Comparison of infrasound emissions observed during a tornado with potential fluid mechanisms

Infrasound may be emitted by tornado-producing storms up to 2 h before tornadogenesis, and due to their low atmospheric attenuation, these low frequencies may be detected several hundreds of kilometers away. Therefore, passive infrasound monitoring shows potential for the study and prediction of tornadoes, provided received infrasound signals can be correlated with the flow-fields of tornadoes. Literature indicates that tornadoes do cause high infrasound levels between 0.5 Hz and 10 Hz, but the radially vibrating vortex mechanism commonly proposed to explain this production [Abdullah, Mon. Weather Rev. 94, 213–220] has been shown to be non-physical. Schecter [Mon. Weather Rev. 140, 2080–2089] showed these limitations and showed using numerical experiments of a tornado-like vortex produced infrasound from around the storm’s melting level. As this level contains diabatic processes involving hail, it also appears that hail production could be connected to tornado infrasound. In the current work, observations of atmospheric infrasound during a small tornado that occurred on 11 May 2017, will be evaluated in light of these previous studies.