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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 210358
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
208 UTC Sat Apr 21 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 0000 UTC surface analysis and satellite imagery through
0245 UTC.

...SPECIAL FEATURES...

Northerly winds across and downstream of the Gulf of Tehuantepec
continue to gradually diminish, but will remain in the 20 to 30 
kt range overnight as nocturnal drainage flow augments the winds.
Seas are slowly subsiding and are now down to 8-11 ft. Winds 
will begin to more rapidly diminish in areal coverage after 
sunrise. Supporting high pressure across the southern U.S. behind
a stalled cold front over the northern Gulf of Mexico is 
shifting slowly eastward, and is allowing the pressure gradient 
across the Isthmus of Tehuantepec to continue weakening. Winds 
will become light and variable and seas will subside below 8 ft 
by Sat evening. Another cold front entering the NW Gulf of Mexico
could induce the next gap wind event over the Gulf of 
Tehuantepec Mon through Thu. Gales are not expected during this 
event.

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

A surface trough extends from 07N77W to 06N86W to 05N113W. The 
ITCZ continues from 05N113W TO 05N125W to beyond 06N140W. 
Scattered moderate and isolated strong convection is present 
from 05N to 07N between 86W and 91W, and from 05N to 09N between
105W and 112W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Fresh NW winds and seas of 5 to 8 ft prevail across the offshore 
waters of Baja California as a tight pressure gradient exists 
between a ridge building in from the NW and lower pressure over 
the SW United States and NW Mexico. NW swell following a front 
that swept through the area last night will maintain seas at 5-8 
ft tonight. Winds and seas W of the peninsula will then diminish
Sat through Mon as the high to the NW weakens. Moderate NW winds
prevail over the N Gulf of California, while fresh NW winds are 
observed through the central Gulf. Winds will subside over the 
Gulf Sat and Sun as the high weakens slightly and the area of low
pressure moves east. 

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 from nightfall through morning to 20-25 kt 
across and downstream of the Gulf of Papagayo through at least 
Tue night with seas peaking each night between 7 and 9 ft.

Gulf of Panama: Fresh northerly winds and seas of 5 to 7 ft in 
SW swell prevail across the Gulf of Panama and offshore of 
Panama and Colombia to 250 nm today. Very active convection has
been developing at night along the coast of Colombia. More
convection could produce strong gusty winds and very rough seas 
to near 8 ft later tonight. Northerly winds will become gentle 
to moderate Sat through Sun across the Gulf of Panama, while 
farther offshore and SW, gentle to moderate SW winds will 
develop. Seas will generally run between 4 and 6 ft.

Elsewhere, mainly light to gentle winds are expected S of 06N 
through Tue. Cross-equatorial swell will mix with residual swell 
downwind from Papagayo through Tue, 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. 

REMAINDER OF THE AREA... 

Strong high pressure is centered W of California near 140W. The 
high ridges 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 to strong NE trades N 
of the ITCZ generally between 05N and 20N W of 125W through 
Saturday. The combination of these winds, NW swell and SW swell 
will support combined seas of 8 to 11 ft over these waters into 
Saturday, expanding N to 30N by Sunday as NW swell propagates 
into the northern waters. The NW swell will begin to decay below 
8 ft Sunday night before becoming reinforced by another pulse of 
NW swell by Monday night. 

Cross equatorial SW swell moving into the southern forecast 
waters continue to decay and seas have subsided to 8 ft or less 
near the equator. Another round of SW swell could cause waters 
near the equator to build to 8 ft or above on Mon or Tue.

$$
CAM