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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 310925
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Wed Aug 31 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 0600 UTC surface analysis and satellite imagery through
0900 UTC.

...SPECIAL FEATURE... 

Lester is again a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale heading toward the Central Pacific. At
31/0900 UTC, the eye of Hurricane Lester is centered near 17.7N
137.5W or about 1160 MI...1865 KM E of Hilo Hawaii, moving west
or 265 degrees at 10 kt. Estimated minimum central pressure is
948 mb. Maximum sustained winds are 120 kt with gusts to 145 kt.
Some weakening is forecast during the next 48 hours, though
Lester is anticipated to remain a strong hurricane. Numerous
moderate to strong convection is noted within 90 nm of the center.
Numerous moderate to isolated strong convection is noted elsewhere
within 120 nm of center. Refer to the latest NHC forecast/advisory
under AWIPS/WMO headers MIATCMEP3/WTPZ23 KNHC, and the latest high
seas forecast under WMO header FZPN02 KWBC for additional details.

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

The monsoon trough axis extends from 09N91W to 13N100W to 12N110W
to 11.5N120W to 13N126W. Scattered moderate to isolated strong
convection is from 09N to 13N between 91W and 98W. Scattered
moderate convection is near 06N88W, near 12N87W, from 09N to 12N
between 109W and 113W, and from 15N to 18N between 106W and 108W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A sub-tropical ridge is maintaining moderate NW flow with seas of 
4 to 6 ft across the Pacific waters along the Baja California
peninsula. Light and variable winds are expected elsewhere along
the Pacific coast of Mexico, with combined seas of 4 to 6 ft
primarily due to long-period cross-equatorial swell. A thermal
trough will meander over the Baja Peninsula, and across the
northern Gulf of California supporting light southerly flow across
the Gulf of California into the upcoming weekend when moderate to
locally fresh southwest flow is forecast N of 30N.

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

Moderate to locally fresh southwesterly winds will prevail south of
the monsoon trough axis with light to gentle west to northwest winds
forecast north of the trough axis. Long period cross equatorial
SW swell will continue to dominate the area with seas ranging
between 4 and 7 ft. The exception will be forecast zone PMZ115
(NORTH COSTA RICA TO WEST PANAMA TO 250 NM OFFSHORE) where marine
guidance indicates moderate to fresh SW winds and building seas up
to 9 ft tonight and Thursday. Winds and seas will diminish across
this area by Thursday night.

REMAINDER OF THE AREA...

A surface ridge covers most of the waters N of 20N, extending
from 1028 mb high pressure located NW of the forecast area. The
pressure gradient between the ridge and Lester continues to
produce a band of fresh to occasionally strong winds roughly from
20N to 25N W of 135W based on a recent scatterometer pass. Lester
is forecast to cross 140W by tonight. As a result, winds and seas
will gradually diminish across the western waters over the next
couple of days.

Marine guidance continues to suggests an increase in the monsoonal
flow in about 24 hours with seas building to 8 ft across the
waters from 08N to 10N between 102W and 110W. A pair of weak low
pressure centers along the monsoon trough appear to be enhancing
these winds.

An area of low pressure is forecast to form a few hundred miles
south of the south-central coast of Mexico in a couple of days.
Environmental conditions are expected to be conducive for slow
development, and a tropical depression could form over the weekend
while the low moves west-northwestward or northwestward. Currently,
the chance of tropical cyclone formation is assessed to be medium
or 60 percent through 5 days.

$$
GR