939
AXPQ20 PGUM 140124
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1124 AM ChST Mon Jul 14 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...
Within the monsoon tail extending south-southwest into the region
near 25N142E and into the monsoon trough in western Micronesia, a
cluster of heavy showers and thunderstorms is centered near 22N137E,
near where the CIMMS a broad area of vorticity within the 850-500 mb
layer. Overnight scatterometer did not show a discernible surface
circulation and this morning scatterometer data has not reached this
area yet. Models do not support the development of a circulation in
this area but support locally heavy rain with the monsoon tail as it
slowly moves north-northwest, pulled by systems near Japan. Otherwise
scattered showers and isolated thunderstorms extend across the
monsoon tail.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The main axis of the monsoon trough enters the region near 16N130E
and extends east-southeast to 13N140E where it turns southeast
ending south of Chuuk Lagoon as it meets up with a developing near-
equatorial trough. Southwest winds, scattered showers, and isolated
thunderstorms extend across the Republic of Palau and Yap State, with
locally heavy showers seen just west of Palau. Near Chuuk State,
showers become more spotty as there is an area of divergent flow
where the monsoon trough meets up with the near-equatorial trough,
which is also creating some light and variable winds across western
Chuuk State as winds transition from southwest in Yap State to east-
northeast near Weno. The monsoon trough is expected to continue to
lift north to northwest over the next several days, keeping a wet
monsoon pattern across the Republic of Palau and most of Yap State.
Model guidance suggests a broad circulation, potentially a monsoon
or tropical disturbance, developing northwest of Palau and Yap later
in the week, which could increase winds across Palau and Yap, also
leading to higher seas and surf along west facing reefs.

NEAR EQUATORIAL TROUGH...
A near-equatorial trough (NET) extends west-northwest from near the
equator near 162E, across southern Pohnpei State, and into Chuuk
State as it meets the monsoon trough near 7N148E. The NET, along with
the ITCZ, is producing numerous to widespread showers and isolated
thunderstorms from Kapingamarangi to Pohnpei. The near-equatorial
trough will shift westward, increasing showers across Chuuk State
later this evening and into Tuesday, with some decrease in showers
across Pohnpei.

TRADE-WIND TROUGHS...
A few trade-wind troughs are evident across the region. The first is
found east of the Marianas, extending from 14N153E to 21N155E.
Scattered showers and isolated thunderstorms are developing along and
east of the trough axis. This trough is expected to move west-
northwest into the northern Mariana Islands late tonight or Tuesday.

The second trough is east of Wake Island extending from 17N169E to
22N171E, producing scattered showers and isolated thunderstorms and
is moving towards Wake Island, likely reaching the island this
evening.

The third trough is moving through the Marshall Islands near
Kwajalein, extending from 6N166E to 12N169E. Scattered showers and
isolated thunderstorms extend along the trough axis, with the
heaviest showers currently located south of Kwajalein. This trough is
expected to shift westward, passing north of Kosrae.

The final trough is east of Majuro, extending from 2N175E to 7N178E.
Similar to the other troughs, scattered showers and isolated
thunderstorms are developing along the trough axis. This trough is
drifting westward, passing near Majuro tonight or Tuesday.

TUTT...
The TUTT enters the area near 25N180, extending west-southwest into
a TUTT cell centered near 21N161E, then continues west-southwest to
end near 11N152E. Scattered showers and isolated thunderstorms are
found with the TUTT cell west-northwest of Wake Island, and these
showers and isolated thunderstorms are located between the two
trade-wind troughs. The TUTT looks to remain quasi-stationary as the
TUTT cell drifts west and towards the Marianas, likely increasing the
potential for thunderstorms across the Marianas later this week.

...ITCZ...
The ITCZ is staring to fragment but remains active across Pohnpei
State, extending eastward from 7N154E and ends near 5N166E, east of
Kosrae. The ITCZ is interacting with the NET in southern Pohnpei
State, generating widespread showers and isolated thunderstorms near
and west of Pohnpei, with showers decreasing across Kosrae State. The
ITCZ is expected to weaken around Pohnpei over the next few days as
the near-equatorial trough becomes the main feature in the area.

$$

Schank