593
AXPQ20 PGUM 170058
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1058 AM ChST Thu Jul 17 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...
The monsoon trough extends southeast from Invest 96W, crossing 130E
near 15N, to end north of Palau near 10N134E. Convergence associated
with the trough is generating scattered to numerous showers and
isolated thunderstorms along and west of the trough. The monsoon
trough looks to spread east as it drifts northeast over the coming
days, spreading increased convection across northern Yap State and
into the Marianas.

NEAR EQUATORIAL TROUGH...
A near-Equatorial Trough (NET) is no longer seen across Chuuk. It
appears that the NET has transitioned into a broad trade-wind
trough. This trough will be discussed in the trade-wind trough
section.

TRADE-WIND TROUGHS...
There are several trade-wind troughs evident across the region. The
first is seen approaching the northern CNMI, extending north-
northeast from near 12N147E to 22N151E. This trough is interacting
with the TUTT and a TUTT cell to produce scattered showers and
isolated thunderstorms along the trough to the east of the Marianas
and the northern CNMI. This trough is expected to drift west,
increasing convection across the Marianas tonight into Friday.

The next trough is seen over western Chuuk/eastern Yap State. The
NET has transitioned into this broad trade-wind trough. It is
interacting with the southern end of the TUTT to produce enhanced
convection along the trough, to the east of Yap Proper, Ulithi and
Sorol. The trough will continue to move slowly west, possibly
merging with the monsoon trough in a couple of days.

The next few troughs are found across Micronesia, interacting with a
weakening ITCZ. The first of these is found just west of Weno,
Chuuk, extending north-northwest from near 5N149E to near 11N151E.
The trough is interacting with the ITCZ to produce scattered to
numerous showers and isolated thunderstorms across western Chuuk and
eastern Yap States. The next trough in this series is found between
Pohnpei and Kosrae, extending north-northesast from near 3N159E to
end near 8N162E. Scattered to numerous showers and isolated
thunderstorms are found just south of Pohnpei. These troughs and
associated convection will continue to move west over the coming
days.

The last trough is found over the Marshall Islands, extending north-
northwest from near 5N173E to end near 11N170E. There are isolated
showers currently associated with this trough. However, this is
expected to change as the trough pushes west and begins to interact
with the weak ITCZ.

TUTT...
A weak TUTT cell is centered near 25N180, with the TUTT extending
southwest to near 20N171E, where it turns northwest to beyond 25N
near 163E. It then re-enters the area near 25N144E, extending south
through a cell centered over the northern CNMI near 20N145E to end
well south of Guam near 7N134E. Strong divergence to the east of the
TUTT and cell centered near the Date Line is generating scattered to
numerous showers and isolated thunderstorms well east of Wake
island. For the TUTT and cell over the Marianas, strong upper-level
divergence is producing scattered to numerous showers and isolated
thunderstorms near and east of the TUTT and cell. The TUTT and
associated cells looks to drift slowly west over the next few days.

OTHER SYSTEMS...
A weak high pressure ridge is found to the east of Palau and over Yap
Proper. Strong low-level convergence west of the ridge is generating
scattered to numerous showers and isolated thunderstorms over
Palau and to the south and west of Palau. The ridge looks to
continue to slowly weaken over the next few days, allowing the
monsoon trough the extend into the area.

...ITCZ...
A weakening ITCZ extends east from well south of Guam near 7N145E to
just east of Majuro near 7N170E. Mostly isolated showers are found
along the ITCZ, except where there is an interaction between the ITCZ
and trade-wind troughs east of Weno, Chuuk and between Kosrae and
Pohnpei. The ITCZ looks to remain weak over the coming days with
transiting troughs generating the the strongest convection.

$$

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