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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 241536

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Sat Sep 24 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.


A large low pressure area, analyzed as a 1007 mb low pressure near
13N118W on the 1200 UTC surface map, is producing disorganized
shower and thunderstorm activity. Satellite images indicate that
the low's circulation, although still broad, is gradually becoming
better defined, and a band of moderate to isolated strong convection
is seen within about 90 nm of a line from 13N117W to 12N120W to
14N120W. Currently, the pressure gradient is supporting strong S
to SW winds within 120 nm SE semicircle of low center with seas of
8 to 9 ft. Environmental conditions are conducive for a tropical
depression to form during the next day or two. This disturbance is
expected to move slowly northward during the next few days. A
gale warning is already in effect in association with this feature
beginning on Sunday morning. Please refer to the latest Graphical
Tropical Weather Outlook for more information at


A tropical wave is analyzed N of 10N along 95W. The axis crosses
the Gulf of Tehuantepec. Scattered moderate to isolated strong
convection is noted on either side of the wave axis mainly N of
13N between 91W and 99W. Expect the wave to gradually lose
identity over the next few days.


The monsoon trough extends across parts of Panama and southern
Costa Rica from 09N79W to 09N85W to 11N95W to 10N107W...then it
resumes at 12N119W to 1009 MB low pressure located near 12N132W
to 10N140W. Scattered moderate convection can be found from 08N
to 12N between 91W and 98W...and from 09N to 11N between 127W and 



A sub-tropical ridge extends from NW to SE across the offshore
zones W of the Baja Peninsula to near 21N115W producing mainly
gentle to moderate NW winds. Seas of 8 to 10 ft in NW swell are
noted per an altimeter pass within this area. Moderate to locally 
fresh NW winds are observed based on scatterometer data between
Punta Eugenia and Cabo San Lazaro. The pressure gradient is
forecast to quickly relax today with gentle NW to N flow expected
W of the Baja California Peninsula through the remainder of the

Scatterometer data also show gentle to moderate NW winds across
the N part of the Gulf of California particularly N of 30N. Winds
are forecast to increase to 20-25 kt across the gulf waters N of
30N by late Sunday as a moderate to strong high pressure builds
across the Great Basin. 

A cold front is forecast to move across the Gulf of Mexico waters.
High pressure behind the front will likely induce the first Gulf
of Tehuantepec gap wind event of the season by late Tuesday into
Wednesday morning. At this time, marine guidance suggests
Northerly winds of 20-25 kt and building seas to 8 ft. Winds will
further increase to 25-30 kt Wednesday night into Thursday morning
with seas up to 9-10 ft.


Mainly light and variable winds are noted N of the monsoon trough 
while gentle to locally moderate S to SW flow is expected S of
monsoon trough through early next week. Combined seas of 4 to 7
ft will continue today primarily in long-period SW swell, then
subside to 4 to 5 ft late on Sun and continuing into early next


A 1009 mb low pressure area is analyzed along the monsoon trough
near 12N132W. Expect the low to likely reach 140W on Monday, then
will remain near 140W through mid-week. The pressure gradient
between this low and the subtropical ridge to the N is resulting
in an area of fresh to strong NE trades, and combined seas of 6
to 9 ft, across the discussion waters from 17N to 26N W of 130W.
These marine conditions area forecast to gradually diminish in
about 24 hours as high pressure located N of area near 34N137W
moves NE to a position near 40N133W by Sunday morning.