Tropical Weather Discussion
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000
AXPZ20 KNHC 230225
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2342 UTC Thu Jun 22 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.

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

The monsoon trough axis extends from 11N86W to a 1007 mb low
pressure near 12N95W to 10N105W to 11N116W to 10N121W. The ITCZ
axis continues from 10N121W to 07N130W to beyond 06N140W. Scattered
moderate convection is from 08N to 10N between 91W and 94W...and
from 07N to 10N between 110W and 120W.

A cluster of moderate to strong convection is noted across the
Isthmus of Tehuantepec and parts of the Gulf of Tehuantepec. A
diffluent pattern aloft is helping to induce this convective
activity.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A surface trough is west of Baja California and extends from
27N119W to 21N121W. This trough is a reflection of an upper-level
low located near 25N121W, and it is also breaking up the usual
subtropical ridge in the area, maintaining a fairly light
pressure gradient and subsequent wind pattern. Ship observations
and scatterometer data confirm the presence of light to gentle
winds near the trough. A recent altimeter pass indicated long
period northwest swell, with wave height of 8 to 9 ft reaching
the western waters of forecast zones PMZ011 and PMZ013. Seas are
forecast to subside below 8 ft by early Friday. The trough will
dissipate through late Friday, allowing the ridge to build
eastward. This will support moderate to occasionally fresh
northwest winds along the coast of Baja California through Sunday
with building seas of 5 to 7 ft seas. Looking ahead, the pattern
will repeat again as another weak trough develops off the Baja
coast allowing winds to diminish slightly early next week.

The most recent scatterometer pass indicates gentle to moderate
southerly flow across the southern Gulf of California, and
moderate to fresh winds across the central part of the Gulf.
Moderate to fresh southerly winds are also expected over the
northern Gulf tonight. On Friday, winds will be mainly light and
variable across much of the Gulf of California.

Farther south, a broad area of low pressure of 1007 mb is located
near 12N95W. This low is producing disorganized showers and
thunderstorms. Environmental conditions appear conducive for some
development of this system by early next week while it moves
slowly west-northwestward parallel to the coast of Mexico. So
far, fresh to strong winds are expected across the Gulf of
Tehuantepec in association with this system Sunday night through
Tuesday, with seas building to 8 ft by late Saturday.

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

Gentle to moderate southwest to west winds are expected across
most of the forecast area during the forecast period, with the
exception of mainly south winds between Ecuador and the Galapagos
Islands, as the pressure gradient remains weak. Additional pulses
of long period SW swell will continue to impact the forecast
waters, but seas will remain below 7-8 ft. Seas will continue to
subside to 4-5 ft during the upcoming weekend.

REMAINDER OF THE AREA...

A ridge dominates most of the waters north of the convergence
zone and west of 125W. Scatterometer data indicate moderate to
locally fresh N to NE winds in association with this ridge.

Northerly swell will continue to propagate across the waters
N of 20N, building seas up to 11-12 ft N of 28N through Friday,
as fresh swell moves in around a low pressure system forecsat to
move from east to west just N of the area. Seas will gradually
subside from east to west through the upcoming weekend as the low
weakens.

$$
GR


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