552
AXPQ20 PGUM 300104
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1104 AM ChST Tue Dec 30 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...

SURFACE TROUGHS...
A surface trough extends E across 21N130E to end near 21N138E.
Extensive cloudiness with scattered showers are seen N of the trough
to beyond 25N. This trough is enhancing convergence to the S where
it is interacting with the W end of a shear line to produce numerous
showers and isolated thunderstorms between the shear line and the
trough from 130E to 134E. This trough will move toward the NE over
the next few days as it slowly strengthens.

A weak circulation has developed at 925mb just S of the W end of the
ITCZ, centered near 3N166E. A surface trough extends WNW from the
circulation to end SW of Kosrae near 4N162E. Scattered showers and
isolated thunderstorms are found with this system over Kosrae to 2N.
The circulation is enhancing convergence along the W end ITCZ. The
trough looks to drift WSW while the circulation dissipates, opening
into a more elongated trough. This will help strengthen the trough
as it transitions into a trade-wind trough.

TRADE-WIND TROUGHS...
A pair of trade-wind troughs are found well S of Guam. The first one
extends N from EQ143E to 3N143E. Scattered showers and isolated
thunderstorms are found W of the trough. The second trough extends
NW from near 3N147E to end near 9N143E. Scattered to numerous showers
and isolated thunderstorms are found W of the trough, over Eauripik
to just E of Ngulu, as far S as 2N. These troughs will continue to
move W over the next few days, likely merging into a single, stronger
trough as they move through S of Yap Proper and toward Palau.

A weak trade-wind trough is found between Weno, Chuuk and Pohnpei,
extending NW from 2N157E to 8N 153E. Convection is increasing to the
W of this trough, with scattered to numerous showers seen to the SSW
of Weno. This trough will slowly strengthen as it moves W over the
next couple of days.

OTHER SYSTEMS...
A cold front extends SW through 25N170E to 20N160E, then continues
WSW as a shear line to pass over the Marianas just S of Tinian near
14N145E, then turns WNW to end near 18N131E. Extensive cloudiness
with scattered showers and isolated thunderstorms extends up to 250
miles NW of the front. Patchy clouds and showers are found along the
shear line E of 134E. W of 134E, a surface trough is enhancing
convection along the shear line to generate numerous showers and
isolated thunderstorms between the shear line and the trough. The
cold front will continue to move E with no change in intensity
while the shear line drifts S as it slowly weakens.

Another shear line extends WSW across the Date Line near 14N to end
NW of Pohnpei near 8N156E. Patchy clouds and showers are found along
the shear line. This shear line will be quasi-stationary over the
next few days as it continues to weaken.

...ITCZ...
The ITCZ extends E from N of the weak circulation over Butaritari,
crossing the Date Line near 4N. Scattered to numerous showers and
isolated thunderstorms are found along the W end of the ITCZ where
it is interacting with the weak circulation mentioned above.
Otherwise, isolated showers are found along the ITCZ E of Makin and
Butaritari. The ITCZ looks to remain quasi-stationary over the next
few days with little change in intensity.

$$

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