064
AXPQ20 PGUM 180124
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1124 AM ChST Fri Jul 18 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 enters the area near 14N130E, extending southeast
to end northeast of Koror, Palau near 8N137E. Scattered to numerous
showers and isolated thunderstorms are found in the area of strongest
convergence. The monsoon trough looks to remain quasi-stationary over
the next couple of days with little change in intensity. Convection
may increase as upper-level divergence associated with the TUTT
approaches the southeastern end of the trough.

TRADE-WIND TROUGHS...
There are four primary trade-wind troughs seen across the region. The
first of these is found just east of Yap Proper and Ngulu, extending
north from near EQ140E to near 10N140E. Upper-level divergence
associated with the TUTT is interacting with this trough to generate
numerous to widespread showers and isolated thunderstorms between Yap
Proper and Sorol, over Ulithi and Ngulu. The trough and associated
convection will continue to move slowly west over the next couple of
days.

The next trough is found west of Weno, Chuuk, east of the Marianas.
It extends north-northeast from near 6N148E to near 15N152E.
Scattered showers and isolated thunderstorms are found with this
trough. The trough is expected to continue to move west with
increasing convection as it moves into an area of increased upper-
level divergence associated with the TUTT.

The next trough is seen between Pohnpei and Kosrae, extending
northeast from near 6N160E to 12N168E. The trough is interacting with
a fragment of the ITCZ to generate scattered showers and isolated
thunderstorms northeast of Pohnpei across the Marshall Islands north
of Kwajalein. The trough is expected to continue to move west over
the next several days, bringing increased convection into Pohnpei and
Chuuk.

The last trade-wind trough is seen east of Majuro, extending
northeast from near 4N177E across the Date Line to end near 10N179W.
This trough is interacting with another weak fragment of the ITCZ to
generate scattered showers near the Date Line. The trough will
continue west over the coming days, bringing increased convection to
the Marshall Islands, including Majuro.

TUTT...
A TUTT enters the area near 25N156E, extending east-southeast
through a cell centered near 24N166E, to end near 19N176E. Scattered
showers and isolated thunderstorms are seen north to northeast to
east of Wake Island. The TUTT and cell are expected to slowly drift
westward as it slowly weakens.

Another TUTT enters the region near 25N145E, extending southwest to a
cell centered near 19N142E. It then continues south to end near
7N140E. Divergence associated with the TUTT is generating scattered
showers and isolated thunderstorms across the northern CNMI to
southwest of Guam. The divergence to the west of the southern end of
the TUTT is interacting with a trade-wind trough to generate
numerous to widespread showers and isolated thunderstorms between
Yap Proper and Sorol, over Ulithi and Ngulu. The TUTT and cell are
expected to continue to slowly drift west over the next several days.

OTHER SYSTEMS...
A weakening ridge remains to the south of Palau. This ridge is
promoting drier conditions over Palau. The ridge will continue to
weaken and is expected to be dissipated within the next couple of
days.

...ITCZ...
The ITCZ has fragmented across eastern Micronesia. One fragment is
found northwest of Pohnpei near 9N157E to near 9N163E. Only spotty
showers are found along this fragment, except where it is
interacting with a trade-wind trough, producing scattered showers
and isolated thunderstorms north of Kosrae to northeast of Pohnpei.
The other fragment extends west from the Date Line near 6N to just
south of Majuro near 6N171E. Another trade-wind trough is
interacting with this trough to produce scattered showers over and
east of Majuro. The ITCZ is expected to strengthen over the next
couple of days, increasing convection across eastern Micronesia.

$$

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