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AXPQ20 PGUM 120043
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1043 AM ChST Wed Aug 12 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 weak disturbance, Invest 90W, is centered NW of Kwajalein near
12.1N 164.8E, moving slowly WNW. The Low-Level Circulation Center
(LLCC) remains relatively cloud free, with the associated convection
seen to the W of the center, along a band of convergence S of a col
region. Scattered showers are found in this region. Invest 90W is
expected to continue to move slowly WNW over the coming days with
little change in intensity. Convection, however, may increase closer
to the center of 90W.

A more organized disturbance, Invest 91W, is centered WNW of Maug
Island near 21.8N 140.8E. Invest 91W was increased to medium
overnight, which means that tropical cyclone development is likely,
but expected to occur beyond 24 hours. Latest satellite data and
surface analysis show a more organized cloud covered LLCC. other
factors remain favorable for TC development as well, with low
vertical wind shear, good upper-level outflow and warm sea surface
temperatures. Numerous showers and isolated thunderstorms are found
along the southern periphery of 91W, within 230 miles of the center
and the monsoon trough. Although Invest 91W is not expected to have
a direct impact on the Marianas, increasing convection S of the
monsoon trough and 91W could move into the Marianas, especially
Tinian and Saipan northward, over the next couple of days. Invest
91W will continue to be monitored closely.

For more information on Invest 91W, please see bulletins issued by
the Joint Typhoon Warning Center (JTWC) under WMO header ABPW10
PGTW.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough enters the region near 25N130E, extending ESE
into Invest 91W. It then turns NE to beyond 25N near 145E, extending
into TD Peilou. As Peilou continues to weaken and move NE, the
monsoon trough is showing signs of redeveloping farther S, possibly
interacting with Invest 90W. This will be monitored over the coming
days. Numerous showers and isolated thunderstorms are seen along and
up to 300 miles S of the monsoon trough. As Invest 91W continues
moving ENE to NE, the monsoon trough will move with it, weakening as
91W advances.

SURFACE TROUGHS...
A surface trough extends SE from Invest 91W into Invest 90W. This
trough may be the attempt for the monsoon trough to re-establish
farther S. A small band of scattered showers and a few thunderstorms
is seen to the E of the far northern CNMI. Farther S, scattered to
numerous showers and isolated thunderstorms are found W of the
trough, N of Pohnpei and Kosrae. As Invest 90W drifts W, the trough
and associated convection are expected to strengthen, with increasing
convection along the trough. This does not look sufficient to
develop Invest 90W, just to keep convection active W of the center.

OTHER SYSTEMS...
A band of showers and thunderstorms is found WNW of Wake Island,
with another band E of Wake. These two bands are the remnants of
inflow into what is left of TD 13W and 15W. As both TDs continue to
weaken, these bands of convection will gradually decrease.

$$

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