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Updated: 10/17/2017 04:40:29

Overview

ExtendWeather has been following the long and difficult fire season in the western parts of North America. The season looks likely to persist into the fall and will likely ultimately conclude when cooler and wetter weather persists as the winter season arrives. ​We will maintain four daily updates of the Haines Index through to December with movies generated for a five day forecast period based on three hourly time steps.

About

Haines (1988) developed the Lower Atmosphere Stability Index, or Haines Index, for fire weather use. It is used to indicate the potential for wildfire growth by measuring the stability and dryness of the air over a fire. It is calculated by combining the stability and moisture content of the lower atmosphere into a number that correlates well with large fire growth. The stability term is determined by the temperature difference between two atmospheric layers; the moisture term is determined by the temperature and dew point difference. This index has been shown to be correlated with large fire growth on initiating and existing fires where surface winds do not dominate fire behavior.

The Haines Index can range between 2 and 6. The drier and more unstable the lower atmosphere is, the higher the index.
​Haines, D.A. 1988. A lower atmospheric severity index for wildland fire. National Weather Digest. Vol 13. No. 2:23-27.