NHC Tropical Weather Discussion (East Pacific)

04/23/2018 02:20 AM
NHC East Pacific Tropical Weather Discussion

AXPZ20 KNHC 230919

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
614 UTC Mon Apr 23 2018

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 0600 UTC surface analysis and satellite imagery through
0845 UTC.


A surface trough extends from 10N73W to 09N80W to 06N87W to
05N95W. The ITCZ continues from 05N95W to 06N113W to beyond
05N140W. Scattered moderate and isolated strong convection is
present from 03N to 10N between 76W and 87W and within an area
bounded by 11N109W to 15N116W to 05N131W to 05N108W to 11N109W.
Scattered moderate convection is found from 08N to 12N W of 130W.



Moderate NW winds and seas of 5 to 7 ft are currently noted
across the offshore waters of Baja California as ridging from the
NW and lower pressure over the SW United States and NW Mexico
combine to maintain a modest pressure gradient over the area.
Winds W of the peninsula will gradually diminish through Tue as
the high to the NW weakens and lower pressure over the SW United
States and NW Mexico fills and shifts east. However, NW swell
will help to maintain seas in the 5-7 ft range today, except
around 8 ft to the N through W of Isla Guadalupe. Winds and seas
will then diminish very slightly tonight through Wed. Light to
gentle variable winds prevail throughout the Gulf of California,
and are expected to persist through Wed as the high gradually
weakens and the area of low pressure weakens and moves east.
Winds and seas in the region will gradually increase on Thu and
Fri as the ridge from the NW rebuilds.

Winds in the vicinity of the Gulf of Tehuantepec are light and
variable. However, high pressure building over the NW Gulf behind
a cold front will induce the next gap wind event over the Gulf
of Tehuantepec tonight through Thu. A small plume of N to NE
winds will periodically affect the immediate Gulf waters, and
will be strongest during nocturnal drainage flow. This event will
be modest with winds peaking at strong speeds and seas peaking at
8 ft or less.


Gulf of Papagayo: Fresh NE to E winds across the region are
expected to pulse between nightfall and mid morning to 20-25 kt
across and downstream of the Gulf of Papagayo through at least
Tue night with seas peaking each episode between 6 and 7 ft.
Winds over the Gulf will be lighter Wed through Fri as high pres
N of the Caribbean weakens.

Gulf of Panama: Gentle to moderate N to NE winds and seas of 2
to 4 ft are seen across the Gulf of Panama with seas of 3 to 6 ft
offshore of Panama and Colombia to 250 nm this morning. Active
convection continues across the region this morning near and S of
Panama and Costa Rica as well as along the SW coast of Colombia
from 03N to 10N between 76W and 87W as showers and thunderstorms
produce strong gusty winds and rough seas. A surface trough
extending WSW from the border of Panama and Colombia is acting as
a focus for the convection. Winds across the Gulf will remain
gentle to moderate tonight through Fri, while farther offshore
and SW, gentle to moderate SW winds will prevail through Fri.
Corresponding seas will generally run between 4 and 6 ft.

Elsewhere, mainly light to gentle winds are expected S of 08N
through Fri. Cross-equatorial swell will mix with residual swell
downwind from Papagayo through Wed, and maintain seas in this
area between 5 and 7 ft. Elsewhere seas of 4 to 6 ft will rebuild
to between 6 and 8 ft tonight through Wed as another round of SW
swell arrive.


High pressure centered well offshore of Northern California near
37N133W has begun to weaken and shift NE as a new cold front
approaches 140W from the NW. The high continues to ridge SE
across the northern forecast waters to near the Revillagigedo
Islands. The pressure gradient between the ITCZ and the high will
remain strong enough to support fresh NE trades N of the ITCZ
generally between 08N and 22N W of 125W through Thu. The
combination of these winds, NW swell and SW swell will support
combined seas of 7 to 9 ft over these waters. Active convection
continues across this trade wind belt this morning as a deep
layered trough extending from near 20N118W to 01N116W maintains
unstable conditions aloft.

A cold front will reach the far NW corner of the discussion area
Tue morning, barely preceded by the next pulse of NW swell. The
front will dissipate as it moves beyond 28N137W on Wed as fresh
to locally strong winds affect the far NW waters. Seas in excess
of 8 ft will only briefly impact the NW waters during this time.

A new pulse of SW swell is moving into the equatorial waters W
of 100W this morning, Seas of 8 ft or higher will primarily be
confined to S of the equator, but the swell will continue
spreading NE towards the offshore waters through Wed. This cross-
equatorial swell will combine with NW swell to create an even
larger area of 7 to 9 foot seas S of 20N and W of 100W Tue
through Thu.


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