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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 291602

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1230 UTC Mon Aug 29 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.


Lester is already a major hurricane and continues to intensify.
At 29/1500 UTC, it is centered about 1120 NM W of the southern
tip of Baja California near 18.1N 129.2W moving W or 270 degrees
at 13 kt. Estimated minimum central pressure is 957 mb. Maximum
sustained winds are 110 kt with gusts to 130 kt. Lester is now a
strong category 3 hurricane on the Saffir-Simpson Hurricane Wind
Scale. Some additional increase in strength is expected today. A
slow but steady weakening trend is then expected to begin by
Tuesday. Lester is forecast to cross 140W and move into the
central Pacific basin by Wednesday night while continuing on a
westward motion. Numerous moderate and scattered strong
convection is seen within 75 NM of the center. Scattered moderate
and isolated strong convection is present elsewhere within 120 nm
of the center. See latest NHC forecast/advisory under AWIPS/WMO
headers MIATCMEP3/WTPZ23 KNHC for more details.


The monsoon trough axis extends from 11N90W to 11N97W to 13N105W
to low pres near 13N115W 1010 MB to 13N120W. Scattered moderate
and isolated strong convection exists within 240 nm either side of
the monsoon trough axis E of 104W.



A ridge extending from 32N130W to 16N110W dominates the waters
off Baja California. The ridge is producing moderate to locally
fresh northerly winds and seas generally under 6 ft. Little change
in this weather pattern is expected through the end of the week.
Marine guidance suggests seas will build close to 8 ft in NW swell
across the western part of zone PMZ011 on Tuesday night and
Wednesday, then subside. Surface troughing over the Baja
peninsula will maintain a light and variable wind regime in the
Gulf of California through the end of the week with seas generally
2 ft or less. Farther south, winds will be mainly gentle to
moderate and WNW with combined seas of 4 to 6 ft. A light and
variable wind pattern is expected across the Gulf of Tehuantepec
through Thursday.


Gentle to moderate SW winds will prevail S of the monsoon trough
with mainly light to gentle winds N of it through Friday. Long
period cross equatorial SW swell will continue to dominate the
area with seas ranging between 4 and 7 ft.


Hurricane Madeline is W of 140W. However, mixed swell on the E
side of Madeline will maintain seas at 8 ft from 18N to 23N W of
139W. These marine conditions will merge with those produced by
hurricane Lester in about 12 hours. Hurricane Lester will reach
the W central waters this afternoon.

A broad surface ridge covers most of the northern waters,
extending from 1023 mb high pressure near 33N130W. A weak surface
trough crosses the NW part of the forecast area from 27N140W to
32N137W. Ascat satellite imagery continues depicting the wind
shift associated with this trough. Scattered low-topped showers are
occurring in the vicinity of this feature. The pressure gradient
between the ridge and Lester will produce a band of fresh to
occasionally strong winds from 20N to 25N between 125W and 135W,
with combined seas ranging from 9 to 12 feet.

Weak low pres of 1010 mb remains embedded in the monsoon trough
near 13N115W. Convection associated with this system has
gradually increased in both areal coverage and intensity over the
past 24 hours. Satellite imagery shows scattered moderate to
isolated strong convection from 11N to 15N between 111W and 120W.
Chances for tropical cyclone formation for this system are
forecast to remain low through the next several days as it tracks
slowly westward along the monsoon trough. Scatterometer imagery
shows moderate to fresh SW winds feeding into the monsoon trough
S of the low. Marine guidance suggests that an area of fresh SW
to W winds will persist S of the low center during the next 48
hours, with seas building to 8 ft in the vicinity of the low
during this time frame.

SW swell crossing the equator will produce and area of seas S of
Mexico between 8 and 10 ft generally from 06N to 13N between 94W
and 112W during the next couple of days.