Most tornado related deaths occur in the southeastern United States, not Tornado Alley. This is due, in part, to the hilly terrain that limits the use of weather radar in this region. Deaths are likely to rise since there is evidence indicating that Tornado Alley is shifting eastward. This has motivated a return to considering infrasound (sound below human hearing) from tornadoes as a potential means of improving warnings in hilly terrain. Current warnings do not make use of these sounds due to the lack of understanding of the physical mechanism responsible for its production. This paper presents recent observations of tornadoes and a funnel cloud from fixed and mobile infrasound sensors. Then a review of the potential mechanisms for the infrasound is presented and discussed in light of the observations.

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