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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 Guide for Wildland Fire Modules, PMS 431

Date: May 14, 2025
Questions?  Please contact:
Fire Use Subcommittee

The updated NWCG Guide for Wildland Fire Modules, PMS 431 serves as a supplemental resource for wildland fire module operations, providing information frequently used in the field.

PMS 431 defines the organizational structure, staffing, and qualifications for Type 1 and Type 2 Wildland Fire Modules, outlining their roles in wildland fire suppression, prescribed fire, and resource management. The NWCG Guide for Wildland Fire Modules, PMS 431, should be used in conjunction with the NWCG Standards for Wildland Fire Module Operations, PMS 430.

References:

NWCG Guide for Wildland Fire Modules, PMS 431

NWCG Standards for Wildland Fire Module Operations, PMS 430

Updated NWCG Standards for Wildland Fire Resource Typing, PMS 200 Now Includes Off-Highway Vehicle Typing Standards

Date: May 13, 2025
Questions?  Please contact:
Mobile Fire Equipment Subcommittee 

The NWCG Standards for Wildland Fire Resource Typing, PMS 200 has been updated to include newly developed Off-Highway Vehicle (OHV) typing standards. These standards organize OHV information into logical categories and outline key safety requirements for occupants.

NWCG Standards for Wildland Fire Resource Typing, PMS 200 establishes minimum typing standards for aircraft, crews, and equipment used in national mobilization to wildland fire incidents. Typing designations are assigned based on measurable capability and performance criteria.

References:

NWCG Standards for Wildland Fire Resource Typing, PMS 200

NEW! S-204, Interpersonal and Critical Thinking Skills for Safety Officers Now Available

Date: May 12, 2025
Questions?  Please contact:
Risk Management Committee

The S-204, Interpersonal and Critical Thinking Skills for Safety Officers self-directed online course is now available! Developed through the Incident Performance and Training Modernization (IPTM) effort, this training supports individuals working towards Safety Officer, Field (SOFF) incident qualifications.

S-204, Interpersonal and Critical Thinking Skills for Safety Officers focuses on facilitating hazard mitigation conversations and building trust to influence safety-related decisions. Individuals can self-enroll through the Wildland Fire Learning Portal (WFLP).

Any changes to qualification pathways will take effect with the next update of the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1.

References:

S-204, Interpersonal and Critical Thinking Skills for Safety Officers 

NWCG Safety Officer, Field (SOFF) Position Page

Wildland Fire Learning Portal

Great Basin Cache Upgrading to New Inventory System

Date: May 7, 2025
Questions?  Please contact:
Great Basin Cache
Phone: (208) 387-5104
Fax: (208) 387-5573

The Great Basin Cache (GBK) is transitioning to a new inventory system to better serve the wildland fire community. During this upgrade, GBK will be unable to process standard orders from Part 1: Fire Supplies and Equipment and Part 2: Publications between May 8-20, 2025, with exceptions made for emergency fire orders. Orders will be accepted through close of business May 7.

To browse the latest available items, please refer to the National Fire Equipment System (NFES) catalogs. 

References:

NWCG NFES Catalog-Part 1: Fire Supplies and Equipment, PMS 449-1

NWCG NFES Catalog-Part 2: Publications, PMS 449-2