Hydrologic Outlook

Hydrologic Outlook
GUC010-220830-

Hydrologic Outlook
National Weather Service Tiyan GU
257 PM ChST Mon Jul 21 2025

...HEAVY RAINFALL EXPECTED LATE IN THE WEEK THROUGH THE WEEKEND...

This Hydrologic Outlook is for the Guam, Rota, Tinian and Saipan.

A tropical disturbance, Joint Typhoon Warning Center`s Invest 98W,
is centered southeast of Guam near 9N154E. This invest is expected
to move toward the Marianas through the week as it slowly develops.
98W is expected to bring heavy rainfall to the Marianas Thursday
evening through Sunday. Models differ on location and strength of
98W as it moves through the Marianas, however, they do agree that
heavy rainfall is likely as early as Thursday, continuing through
the weekend.

There is a potential for Guam and the CNMI to see rainfall amounts
of 5 to 10 inches by Sunday, though locally heavier amounts are
possible. This rainfall is expected to produce minor flooding across
the islands, with flash flooding possible in areas of heavier
rainfall, especially over southern Guam.

Residents on the Marianas need to closely monitor this developing
situation as watches, advisories and warnings could be issued later.

If living near streams and rivers, prepare to move items away from
stream and river banks. Make sure storm drains nearby are not
clogged, especially if living in low-lying areas.

$$

KK