235
AXPQ20 PGUM 300131
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1131 AM ChST Wed Oct 30 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...

TROPICAL AND MONSOON DISTURBANCES...
A weak circulation located just south-southeast of Pohnpei near
6N159E and is being monitored by JTWC as Invest 90W, and is currently
embedded in a trough that extends northward from EQ161E to about
14N160E. Scatterometer does not currently show strong winds
associated with this circulation, just winds around 17 mph (15 kt),
but the numerous showers and isolated thunderstorms developing mainly
around this circulation, and affecting Pohnpei and nearby outer-
islands, could produce strong gusts. This may make local sea
conditions choppy and affect inter-island travel. The potential for
90W to develop into a tropical cyclone (tropical depression) is
currently low, meaning development is unlikely within 24 hours. 90W
is expected to slowly drift westward, generating heavy showers within
Pohnpei State and then potentially bringing heavy showers and gusty
winds to Chuuk Lagoon and nearby islands around Friday.

For more information on Invest 90W, see the bulletin issued by JTWC
under WMO header ABPW10 PGTW.

...OTHER WEATHER SYSTEMS...

TRADE-WIND TROUGHS...
A couple of trade-wind troughs are east of Invest 90W. One extends
from south of Kosrae to about Jaluit atoll and scattered showers
and isolated thunderstorms are developing along the trough and
convergent flow east of 90W, which helps to extend this convection
all the way up to 10N, bringing showers to some of the atolls of the
Marshall Islands such as Kwajalein, Ujae, Ebadon, and nearby
islands. A third trough is currently passing near Majuro and is also
developing scattered showers. These troughs will continue to drift
westward, keeping an overall wet pattern across the region south of
10N, though some drier weather is expected to move into Majuro within
the next couple of days as these troughs move away.

To the west of 90W, a trough extends northwest from 6N155E, passing
through Chuuk Lagoon and ending just southeast of Guam near 12N145E.
A broken line of showers and isolated thunderstorms is developing
along the axis of this trough. This trough will rather be absorbed
into the area of disturbed weather associated with 90W, or swing
southwest and move into Yap and Palau and the ridge shifts
northwest later this week.

UPPER-LEVEL TROUGHS...
Water vapor satellite imagery shows a short-wave trough in the mid-
to upper-levels, near Palau, and Yap from about 2N140E to 15N138E.
This is interacting with convergent south to southeast flow along
the west-southwest edge of the ridge of high pressure near Yap. This
is generating a SSE-NNW line of showers and isolated to scattered
thunderstorms from about 2N139E, extending over Palau and ending
around 18N133E. The short-wave trough and convergent flow is expected
to shift westward, pulling some of the showers and thunderstorms
away from Palau though this may be a slow shift, so there is the
potential for heavy rain over Palau through the day.

A long-wave trough extends southwest and enters the region near
25N176E, passing through a developing upper-level low 22N173E, and
passing south of Wake Island, ending near 14N161E. There not much
shower or thunderstorm along near the trough besides for around
16N176E to 21N174E, well east of Wake Island, where scattered showers
and isolated thunderstorms are developing.

OTHER SYSTEMS...
A ridge of high pressure is over most of Yap State, and this is
keeping showers very spotty. On the western edge of the ridge,
convergent south to southeast flow is producing showers and isolated
to scattered thunderstorms around Palau, and this is being supported
by a upper-level short wave trough discussed above. The ridge is
expected to lift northwest over the next few days, this will allow
weak troughs to move into Yap State and near Palau, potentially
bringing periods of scattered showers to the area.

Near 24N175E, well northeast of Wake Island, there is a clearly
visible exposed low-level circulation on satellite imagery, moving
east to west within the trade-wind flow. Looking at satellite over
the pass 24 hours, it looks like it is from a sharp trough that
passed across the Date Line, but there been very little shower or
thunderstorm activity associated with the trough or circulation. This
circulation is expected to slowly dissipate over the next couple of
days as it remains along the northern edge of the region.

$$

Schank