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Nelson Model

NFDRS header graphic. Decorative.

The Nelson dead-fuel moisture model

The ‘Nelson model’ for Dead Fuel Models is a physical-based model that contains equations for heat and moisture transfer (Nelson 2000). Besides internal water, it also takes into account water at the surface through the processes of adsorption, desorption, rainfall, condensation, and evaporation. Inputs to the Nelson model include air temperature, relative humidity, solar radiation, and amount of rainfall since the last observation. Outputs include moisture content and temperature of the fuel stick at the times corresponding to the weather data inputs. The theoretical model was converted into a finite-difference numerical model, so as to be usable in practice.

Nelson Dead Fuel Classes

Time Lag Stick Radius
1 hour 0.08 in (0.2cm)
10 hour 0.25 in (0.64cm)
100 hour 0.8 in (2.0cm)
1000 hour 2.5 in (6.4cm)

 

NWCG Latest Announcements

NEW! NWCG Standard Operating Procedures, PMS 900

Date:  July 9, 2026
Questions? 
Please contact: NWCG Staff

NWCG is excited to announce the publication of the NWCG Standard Operating Procedures, PMS 900.

The new publication establishes general, consistent, and uniform standards for conducting business with the National Wildfire Coordinating Group.

References:

NWCG Standard Operating Procedures, PMS 900

Quarter Four Materials for the 2025-2026 Wildland Fire Leadership Campaign Now Available

Date:  July 8, 2026
Questions? 
Please contact: Leadership Development Subcommittee

NWCG is excited to announce that Fourth Quarter materials for the 2025/2026 Wildland Fire Leadership Campaign are now available. This annual initiative offers all students of leadership and wildland fire management an opportunity to engage with essential leadership skills and knowledge needed to lead effectively in dynamic environments.

Quarter Four materials focus on Leadership Level 4: Leader of Leaders (Provide Direction). Leadership Level 4 is where you are setting the conditions for others to do things well, even when you are not present. This quarter focuses on equipping experienced leaders with skills to provide direction, build trust across teams, and foster strong decision making. 

References:

2025/2026 NWCG Leadership Campaign - Leadership Levels

Wildland Fire Leadership Development Program

Leadership Development Subcommittee

2026 Week of Remembrance

Date:  June 30, 2026
Questions? 
Please contact: 6 Minutes for Safety Subcommittee

As we approach the 2026 Week of Remembrance (WOR), June 30–July 6, we dedicate this time to reflect on past incidents from 2016 and honor the fallen through learning. Since its inception in 2014, WOR has honored wildland firefighters who made the ultimate sacrifice while encouraging critical discussions that reinforce lessons learned.

Throughout the week, we encourage thoughtful and generative conversations that promote a culture of continuous learning and safety.

References:

2026 Week of Remembrance: Letter to Leadership

Wildland Fire Lessons Learned Center

RMC Memorandum 26-02: SAFENET Modernization and SafeNetX Launch

Date:  June 25, 2026
Questions? 
Please contact: Risk Management Committee

The Risk Management Committee (RMC) is pleased to announce the launch of SafeNetX, the modernized safety reporting system now available to the wildland fire community. Effective June 15, 2026, SafeNetX enables reporting of unsafe, unhealthy, near-miss, and high-risk operations across wildland fire, all-hazard incidents, training, and related work environments.

SafeNetX is the result of a multi-agency modernization effort led by RMC, which began evaluating improvements to the legacy SAFENET system in 2021. To learn more, read the full RMC memorandum in the links provided.

References:

SafeNetX

RMC Safety Memorandum 26-02: SAFENET Modernization and SafeNet X Launch