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PMS 437

Weather: Stability

  1. Measures of Stability
  2. Lower Atmospheric Stability (Haines) Index

Measures of Stability

IndexMajor FactorsPrimary UtilityApplication
Davis Stability IndexLapse rateBasic measure of stabilitySoutheast US
Ventilation IndexMixing height and transport windSmoke dispersionUnited States
Pasquill Stability IndexSolar radiation, cloud cover, and surface wind speed (surface based stability)Smoke dispersionSASEM
Lavdas Atmospheric Dispersion IndexPasquill, mixing height, transport windSmoke dispersion and fire growth potentialFlorida

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Lower Atmospheric Stability (Haines) Index

The Lower Atmospheric Severity Index, commonly known as the Haines Index, was developed during the 1980s as a fire weather tool to estimate the effect of atmospheric dryness and stability on the growth potential of a wildfire. The goal was to identify typical combinations of humidity and stability and contrast them with combinations of stability and humidity prevalent during problem fire outbreaks. Always reference local Climatology, see below.

Haines Index Calculation Criteria

LOW ELEVATION Stability Term (A)LOW ELEVATION Moisture Term (B)
MID ELEVATION Stability Term (A)MID ELEVATION Moisture Term (B)
HIGH ELEVATION Stability Term (A)HIGH ELEVATION Moisture Term (B)
Haines Index (A + B)Potential for Large Fire
950 – 850 mb °C
A = 1 when 3°C or less
A = 2 when 4-7°C
A = 3 when 8°C or more		950 mb T° C – 950 DP° C
B = 1 when 5° C or less
B = 2 when 6-9° C
B = 3 when 10° C or more
850 – 700 mb °C
A = 1 when 5°C or less
A = 2 when 6-10°C
A = 3 when 11°C or more		850 mb T° C – 850 DP° C
B = 1 when 5° C or less
B = 2 when 6-12° C
B = 3 when 13° C or more
700 – 500 mb °C
A = 1 when 17°C or less
A = 2 when 18-21°C
A = 3 when 22°C or more		700 mb T° C – 700 DP° C
B = 1 when 14° C or less
B = 2 when 15-20° C
B = 3 when 21° C or more
2 or 3
4
5
6		Very Low
Low
Moderate
High

U.S. Haines Elevation Classification Map

The Haines, or Lower Atmospheric Stability Index, uses different inputs based on the general classification of terrain elevation. This map displays areas of High, Mid, and Low elevation areas.

Haines Index Climatology

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Date:  March 17, 2026
Questions? 
Please contact: Fire Behavior Subcommittee

NWCG is pleased to announce that the new S-490, Advanced Fire Behavior Calculations (Blended), 2026 course is now available.

This training includes performance-based activities that allow students to apply the knowledge and concepts required for the Fire Behavior Analyst (FBAN), Long Term Fire Analyst (LTAN), and Prescribed Fire Burn Boss Type 1 (RXB1) positions. It supports individuals working towards these incident qualifications.

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The NWCG Leadership Committee is proud to announce the recipients of the 2024 Paul Gleason "Lead By Example" awards. Award categories include Initiative and Innovation, Mentoring and Teamwork, Motivation and Vision, as well as a Lifetime Achievement Award.

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Date:  March 6, 2026
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NWCG is pleased to announce the new S-231, Engine Boss (Single Resource) course is now available on the Wildland Fire Learning Portal (WFLP). Developed through the Incident Performance and Training Modernization (IPTM) effort, this training supports individuals working towards Engine Boss, Single Resource (ENGB) incident qualifications. 

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NWCG is proud to celebrate 50 years of service to the wildland fire community. Beginning in 1976 with an interagency agreement between the Department of Interior and Department of Agriculture, NWCG has grown to include additional member agencies and is recognized as the standard-setting leader in wildland fire operations.

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