420
AXPQ20 PGUM 290055
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1055 AM ChST Sun Jun 29 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...
There are two disturbances found along the monsoon trough. The
first one is Joint Typhoon Warning Center (JTWC) Invest 98W, seen
as an exposed LLCC, centered near 15.0N 137.4E. 98W is meandering
around the Philippine Sea with little change in intensity. This
is expected to continue for the next couple of days, with very low
probability of development into a TD. Convection is only seen to
the southeast of the center and is decreasing.

The second disturbance is JTWC Invest 99W, centered at 16.2N
148.7E, with a trough extending northeast from 99W to end
near 21N153E. 99W is interacting with divergence seen southeast of
a TUTT cell centered near 20N150E. Numerous showers and isolated
thunderstorms are seen to the east of 99W, south of the trough.
The Invest is meandering around to the east of the Marianas.
Little development is expected with 99W as it slowly drifts north
over the coming days.

The main affect that the two disturbances will have across the
region is to help increase monsoon flow across the Marianas over
the next couple of days.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough extends east from a weak circulation centered
near 5N130E, through Invest 98W, across the Marianas near Guam to
Invest 99W. Scattered showers and isolated thunderstorms are
found south of the trough, west of 134E and east of the Marianas.
A monsoon surge is seen from west of Palau to southwest of Guam,
producing areas of numerous to widespread showers and isolated
thunderstorms over Palau and Yap to southwest of Guam. The trough
will very slowly drift north, allowing southwest flow to slowly
spread northward across the Marianas. The monsoon surge looks to
push farther northeast, bringing increased convection to the
Marianas beginning this afternoon.

TRADE-WIND TROUGHS...
One trade-wind trough is evident east of Kosrae, extending north
from near 2N165E to end over Kwajalein near 9N168E. Only spotty
showers are seen with this trough. Convection is expected to
increase with the trough as it moves west toward Kosrae and
interacts with a band of convergence that extends east-southeast
from near Chuuk across Kosrae.

TUTT...
The TUTT enters the area near 25N162E, extending southwest to a
TUTT cell centered near 20N150E. The TUTT continues west-southwest
to beyond 130E near 8N. Divergence south of the TUTT cell and
south of the trough is interacting with portions of the monsoon
trough and Invest 99W to enhance convection, mainly east of the
Marianas. Another area of enhanced convection is found with the
far northeastern end of the TUTT, north of 24N. The TUTT looks to
remain quasi-stationary over the coming days, with the TUTT cell
drifting slowly west. This drift will help increase divergence
across the Marianas resulting in increased convection over the
next couple of days.

OTHER SYSTEMS...
A long band of convergence is seen to the south of Invest 99W,
stretching south-southeast to Weno, Chuuk, to near 4N159E.
Numerous to widespread showers and isolated thunderstorms are
found along this band of convergence, including across Weno.
Another band of convergence extends east-southeast from near Weno
to just east of Kosrae. Scattered showers and isolated
thunderstorms are seen with this band of convergence.

$$

Kleeschulte