[EAS] Cancelling Amber alerts

[Sean Donelan]

> To the best of my knowledge WEA does not provide a mechanism for
> cancellation messages.

WEA has cancellation messages, but WEA handles signalling out of 
band.  WEA cancels the *message*, if the Amber Alert is still in the 
transmission queue.  The public never hears, sees or knows about the WEA 
cancellation message.

Depending on who you ask... EAS alerts the public that something important 
is happening, or is about to happen.  Once the public is alerted, you 
shouldn't interrupt those news and information sources again with another 
message.  Use standard public information officer to news media 
dissimenation channels for the all-clear information.  Standard news media 
can choose to repeat information during an ongoing emergency, without 
needing another EAS interruption.

If the public is interested in knowing more information, after they are 
alerted to an event, there are lots of other information channels they 
can use besides EAS to learn more.

That's the problem with NWS' Flash Flood Warning messages.