Hurricane Watch Issued for Hawaii's Big Island as Nolo Strengthens

A hurricane watch has been issued for Hawaii's Big Island as Tropical Storm Nolo gathers strength south of the island chain, with forecasters warning it could pass close to the island early Saturday as a major hurricane.

Nolo was located about 500 miles south of Honolulu with top winds of 40 mph (64 kph), according to the US National Hurricane Center. Flood watches are also in place for the Big Island, Maui, Lanai, Molokai and Kahoolawe through Saturday.

The Hawaii Emergency Management Agency urged residents and visitors to take the threat seriously, warning that torrential rain on the Big Island and Maui could bring life-threatening flooding and landslides.

Rainfall forecasts are severe: as much as 20 inches (51 cm) may fall across the Big Island, with isolated spots receiving up to 35 inches. Maui could see up to 10 inches, with some areas getting as much as 20 inches, while the rest of the chain may receive 1 to 3 inches.

Hurricane-strength winds of at least 74 mph are possible on the Big Island from Friday, and the southern-facing coastline could experience a storm surge of up to 3 feet. While Nolo is expected to strengthen slowly over the next day, forecasters say it may rapidly intensify as it moves over very warm waters south of Hawaii. Rapid intensification — a rise in top winds of about 35 mph within 24 hours — can leave little time for preparations.

"The time to prepare for significant heavy rain and flooding impacts on the Big Island is now, as heavy rain becomes more likely by Thursday and Friday," senior hurricane specialist Eric Blake wrote in a forecast.

If Nolo veers away as predicted, it would be another near miss in an active storm season fueled by a strengthening El Nino in the equatorial Pacific and unusually warm ocean water around California and Mexico. The storm is already compounding flood damage that has accumulated since last winter, when a series of Kona Lows drenched Hawaii, forcing residents from their homes, closing roads and causing widespread power outages. Hawaii has been threatened by at least five tropical systems this season, including Hurricane Lowell, which triggered warnings on Oahu and Kauai earlier this month, and Lala, which came within miles of making landfall on the Big Island in August.

Meanwhile, powerful Hurricane Polo continues to bring heavy rain and gusty winds to Mexico's west coast. With top winds of 145 mph, Polo is a Category 4 storm on the five-step Saffir-Simpson scale. It is not expected to make landfall but will remain near the coast through Thursday before moving out to sea. Up to 6 inches of rain may fall across Guerrero, causing flooding and mudslides, with heavy rain also expected in parts of Michoacan, Colima and Jalisco.