There are tsunami warnings in effect in Hawaii, Alaska and elsewhere, and tsunami watches and advisories across the entire West Coast of the United States.
Those designations have very different meanings for people on the coasts.
Here’s a guide to what each one means:
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A tsunami warning is the most severe type of emergency alert. In Hawaii, sirens and text messages alerted residents that a tsunami could cause widespread flooding of the coast and nearby waterways. Residents were told to move inland or to higher ground as waves were expected to wrap around the islands.
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A tsunami advisory signals the potential for dangerous currents or waves, though there is less concern about widespread flooding. Southern California is under a tsunami advisory, with strong waves and currents expected around 1 a.m. local time.
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A tsunami watch indicates that there is the potential for a tsunami, but that not enough is known to warrant immediate action. Much of the rest of the West Coast is currently under a tsunami watch, and residents are being encouraged to monitor official channels for updated information as it becomes available.
Frequently, tsunami watches can be upgraded to advisories or warnings. On Tuesday evening, an area of Northern California was upgraded to a tsunami warning. The National Weather Service said that area, which includes Crescent City, Calif., could see waves nearly five feet high.
Talya Minsberg is a Times reporter covering breaking and developing news.
John Keefe leads The Times’s Weather Data team, which helps readers understand extreme weather events.
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