926
AXPQ20 PGUM 260041
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1041 AM ChST Sat Sep 26 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...

None.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The Monsoon Trough enters Guam`s AOR at 19N130E and extends
southeast through a col well north of Yap near 16N138E, where it
turns east to pass through Rota. It then continues east to a col
near 15N160E, turning southeast to exit the AOR at 9N180. South
of this trough, a months-long west to southwest surface flow
continues. Convergence near the trough is promoting the highest
concentration of moisture to it`s immediate south, especially
between 8N and 15N. Here, PWATs in the 2.5 to 2.8 inch range are
common. This increased moisture and resultant instability is
acting upon the nearby convergence to allow a fairly expansive
area of showers and thunderstorms to continue developing, mainly
from Yap eastward to the Date Line. This feature looks to remain
quasi-stationary through the middle of next week with a similar
area of convection probable.

SURFACE TROUGHS...
A surface trough extends north from Kwajalein northward through
Wake Island, exiting Guam`s AOR near 25N169E. Along and east of
this trough, abundant moisture is being pulled northward from the
tropics all the way to 25N and beyond, as evident by MIMIC PWATs
in the 2.5 to 2.8 inch range.. However, despite this excellent
moisture qualify and good surface convergence, convection has
been lack-luster, showing just shallow and widely-scattered
convection stretching from 170E to 173E from 18N to beyond 25N.
However, it wouldn`t be surprising to see an increase in
convective coverage and intensity over the next few days as the
trough heads west given the moisture quality and depth (the
6-layer ALP - All Layer Precipitable Water- shows deep moisture as
well). Additionally, the pattern does favor a potential
circulation developing at some point east of the Marianas, as
satellite imagery shows numerous vorticity centers in the ALP that
are not vertically aligned, yet. Stay tuned though as this could
change by early next week based on pattern recognition and trends
this year.

$$

Doll