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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 251619

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Thu Aug 25 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
1515 UTC.


Tropical Storm Lester is located near 16.6N 112.5W at 1500 UTC,
or about 155 nm to the south-southwest of Socorro Island, or
about 405 nm to the south-southwest of the southern tip of Baja
California. Lester is moving WNW or 295 deg at 10 kt with
maximum sustained winds of 45 kt gusting to 55 kt. The estimated
minimum central pressure is 1002 mb. Lester has strengthened
modestly in the past 6 hours, with improved presentation in
satellite imagery. Numerous strong convection is occurring
within 60 nm across the NW and 45 nm across the SE semicircles,
while scattered moderate to strong convection is elsewhere
within 120 nm of the center. Lester is producing bands of
thunderstorms and strong winds to around 25 kt across the outer
waters offshore of Cabo Corrientes this morning, with seas 8-10
ft. Lester is expected to continue moving west-northwest and
away from the Mexican offshore waters tonight as it gradually
strengthens to a hurricane by Friday morning. Please read the
NHC forecast/advisory under AWIPS/WMO headers MIATCMEP3/WTPZ23
KNHC or the public bulletin under MIATCPEP3/ WTPZ33 KNHC for
more details.

A broad tropical wave is moving along the monsoon trough in the
vicinity of 129W-131W, moving westward near 15 knots. A 1008 mb
low pressure center is suggested near 11.5N129W. Scattered to
numerous strong convection has developed in recent hours within
360 nm across the NW semicircle, while scattered moderate to
strong convection was elsewhere along the monsoon trough within
120 nm of the center. Fresh NE trade winds cover the area from
13N to 19N from 124W westward, where seas are running 6-9 ft.
Environmental conditions are conducive for continued gradual
improvement in organization of this system. It has a medium
chance for tropical cyclone development during the next 48
hours before crossing 140W by 72 hrs. 


No additional waves at this time.


The monsoon trough extends from 10N74W to 08N79W to 09N85W to
10N106W. Scattered to numerous moderate to strong convection is
noted from 05N to 08N east of 88W...and within 150 nm south
ofthe trough between 93W and 110W. 



A narrow surface ridge extends from the NE Pacific southeastward
through 30N129W to north of Lester near 21N113W. This ridge will
change little through the upcoming weekend, and combine with the
persistent trough meandering along the Baja California peninsula
and Gulf of California, to produce mainly light to moderate
northerly flow prevailing outside of the Gulf of California.
Expect mainly light to gentle southerly flow In the Gulf of
California, except for occasionally fresh wind flow in the
northern Gulf where the pressure gradient will be slightly

High pressure in the Gulf of Mexico continues to drive 20-30 kt
northerly winds across the Gulf of Tehuantepec where seas have
built to 6-10 ft. These winds and seas will diminish modestly
today and persist through tonight before falling to less than
20 kt by Friday afternoon.


Moderate to locally fresh offshore winds are expected across
most of the area east of 95W and north of the monsoon trough
today through the early afternoon hours. Global models suggest
that a weak surface trough will develop just east of the Gulf of
Tehuantepec by tonight and help to draw the southwesterly winds
occurring south of the monsoon trough northward into these
coastal areas. A light and variable onshore flow is thus
expected to prevail through the weekend. 


A broad surface ridge covers the remainder of the area,
extending from a large 1036 mb high near 49N142W. The low
pressure center that is along 129W and its associated tropical
wave will move westward during the next few days. The pressure
gradient between this lower pressure and the ridge will yield
fresh winds across the trade wind belt, generally from 21N
southward to near the trough, from just to the northeast of the
low center to beyond 140W. Sea ranging from 6 feet to 8 feet in
this area in mixed swell will increase slightly to 7 to 9 feet
during this time. A large area of fresh southwesterly monsoonal
flow is supporting seas of 6 to 8 feet from 07N northward
between 115W and 125W. The strength and areal coverage of these
fresh winds will increase to the south and southeast of the low
center as it shifts westward during the next few days.