Many transmission line and tower failures worldwide are attributed to high intensity winds (HIW) associated with tornadoes and microbursts. This paper describes models for the wind velocity time-histories of transient tornado and microburst events and the resulting loading on a lattice tower. A dynamic structural analysis has been undertaken for two HIW events, predicting a tornado- induced shear failure, as observed in the field. However, the microburst does not produce failure, due to its lower intensity and longer duration. Indeed, such failures, if they occur in practice, are likely to be associated with a more broad--fronted microburst loading in which conductor loads contribute.
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