621
AXPQ20 PGUM 010119
TWDPQ

Tropical Weather Discussion
National Weather Service Tiyan GU
1119 AM ChST Thu Oct 1 2026

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...
Tropical Storm Choi-Wan (26W) continues to strengthen as it
approaches the CNMI. The latest satellite estimates the LLCC
(Low-Level Circulation Center) is located east-southeast of
Alamagan near 16.7N 147.9E. Movement has been to the west-
northwest at 9 mph. Both visible and infra-red satellite imagery
shows convection continues to try to wrap around the LLCC with
infra-red showing the tallest cloud tops continue to be located
across the western semi-circle of the strengthening tropical
storm. Computer model guidance continues to indicate the tropical
storm becoming a typhoon as it slows down and crosses the CNMI,
or shortly there after. Then, Choi-Wan is expected to make a turn
to the north as it continues to strengthen.

As a result, these are the current tropical-related watches,
warnings, and advisories:

Tinian and Saipan and points northward...

A Tropical Storm Warnings remain in effect for Pagan, Agrihan,
and Alamagan, which are also under a Typhoon Watch.

Additionally, Tinian and Saipan are under Tropical Storm
Warnings.

A Flash Flood Watch is also in effect from this evening through
late Sunday night for Tinian and Saipan as we expect the
developing/strengthening southwest monsoon will bring 4 to 8
inches of rainfall to these locations, with locally higher amounts
possible.

A Coastal Flood Watch is in effect through Monday evening for
Tinian and Saipan as strengthening west to southwest flow will
potentially cause inundation and erosion concerns for the western
reefs.

A High Surf Advisory is in effect from 4 Am Friday through 4 Am
Monday, as is a High Risk of Rip currents for north and west
facing reefs.

Guam and Rota...
A Small Craft Advisory is in effect from 5 PM this afternoon
through 5 AM Friday for sustained winds of 15 to 25 knots with
gusts to 35 knots and seas of 9 to 11 feet.

A Gale Watch has also been issued from late tonight through
Saturday afternoon, as southwest winds of 25 to 30 knots with
frequent gusts to 40 knots are possible, and seas could increase
into the 13 to 15 foot range.

A Wind Advisory for sustained winds of 30 to 35 mph with gusts to
45 mph is in effect from 4 AM Friday through 4 Am Sunday.

A High Surf Advisory is in effect from 4 AM Friday through 4 AM
Monday, as is a High Risk of Rip Currents for north, west, and
south facing reefs.

For more information please refer to bulletins from the Joint
Typhoon Warning Center under WMO header WTPN32 PGTW and from the
National Weather Service under WMO header WTPQ32 PGUM.

...OTHER WEATHER SYSTEMS...

MONSOON TROUGH...
Today the monsoon trough enters Guam`s AOR at 11N130E and extends
northeast to Tropical Storm Choi-Wan near the CNMI. It then dives
southeast through a col at 14N152E, passing through Bikini Atoll
to connect with a broad and weak circulation just northeast of
Majuro, before turning northeast to exit the AOR at 11N180. To the
south of this trough axis, broad west to southwest flow continues.
Additionally, a ~300 mile ribbon of scattered to locally numerous
showers, with a few thunderstorms, is found along and just south
of the monsoon trough. Here, moisture pooling has pushed PWATs
(Precipitable Water Values of 2.5 to 3.5 inches, locally higher.
This has allowed the months-long cross equatorial flow to
continue, but, surf has been low enough to preclude any coastal
erosion concerns across the FSM and RMI. As for the trough, look
for Choi-Wan to drag it north for a few days, likely setting back
south towards next weekend. A similar convective behavior is
expected to persist though as conditions remain favorable for good
surface convergence to continue along the trough.

$$

Doll