663
AXPQ20 PGUM 040106
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1106 AM ChST Fri Jul 4 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 flow is being split by a surface ridge that is
centered over the Marianas. A monsoon trough extends from the
northern Philippines and crosses the area of responsibility (AOR)
to a weak circulation near 16N131E.

One arm of the monsoon trough extends northeast from the weak
circulation, passing well northwest of the Marianas and wrapping
up into Tropical Storm Mun (04W), which is centered north of the
AOR at 29N145E. Pockets of moderate to deep convection are
occurring along and southeast of the trough axis, where it is
being enhanced by upper-level divergence with an upper-level
trough axis located to the northwest of the monsoon trough axis.

Another arm of the monsoon trough extends southeast from the weak
circulation, passing across the main islands of Palau and Yap
Proper and crossing the equator near 145E. Pockets of moderate to
deep convection are occurring within this trough across much of
the Republic of Palau and western Yap State, where it merges with
an approaching surface trough pushing out of eastern Yap State.

The monsoon trough will linger over the coming days, with the
northern extension likely strengthening as a tropical disturbance
intensifying north of the Philippines and increasing the monsoon
flow over the Republic of Palau, western Yap State and the
Marianas by early next week.

SURFACE TROUGHS...
A surface trough merging with the monsoon trough begins near
Eauripik, extending northeast and ending south of Guam. Pockets of
moderate convection are occurring within the trough across western
Yap State, with more isolated showers north of 10N towards Guam.
The surface trough will continue to drift north and west through
the weekend and merging with the monsoon trough near Yap Proper
and the main islands of Palau.

TRADE-WIND TROUGHS...
A trade-wind trough along the leading edge of a fragmented Inter-
Tropical Convergence Zone (ITCZ) begins near the equator at 160E,
extending north-northeast, passing between Pohnpei Proper and
Kosrae and ending near 12N162E. Pockets of moderate to deep
convection are occurring along the trough axis, mainly between
Pohnpei Proper and Kosrae. Convection is being enhanced by upper-
level divergence with the Tropical Upper-Tropospheric Trough
(TUTT) axis that is centered just to the northwest of the surface
trough. This trough will continue to drift west across Pohnpei
State and into Chuuk State through the weekend.

A trade-wind trough along an enhanced section of the ITCZ has
crossed the Date Line and is approaching the southern Marshall
Islands, beginning near the equator at 172E and extending north-
northeast, passing east of Majuro and ending near 9N176E. Deep
convection is occurring along the trough south and east of the
southern Marshall Islands. This trough will continue to push
across the southern Marshall Islands and towards Kosrae and
Pohnpei State through the weekend.

TUTT...
The TUTT extends west from an upper-level low east of the Date
Line and crossing into the AOR at 27N, then extending southwest
and passing through a TUTT low that is centered south of Wake
Island near 17N166E, then ending near Pohnpei Proper and Kosrae.
Pockets of moderate convection are occurring near and south of the
TUTT low, to the south and east of Wake Island and down towards
Pohnpei Proper and Kosrae. The TUTT and TUTT cell will linger for
the next day before drifting south and east and washing out by
early next week.

...ITCZ...
A fragmented ITCZ begins to the west of Kosrae near 6N160E and
extends east across the southern Marshall Islands and crossing
the Date Line near 6N180. Pockets of moderate to deep convection
are occurring along the ITCZ where it interacts with trade
troughs, to the south and west of Kosrae and especially south and
east of Majuro. The fragmented ITCZ will continue to drift west
and slowly weaken through the weekend.

$$

Slagle