The latest five-day forecast track for Tropical Storm Ana shows the storm skirting the southern edge of the Big Island on Saturday and remaining at hurricane strength as it nears Oahu Sunday afternoon.

Late Tuesday night, Ana’s position was 710 miles east-southeast of Hilo and 920 miles east-southeast of Honolulu, with maximum sustained winds of 70 mph and higher gusts, heading west at 9 mph. Tropical storm force winds extend 60 miles from the center.

Strengthening is forecast during the next 48 hours, with Ana expected to become a hurricane on Wednesday and remain at Category 1 strength with winds of 80 to 85 mph when it reaches Hawaii.

“A gradual weakening trend is forecast Saturday and Sunday as the system encounters increasing shear, a slightly drier environment, and the low-level inflow becomes disrupted due to proximity to the Hawaiian islands,” according to the Central Pacific Hurricane Center.

Still, Ana is expected to still have hurricane-force, maximum sustained winds of 75 mph as it closes in on Oahu Sunday.

The storm is first forecast to hit Hawaii island near South Point, and could still bring heavy rain and winds to the Puna area, which has been hit hard by Tropical Storm Iselle in August.

On Oahu, city emergency management officials said while Ana’s effects on Honolulu are uncertain, it may include high surf to southeast shores, winds up to 50 mph, and rainfall of 5 to 10 inches beginning Saturday. 

“All residents should have enough disaster suplies (non-perishable food, water, flashlight, radio, spare batteries, medications, etc.) to last a minimum of five to seven days,” the mayor’s office said. City officials also encouraged residents to monitor local media and emergency management social media feeds for updated information.

Forecasters said there is a large margin of error with the forecast track so all islands need to prepare for the possibility of a direct hit.

“The track is taking it very close to the state and potentially we could see tropical storm force winds on the Big Island as early as Friday. This track could potentially affect all other islands as well,” said John Bravender, a meteorologist with the National Weather Service. “The whole Big Island and the state are well within the cone of uncertainty.”

Bravender said ocean temperatures around Hawaii are about 2 to 3 degrees warmer than usual for this time of year, which is contributing to the development of the storm.

“That warmer water will contribute engergy and help Ana maintain its strength, rather than weaken it as cold water would do,” Bravender said.

Ana in Hawaiian means to measure or evaluate, according to the Mary Pukui/Samuel Elbert Hawaiian Dictionary.

The weather service and civil defense agencies are recommending people make sure they have food, water and medicine for at least seven days in a hurricane kit.

“Keep an eye on the forecast. Stay up to date,” Bravender said.