This paper presents formulae tables, and figures that can be used to estimate the ratio of mean windspeed acting on the flame from a spreading wildland fire to the mean windspeed 20 ft (6 m) above the vegetation cover. The formulae are based upon the logarithinic windspeed variation law characteristic of constant shear turbulent flow, and are restricted to flat terrain with uniform, continuous vegetation cover.By equating integrated bulk drag due to crown foliage to the shear stress at the top of the crown layer, a model for relating windspeed within and below a uniform forest canopy to windspeed 20 ft (6 m) over the canopy is developed. Important variables in this model include stand height, crown closure, foliar surface/ volume ratio, and crown bulk density. Comparison of model predictions with reported experimental measurements shows good agreement.

The hypothesis that lightning fires are caused by a special type of lightning discharge has been presented several times in literature over the past 20 years. Working with laboratory sparks, McEachron and Hagenguth [1942] suggested that ignition by natural lightning is usually caused by a discharge having a long‐continuing current phase. This view is widely accepted [Berger, 1947; Malan, 1963; Loeb, 1966], even though field corroboration has been almost nil. To the authors' knowledge, the two discharges and resultant fires documented by Norinder et al. [1958] are the only natural events reported to date wherein both the discharge and its ignition effects were documented.

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