Tropical Weather Discussion
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AXPZ20 KNHC 222122

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1945 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.


The monsoon trough axis extends from 12N95W to 10N104W to 11N110W
to 08N120W to 07N130W to 06N133W. The ITCZ continues from 06N133W
to beyond 06N140W. Scattered moderate and isolated strong convection
is from 08N to 11N between 111W and 114W, and from 08N to 10N between
114W and 122W.



A surface trough is west of Baja California and extends from
29N116W to 21N117W. This is breaking up the usual subtropical
ridge in the area, maintaining a fairly light pressure gradient
and subsequent wind pattern off the Baja California peninsula,
where various ship observations and scatterometer data confirm
the presence of light to gentle winds. 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 as another weak trough develops off the Baja
coast allowing winds to diminish slightly early next week.

A recent scatterometer pass also 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 through tonight.

Farther south, a broad area of low pressure is located near
14.5N94.5W or a few hundred miles south of the Gulf of Tehuantepec.
This low is producing disorganized showers and thunderstorms,
with satellite imagery showing scattered moderate to isolated
strong convection from 13N to 16N between 94W and 96W. Slow
development of this system is possible by early next week while
it moves west-northwestward parallel to the coast of Mexico.


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. Long period
southwest swell of 5 to 7 ft will gradually decay through the
upcoming weekend.


A ridge dominates most of the waters north of the convergence
zone. Scatterometer and altimeter passes continue to indicate an
area of moderate to fresh winds and seas of 8 to 10 ft roughly
north of 20N and W of 120W. The ridge will shift west as the
above mentioned weak trough drift west, before dissipating by
late Friday.

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 N of the area. Seas will decay through
the upcoming weekend as the low moves NW while weakening.

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