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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 280238

0405 UTC SAT MAY 28 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.


The monsoon trough axis extends from 10N84W to 08N92W to 12N109W
to low pressure near 10N122W 1008 mb to 06N131W. ITCZ axis
extends from 06N131W to 06N140W. Scattered moderate to isolated
strong convection is within 120 nm s of the axis between 88W and
92W...and within 120 nm of the axis between 92W and 98W.
Scattered moderate convection is within 180 nm s of the axis
between 98W and 104W...and within 60 nm of the axis between
124W and 126W.


High pressure north of the area centered near 38N138W extends a
ridge axis southeastward to 32N135W to 24N127W to near 18N112W.
High pressure covers the area north of 15N west 118W. This
subtropical ridge in combination with the convergence zone south
of 11N continues to influence most of the area W of 110W. Ascat
data from Friday afternoon indicated fresh north to northeast
winds north of the ITCZ to near 22N and west of about 118W.

Global models are persistent in depicting a broad, fairly weak
area of low pressure across the central waters in the vicinity
of 10N122W. The models suggest some development of the low
pressure beginning on Saturday as the low remains in a col
region between two centered near 12N135W
...and the other near 15N106W. It is expected that a tight
pressure gradient will develop between the low and the
aforementioned ridge to its north tonight into Saturday. This
gradient will then lead to fresh to strong northeast winds in
the NW quadrant of the low with seas building to 8 to 9 feet by
early Sun morning. The low is forecast by consensus of the model
guidance to meander near the general vicinity of 121W-122W
Saturday then begin to lift to the northeast late Saturday into
Sunday while changing little in intensity. A very active eastern
segment of the monsoon trough may spawn weak low pressure near 
90W on Saturday. 

Elsewhere, gale force northerly winds north of the area near the
California coast are expected to produce an area of N swell that
will extend south of 32N beginning late tonight and affect the
north-central waters N of about 28N between 122W and 129W
through Sunday. Cross-equatorial south to southwest swell with
seas of 8 feet is forecast to arrive into a portion of the far
southern waters early on Saturday...namely south of 05N between
113W and 120W. By late Saturday afternoon, the swell is forecast
to expand west and northwest in coverage to be located south of
05N between 114W and 120W, and south of 03N between 120W and
129W. The swell area is forecast to extend as far southeast as
03.4S95W by Sunday afternoon, and west to 134W south of 03N with
seas at that time expected to build to 9 feet. Otherwise, rather
tranquil marine conditions are expected to prevail across the
remainder of the forecast area through Sun.