161
AXPQ20 PGUM 040038
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1038 AM ChST Wed Jun 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...

NEAR EQUATORIAL TROUGH...
The Near-Equatorial Trough (NET) enters the Area of
Responsibility (AOR) near 12N130E, extending southeast through an
embedded circulation southeast of Yap Proper near 7N141E and
ending southwest of Chuuk Lagoon near 5N150E, where it is cut off
by a southward extension of a subtropical ridge. Moderate to deep
convection is occurring along an south of the NET, from southeast
of Yap Proper and the main islands of Palau, across northern Yap
state and northern Chuuk state. The NET looks to transition into a
monsoon trough within the next 12-24 hours as the west to
southwest flow south of the NET increases across the Republic of
Palau and western Yap state. In addition, the embedded circulation
will drift northwest along the developing monsoon trough across
Yap proper and possibly developing into a tropical cyclone
northwest of Yap and Palau. This will lead to west to southwest
flow over Palau and Yap during the latter half of the week into
the weekend, bringing a prolonged period of unsettled weather with
associated heavy showers and strong gusts.

TRADE-WIND TROUGHS...
Several trade-wind troughs are passing through the AOR. A trough
of note is working west of the Marianas. This trough is
interacting with the TUTT, with moderate to deep convection west
of the Marianas and north of Yap state. This trough will continue
to drift west and merge with the developing monsoon trough.
Another trough of note is pushing across Chuuk Lagoon,
interacting with the ITCZ fragment and developing monsoon trough,
bringing moderate to deep convection across northern and western
Chuuk state. This trough will also merge with the developing
monsoon trough as it passes into Yap state, with a circulation
possibly developing northwest of Yap and Palau.

Another trade trough and surge in trade winds is situated well
east of the Marianas, beginning near 16N153E and extending
southeast and ending in the northern Marshall Islands near 9N163E.
Pockets of showers are occurring along and north of the trough,
mainly over the open ocean. This disturbance will continue to
drift south and west and dissipate over the next couple of days.

Another trough east of Wake Island extends south from a weak
circulation centered 25N167E, ending near 19N175E. Pockets of
showers are occurring within the trough as it works west towards
Wake Island.

TUTT...
The Tropical Upper-Tropospheric Trough extends from an upper-low
east of the Date Line, entering the AOR near 15N and meandering
west across Wake Island through a TUTT low near 18N160E, then
extending southwest through another TUTT low east of the Marianas
near 15N150E and ending near 16N143E west of the Marianas. The
TUTT is interacting with several surface troughs and helping bring
moderate to deep convection, directly west of and over the
Marianas, as well as over and north of Chuuk Lagoon. Spotty
showers and thunderstorms are occurring elsewhere within the
TUTT, with a pocket of convection west of Wake Island. The two
TUTT lows look to gradually merge and shift westward over the
course of the week, lifting north-northwest of the Marianas this
coming weekend, helping enhance showers and thunderstorms.

...ITCZ...
The Inter-Tropical Convergence Zone (ITCZ) east of the Date Line
enters the AOR near 7N, extending west-southwest, passing south of
Majuro and ending south of Kosrae near 2N163E. Pockets of moderate
convection are occurring along the ITCZ, generally south of 5N.
The ITCZ is expected to build north and west through the end of
the week, with showers and thunderstorms moving into the southern
Marshall Islands and into Kosrae and Pohnpei states. The ITCZ is
expected to become poorly-defined by the weekend. An ITCZ fragment
southwest of Chuuk is merging with a trade trough and developing
monsoon trough, brining moderate to deep convection across western
Chuuk state. This fragment will dissipate as the trade trough
pushes west and the monsoon trough develops further.

$$

Slagle