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Unit 5: Fuel Moisture

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Using Dead Fuel Moisture Tables (1-Hour Timelag)

Step 1 : Obtain the following site data for determining dead fuel moisture:

  1. Time of day
  2. Month
  3. Dry bulb temperature
  4. Relative humidity
  5. Aspect (N, S, E, W, Level)
  6. Exposure of fine dead fuels to sun or not

Step 2 : Consider location/elevations for predictions:

  1. Predictions for same site as data gathered
  2. Predictions for site above or below the data site (daytime only with no inversions)

Step 3 : Consider day or night conditions:

  1. Daylight hours (0800 - 1959)
  2. Nighttime hours (2000 - 0759)

Step 4 : Determine reference fuel moisture from dry bulb temperature and relative humidity using table.

Step 5 : Consider exposed or shaded fuel conditions:

  1. At least 50% of fine dead fuels are exposed to sun. Use "clear and/or no canopy" portions on tables 2-4.
  2. At least 50% of fine dead fuels are shaded by clouds or canopy.

Step 6 : Determine fuel moisture correction value considering month, time of day, and aspect:

  1. May, June, July
  2. February, March, April, August, September, October
  3. November, December, January

Step 7 : Determine dead fuel moisture content for prediction sites above or below data site on same slope (daytime only with no inversions). Follow these substeps:

  1. Determine elevation difference between data site and prediction site.
  2. Calculate new temperature for prediction site using usual lapse rate of 3.5 degrees Fahrenheit per 1000 feet.
  3. Determine relative humidity for prediction site by following procedures (using dew point)
  4. Calculate dead fuel moisture content by using new dry bulb temperature and relative humidity for prediction site.

Step 8 : Determine dead fuel moisture content (daytime) by adding correction value (step 6) to reference fuel moisture (step 4).

Step 9 : Determine dead fuel moisture content (nighttime) from dry bulb temperature and relative humidity using table.

Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, November 07). Unit 5: Fuel Moisture. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: http://ocw.usu.edu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_Management_and_Planning/Unit_5__Fuel_Moisture_7.html. This work is licensed under a Creative Commons License Creative Commons License