160
ABPZ20 KNHC 171154
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Thu Sep 17 2026

For the eastern and central North Pacific east of 180 longitude:

Western East Pacific:
A tropical wave continues to produce disorganized showers and
thunderstorms well to the south-southwest of the southern tip of the
Baja California Peninsula. Environmental conditions appear
conducive for gradual development of this system, and a tropical
depression is likely to form this weekend or early next week as it
moves westward at 10 to 15 mph across the western part of the East
Pacific.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 7 days...high...70 percent.

Well East-Southeast of the Hawaiian Islands (Former TD15-E):
Showers and thunderstorms have increased somewhat with an area of
low pressure related to the remnants of Tropical Depression
Fifteen-E. Environmental conditions appear only marginally conducive
for some development of this system as it moves gradually westward,
remaining east-southeast of the Hawaiian Islands.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...low...10 percent.

Southwest of Southwestern Mexico:
Another tropical wave is producing disorganized showers and
thunderstorms several hundred miles south of southwestern Mexico.
Environmental conditions also appear conducive for gradual
development of this system, and a tropical depression is likely to
form late this weekend or early next week while it moves gradually
northwestward turning northward off the coast of southwestern
Mexico.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 7 days...high...80 percent.

$$
Forecaster Papin

734
AXPZ20 KNHC 170832
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Thu Sep 17 2026

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
0830 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: The pressure gradient between high pressure over
southern Mexico and the eastern north Pacific monsoon trough will support
strong to near-gale force N to NE gap winds across the Gulf of Tehuantepec
into Fri. A recent scatterometer satellite pass confirmed gale force
winds across the Gulf of Tehuantepec, and this may persist into the
early morning. Winds may again reach minimal gale force briefly tonight.
Rough seas will accompany these gap winds. Winds and seas will diminish
Fri.

...TROPICAL WAVES...

A tropical wave is along 101W, from 06N northward to southern
Mexico, moving westward at around 10 to 15 kt. Nearby convection
is discussed in the ITCZ/monsoon trough section below. An area
of low pressure could form in association to this wave well
offshore of southwestern Mexico within the next few days.
Environmental conditions appear conducive for some gradual
development, and this system could become a tropical depression
early next week while it moves slowly northwestward or northward.
There is a low chance for development in the next 48 hours, and
a high chance for tropical cyclone development within the next 7
days.

The axis of a tropical wave is near 116W from 07N to 16N, moving
west at 10 to 15 kt. Nearby convection is discussed in the
ITCZ/monsoon trough section below.

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

The monsoon trough extends from 09N79W to 08N90W to 1007 mb low
pressure near 15N129W to 10N140W. Scattered moderate convection
is active from 02N to 06N east of 83W, and from 10N to 16N
between 112W and 116W. Scattered moderate to isolated strong
convection from 08N to 13N between 90W and 100W.

...OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please see Special Features section above for more on a gale
warning in the Gulf of Tehuantepec.

An afternoon scatterometer satellite pass indicated fresh S
winds over the northern Gulf of California, related to lower
pressure in the region. These winds are likely diminishing this
evening. Gentle to moderate winds and 4-7 ft are noted
elsewhere, except 1-3 ft in the central and southern Gulf.

For the forecast, please see the Special Features section for
information about the gale warning in the Gulf of Tehuantepec.
Gentle to moderate breezes and moderate seas will persist
elsewhere through the end of the week. Meanwhile, a tropical
wave is producing disorganized showers and thunderstorms south of
Acapulco. Looking ahead, environmental conditions appear
conducive for gradual development, and there is a high chance a
tropical depression may form late this weekend or early next
week while it moves north- northwestward or northward at 5 to 10
kt off southwest Mexico.

...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA,
AND WITHIN 750 NM OF ECUADOR...

Fresh to strong easterly winds, and moderate to rough seas,
prevail across the Gulf of Papagayo region, extending downstream
to near 90W. Moderate to fresh winds extend downstream from the
Gulf of Papagayo to the outer offshore waters of El Salvador and
Guatemala.

For the forecast, the pressure gradient between a ridge north of the area
and the eastern north Pacific monsoon trough will support pulsing
fresh to occasionally strong easterly winds and moderate to rough
seas across the Papagayo region today, then pulsing to moderate
to fresh thereafter. Moderate winds and seas will prevail
elsewhere.

...REMAINDER OF THE AREA...

The 1007 mb remnant low of TD Fifteen-E is centered near
15N130W. Scattered showers and thunderstorms remain active in
the vicinity of the low. Fresh to strong winds, and rough seas,
supported by the pressure gradient between the area of low
pressure and the subtropical ridge north of the area, cover the
waters from 15N to 25N west of 125W. Moderate to fresh winds,
seas to 7 ft, a scattered showers and thunderstorms are also
active near a 1008 mb low pressure area along the monsoon trough
near 12N112W. Gentle to moderate winds and 4-6 ft combined seas
in mixed swell are noted elsewhere.

For the forecast, environmental conditions appear conducive for
gradual development of the 1008 mb low pressure near 12N112W,
and a tropical depression could form this weekend as the system
moves westward at around 10 kt. There is a low chance for
development in the next 48 hours, and a medium chance for
tropical cyclone development within the next 7 days. Farther
west, a broad area of fresh to strong NE to E winds and moderate
to rough seas in N swell will persist through the remainder of
the week from 15N to 25N west of 125W. Also, as described in the
tropical wave section above, there is some potential for tropical
cyclone development associated with a tropical wave near 101W.

$$
Christensen