The National Weather Service issued a high-surf advisory yesterday for most of the Islands, but the waves are expected to rise rapidly tonight and reach warning levels of 30 to 40 feet.

The high-surf warning is expected to be in effect at 6 a.m. today for north- and west-facing shores of Ni'ihau and Kaua'i, and for north-facing shores of O'ahu, Moloka'i and Maui. The surf is forecast to be in the 12- to 16-foot range early today and rise from west to east throughout the day to about 22 to 28 feet tonight, the NWS said.

By late tonight and Christmas morning, surf heights of 30 to 40 feet with locally higher sets are expected.

On west-facing shores of O'ahu and Moloka'i, the surf is forecast in the 10- to 15-foot range this morning and rise to 15 to 20 feet by this evening. Surf heights could reach 20 to 30 feet late tonight and tomorrow, the NWS said.

The weather service said large surf earlier this month caused significant beach erosion along north and west shores and the new swell could cause additional erosion along exposed shores.

Meanwhile, city lifeguards on the North Shore were involved in at least three ocean rescues, two assists and 400 preventative actions yesterday.

"Although this first swell is subsiding we are anticipating an even larger and potentially dangerous swell to begin arriving late Thursday," said Bryan Cheplic, Emergency Services Department public information officer.