Infrasonic detection and monitoring of active tornadoes

The notion that tornadoes emit an infrasonic signal that can be detected from great distances; and thus be used to aid in the detection, monitoring, and potential tracking of active tornadoes; has been discussed for decades. Much evidence has accumulated showing that tornadoes emit acoustic radiation in at least two distinct frequency bands, an infrasonic band and a low frequency audible band. It is believed that the physical mechanisms responsible for the infrasonic and audible emissions are different. We will focus here on the infrasonic emissions. Experimental evidence that tornadoes do indeed emit an infrasonic signal will be reviewed and the current status of the theoretical understanding of the radiation mechanism will be discussed. Data collected during the passage of storm fronts that did not spawn tornadoes were also analyzed to address the possibility that the observed infrasonic signals might be associated with storm fronts rather than tornadoes. Those results will be presented. Finally, our current research campaign and plans will be outlined.