595
AXPQ20 PGUM 010037
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1037 AM ChST Tue Oct 1 2024

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 broad surface trough sits over far western Micronesia. The
trough roughly begins over eastern Yap State near 10N144E and
extends to the west-southwest, passing just south of Yap Proper
and the Republic of Palau before exiting Guam`s Area of
Responsibility (AOR) near 4N130E. Recent Himawari satellite
imagery shows numerous showers and isolated thunderstorms along
and just north of the trough`s axis, focused southwest of Yap and
building directly over Palau. Model guidance indicates a gradual
westward shift of the trough over the course of the week along
with a a slight increase in steepness, bringing south- to
southeast flow over Palau and Yap around mid- week. For the second
half of the week, the trough looks to shift northwest over the
Philippine Sea and gradually induce a light monsoon flow over far
western Micronesia. Models disagree on the strength and eastward
extent of this budding monsoon trough late in the week, but
generally place Palau and Yap within a dry ridging regime by the
weekend. In the meantime, Palau and Yap can expect on-and-off
scattered showers into at least Thursday as the surface trough
lingers nearby.

TRADE-WIND TROUGHS...
A few trade-wind troughs are seen across the AOR. The first is
located north of the Marianas, extending south from near 19N144E
to around 16N144E. Scattered showers and thunderstorms are seen
just east of the trough axis, over the far northern Marianas,
enhanced by a Tropical Upper Tropospheric Trough (TUTT) cell
located northeast of the Marianas. Further east, the second trade-
wind trough is seen south of Minamitorishima, extending southeast
from around 22N155E to 18N157E. Scattered showers and
thunderstorms are also seen just east of the trough axis, mainly
along the northern extent where there is stronger influence from
the aforementioned TUTT cell. These shallow troughs will continue
shifting westward, dissipating over the next day or so.

Further south, shallow trade-wind troughs are seen just east of
Chuuk from around 12N156E extending southwest to 8N153E, between
Pohnpei and Kosrae from around 6N160E to near 4N160E, and across
the western Marshall Islands from around 12N165E stretching
southeast to near 9N168E before curving southwest to around
4N164E. Scattered to numerous showers and isolated thunderstorms
are seen to the northeast of Chuuk and south of Pohnpei roughly
along trough axes. Scattered showers are roughly focused along the
trough axis over the Marshall Islands. The trough over the
Marshall Islands is weakening and should dissipate over the next
day or so, while the other troughs will continue to meander
westward through eastern and central Micronesia for the next few
days, increasing showers from time to time near Kosrae, Pohnpei,
and Chuuk.

TUTT...
A TUTT cell is seen northeast of the Marianas near 22N155E where it
is interacting with two weak trade-wind troughs, discussed above,
to produce scattered showers and thunderstorms over the far
northern Marianas and to the south of Minamitorishima. A TUTT
extends southwest from this cell to southeast of the Marianas
near 12N147E, and to the northeast, where it exits the AOR near
25N166E. Scattered showers and isolated thunderstorms are seen
to the south and southeast of the TUTT axis, just north of Chuuk
State and west of Wake Island. The TUTT will continue to slide
westward over the coming days, and looks to enhance shower and
thunderstorm development west of and over the Marianas for the
second half of the week before lifting northwest away from the
area this weekend.

A TUTT fragment is also present along the far eastern AOR near
16N180, extending just westward to around 16N178E. Upper-level
divergence associated with this TUTT is helping to enhance showers
well northeast of Majuro. Models show this TUTT fragment lingering
at the far edge of the AOR for the next day or so before shifting
west, moving over the northern Marshall Islands by the coming
weekend where it may contribute to wet conditions across far
eastern Micronesia.

$$

DeCou