Haines Index

The Haines Index is a national fire-weather index based on the stability and moisture content of the lower atmosphere and their direct relationship to the growth of large fires (see Extreme Fire Behavior and Fire and Plumes). The index ranges from 2 to 6, with 6 being the highest potential for large fire growth (Pyne et al. 1996). The more dry and unstable the atmosphere the higher the Haines index value. The Wildand Fire Assessment System produces daily maps of the Haines Index for the U.S.

Several studies have noted deficiencies in the Haines index (Jenkins 2002; Porterie 2001; Potter 2002). It does not incorporate wind variables, and it may only use weather data from widely distributed locations. Environmental conditions could exist whereby a low Haines value would be computed but local wind direction and speed could create a situation conducive to flare-ups and spotting. In addition, upper level atmospheric moisture is not accounted for with the Haines index. Moisture levels above 10,000 feet do not reflect relative humidity and may increase instability in the upper atmosphere leading to thunderstorm development. Jenkins (2002) suggested the Haines Index scale should be expanded past the value of 6 for the best predictive models of fire behavior as influenced by atmospheric conditions.