Weather Forecasts

Weather forecast data are supplied by the National Weather Service (NWS) National Digital Forecast Database (NDFD).

What this tool does

What this tool does not do

Moisture Content and Probability of Ignition

Dead grass fuel moisture content is estimated from a model based on six years of prescribed burning on military ranges near Fairbanks, Anchorage, and Delta Junction, Alaska. Observations were collected from 17 sites over 74 days between 2009-2014, mostly during prescribed burning between 08:00 and 20:00. Two-hundred eighty five pairs of weather and moisture content measurements were used to develop models of moisture content. Moisture contents ranged between 4 and 29%. Moisture content is generally very close to its equilibrium moisture content (EMC) and can be adequately modelled using an EMC equation. This website predicts moisture content using Anderson's (1990) EMC equation for recently-cast cheatgrass based on temperature and relative humidity. (Anderson, H. (1990). Predicting equilibrium moisture content of some fo- liar forest litter in the northern Rocky Mountains, volume INT-429 of Research Paper. U.S.Forest Service, Intermountain Forest and Range Experiment Station, Ogden, UT, USA.)

Probability of Ignition is also empirically calculated from numerous dead grass ignition trials in a laboratory. Dead grass samples were brought to zero percent moisture content in a drying oven. Moisture was re-introduced into the samples in known quantities. Ignition probability curves were developed based on the moisture content using logistic regression.

This tool vs. Fire Danger Indices

Unlike the Canadian or U.S. National Fire Danger Rating Systems (CFFDRS or NFDRS) which produce indices (abstractions of reality), this tool predicts actual fuel moisture content and actual probability of ignition estimates.



Change Log

In the 2010 version of this standing dead grass calculator moisture content was based on dew point temperature and wind speed. Subsequent sampling and analysis demonstrates that relative humidity is a better predictor than dew point and that moisture content is not dependent on wind speed in standing dead grass. New fireline tables have been issued (pdf).

Send comments and bug reports to:
Eric A. Miller
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Last website update 26 March 2015