A FOREST firefighter has three main enemies: low humidity, high temperatures and strong winds. The most dangerous of these is wind. A blaze in the aspen forest north-east of Tucson, Arizona, which burnt up 350 square kilometres (including 333 houses) in less than 5 weeks before it was contained last month, was driven chiefly by the local Santa Ana winds.
The Santa Ana is typical of a particular type of wind that begins over the sea and blows onto coastal mountain ranges before plunging into valleys on the other side. The best-known example is the chinook, which blows across the…
