Tropical Weather Discussion
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AXPZ20 KNHC 211602

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 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 1200 UTC surface analysis and satellite imagery through
1445 UTC.


A surface trough extends from 09N74W TO 04N100W TO 07N113W. The
ITCZ continues from 07N113W to 08N134W to beyond 07N140W.
Scattered moderate to strong convection is present within 150 NM
N AND 120 NM S OF TROUGH BETWEEN 76W AND 100W. Scattered
moderate isolated strong convection is present 04N TO 12N
BETWEEN 108W AND 125W. Widely scattered moderate isolated strong
convection is present within 120 NM N OF ITCZ W OF 128W.



Fresh NW winds and seas of 5 to 8 ft prevail across the offshore
waters of Baja California as a modest pressure gradient
continues between a ridge building in from the NW and lower
pressure over the SW United States and NW Mexico. NW swell
following an old front will maintain seas at 5-8 ft through this
afternoon then diminish slightly through Sun. Winds and seas W of
the peninsula will then diminish Sun through Tue as the high to
the NW weakens and lower pressure over the SW United States and
NW Mexico fills and shifts east. Moderate NW winds prevail over
the N Gulf of California, while fresh NW winds are observed
through the central Gulf. Winds will subside as well over the
Gulf Sun through Tue as the high gradually weakens the area of
low pressure weakens and moves east.

N to NE winds across the Gulf of Tehuantepec will hover in the
20 to 25 kt range this morning then diminish throughout the day.
Seas are slowly subsiding and are now down to 7-8 ft. 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 over the
Gulf of Tehuantepec will become light and variable and seas will
subside below 8 ft by late this afternoon. 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.


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 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. Convection this
morning extends W along both sides of the E to W trough across
the region to 88W. Northerly winds across the Gulf will become
gentle to moderate tonight through Mon, while farther offshore
and SW, gentle to moderate SW winds will prevail Sun through
Wed. Corresponding seas will generally run between 4 and 6 ft.

Elsewhere, mainly light to gentle winds are expected S of 06N
through Wed. 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 is centered will offshore of Northern
California near 39N136W. 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 07N
and 20N W of 120W 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

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 near 8 ft Mon and Tue.

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