059
AXPQ20 PGUM 150106
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1106 AM ChST Thu May 15 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.

NEAR EQUATORIAL TROUGH...
A Near Equatorial Trough (NET) stretches east from Mindanao, crossing
130E near 5N and turning southeastward to end in a buffer circulation
near 1N142E. Scattered showers and isolated thunderstorms are found
along and south of the NET. There are a couple of trade-wind troughs
moving along the northern edge of the NET, producing scattered
showers near 130E and east-southeast of Palau, discussed in more
detail below. Little change in intensity or location is expected with
the NET over the next couple of days, with convection varying in
coverage and intensity as other features move through and interact
with the NET.

TRADE-WIND TROUGHS...
There are several trade-wind troughs moving through the region. The
first two are traveling along the northern edge of the NET, with one
west of Palau and near 130E and the second east-southeast of Palau.
Both troughs are generating scattered showers and isolated
thunderstorms. As these troughs move westward, the first will exit
the region later today, while the second will pass near or south
Palau, which should cause scattered showers to move into Palau later
today or tonight.

The next trade-wind trough is on the edge of Yap State and Chuuk
State, extending southeast from near Pikelot and through southern
Chuuk State. Scattered showers and isolated thunderstorms extend
along the trough axis, with Chuuk Lagoon on the eastern edge of the
showers being generated by the trough and should see showers decrease
this afternoon as the trough pushes westward into Yap State.

The final trough extends northeast from near Kapingamarangi in
southern Pohnpei State and ends northwest of Kosrae. Showers are
spotty to low-end scattered around Kapingamarangi but increase in
coverage northward along the trough as it moves through Pohnpei
State, with the Global Lightning Detection (GLD) network detecting
isolated thunderstorms within the convection associated with the
trough north of 3N. Currently, Pohnpei is right on the western edge
of the convection associated with the convection associated with the
trough, while Kosrae is right on the eastern edge. As this trough
continues westward, drier weather will move into Kosrae this
afternoon, while convection will increase at Pohnpei through the
day. The trough will then shift west of Pohnpei overnight, moving
into Chuuk State.

TUTT...
An upper-level trough that has been in the region is starting to be
cut off from the mid-latitudes and has taken on characteristics more
like a TUTT. This trough enters the region near 16N180 and extends
west-southwest across the far northern Marshall Islands into a TUTT
cell centered near 14N154E. The trough then turns west-northwest and
ends in the northern Mariana Islands near Alamagan. There is very
little convection along most of the trough`s axis due to the lack of
surface features, but isolated thunderstorms are currently seen well
east of Alamagan, near 18N149E. The TUTT is expected to shift
eastward as an upper-level ridge, north of Wake Island, expands and
shifts eastward. The TUTT cell may break off from the TUTT, but
models show this cell weakening over the next couple of days, with
little change from its current position.

...ITCZ...
An ITCZ is starting to develop between 3N and 6N, along the boundary
where southeast flow near the equator meets the northeast flow,
extending from 167E and extending eastward and beyond the Date Line.
Scattered showers and isolated thunderstorms are developing along the
axis of the ITCZ, along the southern edge of the Republic of the
Marshall Islands. The ITCZ is expected to shift west-northwest over
the next couple of days increasing showers and thunderstorms across
the Marshall Islands, near Majuro, and pushing into Kosrae and up to
Pohnpei by the weekend. The northern Marshall Islands, especially
north of Majuro, are not expected to see much convection associated
with the NET, continuing drought conditions across these
islands/atolls. Late this weekend, models show the southeast flow
dipping south of the equator, which will weaken the ITCZ as it
becomes a broad area of trade-wind convergence or series of trade-
wind troughs.

$$

Schank