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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

The Incident Position Standards and Next Generation Position Task Book are now available for Medical Unit Leader (MEDL)

Date: October 16, 2024
Contact: Incident Medical Subcommittee

NWCG is excited to announce that the NWCG Incident Position Standards for Medical Unit Leader, PMS 350-39 and NWCG Position Task Book for Medical Unit Leader (MEDL), PMS 311-39 are now available.

The Performance Support Package, which for MEDL includes the Incident Position Standards and Next Generation Position Task Book, were developed through the Incident Performance and Training Modernization (IPTM) effort. The Performance Support Package will support trainees, those qualified in the position, and evaluators.

References:

NWCG Medical Unit Leader Position Page

NWCG Incident Position Standards for Medical Unit Leader, PMS 350-39

NWCG Position Task Book for Medical Unit Leader (MEDL), PMS 311-39

The Wildland Fire Learning Portal is Now Available

Date: October 9, 2024
Contact: Wildland Fire Learning Portal

The Wildland Fire Learning Portal (WFLP) is back online following a migration to a new learning management system (LMS) application. The WFLP team is actively addressing any issues that may arise as a result of the update, and appreciates your patience as the team works to enhance your experience. NWCG will share information from the WFLP as it is available.

Should you have any issues with accessing or using the WFLP, please use the link below to submit a ticket through the Help Center.

References:

Wildland Fire Learning Portal

Wildland Fire Learning Portal Help Center

NWCG Equipment Technology Committee Releases New Equipment Bulletins

Date: September 27, 2024
Contact: Equipment Technology Committee

The Equipment Technology Committee (ETC) has released three new Equipment Bulletins:

  • ETC-EB-24-003 Diesel exhaust fluid (DEF) in fuel containers.
  • ETC-EB-24-004 Two-compartment fuel and oil container (Dolmar) unavailable in the United States (US) and reminders for upkeeping current inventories.
  • ETC-EB-24-005 Personal Protective Equipment (PPE): Inspection, Care, and Maintenance.

These bulletins remind field going personnel of important issues related to equipment for wildland firefighting efforts.

References:

NWCG Alerts

ETC-EB-24-003 Diesel exhaust fluid (DEF) in fuel containers

ETC-EB-24-004 Two-compartment fuel and oil container (Dolmar) unavailable in the United States (US) and reminders for upkeeping current inventories

ETC-EB-24-005 Personal Protective Equipment (PPE): Inspection, Care, and Maintenance

The Experiential Learning Subcommittee is looking for your feedback on Staff Rides

Date: September 20, 2024
Contact: Ashleigh D'Antonio and George Risko, Leadership Committee

The Experiential Learning Subcommittee needs to hear from the field about where the greatest need lies regarding staff rides and their accessibility.

  • Do you have an event you would like to turn into a learning experience?
  • Do you have a staff ride built, but are struggling to implement the delivery?
  • Do you need help building capacity?
  • What other ideas do you have to support experiential leadership training?

Fill out this short survey below to help us help you.

References:

Staff Rides: Feedback

Staff Rides