A newly formed tropical storm southeast of Hawaii is expected to strengthen into a hurricane as it heads toward Hawaii this weekend.

The center of tropical storm Ana was 925 miles east-southeast of Hilo and 1,135 miles east-southeast of Honolulu about 11 p.m. Monday. It had maximum sustained winds of 45 mph, and was moving northwest at 7 mph, according to the Central Pacific Hurricane Center. This general motion is expected to continue through Wednesday, although a slight turn to the west is forecast, according to the center.

Gradual strengthening is forecast during the next 48 hours and it is expected to be a hurricane by Thursday. Tropical storm force winds extend outward up to 25 miles from the center.

The storm’s forecast track has it nearing the Big Island by late Saturday, moving toward the hard-hit Puna area of the Big Island, which is still recovering from Tropical Storm Iselle in early August and watching a lava flow that could reach Pahoa in  two weeks.

Hurricane trackers at the Central Pacific Hurricane Center caution that a lot can happen in the next five days before the storm reaches Hawaii.

“Precaution is what we should be talking about right now, in case it does impact Hawaii,” said Tom Evans, a meteorologist with the Central Pacific Hurricane Center. “Be aware. Prepare early … Make sure you have enough water, a gallon per person and pets per day for seven days, non-perishable foods for seven days, and a can opener.”

“The conditions are conducive for development (of a hurricane), but a five-day forecast is highly uncertain, not only with track, but with intensity,” Evans said.

The ocean between Hawaii and the storm is warm enough to cause the storm to intensify. But a weather system could form between Hawaii and the storm that could cause wind shear and weaken the tropical cyclone’s development, Evans said.

The storm could also take a path north or south of the islands that would avoid a direct hit.

The storm is likely to bring surf, wind and rain to Hawaii this weekend. But its effect on Hawaii will depend on how close it gets and how strong the winds are.

“We would expect winds and rain to begin probably Friday for the Big Island and the rest of the islands afterward,” Evans said. “It’s moving in our general direction and it’s going to be strengthening over the next several days, but by the time it gets close to Hawaii there is still some high uncertainty with the track.

Surf will also depend on how strong the winds get. Hawaii could start seeing rising surf from the southeast on Thursday or Friday, Evans said.

“Stay informed,” Evans said. “The forecast will most likely change somewhat and with the uncertainty, staying informed is important.”