Hilda remained a hurricane Tuesday as wind shear began weakening and slowing the storm down. 

The forecast track for Hurricane Hilda shifted slightly south and the storm is forecast to pass near or over the Big Island on Thursday as a tropical storm or tropical depression. But all islands except Kauai and Niihau remain in the so-called "cone of uncertainty" as it continues to track northwestward toward Hawaii.

The storm remained a category 1 hurricane Tuesday morning with sustained winds of 85 mph. Its strength peaked as a category 4 hurricane on Saturday with 140 mph winds.

The westerly winds are also slowing the progress of the storm, which was about 290 miles east-southeast of Hilo and 505 miles east-southeast of Honolulu at 5 a.m. Tuesday. The storm was moving northwest at just 7 mph, up from 5 mph on Monday.

As the storm weakens, trade winds from the east and northeast are steering it on a more southerly track. Hilda is expected to move toward the northwest at nearly 5 mph through Wednesday morning and turn toward the west-northwest with a slight increase in speed on Wednesday night.

The latest forecast calls for Hilda to weaken to a tropical storm Tuesday night. It will bring rough seas, high humidity and rain to the islands before the storm actually hits. 

“Although Hilda is a compact tropical cyclone, the low-level moisture field surrounding it rather broad, which means that the eastern islands could see an increase in shower activity even when Hilda is several hundred miles away,” the weather service said.

Hilda’s hurricane-force winds of 74 mph or more extend 25 miles from the center and its tropical storm-force winds of 39 mph or more extend 70 miles out. 

“There still could be a significant rain threat as it (Hilda) gets closer a few days from now,” said Derek Wroe, a meteorologist with the Central Pacific Hurricane Center in Honolulu. “People should be prepared if we do have a heavy rain situation.”

Even though the current track has the storm passing over the Big Island, Wroe said the average margin of error on a 3-day forecast is about 150 miles, which means the storm could bring heavy rain to any of the Hawaiian islands.

“Everything is pretty much open at this point,” Wroe said. 

As they did with the former Hurricane Guillermo, which had a close encounter with the islands last week, U.S. Air Force hurricane hunter airplanes are flying mission through the storm to provide additional insight into the storm. 

Forecasters are monitoring changes in Hilda’s intensity and changes in the atmosphere around Hilda.

If Hilda weakens faster than expected, it will take a more southerly path. If it maintains its strength, its track could move to the north.

“Interests in Hawaii should closely monitor the progress of Hilda,” forecasters said.

A tropical storm watch was also posted for Hawaii island Tuesday morning. A tropical storm watch is usually issued 48 hours before the possible arrival of tropical storm-force winds.

The storm is already bringing high surf to east and southeast shores. 

A high surf advisory for east-facing shores of the Hawaii island and Maui is in effect until 6 a.m. Wednesday.

Surf is expect to rise to 10 to 15 feet through Tuesday night.

The strong breaking waves, shore break and rip currents could make swimming difficult and dangerous, forecasters said.

A hurricane warning is in effect for waters southeast of the islands 40 to 240 nautical miles from the islands, including a portion of the Papahanaumokuakea Marine National Monument east of French Frigate Shoals. Seas of 12 feet or higher and winds of 40 mph or higher are expected as the hurricane continues to approach the islands.

The forecast for Hawaii Tuesday calls for partly cloudy skies with scattered windward and mauka showers and isolated leeward showers, with tradewinds blowing at 10 to 20 mph. Highs will be between 86 to 91 degrees on all islands except the Big Island, which could see 83 to 88 degree highs.

Wednesday’s forecast will depend on the progress of Hurricane Hilda.