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Eastern North Pacific Tropical Weather Discussion (Text)



000
AXPZ20 KNHC 251540
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Sun Sep 25 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.

...SPECIAL FEATURES...

At 25/1200 UTC...shower and thunderstorm activity associated with
a low pressure system located near 15.2N 119.7W or about 715 nm
southwest of the southern tip of the Baja California peninsula has
become a little better organized overnight. Satellite imagery also
suggests that the circulation is gradually becoming better
defined, with a cluster of moderate to strong convection within
about 150 nm SW of low center. Scattered moderate convection is
also noted to the NE of the center, particularly from 14.5N-17.5N
between 115W-119W. Environmental conditions are conducive for
additional development, and a tropical depression is likely to
form later today or tonight while the system moves slowly
northward. A gale warning is already in effect in association with
this feature beginning this evening. Based on the computer models...
this system could reach tropical storm force on Monday. Please
refer to the latest Graphical Tropical Weather Outlook for more
information at http://hurricanes.gov.

...TROPICAL WAVES...

A tropical wave is located to the N of 08N along 97W. Scattered
moderate isolated strong convection is observed on either side of
the wave axis, and where the wave meets the monsoon trough, but
mainly N of 12N...including the Gulf of Tehuantepec between 93W-
96W...and from 08N-10N between 93W-102W. Expect the wave to
gradually lose identity over the next few days.

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

The monsoon trough extends across the far SW Caribbean and
northern Costa Rica in to EPAC along 10N86W to 11N97W to 09N110W,
then it resumes just SW of the surface low located near 15.2N
119.7W, and continues along 12N130W to a 1010 mb low pressure
near 12N137.5W. Scattered moderate convection is noted from 08N-
10N between 93W-102W...from 09N-11N between 123W-128W, and from
10N-13.5N W of 130W. A cluster of moderate to isolated strong
convection has developed south of the Azuero peninsula, within
about 60 nm of 05N81W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

mainly light to gentle winds are noted north of 20N between the
subtropical ridge to the west and weak trough over the Gulf of
California. Northerly swell to 8 ft persist off Baja California
Norte per the most recent altimeter pass, particularly N of 27N
between 120W-125W, but will be decaying to below 8 ft late today. 
Building high pressure over the Great Basin to the north of the
region will allow a brief surge of fresh to strong northerly winds
into the northern Gulf of California this afternoon, diminishing
to 20 kt tonight, then veering more east to southeast on Monday
on the tail end of a weak frontal boundary drifting into northern
Mexico.

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 Tuesday
night 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.

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

Mainly light and variable winds are noted north of the monsoon
trough while gentle to locally moderate south to southwest flow
is expected south of monsoon trough the middle of the week. Combined
seas of 3-6 ft, primarily in long-period southwest swell, are
expected through the middle of the week.

REMAINDER OF THE AREA...

An area of low pressure located near 12N137.5W or about 1105 nm
east-southeast of the Big Island of Hawaii continues to produce
disorganized showers and thunderstorms. Satellite imagery
indicates scattered moderate convection from 10N-14N between
135W-140W. Currently, convection is limited near the low's center.
Any development of this disturbance should be slow to occur during
the next couple of days. After that time, environmental conditions
could become more conducive for development. This system is
expected to move west-northwestward during the next couple of
days, and then turn northward as it approaches the Central Pacific
basin. The pressure gradient between this low and the subtropical
ridge to the north is resulting in an area of fresh to strong
northeast from 13N-22N W of 130W. An earlier altimeter pass
provided observations of combined seas of 8 to 12 ft within the
area of the trade winds. This marine conditions will diminish in
areal extent, covering the waters from 13N to 17n between 135W and
140W by this evening. Seas of 8 to 9 ft will persist from 12N to
16N west of 138W through early Monday morning, just north of the
low pressure.

$$
GR

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Page last modified: Sunday, 25-Sep-2016 15:40:38 UTC