DEFINITION:

The Haines Index is a fire weather index created by Donald Haines of the Forest Service in 1988 to measure the potential growth for existing wildfires. The index is evaluated by summing up a stability term with a dryness term to get the Haines Index over a particular region.

The stability term is included to represent the atmospheric potential to enhance the vertical size of the smoke column. Strong surface winds converge into wildfires to fill the space left as the column of smoke rises. More intense winds can fuel the fire if more air is removed from the surface in a larger smoke column. The dryness term is included because dry conditions enhance the availability of fuel for the fire.

The stability term is calculated from model output of the temperature change between two different levels while the dryness term is calculated from the temperature/dew-point difference at the lower level. The levels represented by the index are 700-500mb for the high index, 850-700mb for the mid index and 950-850mb for the low index.