523
AXPQ20 PGUM 210018
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1018 AM ChST Thu Aug 21 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 has moved out of Guam`s AOR to the west.

...OTHER WEATHER SYSTEMS...

TRADE-WIND TROUGHS...
A long surface trough in the trades extends northeast from
southern Palau near Helen`s Reef east-northeast to 6N140E where it
turns northeast, passing just east of the Marianas before ending
near a col at 21N151E. Most of the convection extends along the
trough from 15N and points to the southwest along the trough axis,
with virtually no convection north of there. This is due to
weaker convergence and less moisture (PWATs near 2 inches)
compared to south of there (strong convergence and PWATs of 2.4 to
2.8 inches). This looks to remain the case the next several days
as the trough heads west.

Another more subtle trough has pinched off from the parent
trough, stretching from west of Nukuoro to Pohnpei. Scattered
showers and a few thunderstorms will continue as this piece of
energy continues west in the coming days.

Finally, a trough in the trades extends northeast from Kosrae to
between Kwajalein and Majuro before turning more east to 10N180.
The better trough convergence is from Namorik east-northeast to
the Date Line where scattered showers and a couple thunderstorms
are occurring. This feature looks to get more convectively active
by the weekend as moisture and convergence increases, then
continuing for several days as it too heads west.

TUTT...
The TUTT continues to reorganize, with the axis today stretching
from 25N180 to a cell northwest of Wake Island at 24N171E, with
the axis extending west-northwest to another cell at 25N153E,
extending southwest to a cell northwest of Saipan at 20N140E, with
the trough axis extending southwest, ending at a col northwest of
Yap/north of Koror at 12N135E. Most convection today is found
within a couple hundred miles, and across the southern Marianas
where divergence south of the TUTT is providing increased ascent
for convection developing along a surface trough.

...ITCZ...
The ITCZ is weaker and more fragmented today, with any relevant
convection tied to the surface troughs mentioned above. With that
said, the models do maintain a weak ITCZ through Sunday morning,
before it strengthens Sunday night and expands west early next
week.

$$

Doll