387
AXPQ20 PGUM 200058
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1058 AM ChST Sun Apr 20 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) has lifted back into the region,
extending northwest from the equator near 139E and exiting the region
around 4N130E. The NET is interacting with a trade-wind trough just
east of Palau and south of Yap Proper, generating numerous locally
heavy showers and isolated thunderstorms between 2N and 8N from 140E
to 134E, with scattered showers then extending westward between 5N
and 8N to 130E. Models have the NET slowly shifting south-southwest
again over the next couple days, potentially shifting south of the
equator again early in the week.

TRADE-WIND TROUGHS...
There are four trade-wind troughs moving across the region,
according to satellite imagery. The first trough was discussed above
with the NET. The second trough starts in southern Pohnpei State,
near the equator and 158E, and extends northeast through Kosrae State
and ends between Kwajalein and Majuro, near 8N171E. Scattered to
numerous showers and isolated thunderstorms extend up 150 miles from
the trough axis, with additional showers near Majuro extending along
a band of trade convergence extending eastward from the trade-wind
trough. These two troughs will continue to drift westward, with the
first trough continuing to bring scattered showers and isolated
thunderstorms to Palau through Monday, while the second trough moves
further into Pohnpei State and then into Chuuk State later in the
week.

The third trough is east of the Marianas extending from 15N149E to
9N153E, with scattered showers extending along the trough axis.
These showers look to be fairly modest with cloud top temps measured
by infrared satellite, around 8C, suggesting the showers are fairly
shallow. This trough is expected to move through the Marianas later
tonight or early Monday morning, with little change in intensity. The
final trough is west of Wake Island, extending from 19N159E to
25N162E. This trough is producing scattered showers and isolated
thunderstorms and is not expected to move much over the next couple
of days as models show it slowly combining with a developing cold
front.


OTHER SYSTEMS...
A surface low looks to be developing to north of the Marianas and
north of the region, near 26N148E. From the surface low, a cold
front is developing and enters the region around 25N148E and ends in
the far northern Marianas Islands near 20N144E. This cold front is
expected to shift east as it follows the surface low, absorbing the
trade-wind trough west of Wake Island.

An upper-level trough extends into the region from the mid-
latitudes near 25N180, passing just north of Wake Island and ending
near 20N160E. This trough is providing some upper-level support to
the trade-wind trough west of Wake Island, aiding in the development
of thunderstorms within the trough. Models show this trough briefly
being cut-off from the mid-latitudes, slowly drifting southeast,
before being swept away by westerly flow the next few days.

$$

Schank