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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 272205
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2123 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 1800 UTC surface analysis and satellite imagery through
2145 UTC.

...SPECIAL FEATURES...

Tropical Storm Roslyn is centered at 18.38 116.6W at 27/2100Z, or
about 448 nm WSW of the southern tip of the Baja California
Peninsula, moving northeast or 045 degrees at 8 kt. The estimated
minimum central pressure is 1003 mb. Maximum sustained winds are 
40 kt with gusts to 50 kt. Latest satellite imagery shows that
Roslyn remains a sheared tropical cyclone with the low- level
center removed to the southwest of the remaining convection due
to moderate to southwesterly winds aloft. The imagery shows the
remaining plume of scattered moderate to isolated strong
convection between 60 nm and 150 nm of the center in the north
quadrant. Scattered moderate convection is within 30 nm of a line
from 20N113W to 22N113W. Roslyn is forecast to weaken to a
tropical depression late tonight, then to a post- tropical remnant
low by early Wed afternoon...then begin to track to the northwest
later on Wednesday afternoon and through Thursday while
dissipating. 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.

Tropical Storm Ulika is located in the far western edge of the 
discussion and high seas forecast area near 12.4N 140.0W at
27/2100Z, or about 986 nm ESE of Hilo Hawaii, moving northeast or
045 degrees at 4 kt. The estimated minimum central pressure is 997
mb. Maximum sustained winds are 50 kt with gusts to 60 kt. Latest 
satellite imagery shows that Ulika is becoming better organized 
during the afternoon with tightly coiled banding features around 
what appears to be an obscured eye feature. Scattered strong
convection is within 60 nm of the center in the northern
semicircle, and within 30 nm of the center in the southern
semicircle. Scattered moderate convection is within 45 nm of a
line from 13.5N133W to 15N135W to 15N138W. 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.

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

The monsoon trough axis extends from northwest Panama at 10N84W
to 11N92W to 11N100W to 11N105W to 12N112W. It resumes at 14N117W
to 13N125W to 14N130W to 13.5N136W. Scattered moderate isolated
strong convection is observed within 240 nm south of the axis 
between 90W and 93W. Scattered moderate convection is within 
60 nm of the axis between 130W and 133W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A northwest to southeast oriented surface trough is analyzed from
11N96W to near Acapulco Mexico. Scattered moderate to isolated
strong convection is noted from 09N to 16N between 98W and 103W.

Relatively weak high pressure covers the area to the north 
of the tropical cyclones Rosyln and Ulika. The associated gradient
is producing light to gentle N to NE winds to the west of the
Baja Peninsula, with the exception of waters near and around the 
Rosyln. Pockets of diminishing showers and thunderstorms and
strong E winds and combined seas of 7 to 11 ft will expand
northeastward across the waters generally from 18N to 23N W of
114.5W through Wednesday night as Tropical Storm Roslyn continues
northward while weakening. 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.

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.

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

Light to gentle S winds expected N of the monsoon trough, while
gentle to locally moderate S to SW flow is expected to the south
of 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.

REMAINDER OF THE AREA... 

A cold front moving SE out of the N central Pacific will weaken
the subtropical ridge north 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 south of the monsoon trough for at
least the next couple of days.

$$
AGUIRRE