Variations in the stratospheric polar vortex, so-called vortex events, can improve predictions of surface weather and climate. There are various ways to detect such events, and here we use the amount of wave energy that propagates into the stratosphere. The new definition is tested against so-called stratospheric sudden warmings (SSWs). We find that the wave definition has advantages over SSWs, for example in terms of a stronger surface response that follows the events.