851
AXPQ20 PGUM 210104
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1104 AM ChST Tue Jul 21 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.

...SPECIAL FEATURES...

TROPICAL AND MONSOON DISTURBANCES...
A very broad, weak disturbance has begun to take shape within the
monsoon trough north of Palau and Yap near 13N135E, now dubbed
Invest 92W by the Joint Typhoon Warning Center (JTWC). 92W is rated
"sub-low", meaning it is not expected to develop into a significant
tropical cyclone (a tropical depression) over the next few days, but
will continue to be monitored for development. Himawari visible
satellite imagery this morning shows an area of broad, flaring
convection within the convergence along 92W`s southern flank,
associated with the monsoon pattern feeding into it. Moderate to
locally heavy rainfall has persisted over Yap Proper this morning,
and models suggest this will gradually diminish through tonight as
92W shifts northwestward. While showers are patchier to the
southwest near Palau, locally heavy rainfall can be expected at times
through tonight. Over the next few days, Invest 92W looks to
gradually develop a very broad circulation over the Philippine Sea as
it meanders northwestward, potentially exiting west of Guam`s Area
of Responsibility (AOR) by the end of the week, and potentially as a
tropical depression. Overall, 92W will help maintain a wet monsoon
pattern over far western Micronesia for much of the remaining week.

Additionally, a weak disturbance is seen to the northeast of Majuro
Atoll near 12N178E, now dubbed Invest 93W by JTWC as of earlier this
morning. 93W is also rated as a "sub-low", and development is not
expected over the next few days. Latest scatterometry data depicts a
small circulation here with 15 to 20 mph winds along its northern
flank, and a small embedded area of 25 mph winds associated with
nearby convection. There is another weak circulation nearby to its
southwest, located southeast of Majuro near 4N174E. CIMSS 850mb
vorticity analysis shows the stronger low-level vorticity is focused
around 93W, and models support slight consolidation around this area
over the next few days. At the same time, some of the vorticity near
Majuro looks to shift westward and away, potentially slowing the
development of Invest 93W somewhat as it meanders west-
northwestward.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough has shifted slightly northward over the last 24
hours, extending east-northeast into Guam`s Area of Responsibility
(AOR) at 12N130E, passing well north of Palau and Yap through Invest
92W before curving slightly east to pass just south of the Marianas.
The monsoon trough then curves to the east-southeast where it enters
eastern Micronesia, passing just north of Pohnpei and Kosrae, and
then into a weak surface circulation southeast of Majuro near 4N174E.
The trough then curves sharply northeast, exiting the region at
8N180. From the circulation southeast of Majuro, a trough extends
southward to EQ172E, and north-northeast to another weak surface
circulation around 12N177E, now dubbed Invest 93W. Patches of
scattered showers are seen within the monsoon trough over and east of
the Marshalls, associated with weak convergence along the nearby
pair of circulations. Showers are more numerous farther west, within
a broad northwest-southeast oriented band that skirts Pohnpei and
Kosrae waters immediately to the south. These heavy showers are
associated with a strong area of convergence along the far northern
outskirts of a buffer circulation south of the Equator, and west of
the weak circulation near Majuro.

Over far western Micronesia, deep, flaring convection is seen along
and south of the monsoon trough axis, including over Yap Proper and
portions of the Republic of Palau, within the convergent inflow into
Invest 92W. As described above, this portion of the monsoon trough,
and Invest 92W, look to gradually lift west-northwest and maintain a
wet pattern across far western Micronesia over the next few days.
See the Special Weather Statement for Palau and Yap for more details.

UPPER LEVEL TROUGHS...
A broad, weak, upper-level trough extends southwest into the region
from 25N147E, passing northwest of the Marianas and into far western
Micronesia to the west of Palau, near 7N130E. This upper-level
trough is interacting with a remnant cold front along 150E just east
of Iwo To, and the monsoon pattern over western Micronesia. This is
producing bands of thunderstorms east of Iwo To, and scattered to
numerous heavy showers and thunderstorms across Yap and Palau. This
upper-level feature looks to shift west and exit the region over the
next few days.

A weak upper-level trough and low are seen just east of the
Marianas, with the low centered east of Guam and Rota near 13N147E
and the trough extending southward into it from around 17N147E. A
trough then extends southeast and passes between Chuuk and Pohnpei
to around EQ161E, and is interacting with surface convergence to
support a band of deep convection there. This overall feature will
shift westward, and may help to support deep convection within the
monsoon pattern over western Micronesia and Invest 92W over the next
few days.

A broad upper-level trough is seen to the north of eastern
Micronesia, extending southwest into the region from from 20N180, to
an upper-level low south of Wake Island near 14N168E, and to the
northwest of Pohnpei near 9N155E. A series of smaller, weak upper-
level troughs are also seen from just east of Majuro to around
Pohnpei. These features are producing scattered showers to the
northeast of Wake, and are interacting with the pair of surface
circulations near the Marshalls to produce patches of scattered
showers and isolated thunderstorms. These upper-level features will
shift westward across eastern and central Micronesia throughout the
week and may support showers and thunderstorms associated with the
monsoon trough, and any transient weak surface features.

OTHER SYSTEMS...
A remnant cold frontal boundary extends westward into the region
along 25N, from 155E to 143E just east of Iwo To. A band of heavy
showers and thunderstorms extends along this boundary. This feature
looks to very gradually drop southward over the next few days with
a slight decrease in strength.

$$

DeCou