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Weather: Stability

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

Measures of Stability

Index Major Factors Primary Utility Application
Davis Stability Index Lapse rate Basic measure of stability Southeast US
Ventilation Index Mixing height and transport wind Smoke dispersion United States
Pasquill Stability Index Solar radiation, cloud cover, and surface wind speed (surface based stability) Smoke dispersion SASEM
Lavdas Atmospheric Dispersion Index Pasquill, mixing height, transport wind Smoke dispersion and fire growth potential Florida

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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)
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
MID ELEVATION Stability Term (A) MID ELEVATION Moisture Term (B)
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
HIGH ELEVATION Stability Term (A) HIGH ELEVATION Moisture Term (B)
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
Haines Index (A + B) Potential for Large Fire
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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Updated NWCG Standards for Airtanker Base Operations, PMS 508

Date: March 31, 2025
Questions?  Please contact:
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The updated NWCG Standards for Airtanker Base Operations (SABO), PMS 508 standardizes operations and procedures at interagency airtanker bases to ensure safe, efficient, and effective operations in support of interagency goals and objectives.

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NWCG Standards for Airtanker Base Operations, PMS 508

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Date: March 14, 2025
Questions?  Please contact:
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The 2025 Core Component Module Package for RT-130, Wildland Fire Safety Training Annual Refresher (WFSTAR) and the 2024 Fire Year in Review are now available on the NWCG website. The 2025 Core Component Module Package provides all content needed to deliver RT-130.

References:

2025 Core Component Module Package

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Date: March 12, 2025
Contact: Wildland Urban Interface Mitigation Committee

The NWCG Wildland Urban Interface Mitigation Field Guide, PMS 053 provides mitigation practitioners at all experience levels with recommendations on the most effective and efficient ways to accomplish mitigation work in communities at risk to wildfire damage or destruction. The content in this guide was written in coordination with the NWCG Standards for Mitigation in the Wildland Urban Interface, PMS 052.

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NWCG Wildland Urban Interface Mitigation Field Guide, PMS 053 

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Contact: Fire Use Subcommittee
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The NWCG Standards for Wildland Fire Module Operations, PMS 430 standardizes procedures and expectations for Wildland Fire Modules (WFMs). These standards are to be used by staff, supervisors, specialists, and technicians for planning, administering, and conducting WFM operations. These standards will also be used as a measure of WFM qualifications, capabilities, and expected performance, for both Type 1 and Type 2 WFMs.

References:

NWCG Standards for Wildland Fire Module Operations, PMS 430