Tropical Weather Discussion
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000
AXPZ20 KNHC 222208
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Sun Apr 22 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 1800 UTC surface analysis and satellite imagery through
2045 UTC.

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

A surface trough extends from 09.5N73W TO 09.5N76W TO 06N97W.
The ITCZ continues from 06N97W TO 08N107W TO 05N126W to beyond
06N140W. Scattered moderate TO strong convection is present from
04N TO 09N BETWEEN 77W AND 85W...within 120 nm N AND 150 nm S OF
the trough between 85W AND 97W...from 08N TO 13.5N between 107W
AND 117W...and within 180 nm N and 150 nm S of the ITCZ W of
117W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Moderate NW winds with seas of 5 to 7 ft currently prevail
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, new
NW swell moving into the region today will help to maintain seas
in the 5-7 ft range through Monday, except around 8 ft to the N
through W of Isla Guadelupe. Winds and seas will then diminish
very slightly Mon night 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.

W across the Gulf of Tehuantepec region have become light and
variable this afternoon. Another cold front moving across the NW
Gulf of Mexico today and tonight will induce the next mild gap
wind event over the Gulf of Tehuantepec Mon through Thu. A small
plume of N to NE winds will be intermittent across the immediate
Gulf waters, and will be strongest during nocturnal drainage
flow. Gales are not expected during this event.

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

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 8 ft.
Winds over the Gulf will be lighter on Wed and Thu as high pres
N of the Caribbean weakens.

Gulf of Panama: Gentle to moderate N to NE winds with seas of 3
to 6 ft in SW swell prevail across the Gulf of Panama and
offshore of Panama and Colombia to 250 nm this afternoon. Active
convection continues across the region today from 04N TO 09N E
of 85W, with thunderstorms producing strong gusty winds and
rough seas. A surface trough extending W across Panama and Costa
Rica, then WSW to 06N97W is acting as a focus for the
convection. Winds across the Gulf will remain gentle to moderate
tonight through Thu, while farther offshore and SW, gentle to
moderate SW winds will prevail Sun through Thu. Corresponding
seas will generally run between 4 and 6 ft.

Elsewhere, mainly light to gentle winds are expected S of 08N
through Thu. 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 will subside to 3-5 ft
by Sun as long period SW swell from the Southern Hemisphere
decay, then rebuild to between 5 and 7 ft on Mon and Tue as
another round of SW swell arrive.

REMAINDER OF THE AREA...

Strong high pressure centered well offshore of Northern
California has begun to weaken and shift NE today, 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 to
the north will support fresh NE trades N of the ITCZ generally
between 08N and 22N W of 125W through tonight. The combination
of these winds, NW swell and SW swell will support combined seas
of 8 to 10 ft over these waters. Active convection continues
across this trade wind belt this afternoon as a deep layered
trough just to the NW is maintaining unstable conditions aloft.
The area of 8 ft seas will gradually shrink in coverage through
Tue as the ridge to the N weakens.

A cold front will reach the far NW corner of the discussion area
Tue morning, preceded by the next pulse of NW swell. The front
is not expected to move beyond 28N137W by Wed afternoon, with N
to NE winds of 20-25 kt prevailing across the far NW waters.
Seas in excess of 8 ft will only impact the NW waters during
this time.

A new pulse of SW swell is moving into the equatorial waters W
of 100W this afternoon, and will spread NE towards the offshore
waters through Tue. This cross-equatorial swell will combine
with NW swell to create an even larger area of 7 to 9 foot seas
W of 81W through Tue, and reach as far N as 06N.

$$
Stripling



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