wind speed
is 40 kt with gusts to 50 kt. Scattered moderate isolated strong
convection is sheared into the NE quadrant within 180 nm of the
center. Roslyn is forecast to weaken to a tropical depression
tonight, then to a remnant low late on Wed. Roslyn is expected to
finally dissipate on Sat. Refer to the latest NHC
forecast/advisory under AWIPS/WMO headers WTPZ23 KNHC/TCMEP3, or
visit the NHC website at for additional

Tropical Storm Ulika is centered on the W edge of the area at
12.4N 140.0W at 27/1500Z, or about 975 nm ESE of Hilo Hawaii,
moving NE, or 045 degrees at 4 kt. The estimated minimum central
pressure is 999 mb. Maximum sustained winds are 45 kt with gusts
to 55 kt. Scattered moderate convection is present within 150 nm
of the center. CPHC is continuing to issue forecasts and
advisories under AWIPS/WMO headers WTPA22 PHFO/TCMCP2. Visit the
CPHC website at for additional


The monsoon trough extends from N of Panama at 10N78W to 10N87W
to 13N95W, continues from 13N102W to 09N110W to 10N114W and
finally resumes from 12N123W to 14N132W to 13N136W. Isolated
moderate to strong convection is observed within 150 nm either
side of a line 06N77W to 11N94W and within 90 nm either side of a
line from 12N127W to 13N136W.



A surface trough reaches from 11N96W to near Acapulco Mexico at
17N100W. Scattered moderate and isolated strong convection is
observed from 08N to 17N between 97W and 103W.

A sub-tropical ridge axis extends from NW to SE across the
offshore zones W of the Baja Peninsula terminating near 26N116W.
Light to gentle N to NE winds are observed W of the Baja Peninsula
with little change expected until Friday.

Scattered convection, strong E winds and combined seas of 7 to 11
ft will expand NE across the waters generally from 18N to 23N W of
114.5W through Wed as Tropical Storm Roslyn continues northward.
The subtropical ridge will extend from 29N120W to 20N106W on Fri
with gentle N flow returning. The pressure gradient will tighten
Fri. Moderate to fresh NW winds and 5 to 8 ft seas will prevail W
of Baja Sat and Sun. Winds could become fresh to strong N of 26N
Mon and Tue.

Light to gentle NW winds are expected across the entire Gulf of
California through Thu. Light and variable winds expected on Fri
across the far northern gulf waters.

Strong drainage flow will pulse across the Gulf of Tehuantepec
during the late night and early morning hours from late Wed
night to early Mon morning.


Light to gentle S winds 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 are expected this week.


A cold front moving SE out of the N central Pacific will weaken
the subtropical ridge N of the region during the next couple of
days. This will maintain gentle to moderate NE winds and 5 to 6 ft
seas for the areas N of the monsoon trough not affected by Roslyn
or Ulika. Moderate to occasionally fresh southerly flow and 6 to
7 ft seas will dominate S of the monsoon trough for at least the
next several days.