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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 222208

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.


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 



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.


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.


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.