467
AXPQ20 PGUM 310041
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1041 AM ChST Sun Aug 31 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 90W, now rated low for development from JTWC (the Joint
Typhoon Warning Center), is located near 11N130E. With a low
rating development will not occur until well beyond the next 24
hours, at which time it`ll be west of Guam`s AOR. Still,
widespread cloud cover continues with fairly robust convection
developing in a cyclic nature around the center of the LLCC (Low-
Level Circulation Center), which will continue for the next 24
hours.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
A west to southwest monsoon trough exists between the equator and
11N. generally from 130E to 146E. Although currently there`s not
much convection directly associated with it, where convection is
occurring increased surface convergence would help foster
convective expansion from time to time over the next several days,
as the models forecast this feature to remain in place in the
general area it`s currently found. Over the next 24 hours, mid to
high-level cloud cover is expected to keep convection to a
minimal coverage.

TRADE-WIND TROUGHS...
A surface trough extends northeast from 95W northeast to near
21N142E. Widespread cloud cover with scattered showers and the
occasional thunderstorm redeveloping, and this pattern will continue
as both features (95W and it`s attendant surface trough) move west
the next few days.

Farther south, a leading surface trough stretches from just west
of Nukuoro to between Chuuk and Pohnpei, then in a north-
northwest fashion to 19N152E. Widespread cloud cover with
scattered to locally numerous showers are occurring along this
axis, with a few thunderstorms mixed in as well. This axis is
found in a region of excellent convergence between the surface and
250mb as the surface trough interacts with a "dirty" high aloft
that`s centered east of Rota.

Finally, another trough in the trade flow extends from Kosrae to
between Kwajalein and Majuro, to 12N180 and beyond. Here too
widespread cloud cover is present, with scattered showers and the
occasional thunderstorm continuing to develop. This will be the
case the next several days as it heads off to the west.

TUTT...
Currently the TUTT extends from east of the Date Line at 25N to a
cell centered at 24N170E, then westward through a col north of
Alamagan in the CNMI to a cell at 20N137E, ending in an area of
divergence over Helen`s Reef in southern portions of the Republic
of Palau. The TUTT is forecast to strengthen and expand westward
this week as it adjusts southward somewhat. Widespread convection
continues to develop along the periphery of the TUTT cells and to the
south of the TUTT axis where divergence helps provide increased
updraft vertical velocities while maintaining storm top
ventilation.

Another surface trough north to northwest of Wake Island extends
from 22N163E to 25N165E with widely-scattered showers developing.
A TUTT is also strengthening across the region, thus, a
thunderstorm or two may develop as well. This looks to be the case
the next several days as the trough continues its westward
journey.

...ITCZ...
The ITCZ is found between 5N and 15N from 152E to 160E, before
narrowing to a cone-line feature between 6N and 13N from 168E to
the Date Line and beyond. In general, the most notable convection is
found along surface troughs mentioned above where the convergence is
maximized. This pattern looks to continue through the middle of the
week before a reorientation/configuration of the ITCZ takes place.

$$

Doll