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Nelson Model

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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

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

2025 Wildland Fire EMS Awards

Date:  June 12, 2026
Questions? 
Please contact: Emergency Medical Committee

The NWCG Emergency Medical Committee (EMC) announces the recipients of the 2025 Wildland Fire Emergency Medical Service (EMS) Awards. EMC annually recognizes individuals and groups who have demonstrated outstanding actions or accomplishments that are above and beyond the expectation of one’s normal mission or job duties.

Congratulations to all the awardees and nominees. Through leadership and initiative, they have made significant contributions to the safety of the wildland fire community. These awards are well deserved.

References:

2025 Wildland Fire EMS Awards

Emergency Medical Committee

Incident Position Standards and the Next Generation Position Task Book Now Available for RAMP

Date:  June 12, 2026
Questions? 
Please contact: Airtanker Base Operations Unit

NWCG is excited to announce that Incident Position Standards and the Next Generation Position Task Book are now available for Ramp Manager (RAMP).

The Performance Support Package for this position was developed as part of the Incident Performance and Training Modernization effort. These resources support trainees, qualified personnel, and evaluators in their respective roles.

Any changes to qualification pathways will take effect with the next update of the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1, scheduled for release in January 2027.

References:

NWCG Ramp Manager Position Page

National Interagency Aviation Committee

Make an Impact: Serve the Wildland Fire Community as an IPTM SME!

Date:  June 11, 2026
Questions? 
Please contact: NWCG SME Specialist

Note: Positions with an * will last approximately 6 months.
Positions with ** will last 12 - 18 months.

NWCG is seeking experienced wildland firefighters and support personnel to serve as Subject Matter Experts (SMEs) for the Incident Performance and Training Modernization (IPTM) initiative. IPTM aims to transition NWCG’s training and qualification system to a performance-based model by updating position descriptions, Incident Position Standards, Next Generation Position Task Books (Next Gen PTBs), and training where needed.

NWCG is currently recruiting SMEs for the Fall 2026 positions listed below:

  • Equipment Manager (EQPM)*
  • Fixed Wing Parking Tender (FWPT)**
  • Mixmaster (MXMS)*
  • Public Information Officer Complex (PIOC)*
  • Retardant Crewmember (RTCM)*
  • Strike Team Leader Crew (STCR)*
  • Strike Team Leader Engine (STEN)*
  • Strike Team Leader Heavy Equipment (STEQ)*
  • Task Force Leader (TFLD)**
  • Wildland Fire Investigator (INVF)** 

Projects begin October 2026. Sign up by July 10, 2026, at the link below and review the attached document for additional details. 

References:

NWCG SME Interest Sign-up

IPTM Subject Matter Expert Duties and Expectations Document

Incident Performance and Training Modernization (IPTM)