Wind types

Wind is an important, sometimes critical factor in fire behavior. Wind moves air across burning materials, supplying more oxygen for combustion. It also redirects flames and convective heat away from their normal upward path, pushing them closer to the ground and unburned fuels. Strong winds can carry burning materials such as leaves, sparks and brands beyond the fire to cause spot fires. Wind determines the direction smoke travels, and generally determines the direction of the fire as well. It greatly influences the rate of spread and control of the fire. Wind direction, steadiness and velocity are important in predicting fire behavior.

There are several types of winds that you should be familiar with:

• General winds affect large areas. These are the high-level winds that move weather systems across the earth.
• Surface winds are those normally measured at 20 feet above the ground. These are the winds reported in daily weather forecasts.
• Local winds are produced by features of the local terrain.
• Mid-flame winds occur at the midpoint of flame height. They have the greatest effect on the direction that a fire will burn.