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AXPQ20 PGUM 130921 CCA
TWDPQ

Tropical Weather Discussion...CORRECTED
National Weather Service Tiyan GU
721 PM ChST Thu Aug 13 2026

Tropical Weather Discussion for the Western North Pacific between
the Equator and 25N from 130E to 180. The following information is
based on recent satellite imagery/data, weather observations, radar,
and meteorological analysis.

Updated Tropical and Monsoon Disturbances section to include
information on Invest 93W, now the subject of a Tropical Cyclone
Formation Alert.

Corrected typo in Tropical and Monsoon Disturbances section.

...SPECIAL FEATURES...

TROPICAL AND MONSOON DISTURBANCES...
Invest 91W was been upgraded to Tropical Depression Nangka (16W)
yesterday by the Joint Typhoon Warning Center (JTWC). As of this
morning`s TCP issuance, its center was located near 25N147E and
moving northeast. Due to its center and forecast track remaining
outside of WFO Guam`s Area of Responsibility (AOR), we will no
longer be advising on this system.

Invest 90W, previously sub-low, was closed by the Joint Typhoon
Warning Center (JTWC) yesterday.

A weak disturbance, Invest 92W, is centered near 9N161E, just
northeast of Pohnpei. The JTWC has dubbed 92W as sub-low, meaning
tropical cyclone development is not expected for the next few
days. A broad area of rotation is associated with this
disturbance, with convection mainly situated in its western
quadrants. Convergent flow from the northwest is leading to
widespread cloud cover, high-end scattered to numerous showers,
and isolated thunderstorms centered about a southeast-to-northwest
oriented axis from 9N161E to 15N152E. This disturbance is
expected to remain quasi-stationary and loosely organized over the
next few days.

Another weak disturbance is located around 22N138E, roughly 250
miles southwest of Iwo To and 750 miles northwest of Guam, and was
dubbed Invest 93W by JTWC earlier this afternoon. At 400 PM ChST,
93W became the subject of a Tropical Cyclone Formation Alert,
meaning that development into a significant tropical cyclone
(tropical depression) is expected within the next 24 hours. Latest
scatterometry data reveals a small, elongated surface circulation
with 20 to 25 knot winds to the south of 93W`s center, and 15 to
20 knot winds to the west and north. 93W is expected to shift
east-northeast over the next few days, and looks to pass near Iwo
To to its south late tonight through Friday, slowing down east of
the island Friday night, then likely exiting the AOR by Saturday
morning. No direct impacts are expected from Invest 93W, but its
development may help to enhance the monsoon pattern to its south,
helping to increase shower chances for the Marianas this weekend
through early next week.

For more information on Invest 92W and Invest 93W, please see
bulletins issued by the Joint Typhoon Warning Center (JTWC) under
WMO header ABPW10 PGTW and WTPN21 PGTW.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough enters the region near 18N130E, extending
northeast into TD Nangka. Multiple outflow boundaries can be seen on
visible satellite imagery propagating in a southeast direction. A
squall line is also situated within the monsoonal flow, extending in
a southwest-to-northeast line from 15N131E to 16N136E. Widespread
cloud cover, numerous showers, and isolated thunderstorms are found
along this axis. The monsoon trough will gradually shift southward
through the weekend, possibly aiding in the development of Invest 92W
next week. This feature will continue to be closely monitored over
the next several days.

SURFACE TROUGHS...
A surface trough is centered east of Wake Island, near 19N168E and
extends north-northeast into TD Peilou well outside of our AOR. A
fleeting moment of rotation can be seen on the most recent frames of
satellite imagery. Partly cloudy skies and scattered showers can be
seen with this feature, but pop-up convection was observed in the
early morning hours, leaving behind mid- to upper-level cloud debris
currently. This trough will continue to be absorbed by the inflow
into TD Peilou over the next couple of days.

TRADE-WIND TROUGHS...
A trade-wind trough is just entering the AOR near 17N180. Mostly
cloudy skies and scattered showers are associated with this feature.
Convection appears to be limited, with only a couple of lightning
strikes recently indicated. This feature is expected to dissipate
over the next day or two as a subtropical high pressure ridge builds
in from the northeast.

OTHER SYSTEMS...
A broad area of convergence spans from 2N to 5N and 134E to 143E,
just south of Sorol and Eauripik. Convection is persistent with this
feature, resulting in isolated to scattered thunderstorms and
numerous showers within its heaviest pockets. This feature looks to
remain quasi-stationary and weaken over the next day as an
anticyclone develops in its wake.

$$

DeCou/Mesa