508
AXPQ20 PGUM 020128
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1128 AM ChST Sat Aug 2 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...

None.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough extends east of Taiwan and enters the Area of
Responsibility (AOR) at 24N130E, turning northeast and quickly
exiting the AOR, passing through Joint Typhoon Warning Center`s
(JTWC) Invest 93W northwest of Iwo To and on through Tropical
Storm Krosa east of Japan. The monsoon surge extends south and
east of the trough roughly 600 to 700 miles, staying well to
the north of the main islands of Palau, Yap Proper and the
Marianas. Moderate to deep convection is occurring within the
surge, including over Iwo To, along with fresh to near-gale winds.
The monsoon trough and surge are expected to lift north as the
tropical systems push off to the northeast, and as a ridge of high
pressure south of the tough shifts further north and west.

SURFACE TROUGHS...
Multiple surface troughs pinwheel off a broad, weak circulation
centered just east of Guam. More notable troughs extend
southwest towards Yap Proper, southeast towards Chuuk lagoon and
north-northwest across the Marianas. Moderate to deep
convection are occurring along the troughs southwest and southeast
of the circulation where convergence and moisture are enhanced.
Spotty showers are occurring north of the circulation, including
over the Marianas. The circulation and troughs will push west
across the Marianas, Yap State and the Republic of Palau through
the weekend into early next week.

Multiple surface troughs also extend off a circulation to the
southeast of Pohnpei and southwest of Kosrae centered near 4N159E.
One noted trough extends southwest from the circulation, crossing
Kapingamarangi and ending at the Equator near 153E. Another trough
extends east-northeast along the Inter-Tropical Convergence Zone
(ITCZ) across Kosrae and ending south of Kwajalein near 8N168E.
Moderate to deep convection is occurring near the circulation and
along the troughs, including over eastern Pohnpei State, Kosrae
State and southwestern Marshall Islands. The circulation and
troughs will drift north and west across Pohnpei State, Chuuk
State and towards the Marianas through the weekend into early next
week.

A surface trough extends north-northeast from the ITCZ, beginning
near 9N177E, crossing the Date Line near 12N and passing through
Tropical Storm Iona centered near 15N178W and ending near
22N179W. Pockets of moderate to deep convection are occurring
along the trough, generally along and east of the Date Line near
TS Iona and exiting north. The trough, along with TS Iona, will
work to the northwest and weaken through the weekend into early
next week. TS Iona is expected to shortly cross the Date Line and
pass to the northeast of Wake Island as a weak Tropical Depression
on Monday, possibly becoming extra-tropical before closest path of
approach (CPA).

TUTT...
The Tropical Upper-Tropospheric Trough extends southwest from an
upper-level low east of the Date Line and enters the AOR at 23N,
then passing southwest over Wake Island and through multiple weak
TUTT cells east of the Marianas and north of Chuuk, Pohnpei
states, ending southwest of Weno, Chuuk near 6N148E. Pockets of
showers are occurring along, south, and east of the TUTT, with
occasional lightning strikes beneath the TUTT cells east of the
Marianas and southwest of Wake Island. The TUTT will dissipate due
to frictional forces as the upper-level ridge to the north shifts
east, with the TUTT cells splitting off and drifting west.

...ITCZ...
The ITCZ begins east of the Date Line and enters the AOR near 9N,
extending east-southeast and passing just north of Majuro, across
Kwajalein, north of Kosrae and ending at a leading edge
circulation to the southeast of Pohnpei Proper and southwest of
Kosrae, centered near 4N159E. Moderate to deep convection is
occurring along and south of the ITCZ, especially across eastern
Pohnpei State, Kosrae State and southwestern Marshall Islands. The
ITCZ will slowly drift west and dissipate as the circulation and
parent surface trough along the leading edge of the ITCZ shift
west and surface ridging builds in across eastern Micronesia
behind it.

$$

Slagle