625
AXPQ20 PGUM 080047
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1047 AM ChST Wed Oct 8 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...
Invest 95W is centered near 18N138E and is rated as a TCFA
(Tropical Cyclone Formation Alert) from JTWC, meaning the
formation of a cyclone is likely within 24 hours. Satellite
imagery shows increased poleward outflow from the southern through
western flanks, but the disturbance remains asymmetric (as most
systems have this year) where the greater concentration of
convection is. A slow strengthening remains possible as it heads
quality northwest over the next few days, with convecting
coverage potentially attempting to wrap around the circulation.

For more information please refer to bulletins from the Joint
Typhoon Warning Center under WMO header WTPN21 PGTW or APBW10
PGTW.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough enters Guam`s AOR at 15N130E and extends to
Invest 95W. South of this line, southwesterly winds are bringing
scattered showers to the open ocean north of Koror and Yap, and
west of the Marianas. These features will continue to lift
northwest the next few days with an overall similar pattern.

TRADE-WIND TROUGHS...
A very long surface trough stretches from EQ145E to Chuuk,
continuing northeast to 18N160E (west-southwest of Wake Island),
ending at 22N165E (north-northwest of Wake Island). Scattered
showers and a few thunderstorms are occurring from the equator to
5N along the trough due to increased surface convergence, and from
13N to 22N as this portion of the trough interacts with a mid-
latitude trough thats dropping south across the tropics. A
similar convective behavior is expected through the weekend as it
continues to head west.

TUTT...
A trough dropping south from the mid latitudes stretches from
25N180 where it enters Guam`s AOR, through Wake Island to Saipan,
ending just west of there at 17N142E. Scattered showers and a few
thunderstorms continue to develop along and south of this feature
due to divergence.

This trough is transitioning into a TUTT, with both the GFS and
ECMWF forecasting a cell to form south of Wake Island in 48 hours,
drifting south to between Bikini Atoll and Kwajalein by Friday,
with the TUTT axis stretching west to a weaker cell that`ll try to
develop somewhere near Guam. This also occurs as a fairly stout
upper ridge builds from near Taiwan east to the Date Line between
20N and 30N. The increased gradient allows the winds to increase
between these features due to a tightening pressure gradient. This
signals a potentially interesting period from the Marianas
eastward for the weekend and through at least the middle of next
week, possibly longer. Stay Tuned!

...ITCZ...
The ITCZ is more distinguishable today as it attempts to reform.
Currently it stretches from Chuuk eastward to the Date Line.
However, this feature itself is void of any appreciable
convection, with embedded troughs being the focus for any
increased convective potential. This looks to be the case through
the weekend and into early next week.

$$

Doll