Rainfall evaporation in thunderstorm downdraughts

It is explained that in air descending at speeds of some m sec−1 raindrop evaporation must proceed at a large subsaturation. Under some simplifying steady‐state assumptions, the vertical temperature profiles in thunderstorm downdraughts of a range of speeds are estimated, and it is shown that the most favourable conditions for the production of strong draughts are a small raindrop size, and, especially, an intense rainfall rate and a general lapse‐rate close to the dry adiabatic. The two latter conditions are often associated in severe storm situations, and the downdraught then arrives near the ground with a rather low relative humidity, and a temperature little lower than found generally at the same level.