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Fuel Moisture: Dead Fuel Moisture Content

  1. Nelson Model 1 and 10-hr Fuel Moisture Estimation Methods
  2. Fosberg Model 1-hr Fuel Moisture Estimation Methods
  3. 10-hr, 100-hr and 1000-hr Fuel Moisture Content
  4. Fuel Moisture Conditioning in U.S. Spatial Fire Growth Models

Nelson Model 1 and 10-hr Fuel Moisture Estimation Methods

Ralph M. Nelson (2000) developed a fuel moisture model for estimating the diurnal fuel moisture changes in a 10-hr NFDRS fuelstick. Requiring hourly observations, it produces a more dynamic estimate that better reflects changes in precipitation, humidity, and sunshine. The National Fire Danger Rating System (NFDRS) uses this methodology.

SimpleFFMC 1-hr Fuel Moisture Estimation Tables based on the Nelson Model, have been calibrated for the southeastern U.S. by W. Matt Jolly (2016) and are available as a web-app for online users.

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Fosberg Model 1-hr Fuel Moisture Estimation Methods

Michael A. Fosberg and John E. Deeming (1971) documented procedures for estimating 1 and 10-hour Timelag Fuel Moistures. The methodology, along with seasonal adjustment tables, were integrated into Richard Rothermel’s (1983) tools and methods for surface fire behavior predictions.

Daytime Estimation Procedure

  1. Using Table A, determine Reference Fuel Moisture (RFM). Percentage from intersection of temperature and relative humidity. Record this RFM percentage.
  2. Select Table B, C, or D to adjust RFM for local conditions by finding current month in table title.
  3. Is the fine fuel more than 50% shaded by canopies and clouds? If yes, use bottom shade portion of table. If no, use top exposed portion of table.
  4. Determine the appropriate row based on aspect and slope.
  5. Determine the appropriate column based on time of day and elevation of area of concern when compared to the wx site elevation. Use (A)bove if the fire is 1-2000’ above your location, (B)elow if the fire is 1-2000’ below you, and (L)evel if the fire is within 1,000’ above or below you.
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    Below fire, at fire level, and above fire chart.
  6. Obtain the 1-hr Moisture Content Correction (%) from the intersection of row and column.
  7. Add the resulting 1-hr Moisture Content Correction (%) to the RFM (%).

Nighttime Estimates of 1-hr Fuel Moisture

Published RFM and Correction Tables for Nighttime Conditions are not included here based on recommendation from Pat Andrews at the Missoula Fire Lab. She recommends:

  • Estimate Dry Bulb Temperature and relative humidity (RH) for the location of interest.
    Use Table A to estimate the RFM.
    Use the appropriate 1-hr Moisture Content Correction Table based on the time of the year.
    Obtain the correction for 0800, shaded conditions, and appropriate aspect from that table and add it to the RFM to estimate 1-hr moisture content for nighttime conditions.

Table A. Reference Fuel Moisture

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1-hr Fuel Reference Fuel Moisture Table. Integrates Dry Bulb Temperature and Relative Humidity.

Table B. 1-hr Fuel Moisture Corrections-May-June-July

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1-hr Fuel Moisture Corrections for May, June, and July. Used to adjust reference fuel moisture to local conditions of shading, slope, aspect, and time of day.

Table C. 1-hr Fuel Moisture Corrections-Feb-Mar-Apr and Aug-Sep-Oct

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1-hr Fuel Moisture Corrections for February, March, April, August, September, and October. Used to adjust reference fuel moisture to local conditions of shading, slope, aspect, and time of day.

Table D. 1-hr Fuel Moisture Corrections-Nov-Dec-Jan

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1-hr Fuel Moisture Corrections for November, December, and January. Used to adjust reference fuel moisture to local conditions of shading, slope, aspect, and time of day.

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10-hr, 100-hr, and 1000-hr Fuel Moisture Content

10-hr and 100-hr fuel moisture may be estimated in the following ways and applied along with the Fosberg fuel moistures in surface fire behavior predictions. 1000-hr fuel moisture is not usually needed for fire behavior calculations.

  • After estimating 1-hr moisture content, 10-hr and 100-hr fuel moisture content can be estimated by adding incremental amounts (e.g. adding 1-2% for 10-hr and 2-4% for 100-hr).
  • Using a local Remote Automatic Weather Station (RAWS) or the Geographic Area’s Predictive Service summaries.
  • The National Fuel Moisture Database may have sampling locations near your setting that have estimates for these fuel moistures.

In NFDRS, if danger rating calculations are suspended in the dormant season, default dormant fuel moistures are provided for 100-hr (10%-25%) and 1000-hr (15%-30%) fuel moistures when calculations are restarted in the spring. Default values are established with climate class designation for the location.

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Fuel Moisture Conditioning in US Spatial Fire Growth Models

Deterministic spatial analyses in Wildland Fire Decision Support System (WFDSS) (Basic, Short Term Fire Behavior [TFB], and Near Term Fire Behavior [NTFB]) use estimates from historic weather data in the Wildland Fire Applications Information Portal (WIMS) implementation of NFDRS as default initial fuel moistures inputs. Forecast and/or observed weather (for retrospective periods) from the selected weather stations are used to estimate hourly adjustments to dead fuel moistures for those analyses. Initial dead fuel moistures in deterministic analyses default to estimates using the Fosberg dead fuel moisture model while conditioning weather uses the Nelson Model to adjust 1-hr, 10-hr, and 100-hr fuel moisture content over one to several days. In most cases, one or two days of conditioning is sufficient. 

Take care to review the conditioning weather inputs for both observed and forecast days. Precipitation amounts, high overnight humidity recovery, and/or significant cloud cover can raise fine fuel moisture significantly. Use the Basic Outputs from Flammap or Short Term Fire Behavior analyses to review resulting 1-hr and 10-hr fuel moistures and edit inputs as necessary.

Desktop software (FLAMMAP and FARSITE) can use any initial fuel moisture and weather stream that the user supplies to apply these conditioning adjustments.

WFDSS FSPro draws its dead fuel moistures (1-hr, 10-hr, and 100-hr) in the Energy Release Component (ERC) table from the WIMS implementation of NFDRS. It ranks and groups ERC values from the selected weather station climatology and provides average fuel moisture values from the underlying data for each of those groups, or percentile classes. It uses the Fosberg model for all dead fuel moisture defaults. They are held static during the simulation and are not conditioned or changed during any simulation for the period that they are drawn from and used.

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NWCG Latest Announcements

Updated NWCG Standards for Fire Unmanned Aircraft Systems Operations, PMS 515

Date: April 23, 2025
Questions?  Please contact:
Interagency Fire Unmanned Aircraft Systems Subcommittee

The NWCG Standards for Fire Unmanned Aircraft Systems Operations, PMS 515 standardizes processes and procedures for the interagency use of Unmanned Aircraft Systems (UAS), including pilot inspections and approvals. This updated publication provides the aviation community with standards to ensure UAS are used safely, effectively, and efficiently in support of fire management goals and objectives.

References:

NWCG Standards for Fire Unmanned Aircraft Systems Operations, PMS 515

NWCG National Interagency Aviation Committee

ETC Bulletin 25-001: Retrofitted Hot/Cold Beverage Kits - 2025 Field Season

Date: April 16, 2025
Questions?  Please contact:
Equipment Technology Committee

Due to spout failures and the associated risk of burn injuries, manufacturers have retrofitted the Hot/Cold Beverage Kits using a heat-shrinking band to secure the black spout at the insertion site. The updated kits feature a fluorescent label on each full kit assembly for easy identification. Catering units are encouraged to confirm the clear heat-shrinking bands are intact around each spout before filling.

ETC Bulletin 24-001 regarding Hot/Cold Beverage Kits has been archived and replaced by ETC Bulletin 25-001 for the 2025 season.

References:

NWCG Alerts

ETC-EB-25-001 Retrofitted Hot/Cold Beverage Kits

NWCG Standards for Wildland Fire Chainsaw Operations, PMS 212, and Next Generation Position Task Book for Basic Faller Are Now Available

Date: April 14, 2025
Questions?  Please contact:
Hazard Tree and Tree Felling Subcommittee

The updated NWCG Standards for Wildland Fire Chainsaw Operations, PMS 212, and NWCG Position Task Book for Basic Faller (FAL3), PMS 311-19 are now available.

The NWCG Standards for Wildland Fire Chainsaw Operations, PMS 212 includes position standards designed to be used in conjunction with the Next Generation Position Task Book (Next Gen PTB). The Next Gen PTB for Basic Faller (FAL3) includes an evaluation guide with suggested rating elements to consider when assessing trainees.

References:

NWCG Standards For Wildland Fire Chainsaw Operations, PMS 212

NWCG Position Task Book for Basic Faller (FAL3), PMS 311-119

NWCG Basic Faller (FAL3)

RMC Memo 25-01: Summary of Updates to Safety Officer Positions

Date: April 9, 2025
Questions?  Please contact:
RMC Member Eric Fransted

The Risk Management Committee (RMC) serves as the position steward for all Safety Officer incident positions and continues to improve position standards, training, and naming conventions. The implementation of Complex Incident Management (CIM) required changes to position titles. RMC collaborated with the NWCG Incident Position Standards Committee (IPSC) to propose and implement these updates. 

References:

RMC Memo 25-01: Summary of Updates to Safety Officer Positions 

NWCG Position Catalog