National Weather Service forecasters in Honolulu and city Ocean Safety officials are expanding the descriptions used in messages sent to alert the public about the impact of high surf on Oahu’s North Shore and how to prepare for it.

While the criteria for high surf advisories and warnings have not changed, safety messages that accompany the alerts will be more descriptive in an effort to increase awareness of the dangers associated with seasonal high surf episodes that affect all coastal areas of the state.

The goal is for visitors and residents to better understand dangerous surf conditions, which annually attract thousands of people eager to see spectacular seasonal North Shore waves.

The expanded messages can be found on the weather service website, where there is information about the impact of — and preparedness for — various danger levels that are designated. High surf alerts, which range from advisories to warnings, are based on height and effects on the ocean and coastal areas.

The information available on its website might be the only advice residents or visitors receive if they go to places that have no lifeguards, said Michael Cantin of the weather service.

To warn the public of approaching surf hazards, the weather service said in a news release that it provides daily surf forecasts for Oahu as well as high surf warnings and advisories for the entire state.

Cantin stressed that the expanded messages apply only to Oahu’s North Shore and that the criteria for surf advisories and warnings are not changing.

For people unfamiliar with the effects of waves and the quick-changing conditions of the North Shore, the information could protect them from potential injury and death, officials said.

“Messaging is just so important,” Jim Howe, operations director for Oahu Ocean Safety, said in a news release. “While our lifeguards do everything within their power to protect beachgoers, there really is no substitute for folks understanding ocean hazards before they enter the water.”

Described by safety officials as “enhanced impact and call to action messages,” each will label the overall threat: extreme, very high, high, or moderate.

Especially in winter months, wave heights can double unexpectedly in less than an hour.

The weather service said in the case of “extreme” conditions of waves with 45-foot faces or more, the waves can cross beach parks and roll onto roadways, and that coastal travel should be avoided.

Such extreme conditions could create hazardous ocean currents and close roads and prompt coastal evacuations, in addition to the potential of damaging piers, docks, ramps and boats.

“Anyone entering the water could face significant injury or death, the weather service said.

Waves with heights between 35 and 44 feet pose similar dangers but do not contain the advisory against coastal travel.

The expanded information, developed in collaboration with ocean safety officials, also incudes language about “moderate” and “generic” warnings.

Officials will begin to use the expanded explanations perhaps as early as Friday, when ocean swells are expected to again grow to advisory and warning levels.