288
AXPQ20 PGUM 140116
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1116 AM ChST Mon Sep 14 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 developing disturbance, Invest 90W, is centered E of Guam along
the monsoon trough near 13.0N 154.5E. Invest 90W is currently moving
slowly NW and has become a bit more organized over the last 24
hours. 90W remains low, however, it is likely that it will be
upgraded to medium later this morning due to favorable conditions
for development. Medium indicates that development is expected, but
not within the next 24 hours. Deep convection has increased
significantly in the last 24 hours to the E-S-W of 90W, showing that
the system is becoming better organized. Scattered to numerous
showers and isolated thunderstorms are found in these areas,
extending into the Marianas. It is still difficult to identify a good
Low-Level Circulation Center (LLCC), however, satellite shows the
possibility of a weak LLCC ESE of Guam near 12N151E. Invest 90W is
expected to move NW over the coming days, heading toward the northern
CNMI as it slowly develops.

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, extending E
through a weak circulation ESE of Guam near 12N151E to Invest 90W.
It then turns ESE to the northern Marshall Islands near 10N174E,
turning back to the E, crossing the Date Line near 10N. Scattered to
numerous showers and isolated thunderstorms are found S of the
trough, across Palau to well S of Yap, within a weak monsoon surge
and a band of convergence. Farther E, mostly numerous showers and a
few thunderstorms are found across western Yap State and Chuuk
State, including Weno, but north of Namoluk. This surge is producing
near- gale to gale force gusts across this area along with the
convection. E of Invest 90W, scattered to numerous showers are seen
well N of Kosrae, across the western Marshall Islands, with
convection becoming isolated E of Kwajalein. The monsoon trough
looks to slowly drift NW over the eastern portion of the trough as
Invest 90W tracks NW. The remainder of the trough is expected to
remain quasi- stationary. The intensity looks to remain unchanged
except near Invest 90W, where strengthening is likely as 90W
develops.

TRADE-WIND TROUGHS...
A trade-wind trough extends NNW from W of Guam near 14N144E to end
near 23N140E. This trough is generating scattered to numerous
showers and isolated thunderstorms across the CNMI and northern CNMI
to near Iwo To. This trough looks to continue to move W over the
next few days, maintaining convection near and just E of the trough.

$$

Kleeschulte