Might want to look at page 51 and 52 of the manual. Talk about the skywarn. Below is a copy from the manual. When say pressing the key they mean the tornado key.
Skywarn Scanlist works like any other the PSR-800 Scanlist. It
can be enabled and disabled for scanning along with the 200
regular Scanlists. The Skywarn Scanlist can also be accessed
quickly by pressing the key while the PSR-800 is in Weather
Monitor mode. When activated from Weather Monitor mode, all
other Scanlists are temporarily disabled, and only objects
mapped to the Skywarn Scanlist will be monitored.