Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 170938

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sun Oct 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
0915 UTC.


Gulf of Tehuantepec Gale Warning: High pressure is building 
across the Gulf of Mexico as a cold front pushes across the 
basin. The associated tight gradient has initiated gale force 
gap winds over the Gulf of Tehuantepec. These winds will continue
through early Mon. Seas are expected to build to 9-13 ft 
downwind of the gale force winds by early Sun evening, then 
slowly subside Mon. Please see the latest High Seas Forecast at 
http://nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. 


A tropical wave has its axis along 86W north of 02N to inland 
western Nicaragua and central Honduras. It is moving westward at
10-15 kt. This wave is within a very moist and unstable
environment. Scattered moderate convection is within 120 nm east
of the axis from 07N to 09N.

A tropical wave has its axis along 98W/99W from 02N to 17N, 
moving westward at 10-15 kt. Isolated showers and thunderstorms 
are noted within 180 nm west of the axis from 07N to 11N.

A tropical wave has its axis extending from 02N115W to 16N114W. 
It is moving westward near 15 kt. This wave is surrounded by a 
moist and unstable environment. Scattered showers and isolated 
thunderstorms are seen within 60 nm east of the axis from 08N 
to 11N and within 60 nm west of the axis from 10N to 15N.


The monsoon trough axis extends from the far south-central
Caribbean Sea near 12N73W westward to across central Costa 
Rica and to 10N85W to 11N96W to 11N110W to 09N120W to 14N130W
and to beyond 12N140W. Aside from the convection associated with
the tropical waves discussed in the section above, scattered 
moderate to isolated strong convection is within 60 nm south of 
the trough between 113W-115W. Scattered moderate convection 
is within 120 nm south of the trough between 99W-101W.


See the Special Features section above for more information on 
the ongoing Gale Warning for the Gulf of Tehuantepec.

The gradient associated with a high pressure ridge over these 
waters is allowing for mainly gentle to moderate northwest winds 
north of 20N, with seas in the range of 4-6 ft due to a mix of 
northwest and southwest swell. Light breezes persist south of 20N
outside of the Gulf of Tehuantepec, with 3 to 5 ft seas in a 
southwest swell. Winds over the far northern Gulf of California 
have diminished, but are expected to become southwest at fresh
to strong speeds tonight ahead of a trough that will approach 
far northern Baja California. These winds will diminish to 
mainly fresh speeds early on Mon and continue through late Mon 
night. Winds there then become north at fresh speeds early Tue, 
with passage of the trough. This trough will precede a dissipating
cold front.

For the forecast, gentle to moderate winds will persist 
elsewhere into mid-week. Looking ahead, seas will build off Baja 
California north of Cabo San Lazaro beginning Tue night as a 
northwest swell moves through the northern offshore waters.


Light to gentle north winds prevail north of the monsoon trough,
while gentle to moderate southwest winds are to its south. 
Scattered showers and isolated thunderstorms are noted in
the Gulf of Panama and offshore the border between Costa 
Rica and Panama. Seas over these waters are in the 4-6 ft range.

For the forecast, seas off western Guatemala beyond 120 nm may 
peak to 8 ft into Mon in a mix of north swell from the 
Tehuantepec region and longer-period southwest swell. Elsewhere 
seas will average about 4-6 ft due to a southwest swell. Fresh 
to northeast to east winds are expected in the Gulf of Papagayo 
Mon night and Tue. Scattered showers and isolated thunderstorms 
are expected to continue across the region through early next 


Moderate to locally fresh northeast winds continue over the
waters north of the monsoon trough and west of 120W, with gentle
to moderate winds south of the monsoon trough. Overnight altimeter
satellite data showed seas just below 8 ft due to a northwest 
swell north of 29N between 125W and 130W. An area of 8 ft in a 
northwest swell is evident from 07N to 09N between 106W- 110W. 
These seas will subside to less than 8 ft by early Sun evening. 
Elsewhere, gentle to moderate north to northeast winds and seas 
in the 5-7 ft range will change little into the early part of the 
upcoming week. A northwest swell expected to raise seas to 8 ft 
will move into the waters north of 27N between 120W-130W Tue into
Wed, then subside. Looking ahead, a more substantive area of 
northwest swell will accompany a cold front that will move into 
the waters north of 28N and west of 130W Tue night, with seas in 
excess of 8 ft dominating the waters northwest of a line from 
Guadalupe Island to 14N140W by late Thu.


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Page last modified: Sunday, 17-Oct-2021 09:38:25 UTC