Tropical Weather Discussion
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113
AXPZ20 KNHC 180949
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Nov 17 2017

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
0945 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: Pulses of strong northerly
drainage flow will diminish to 20 kt or less around sunrise this
morning, with winds becoming light and variable this afternoon.
Strong to near gale force conditions will resume late tonight in
the wake of a cold front in the Gulf of Mexico, and then quickly
increase to gale force on Sun morning, and continue through
through sunrise on Mon morning, with seas building to a max of
16 ft downstream of the gulf waters near 14N95.5W on Sun night.
Winds will diminish to 20 kt or less around sunrise on Tue.

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends W off the coast of Costa Rica at
09N84W to 10N92W, then dips SW to 09N105W where scatterometer
winds indicate a transition to an ITCZ which continues W-NW to
beyond 11N140W. Scattered moderate convection is noted within 60
nm of 08N95W and within 180 nm of 10N114W. Scattered moderate
isolated strong convection is noted within 150 nm 13N125W, and
within 90 nm either side of a line from 08N132W to 11N140W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

See Special Features paragraph for Gulf of Tehuantepec Gale
Warning.

A NW to SE orientated ridge just beyond 250 nm seaward will
maintain moderate to locally fresh NW flow W of the Baja
Peninsula through sunrise on Sun when the pressure gradient will
relax, supporting moderate NW flow through sunrise on Mon. Light
N winds winds then expected through sunrise on Thu.

Gulf of California: Light and variable winds at sunrise this
morning will quickly become northerly this morning with strong N
winds developing across the gulf waters N of 30N by early this
afternoon. These strong NW winds will shift S across the central
gulf waters tonight surrounded by fresh NW flow elsewhere.
Little change then expected through Sun morning when the
pressure gradient will relax with moderate NW flow forecast
across the entire gulf waters by sunrise on Mon, becoming light
northerly flow Mon night.

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

Gulf of Papagayo:  Moderate to locally fresh NE drainage winds
are forecast during the overnight hours through the middle of
next week with seas building to 5 ft downstream near 10N87W.

Light and variable winds, and 3 to 5 ft seas, are expected
elsewhere to the N of 09N, while moderate to locally fresh
southerly winds, and 4 to 7 ft seas, are forecast S of 09N
through the middle of next week.

REMAINDER OF THE AREA...

A pair of 1017 mb surface lows are weakening over the NW waters
and should dissipate tonight as a NE to SW aligned ridge builds
from 32N124W to beyond 20N140W. Fresh to locally strong
southerly flow will develop across the waters N of 26N W of 134W
tonight, with seas building to 9 ft. Expect strong southerly
winds N of the ridge, generally across the waters N of 23N W of
137W on Sun through Tue, with seas building 8 to 12 ft. The
associated cold front will arrive at 32N140W late Wed, with seas
building 12 to 18 ft W of the front through Thu.

Moderate to locally fresh anticyclonic flow expected across the
tropics N of the ITCZ and W of 120W through the middle of next
week with seas building to 8 ft.

$$
Nelson



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