031
AXPQ20 PGUM 300018
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1018 AM ChST Tue Sep 30 2025

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 weakly-organized circulation, known as Invest 93W from JTWC is
rated as having a low probability of development. It`s currently
located near 13N137E. Widespread cloud cover with scattered
showers and isolated thunderstorms are occurring with the greatest
concentration on the western flank of the system. This feature
will continue to slowly organize as it heads west the next several
days, but to what extent remains in question. Some of the
ensemble members do eventually develop a tropical depression, but
this remains to be seen.

...OTHER WEATHER SYSTEMS...

TRADE-WIND TROUGHS...
A trade-wind trough that has been marching west between 12N and
18N for several days now has a parent circulation at the bottom of
the trough, labeled as Invest 93W as described above. This trough
and the circulation will continue west the next several days with
scattered showers and isolated thunderstorms occurring. With the
trough stretching between 13N138E to 18N 135E, it should exit
Guam`s AOR at 130E by Thursday.

The next surface trough stretches from a broad/weak circulation
near 10.2N 160E, extending northwest to 15N156E. Then a second
trough from the circulation extends due north to near Wake Island,
ending near 20N160E. A third "spoke of energy"/trough extends
southwest to near Pohnpei at 7N 157.5E. All of these troughs have
scattered showers and isolated thunderstorms developing near them.
The first two troughs will continue west the next several days in
a similar convective manor. It remains unclear if the circulation
will persist as none of the models picked up on it (not unusual
as these "cusp: circulations sometimes maintain integrity, and
sometimes they don`t. This also casts doubt on the third,
southwest-extending trough and it`s longevity/convective behavior.

TUTT...
The TUTT axis enters Guam`s AOR at 21N180 and connects to a cell
at 20N170E, northeast of Wake Island. The TUTT then extends west
to another cell just east of Minamitorishima at 23.8N 155E,
extending west to another cell west-southwest of Iwo To at
23N133E, exiting Guam`s AOR at 22N130E.

Another trough axis in the TUTT extends southwest from the Wake
Island Cell to near Kosrae at 6N163E. Scattered showers and
isolated thunderstorms are occurring near the cells, with
scattered to numerous showers and isolated thunderstorms occurring
along the southwestern extension of the TUTT and along the
southern flank of the TUTT axis connecting the cells.

In general, this TUTT orientation and convectively-related pattern
looks to remain the same through the end of the week, with the
whole pattern perhaps shifting south a couple hundred miles.

...ITCZ...
A west-northwest to east-southeast orientated ITCZ fragment
stretches from Majuro to Ujelang at 9.7N 161E, ending at the
circulation mentioned above (10.2N 160E). Scattered to locally
numerous showers and isolated thunderstorms are occurring with
this fragment. This fragment will continue to dissolve as it lifts
north and west over the next few days, with a new ITCZ taking
shape near Majuro towards the end of the week.

$$

Doll