Hurricane Nolo continues to move west as it lashes the Big Island of Hawaii with torrential rain, gusty winds and dangerous surf.

Nolo is expected to strengthen to a major hurricane by Sunday as it moves south of the island chain.

Happening now

The storm has begun to move westward away from the Big Island at about 5 mph, but tropical storm conditions are expected to continue throughout the night. Nolo is the closest a storm this powerful has passed to the Big Island since the 1950s.

Pockets of heavy rain are expected to expand across the rest of the Big Island and Maui. Strong winds are gusting across the Big Island and also in some wind-prone areas of Maui County, Oahu and Kauai.

Rainfall totals over 7 inches have been reported on the Big Island.

These are the current watches and warnings in effect, as seen on the map below:

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• Big Island: Tropical storm warning
• Maui: Tropical storm watch

What is the forecast?

Nolo continues to crawl west after being stationary for hours earlier today, and it is finally picking up some forward speed. The storm should move into warmer water during the next 24 hours, which will help it intensify into a major hurricane on Sunday or Monday.

The current forecast cone from the National Hurricane Center is shown below.

(MORE: What a forecast cone really means)

For now, the forecast keeps the core of Nolo — and thus the worst of its wind impacts — south of the islands.

But storms tend to wobble near land, especially when they are barely moving. Should the storm wobble to the north, there could be a ramp-up of winds.

Parts of the islands will continue to see the triple threat of rain, winds and waves, regardless of how close Nolo's center tracks to the Big Island.

Impacts

Flooding rainfall

As the storm passes south of the islands, heavy rain will continue to impact parts of the Big Island, Maui, Lanai, Molokai and Kahoolawe. Flood watches remain in effect for those areas.

Here are the peak rainfall forecasts from NOAA's Weather Prediction Center. These peak totals are most possible over mountain slopes:

• Parts of the Big Island: Additional 3 to 6 inches is possible, bringing storm totals to as much as 25 inches
• Parts of Maui: Additional 2 inches is possible, bringing storm totals to as much as 8 inches
• Rest of islands: Up to 3 inches possible for the entire duration of the storm

This could lead to life-threatening, potentially catastrophic flash flooding and mudslides on the Big Island and life-threatening flooding and mudslides on Maui, according to the National Hurricane Center.

The Big Island and parts of Maui County were hit hard by flooding, mudslides and strong winds from Hurricane Lala in mid-August, and some places just recently got power restored.

Winds

The best chance of winds capable of at least some tree damage and power outages is expected across parts of the Big Island.

In addition, wind gusts will likely be stronger both at the tops of and downwind of mountain slopes in the entire island chain.

Coastal flooding, high surf

Larger swells are producing dangerous surf and rip currents.

Nolo will continue to bring a threat of coastal flooding to parts of the Big Island through the weekend.

Big Island's strongest hurricane in decades?

Only one other major (Category 3 or stronger) hurricane has tracked within 150 miles of the Big Island, according to NOAA's hurricane database.

That was August 1959's Hurricane Dot, which went on to slam into Kauai after brushing south of the Big Island.

So Nolo is the strongest Big Island impact from a hurricane in 67 years.

Fourth potential flood event

This system will become the fourth to at least graze Hawaii, bringing flooding and winds to most of the state.

We first had Hurricane Lala in mid-August, whose eyewall grazed the southern end of the Big Island. Torrential rain hit, and gusty winds caused power outages to skyrocket. 

(MORE: Lala Recap)

Next up was Tropical Storm Moke, which tracked farther south than Lala but still hit parts of the Big Island with rain and winds from its outer bands. Moke’s impacts were less significant, but flooding still occurred because the ground was still saturated from Lala.

Then there was Hurricane Lowell, a powerful hurricane that reached Category 5 strength at its peak. The storm weakened before making its closest pass, but it slammed the western islands with wind, rain and waves.  

(MORE: Lowell Recap)