365
AXPQ20 PGUM 300058
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1058 AM ChST Mon Jun 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...

TROPICAL AND MONSOON DISTURBANCES...
Two tropical disturbances remain across the region this morning.
Invest 98W is seen well west of the Marianas, centered near 15.2N
134.1E, drifting west over the last 24 hours. Little convection is
seen with 98W, with patchy clouds, isolated showers and only a couple
of lightning strikes evident. 98W is expected to continue to move
west with little development over the next day or so.

Invest 99W is located over the far northern CNMI, with no clear
circulation center evident on satellite. 99W continues to move
toward the north-northwest. A pronounced TUTT cell is seen farther
north, with the TUTT extending south then west. There is a large
area of divergence evident south of the TUTT and TUTT cell, enhancing
convection with 99W to produce numerous to widespread showers and
scattered thunderstorms near and east of 99W.

The two disturbances are connected by the monsoon trough with the
main influence of these Invests being to enhance the monsoon flow
across Palau, Yap and the Marianas over the next couple of days.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
The monsoon trough extends east from the Philippines into Invest
98W, then continues northeast through Invest 99W to end near
21N147E. The trough is interacting with upper-level divergence from
the TUTT and TUTT cell, discussed below, along with a weak monsoon
surge to generate a large area of numerous showers and isolated
thunderstorms across Palau and northwestern Yap State to southeast
of Guam. Another area of deep convection is seen to the east of the
Marianas and the northern CNMI. As Invest 99W continues to move
north, the monsoon flow is expected to be enhanced across the
Marianas, while the western end of the trough remains quasi-
stationary.

TRADE-WIND TROUGHS...
There are four trade-wind troughs evident across the region. The
first is found well south of Guam, southeast of Weno, Chuuk,
extending north from near EQ144E to near 5N145E. Scattered showers
and isolated thunderstorms are seen along the trough. This trough
looks to continue to move west over the coming days, hugging the
Equator until the monsoon flow pushes it toward the north.

The next two troughs are found very close to each other, the first
is seen to the east of Weno, extending north from near 5N155E to
near 10N155E. The next one is found a little east of Pohnpei,
extending north from near 5N151E to 9N151E. Only patchy showers are
found with both of these troughs. They are expected to continue to
move west with increasing convection over the next day or so.

The last trade-wind trough is found west of Butaritari and Tarawa to
east of Majuro, extending northeast from near 1N170E to 8N175E. This
trough is interacting with a developing ITCZ to generating numerous
showers to the east of Majuro to west of Butaritari. This trough will
continue to progress west, pushing the ITCZ with it, spreading
increased convection across Majuro, Kosrae and Pohnpei over the next
few days.

TUTT...
The TUTT has become fragmented over the region. One segment of the
TUTT enters the area near 22N180, extending southwest into a weak
cell centered east of Wake Island near 19N172E. The TUTT then
continues south to end near Majuro. Divergence of the cell is
generating a band of numerous showers and scattered thunderstorms
southeast to east to north-northeast of Wake Island. The TUTT and
TUTT cell will remain quasi-stationary over the next couple of days
with a slight increase in intensity.

Another branch of the TUTT enters the area near 25N149E, extending
south to a robust TUTT cell centered just east of the far northern
CNMI near 21N148E. The TUTT then continues south to just north of
Saipan where it turns west to end near 15N135E. Divergence associated
with the TUTT and TUTT cell is interacting with Invest 99W and the
monsoon trough to generate numerous showers and isolated
thunderstorms east of the northern CNMI and over northwestern Yap
State and Palau, with increasing convection evident over the
Marianas. This portion of the TUTT and TUTT cell will remain quasi-
stationary over the next few days, enhancing convection associated
with the monsoon trough.

OTHER SYSTEMS...
A band of convergence remains over the area east of the Marianas,
extending south from near 17N150E to near 12N150E. Scattered to
numerous showers and isolated thunderstorms are found south of Invest
99W along and east of the convergence between 149E and 154E. The band
is expected to drift north as the monsoon trough and Invest 99W drift
north.

...ITCZ...
A developing ITCZ is seen over the southern Marshall Islands,
extending west-northwest across the Date Line near 4N to near
6N174E, then turns southwest to end near 3N168E. A trade-wind trough
seen east of Majuro is interacting with the ITCZ to produce
widespread showers and isolated thunderstorms within 150 miles of the
ITCZ. Shower coverage decreases farther west, west of 170E. The ITCZ
looks to drift west over the coming days, spreading convection into
Majuro, Kosrae and Pohnpei over the next few days.

$$

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