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AXPQ20 PGUM 300202
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1202 PM ChST Wed Jul 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 CYCLONES AND MONSOON SURGE...
Tropical Storm Krosa, located north of Iwo To near 28.7N 142.8E
remains well north of Guam`s Area of Responsibility (AOR), but it has
been semi-stationary over the last day or so and its effects continue
to be felt within the region. Tropical Storm Co-may, and the monsoon
trough linking the two tropical systems, continue to shift further
north of the AOR. A band of numerous showers and scattered
thunderstorms remains northwest of the Marianas extending along 20N
within the strong monsoon flow feeding into TS Krosa. Yesterday`s
scatterometry showed a broad area of fresh to strong trade winds
within the AOR north of the CNMI, but there has been no overnight
update in scatterometry data which makes it difficult to assess the
current monsoon surge within the AOR. Latest altimetry data indicates
that elevated seas north of the CNMI have diminished well below
hazardous levels of 15 feet, with combined sea heights of 8 to 12
feet seen from 20N to 25N and 135E to 145E. TS Krosa looks to
gradually meander northwest through the end of the week with little
change in strength before shifting east across the north Pacific
through the weekend. Model guidance indicates fresh to strong
southwest monsoon winds will continue to be felt within the AOR
northwest of the CNMI through the end of the week.

For more information on TS Krosa and TS Co-may please refer to
bulletins from the Joint Typhoon Warning Center under WMO header
WTPN31 PGTW and WTPN33 PGTW, respectively.

...OTHER WEATHER SYSTEMS...

TRADE-WIND AND SURFACE TROUGHS...
There is a surface trough extending southwest from 10N149E to far
south of Yap Proper near 4N149E. Numerous showers and isolated
thunderstorms are seen along the trough across much of southern Yap
State, including over Eauripik, Ifalik, and Satawal. This broad
trough and associated convergence looks to diminish over the area as
it drifts north, increasing showers near Yap Proper and south of the
Marianas through Thursday.

Over eastern Micronesia, there is series of weak transient troughs
generating scattered showers across much of the region west of the
RMI. A more significant trade-wind trough is seen just east of
Majuro, extending south-southeast from around 13N172E to 7N174E.
Numerous showers extend along the trough axis. This trough looks to
gradually shift west along a disorganized ITCZ over the next few
days, maintaining showers over much of the northern RMI before
diminishing this weekend.

TUTT...
The TUTT extends north-northeast from 16N158E through a TUTT low
centered near Wake Island at 21N167E, continuing northeast through
25N175E. There is little interaction with features at the surface,
but scattered showers and patchy clouds are seen south of Wake along
the southern edge of the TUTT low where there is subtle surface
troughing. The TUTT will remain quasi-stationary through the week as
it extends further southwest to the north of Chuuk and Pohnpei
States.

OTHER SYSTEMS...

...ITCZ...
The ITCZ has become more fragmented over the last day, extending
west into the region near 5N180, across the southern Marshall Islands
passing near Majuro to around 5N164E. Scattered to numerous showers,
isolated thunderstorms, and extensive cloudiness are seen along and
north of the ITCZ, covering much of the eastern RMI. Convection is
mainly focused over and east of Majuro along a broad trade-wind
trough just east of the RMI. To the west, showers and cloud cover
are disorganized and patchy across much of eastern Micronesia where
the ITCZ has fragmented into a series of weak troughs. Troughs and
associated scattered to numerous showers are seen east of Chuuk
Lagoon, just east of Pohnpei, and east of Kosrae. The ITCZ looks to
remain fragmented and disorganized through the rest of the week as a
series of weak transient trade-wind troughs across eastern and
central Micronesia.

LOW-LEVEL RIDGE...
A broad low-level ridge extends southwest across the region from
25N165E, passing near the Marianas and continuing over Yap and Palau
in far western Micronesia. Within the ridge, drier conditions
prevail over and east of the Marianas, over northwest Yap State, and
the Republic of Palau. This ridging pattern looks to continue through
the rest of the week.

$$

DeCou