939
AXPQ20 PGUM 300124
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1124 AM ChST Wed Sep 30 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 found along the monsoon trough, Invest 93W,
is centered east of Saipan near 15.6N 151.9E. 93W is now rated TCFA
by the Joint Typhoon Warning Center (JTWC), meaning that development
into a significant tropical cyclone (tropical depression) is expected
within the next 24 hours. Invest 93W continues to move slowly west-
northwest. Convection has been persistent to the west and south of
the center, with scattered to numerous showers and isolated
thunderstorms found up to 300 miles from the center. Spotty showers,
though increasing, are also seen north to east of the center. Invest
93W is expected to continue strengthening as it moves west-northwest
over the coming days, passing north of Saipan late in the week.

For more information on Invest 93W, see bulletins issued by JTWC
under WMO header ABPW10 PGTW.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough enters the AOR around 12N130E and extends east-
northeast through a weak circulation around 14N137E. This circulation
is producing scattered showers with isolated thunderstorms on its
leading edge well northwest of Yap Island. From here, the monsoon
trough continues east through Invest 93W which is centered near
16N152E, extends southeast through a couple of weak circulations
along 10N before exiting the AOR around 8N at the Date Line. The
heaviest convection is associated with the monsoonal tail of 93W,
where widespread cloud cover, numerous showers, and isolated
thunderstorms are present between the Marianas and Chuuk. The monsoon
trough is also producing scattered showers and isolated pockets of
convection over Palau and Yap. As for eastern Micronesia, showers
look to be backbuilding from an embedded circulation just west-
northwest of Kwajalein. In addition, scattered showers and isolated
convection are evident south of Majuro due to the interaction between
the westerly winds and the embedded weak circulation just east of
Majuro. There will be little change in intensity with the trough and
should gradually lift northward with 93W over the next few days.

TRADE-WIND TROUGHS...
A trade-wind trough extends from Invest 93W north to about 25N153E
where it exits our AOR. Scattered showers and isolated pockets of
convection are evident along and within 200 miles of the trough axis.
Cloud cover is more extensive along this trough compared to the
cumulus clouds characteristic of the background trade-wind pattern
elsewhere in the region. This trough will continue moving west-
northwest with 93W, remaining unchanged in intensity for the next
day.

$$

Mesa