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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 170945

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon May 17 2021

Tropical Weather Discussion for the eastern Pacific Ocean from
03.4S to 30N, east of 120W including the Gulf of California, and
from the Equator to 30N, between 120W and 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
0930 UTC.


The monsoon trough extends from northern Colombia to 09N79W to 
08N90W to 09N110W to 08N115W and to 09N130W, where overnight
scatterometer data indicates that it transitions to the ITCZ to 
05N135W and to beyond 05N140W. Scattered moderate to isolated 
strong convection is within 240 nm south of the trough between 
78W- 80W and within 60 nm of trough between 104W-107W. Scattered 
moderate convection is within 120 nm north of the trough between
111W-113W and within 30 nm of the trough between 105W-108W. 


A ridge dominates the offshore forecast waters of Baja California
producing mainly moderate to locally fresh northwest to north
winds. A small area of fresh to strong northwest winds is noted 
near Cabo San Lucas. These winds are forecast to continue through 
late Tue night. Fresh to locally strong northwest winds are 
expected primarily north of Cabo San Lazaro this evening and into
Tue as the pressure gradient tightens some. Seas will build to 
5-7 ft. Winds will further increase to fresh to strong speeds 
mainly west of central and northern Baja California beginning 
late Thu as stronger high pressure builds southeastward across 
the waters west of Baja California. South to southwest swell will
build seas as it propagates across the waters north of Punta 
Eugenia beginning on Tue. Looking ahead for later in the week, a 
trough or low may form south of the Gulf of Tehuantepec region.

Gulf of California: The earlier fresh to strong southwest winds 
over the northern section of the Gulf have become west to
northwest 10-15 kt winds, with seas of 3-4 ft. These winds will 
become moderate to fresh and southeast in direction through
Thu, then fresh southwest winds Thu night. The seas will build 
slightly Thu, then up to 6 ft Thu night. Elsewhere, gentle to 
moderate southerly winds are expected through Thu, with seas 
of 3-4 ft, except slightly higher seas in the southern section.


Fresh northeast to east winds across the Papagayo region will 
become gentle east winds in the afternoon, then shift to the
south tonight before becoming moderate northeast to east winds 
early on Tue and variable thereafter through mid-week. Seas of 
5-7 ft will change little through mid-week. Long-period cross 
equatorial southerly swell will continue to impact the offshore 
forecast waters over the next several days. Seas of 8-9 ft 
between Ecuador and the Galapagos Islands will subside to less 
than 8 ft late tonight. Additional pulses of long-period
southwest swell will reach the area by mid-week building seas to
8 ft or higher.


A rather broad surface ridge is the main feature over the northern
forecast waters. It is anchored by a 1028 mb high center that is
located north of the area near 36N139W. The pressure gradient 
between the high pressure and lower pressures in the vicinity of 
the ITCZ is allowing for mainly moderate to locally fresh trade 
winds from 11N to 19N between 120W-136W, with peak seas of 8 ft.
Gentle to moderate trade winds are noted elsewhere, with seas in
the range of 6-7 ft mainly due to a southerly swell component. 
Long-period cross equatorial southerly swell over the waters 
south of about 10N and east of about 111W, except in the lee of 
the Galapagos Islands will decay late tonight, but additional 
pulses of long-period southwest swell will begin to propagate 
through these same waters by mid-week building seas to a maximum
height of 10 or 11 ft west of the Galapagos Islands.

A couple of weak low-level perturbations are moving westward
along the ITCZ west of 130W, and are helping to enhance the 
scattered shower and thunderstorm activity along and near the 
ITCZ over that part of the area. These perturbations will
continue migrating westward through Tue.