Headline:
Tropical Storm Warning issued October 1 at 3:27PM ChST by NWS Tiyan GU
Event:
Tropical Storm Warning
Urgency:
Immediate
Effective:
September 30, 2026 - 10:27pm
Expires:
October 1, 2026 - 4:00am
Description:
...TROPICAL STORM CHOI-WAN MOVING WEST-NORTHWEST AND APPROACHING
ALAMAGAN FROM THE EAST-SOUTHEAST...
.NEW INFORMATION...
A Tropical Storm Warning has been issued for Agrihan in the CNMI.
A Typhoon Watch has been issued for Agrihan in the CNMI.
.AREAS AFFECTED...
This local statement provides important information and recommended
actions for people in the Northern Marianas.
.WATCHES/WARNINGS...
A Tropical Storm Warning has been issued for Agrihan in the CNMI.
A Typhoon Watch has been issued for Agrihan in the CNMI.
A Tropical Storm Warning remains in effect for Tinian, Saipan,
Alamagan and Pagan in the CNMI.
A Typhoon Watch remains in effect for Alamagan and Pagan 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 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 2 PM ChST, the center of Tropical Storm Choi-wan (26W) was located
near latitude 16.8N, longitude 147.5E. This was about 290 miles
northeast of Guam. Choi-wan is estimated to be moving west-northwest
at 18 mph, to then slow down to less than 10 mph tonight. The current
forecast speed is likely to be a result of a center position being
farther west than the prior forecast, skewing the forward speed higher
during this cycle. Storm intensity was 45 mph. Choi-wan is forecast
to intensify through tonight, possibly becoming a typhoon Friday
afternoon.
.SITUATION OVERVIEW...
Tropical Storm Choi-wan (26W) has increased in forward speed to then
once again slow down later tonight, with a slight contraction in the
tropical storm-force wind field expected to the west and southwest,
but remain well within Tinian, Saipan and their adjacent waters as
Choi-wan comes closer. As such, the Tropical Storm Watch was upgraded
to Tropical Storm Warning for Agrihan, and a new Typhoon Watch
issued as well. 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 sometime Friday
afternoon, turning sharply northward, to then move north-
northeastward late Friday night. This forecasted passage along the
axis of the Far Northern Marianas 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,
there is likelihood for typhoon-force conditions to develop
somewhere along the far Northern Marianas. As such, a Typhoon Watch
and Tropical Storm Warning remain in effect for Alamagan and Pagan.
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 continue to monitor
forecasts by the National Weather Service office in Tiyan, Guam.
Remain in sturdy shelter until the all-clear is given.
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 northeast, then
southeast and increase through Friday as Choi-wan moves into the
northern CNMI and strengthens, potentially becoming a typhoon Friday
afternoon as it approaches Agrihan from the south-southwest.
Tropical storm force winds of 39 to 50 mph may begin by Friday.
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 now look to remain just west 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 northeast, then
southeast and increase through Friday as Choi-wan moves into the
northern CNMI and strengthens, potentially becoming a typhoon Friday
afternoon as it approaches Alamagan and Pagan from the south-
southwest. Tropical storm force winds of 39 to 50 mph may begin by
Friday. 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 possible
during closest passage.
.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