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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 312125

2205 UTC TUE MAY 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.


Tropical wave is moving off Costa Rica. Scattered convection is
noted from 05N to 08N between 83W and 87W. 

Tropical wave is along 97W from 05N to !3N. This wave is moving
into an area of strong southwest winds, as noted in earlier
scatterometer data. Low level convergence due to these winds is
supporting a large area of scattered to numerous shower and
thunderstorms from 07N to 11N between 92W and 103W. 


The monsoon trough extends from 10N86W to 09N90W to 11N100W. It
then continues to a low pressure area near 09N110W, then farther
west to another low pressure system centered near 10N116W before
transitioning to the ITCZ near 08N121W. The ITCZ continues to
07N135W then beyond 07N140W. Scattered moderate to isolated
strong convection is noted within 180 nm south of the monsoon
trough between 85W and 105W. 


North of 15N east of 120W - an upper trough is cutting across
the northern reaches of the Gulf of California. A related
surface trough extends across the Baja California peninsula. The
interaction between the subtropical ridge is maintaining a tight
pressure gradient, with resultant fresh to strong northwest
winds off the southern tip of the Baja California peninsula, as
noted in a 11Z Rapidscat pass. These winds will diminish tonight
as the trough shifts east. Altimeter data from this morning
indicated seas 8 to 9 ft south of 20N, in predominantly
southwest swell mixed with northwest swell. This swell is
expected to decay below 8 ft through Wednesday.

South of 15N east of 120W - successive scatterometer passes
since last night have indicated a surge of southwest winds into
the monsoon trough north of 04N between roughly 90W and 115W.
Altimeter data from this area has been showing concurrent wave
heights of 8 to 9 ft, with some contribution of southwest swell.
The winds are to the east of a pair of elongated weak low
pressure areas along the monsoon trough farther west near 110W
and 116W. The winds are expected to diminish after Wednesday as
the low pressure areas drift farther west, allowing seas and
thunderstorm activity to diminish as well.

West of 110W - A cold front is approaching the waters north of
25N to the east of 140W. Although strong winds are noted just
ahead of this front, the front will weaken and stall before
crossing into the discussion area through tonight. Wave heights
of 6 to 7 ft will impact the waters north of 25N and west of
137W through Wednesday related to shorter period swell generated
along the front. Otherwise, broad ridging will prevail across
the waters north of 15N and west of 120W. Farther south into the
tropics, a pair of weak low pressure centered along the monsoon
trough and near 110W and 116W respectively will gradually merge
and deepen through Wednesday, crossing 120W by late Friday. No
tropical cyclone development is expected through mid week, but
the merged low may deepen further by late week according to some
model output. Uncertainty remains regarding the expect track and
intensity of this system at this time, but most guidance keeps
the low pressure system south of 15N moving west through late