154
AXPQ20 PGUM 150113
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1113 AM ChST Tue Jul 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.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
monsoon trough is embedded within the larger area of westerly flow
that is also being supported by tropical systems north of 25N. The
main axis of the trough enters the region near 16N130E
and extends southeast to 8N142E where it meets up with the near-
equatorial trough that is extending through southern Chuuk State.
Southwest winds, scattered showers, and isolated thunderstorms extend
across the Republic of Palau and Yap State, with numerous to
widespread, locally heavy showers seen west to northwest of Palau,
extending to north of Yap Proper and then west of the Marianas,
between 137E to 143E, where convergent southwest flow meets the east
to southeast flow extending across the region east of 144E. The
monsoon trough is expected to continue to lift northwest over the
next several days as models shows broad circulation, potentially a
monsoon or tropical disturbance, develops north of Palau and
northwest of Yap, keeping a wet monsoon pattern across the Republic
of Palau and most of Yap State through the rest of the week. The
development of the circulation could increase winds across Palau and
Yap, also leading to higher seas and surf along west facing reefs.

NEAR EQUATORIAL TROUGH...
A near-equatorial trough (NET) extends west-northwest from near the
equator near 163E, across southern Pohnpei State, through Chuuk
State as it passes through and buffer circulation near 1N149E,
ending 8N142E as it meets the monsoon trough. Scattered showers and
isolated thunderstorms are developing across most of Kosrae,
Pohnpei, and Chuuk State. The near-equatorial trough will shift
westward, continuing to promote shower and thunderstorm development
across Pohnpei and Chuuk, and into eastern Yap State.

TRADE-WIND TROUGHS...
A few trade-wind troughs are evident across the region. The first is
a subtle trough found well east of the Marianas, extending from
14N155. Spotty showers and isolated thunderstorms are developing with
this trough as it is currently under the upper-level trough
extending southwest from from the TUTT cell west of Wake Island. This
trough is expected to move west-northwest, ahead of the TUTT cell,
potentially causing some spotty to scattered showers across Guam and
the CNMI tonight.

There are a couple of trade-wind troughs riding along the northern
edge of the NET, north of Pohnpei and Kosrae between 8N and 13N from
157E to 166E. These troughs generating scattered showers and isolated
thunderstorm north of Pohnpei and extending in the northern Marshall
Islands up to Enewetak and Bikini Atolls,

The final trough is east of Majuro, extending from 2N176E to 9N179E.
Similar to the other troughs, scattered showers and isolated
thunderstorms are developing along the trough axis. This trough is
drifting westward, expected to pass near Majuro tonight or Wednesday.

TUTT...
The TUTT enters the region from a TUTT cell centered near 25N180,
extending west-southwest into another TUTT cell centered near
20N158E, then continues west-southwest to end near 11N148E, east of
the Marianas. Currently scattered showers and isolated thunderstorms
are found only with the TUTT cell west of Wake Island. The TUTT looks
to remain quasi-stationary as the TUTT cells drift westward, with
the TUTT cell west of Wake Island expected to reach the Marianas over
the next few days likely increasing the potential for thunderstorms
across the Marianas.

..ITCZ...
The ITCZ has redeveloped across the southern Marshall Islands,
extending westward from 6N178E and ends near 5N163E where it meets
the NET. The ITCZ generating scattered to numerous showers and
isolated thunderstorms across the Marshall Islands, mainly near and
south of Majuro, with scattered showers extending across Kosrae. The
ITCZ is expected shift slightly west as the NET also moves westward,
continuing the wet pattern across the Marshall Islands, Kosrae, and
Pohnpei, mainly south of 10N.

$$

Schank