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Tropical Weather Discussion...UPDATED
National Weather Service Tiyan GU
421 PM ChST Tue Aug 18 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...

Updated for issuance of TCFA for Invest 92W.

TROPICAL AND MONSOON DISTURBANCES...
Updated discussion: The JTWC has now rated Invest 92W as high,
meaning that development into a significant tropical cyclone is
expected within 24 hours and the JTWC has issued a Tropical Cyclone
Formation Alert (TCFA) for Invest 92W. Invest 92W is currently
located near 8N155E or about 180 NM east of Chuuk. Invest 92W is
moving west at 3 knots but is expected to lift north-northwestward
over the coming days. Numerous to widespread showers and isolated to
scattered thunderstorms are seen along the southern semicircle of
92W. Very heavy rainfall, flash flooding, mudslides, and gusty winds
are possible or ongoing across Chuuk and Pohnpei over the next couple
of days.

Previous discussion: Invest 92W, located near 8N155E (north west of
Pohnpei/east- northeast of Chuuk), is trying to get its act together,
with some improved convective signature across the southern half of
the system. This has led to an increase in rating, with JTWC now
placing a medium rating on it, meaning formation of a tropical
cyclone (tropical depression or stronger) is likely, but beyond 24
hours. It continues to remain quasi-stationary, drifting west to
southwest at 5 mph. The environment is marginally favorable for
further development, as about 15 to 25 knots of easterly wind shear
is fighting the tropical disturbance, as is some dry air on the north
to northeast flank of the system.

Additionally, the vorticity centers aloft are not co-located with
the LLCC (Low-Level Circulation Center). With all of this in
mind, 92W will likely continue to show a slow development pace for
the next 48 to 72 hours, with the real question being when will
it start to track north-northwest (roughly a 340 heading).
Questions also remain as to whether it`ll take a westerly turn
with time towards the end of the week, as a subtropical ridge
strengthens to its north, stretching from China eastward to just
north of Iwo To and Minamitorishima, and east-northeastward. Stay
tuned!


...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough stretches from Invest 94W (which is now located
just west of Guam`s AOR at 21N132E), extending southeast to Guam
where a col is located, before continuing southeast and linking up
with 92W. The trough then continues east-southeast through a col
between Kwajalein and Majuro, passing through Majuro, before
exiting Guam`s at 8N180. West to southwesterly flow of 10 to 20
knots is centered between ~7N and the trough axis, with pockets of
scattered shower and isolated thunderstorm development continuing.
In general, this trend is expected to continue the next few days,
with the exception being near 92W. Here, convective coverage and
intensity will gradually increase as 92W strengthens, while it
also helps to locally augment trough orientation.

$$

Previous: Doll
Update: Williams