Actually the current best predictor of tornadoes is insects. They fly high or low depending on winds and radar will pick-up the bulk of insect swarms (radar watchers call them angels or somesuch). There was a programme on BBC4 recently about winds and a UK university has developed software to track the insects and extract meaning from sudden changes (ie impending tornadoes). The way they were talking it is free info on the back of an existing wind radar set-up and is ready to go live.