Skip to main content

Surface Fire Behavior Worksheet

Table of Contents for This Page

  1. Available Tools and Resources
  2. Required Surface Model Inputs
  3. Surface Model Outputs
  4. Acceleration Effect on Rate of Spread

This comprehensive worksheet can be used with the surface fire behavior lookup tables, the Nomograms and Nomographs, as well as BehavePlus, and runs if you want a paper copy.

Consider using this as your briefing documentation by including a weather forecast narrative, your thoughts about recent fire activity, your sense of how accurate the predictions seem, and when you expect changes through the burn period.

Image
Worksheet for recording information collected and estimates produced when estimating surface fire behavior.

Available Tools and Resources

This section describes how to estimate expected surface fire behavior and provides several references tools used in the process:

  1. A Worksheet (above) designed to document a complete assessment for surface fire behavior and growth using either the lookup tables or the nomographs.
  2. EWS Tables for estimating Effective Windspeed from Slope and Midflame Windspeed. The Effective Windspeeds that result from these tables assumes that wind is blowing ± 30° from upslope. For other situations, manual vectoring using the EWS Table would be necessary.
  3. Surface Fire Behavior Lookup Tables for making estimates of surface fire spread and flame length. Note these assumptions:
    • 10-hr and 100-hr moisture values of 6% and 8% are used in the lookup tables.
    • The *20ft/FCST wind line is provided as a convenience, but only works with stated Wind Adjustment Factor (WAF) & no slope adjustments.
    • Backing & flanking columns are only rough estimates based on ½ and 1 mph windspeeds. Use the Flanking and Backing Fire Behavior Nomograph , or BehavePlus for more precise estimates.
  4. Instructions for Surface Fire Behavior Nomographs and Nomograms.
  5. Flanking and Backing Fire Behavior Nomograph for estimating rate of spread and flame length where fire is spreading more slowly on the flanks and at the back of the fire perimeter.

These tools can help you make expected surface fire behavior estimates. Consider the following:

Return to Top

Required Surface Model Inputs

Return to Top

Surface Model Outputs

  • Rate of Spread is useful in fireline tactical applications; identifying what is at risk in the burn period, escape route limitations.
  • Flame Length/Fireline Intensity is used generally in determining what tactics make sense during the peak burn period, interpreting safety zone concerns, and suggesting spotting potential.
  • Heat per Unit Area is available from nomograms and BehavePlus. Like the Energy Release Component, it may be helpful in suggesting burn duration and fire effects.

Return to Top

Acceleration Effect on Rate of Spread

Image
Fire Spread Acceleration. Fire spread accelerates over a period of time after initiation. The period of time varies based on the fuelbed.

Fire acceleration is defined as the rate of increase in fire spread rate. It affects the amount of time required for a fire spread rate to achieve the theoretical steady state spread rate given 1) its existing spread rate, and 2) constant environmental conditions.

Because initiating fires can take 20 minutes to over an hour to reach a steady spread rate, fire behavior and fire growth can be significantly reduced in the first burn period, and when beginning to spread in subsequent periods.

At this time, fire acceleration is implemented only in FARSITE, using the model developed for the Canadian Forest Fire Behavior Prediction System (Alexander et. al. 1992).

It is active by default, but can be turned off as a model input.

As implemented, inputs are segregated by type of Ignition (point vs. line source) and potentially by fuel type (grass, shrub, timber, slash, a default, or by fuel model). Grass fuels are expected to have more rapid acceleration rates (shorter time to reach equilibrium) than fuel types with larger woody material (slash, etc.).

Return to Top

NWCG Latest Announcements

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