The Siren Board

I first thought these were 2001s but could they be Thunderbeams?
Has some good audio...apparently he was kayaking
http://www.youtube.com/watch?v=rESQm-hHkvY

Pretty scary looking at that cloud front so blue!

I'm leaning more towards a 2001. The sound is very directional and clean cut, a characteristic of 2001s.

Thunderbeams aren't all that directional. They don't direct the sound as well as a true directional siren.