Headline:
Tropical Storm Warning issued October 1 at 9:10AM ChST by NWS Tiyan GU
Event:
Tropical Storm Warning
Urgency:
Immediate
Effective:
September 30, 2026 - 4:10pm
Expires:
September 30, 2026 - 10:00pm
Description:
...NEWLY NAMED TROPICAL STORM CHOI-WAN CONTINUES MOVING WEST-
NORTHWEST TOWARDS THE FAR NORTHERN MARIANAS...
.NEW INFORMATION...
Tropical Storm 26W is now named Choi-wan.
A Tropical Storm Warning is now in effect for Tinian and Saipan and
their adjacent waters in the CNMI.
.AREAS AFFECTED...
This local statement provides important information and recommended
actions for people in Guam and the Northern Marianas.
.WATCHES/WARNINGS...
A Tropical Storm Warning is now in effect for Tinian and Saipan in
the CNMI.
A Tropical Storm Warning remains in effect for Alamagan and Pagan in
the CNMI.
A Typhoon Watch remains in effect for Alamagan and Pagan in the CNMI.
A Tropical Storm Watch remains in effect for Agrihan in the CNMI.
A Tropical Storm Watch means that tropical storm conditions, including
winds of 39 to 73 mph, are possible within 48 hours.
A Typhoon Watch means that typhoon conditions, including winds of 74
mph or more, are possible within 48 hours.
A Tropical Storm Warning means that tropical storm conditions are
expected within 24 hours.
A Flash Flood Watch remains in effect for Tinian and Saipan. Please
listen closely for any Flash Flood Warnings that might be in effect
for your area.
All persons in the Watch areas should review their preparedness plan
and begin to take actions to prepare for conditions as indicated by
your local forecast and additional details, below, for your island.
.STORM INFORMATION...
At 7 AM ChST, the center of Tropical Storm Choi-wan (26W) was located
near latitude 16.3N, longitude 149.5E. This was about 370 miles
east-northeast of Guam. Storm motion was west-northwest, 285 degrees,
at 9 mph. Storm intensity was 40 mph.
.SITUATION OVERVIEW...
Tropical Storm Choi-wan (26W) has increased in forward speed once
again, with a slight expansion in the tropical storm-force wind field
expected to the west and southwest, keeping Tinian and Saipan well
within said wind field. As such, the Tropical Storm Watch was
upgraded to Tropical Storm Warning for Tinian, Saipan and their
adjacent waters. Timing of further intensification and storm trek
remains largely unchanged. Choi-wan will continue west through
tonight, making a turn to the northwest Friday morning as it begins
to approach Alamagan from the south and intensify into a typhoon,
turning sharply northward, to then move north-northeastward late
Friday night. This forecasted passage over Alamagan and Pagan is
still expected to prolong the duration of damaging winds across the
northern islands, likely leading to a lengthy period of time of
damaging to destructive tropical storm conditions beginning this
evening and continuing into Sunday afternoon. As Choi-wan is forecast
to strengthen to a typhoon Friday morning as it approaches Alamagan,
this would bring Alamagan and later Pagan, directly within the
typhoon force winds Friday night through early Saturday morning. So,
a Typhoon Watch and Tropical Storm Warning remain in effect for
Alamagan and Pagan.
It is too early to provide exact wind and surge forecast values for
specific locations. A general concern should be for the possibility
of at least damaging winds likely somewhere within the Northern
Marianas.
Instruction:
Stay indoors during heavy rain and tropical storm-force wind conditions
associated with Tropical Storm Choi-wan (26W). Heed the advice of
your local emergency managers and officials, and continues to monitor
forecasts by the National Weather Service office in Tiyan, Guam.
Remain in sturdy shelter until the all-clear is given.
...WIND INFORMATION...
Breezy northwesterlies today will quickly increase toward the late
afternoon, with tropical storm force winds of 35 to 45 mph with gusts
to 60 mph expected beginning tonight, lasting through at least
Saturday as Tropical Storm Choi-Wan (26W) stalls slightly on approach
to the Far Northern Marianas. This is expected to expose Tinian and
Saipan to a longer period of potentially TS conditions. At this time,
strong tropical storm-force winds look to remain north of Saipan and
Tinian as said winds are expected to remain closely packed near the
center of the system.
...COASTAL INUNDATION AND SURF INFORMATION...
Surf will initially build to 8 to 11 feet along north-facing reefs
by tonight, then quickly spread to west-facing reefs as the center of
Choi-wan crosses the far northern CNMI and exposes a western fetch by
early Friday morning. Surf will continue to increase along all reefs
as Choi-wan continues to strengthen. Coastal inundation of 1 to 2
feet, as well as significant coastal erosion, will be possible along
all reefs.
...OTHER STORM EFFECTS...
Periods of rain, widespread heavy showers and scattered thunderstorms
could produce rainfall totals of 5 to 8 inches by early Monday
morning, with locally heavier amounts possible. So, a Flash Flood
Watch is still expected to be in effect beginning late this evening,
lasting through at least Sunday night. Additionally, a monsoon surge
south of TS Choi-wan will maintain wet conditions across Saipan and
Tinian into next week.
Take small loose object indoors. Identify suitable shelter. Stock up
a few days worth of food and water. If no concrete shelter is
available, look for a cave or something similar. Take action to
protect food crops or other possessions as appropriate.
.WIND INFORMATION...
Northerly winds of 10 to 15 mph will turn toward the northwest,
then southwest and increase through Friday as 26W moves into the
northern CNMI and strengthens, potentially becoming a typhoon
Friday morning as it approaches Alamagan from the south. Tropical
storm force winds of 39 to 50 mph may begin by Friday morning.
Depending on the track and intensity, winds may increase to strong
tropical storm-force of 58 to 65 mph early Saturday morning.
Typhoon force winds greater than 74 mph look to remain just east
of Agrihan at this time.
.COASTAL INUNDATION AND SURF INFORMATION...
Surf will initially build to 8 to 11 feet along east-facing reefs
through Friday morning, then spread along north and west-facing
reefs as the center moves north-northeast through the northern
CNMI Friday night through Saturday night, increasing by several feet
during this time. As Choi-wan continues to strengthen, surf will
continue to increase, likely becoming hazardous during the weekend and
then dangerous by early next week. Significant coastal erosion and
some coastal inundation is expected during Choi-wan's passage.
.OTHER STORM EFFECTS...
Periods of rain, widespread heavy showers and scattered thunderstorms
could produce rainfall totals of 8 to 14 inches by early Monday
morning, with up to 20 inches of rainfall possible near the center of
the system.
Take small loose object indoors. Identify suitable shelter. Stock up
a few days worth of food and water. If no concrete shelter is
available, look for a cave or something similar. Take action to
protect food crops or other possessions as appropriate.
.WIND INFORMATION...
Northerly winds of 10 to 15 mph will turn toward the northwest,
then southwest and increase through Friday as 26W moves into the
northern CNMI and strengthens, potentially becoming a typhoon
Friday morning as it approaches Alamagan from the south. Tropical
storm force winds of 39 to 50 mph are expected to begin by early Friday
morning. Depending on the track and intensity, winds may increase
to strong tropical storm-force of 58 to 65 mph early Saturday morning.
Typhoon force winds greater than 74 mph may begin Friday evening as
Choi-wan nears Alamagan.
.COASTAL INUNDATION AND SURF INFORMATION...
Surf will initially build to 8 to 11 feet along east-facing reefs
through Friday morning, then spread along north and west-facing
reefs as the center moves north-northeast through the northern
CNMI Friday night through Saturday night, increasing by several feet
during this time. As Choi-wan continues to strengthen, surf will
continue to increase, likely becoming hazardous during the weekend and
then dangerous by early next week. SIgnificant coastal erosion and
some coastal inundation is expected during Choi-wan's passage.
.OTHER STORM EFFECTS...
Periods of rain, widespread heavy showers and scattered thunderstorms
could produce rainfall totals of 10 to 16 inches by early Monday
morning, with up to 20 inches of rainfall possible near the center of
the system.
Area Description:
Tinian; Saipan
Forcast Office:
NWS Tiyan GU
Sender:
w-nws.webmaster@noaa.gov