648
AXPQ20 PGUM 130045
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1045 AM ChST Sun Sep 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.

...SPECIAL FEATURES...

TROPICAL AND MONSOON DISTURBANCES...
A weak disturbance found along the monsoon trough, Invest 90W, is
centered along an area of sharp troughing, just W of a circulation
center found N of Pohnpei, near 12.5N 156.6E. 90W is now rated low,
meaning development is unlikely over the next 24 hours. A burst of
convection is seen to the S of the trough, near the centroid of
Invest 90W, extending ESE, S of the monsoon trough and 90W.
Scattered to numerous showers and isolated thunderstorms are found
over this area. Invest 90W will generally drift NW over the next
couple of days and looks to consolidate within the weak circulation
center a little farther E than the current centroid location. 90W is
expected to slowly strengthen over the coming days as it moves in the
general direction of Maug in the northern CNMI.

For more information on Invest 90W, see bulletins issued by the Joint
Typhoon Warning Center under WMO header ABPW10 PGTW.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough enters the region near 14N130E and extends SE
through two weak circulations centered WNW of Yap near 11N137E and S
of Guam near 10N143E. It then turns WNW to Invest 90W where it turns
ESE, passing through a few weak circulations, one centered ESE of
Invest 90W near 11N159E, one NNW of Kwajalein near 10N168E and the
last one E of Majuro near 9N178E. It then continues E across the Date
Line near 9N. The monsoon flow and some associated areas of
convergence are producing scattered to numerous showers and isolated
thunderstorms from 130E, across Palau, following the same general
pattern as the monsoon trough. A stronger surge is seen pushing
numerous showers and isolated thunderstorms into Chuuk and Pohnpei.
Scattered showers and isolated thunderstorms are then seen from N of
Kosrae, across Majuro, to beyond the Date Line. The monsoon trough
looks to remain quasi-stationary over the coming days as the weak
circulations drift WNW to NW with little change to slight
strengthening.

TRADE-WIND TROUGHS...
A trade-wind trough to the E of the northern CNMI is interacting
with upper-level divergence to produce numerous showers and isolated
thunderstorms across the northern CNMI, N of Agrihan. The trough and
divergence will continue to move WNW, dragging the convection with
them. Both features look to remain relatively unchanged in
intensity.

OTHER SYSTEMS...
Upper-level divergence between an upper-level low centered WSW of
Iwo To near 22N136E and an upper-level high E of the Marianas is
enhancing convection from near the low to N of 25N, back S of 25N
near Iwo To, across the northern CNMI, N of Agrihan. A weak trade-
wind trough is interacting with the divergence to produce numerous
showers and isolated thunderstorms over the northern CNMI. The
divergence and trough will continue to move WNW, with little change
in intensity, dragging the associated convection with them.

$$

Kleeschulte