Tropical Storm Nolo has formed in the Pacific Ocean, triggering a hurricane watch for Hawaii’s Big Island, the National Hurricane Center said Wednesday.

Nolo is expected to become a hurricane sometime Thursday and could become a major hurricane by the weekend, the center said. A storm is considered a major hurricane when it reaches Category 3 or higher, meaning it has maximum sustained winds of at least 111 mph. 

Maps show Tropical Storm Nolo’s path

Storm Nolo had maximum sustained winds of 45 mph as of Wednesday afternoon local time. It was moving west-northwest, but a “sharp turn to the north and north-northeast” was expected on Thursday, the hurricane center said. 

Nolo is expected to approach the Big Island either Friday or Saturday.

The storm is expected to bring around 15 to 20 inches of rain to the Big Island, with up to 35 inches possible in some areas. The heavy rain could trigger “catastrophic life-threatening flooding and mudslides, especially in areas of steep terrain,” the hurricane center warned.

Maui could see 5 to 10 inches of rain, with totals of up to 20 inches in some areas. Maui could also see life-threatening flooding and mudslides. The rest of the islands were forecast to get about 1 to 3 inches of rain and could see isolated flooding.

Nolo formed as another storm, Hurricane Polo, continued to swirl farther east in the Pacific, off Mexico’s southwestern coast. 

The latest storms add to an unsually active season in the Pacific. Earlier this month, Hurricane Lowell brought damaging winds and heavy rain to the western Hawaiian islands of Kauai and Niihau, bringing down trees, damaging roads and knocking out power for thousands.

Last month, Hurricane Lala washed away about 100 homes, triggered landslides and caused widespread power outages as it brushed past Hawaii.