What is the significance of an "all clear" message? When is it right to send one? And what should it say?
Academics have begun to do a fair bit of research on this topic. Real consideration of how to cancel and communicate a "false" WEA began following the 2018 message issued by Hawaii about an incoming ICBM. Following that event, a team of researchers reached out to people who had received that message and learned that they truly believed they were going to die and for 38 minutes, they lived in terror.
Shortly thereafter, USGS began to develop post-alert messages for potential false alerts that might occur with the newly launched Earthquake Early Warning system. They developed a whole logic model of the type of false alert that could occur and the messages that might be needed to explain what had happened and the strategies scientists would enact to identify the initial problem. When a false alert was issued to Ridgecrest, CA in 2020 during an EEW test event, scientists learned how effective the post-alert message was by conducting interviews and focus groups with people who received the warning and the all clear messages. Essentially, what was missing from the post-alert message was a clearly stated conclusion that they were safe.
According to those who have received alerts and post-alert messages, they key contents that messages need are clear statements that the threat is over, they are safe, and they can return to the area, conclude their specific protective action, and resume what they were doing. While additional information about what organization is doing to resolve any "falseness" about the alert is useful, it is not an initial informational need of message receivers. This is why, when the National Weather Service issued a tsunami alert to a large portion of CA and OR on December 5, we were really curious about the post-alert messaging.
[Note: there much is left to be learned about the responses to and coordination around the initial tsunami message, but that is a topic that will hopefully receive some attention from researchers is the future.]
There was ONE post-alert message issued via WEA following the tsunami warning. It was sent by Alameda County Office of Emergency Services following local messages that were issued through opt-in alert systems telling residents to evacuate low-lying areas. This WEA, however, targeted all of the wireless devices from Berkeley to Milpitas, blanketing the eastern and southern portions of the San Francisco Bay. The contents of the message were the same for both 90 and 360 character WEAs.
Viewing it, it is quite terse. It includes acronyms for the name of the Alert, the message source, and the original message sender (the National Weather Service, misnamed here as NOAA). However, based upon research about what people NEED following a high-impact, high-uncertainty event, it hits the mark. The message implies that the threat is over (CANCELED), clearly states it is safe, and instructs people to return home (if they have evacuated low-lying areas).
We do wonder if a message like this could have been issued more broadly by other alerting authorities. NWS Bay Area posted a message to their Twitter/X page, that contained a screen shot from the National Tsunami Warning Center indicating that there was no longer a threat. But as some have noticed, to see a message on X, you must be logged in to X. WEAs differ in that it requires a person to opt-out of messages in order to not receive the alert.
We can learn a lot from this event as we consider better strategies to prepare for closing the communication loop. All clear or post-alert messages can help to reduce the uncertainty that comes from messages that instruct people to leave immediately, shelter in place, or take other protective actions. Stay tuned to The Warn Room because more research in this area, and a new supplement to the Warning Lexicon, is forthcoming.
It the meantime, bookmark this page so that you can come back to it when you need to write a complete all clear message that addresses the needs of your population.
If your organization is developing alert and warning messages for ANY type of hazard or event, be sure to take a look at the resources available to help you and your organization to write effective messages in a pinch. Bookmark and download The Warning Lexicon - it's free and offers step-by-step instructions on how to write a better warning messages for 48 hazards.
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