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TWDPQ

Tropical Weather Discussion...UPDATED
National Weather Service Tiyan GU
820 PM ChST Sat Oct 4 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.

Updated for Tropical Cyclone Formation Alert on Invest 94W.

...SPECIAL FEATURES...

TROPICAL AND MONSOON DISTURBANCES...
Invest 94W is now the subject of a Tropical Cyclone Formation Alert,
meaning tropical cyclone development is likely within 24 hours. The
latest location for 94W is 23.8N and 143.3E, well north of the
Marianas and east-southeast of Iwo To. Maximum sustained winds are
23 knots and the system is moving north-northwestward at 4 kt.
Widespread showers and isolated thunderstorms are mainly found
within the eastern sector of 94W from 22N to beyond 25N between
143E and 147E. Similar conditions are seen along a band of
convergence east of the northern CNMI leading into 94W, from 17N
to 22N and between 147E and 151E. 94W is expected to move
northwest over the coming days as it gradually consolidates. For
more information on Invest 94W, see bulletins issued by JTWC under
WMO headers WTPN21 and ABPW10 PGTW.

...OTHER WEATHER SYSTEMS...

TRADE-WIND AND SURFACE TROUGHS...
A west-east oriented trough is seen moving through the Marianas. It
stretches east from near 14N140E to end near 13N149E. Convergence to
the south of this trough is generating scattered to numerous showers
and isolated thunderstorms across western Chuuk and eastern Yap
States to south of Guam. Another area of convergence north of the
trough is feeding into Invest 94W. This convergence is interacting
with the trough to produce scattered showers and isolated
thunderstorms across and east of the Marianas. This trough will
continue to move north over the next few days, pushing the
convection north of the Marianas.

An elongated trade-wind trough extends north from southwest of
Kosrae near 4N159E, across Pohnpei, to end near 13N157E. This trough
is not very active, with mostly isolated showers and thunderstorms
found north of Pohnpei. This trough will continue to move west over
the coming days as it slowly strengthens.

Another trade-wind trough is seen just east of Kwajalein, extending
northwest from near 8N170E to end near 13N167E. This trough is
interacting with the ITCZ to generate scattered to numerous showers
mostly north of Kwajalein. The trough and associated convection will
continue to move west to west-southwest over the next few days.

The last trade-wind trough is seen east of Majuro, extending north
from near 4N179E to end near 12N180. Scattered to numerous showers
and isolated thunderstorms are seen west of the trough, where it is
interacting with the ITCZ. Scattered showers and isolated
thunderstorms are seen over the northern end of the trough. The
trough and associated convection will move west, through the Marshall
Islands, over the next couple of days.

TUTT...
There two branches of the TUTT across the region. The first is seen
entering the region near 21N180, extending west to a cell centered
near 20N164E. The TUTT then turns south to end near 13N165E.
Divergence associated with the TUTT and TUTT cell is generating
scattered to numerous showers and isolated thunderstorms south and
west of Wake Island between 14N and 22N from 159E to 166E. Similar
conditions are seen well southeast of Wake Island between 14N and
18N from 166E to 164E. The TUTT and TUTT cell will continue to slowly
drift west with little change in intensity.

The second branch of the TUTT is found along the eastern edge of the
AOR, entering the region near 25N137E, extending south-southwest
through a cell centered near 19N135E, then turns south near 14N130E,
riding along 130E to end near the equator. Scattered showers and
thunderstorms are found with the TUTT cell, while only spotty showers
and thunderstorms are found with the TUTT, south of the cell. The
TUTT and cell will continue to drift west over the next few days with
little change in intensity.

...ITCZ...
A very weak ITCZ is found from north of Kosrae near 7N164E to 11N169E
to beyond the Date Line near 5N. Scattered to numerous showers and
isolated thunderstorms are found slightly north of the ITCZ where a
couple of weak trade-wind troughs are interacting with it. The ITCZ
looks to meander north and south over the next few days with little
change in intensity.


$$

Kleeschulte/IC