Heavy rain and strong wind warnings have been issued for Samoa and American Samoa, which have already been lashed by two tropical depressions this week.
In American Samoa, wind speeds of up to 65 km/h, with expected gusts of up to 100 km/h, were forecast on Friday morning (Thursday, local time).
Chief meteorologist at the National Weather Service in American Samoa, Elinor Lutu McMoore, said this latest system developed quickly.
"This is the one that we were supposed to get around Thursday night into Friday (local time," she said. "But it was developing really fast into a tropical depression and it is forecast to move fast."
"These are known as midget systems and that what usually happens when they quickly intensified," said Ms McMoore.
Schools in both Samoa and American Samoa remain closed until next week.