Spotting Fire Behavior
 Evaluating Spotting Behavior

Estimating Maximum Spotting Distance
 Western Species Quick Reference Lookup Table
 Southern Pine Quick Reference Lookup Table
 Nomogram Instructions
 Nomogram Worksheet
 NOM 1. Maximum Spotting Distance (Flame Height)
 NOM 2. Maximum Spotting Distance (Flame Duration)
 NOM 3. Maximum Spotting Distance (Firebrand Lofting)
 NOM 4. Maximum Spotting Distance (Maximum Spotting Distance)
 Spotting Likelihood/Probability
 Integrating Spotting Spread into Fire Growth Projections
 Comparing Spotting Estimation Tools
Evaluating spotting fire behavior requires the integration of three factors:
 The source, size, and number of firebrands.
 The distance the firebrand is carried downwind.
 The probability of igniting a new fire at the downwind location.
ShortRange Spotting is not generally considered as significant in the growth of wildfires, because the advancing fire usually overruns the developing spot fire. Based on that, the assumption is that shortrange spotting is typically accounted for in the spread model outputs.
LongRange Spotting is differentiated from shortrange spotting, primarily because firebrands are being lofted by a convection column and carried beyond the immediate fire area.
Estimating Maximum Spotting Distance
Both the included Spotting Distance Nomograms, shown here, and BehavePlus provide methods for estimating the Maximum Spotting Distance from a Torching Tree, or trees.
The maximum spotting distance model requires identification of tree species, height, and DBH (Diameter at Breast Height) of the torching tree to estimate the flame height and duration from the torching tree that will initiate the lofting of the ember into the windfield.
Further, the open windspeed is used to suggest how far the firebrand will be transported as it falls back to the ground, and the nomogram because it assumes level ground uses the surface (20ft) windspeed and direction.
The downwind Canopy, or Tree Cover, Height (reduced by half for open canopies) is used to factor out embers intercepted by the canopy before reaching surface fuels.
The graphic here depicts additional inputs to the BehavePlus spotting module. In mountainous terrain, ridge top winds are used if wind is blowing across valleys as shown. The shape of the valley is considered with inputs for RidgetoValley distance and elevation difference.
Western Tree Species Quick Reference Lookup Table
This table assumes three torching trees 50 ft tall and 10inch DBH with downwind cover and an open stand of 50 ft tall trees.
Maximum Spotting Distance, in miles 20 ft Windspeed, in mph 


Tree Species  0  5  10  15  20  25  30  35  40  45  50 
Balsam Fir  0  0.1  0.3  0.4  0.6  0.7  0.8  1  1.1  1.3  1.4 
Grand Fir  0  0.1  0.3  0.4  0.6  0.7  0.8  1  1.1  1.3  1.4 
Subalpine Fir  0  0.1  0.2  0.4  0.5  0.6  0.7  0.9  1  1.1  1.2 
Lodgepole Pine  0  0.1  0.2  0.3  0.5  0.6  0.7  0.8  0.9  1  1.1 
Engelmann Spruce  0  0.1  0.3  0.4  0.5  0.7  0.8  0.9  1  1.2  1.3 
Ponderosa Pine  0  0.1  0.2  0.3  0.5  0.6  0.7  0.8  0.9  1  1.1 
DouglasFir  0  0.1  0.2  0.4  0.5  0.6  0.7  0.9  1  1.1  1.2 
Southern Pine Species Quick Reference Lookup Table
This table assumes three torching trees 50 ft tall and 10inch DBH with downwind cover and an open stand of 50 ft tall trees.
Maximum Spotting Distance, in miles 20 ft Windspeed, in mph 


Tree Species  0  5  10  15  20  25  30  35  40  45  50 
Shortleaf Pine  0  0.1  0.2  0.2  0.3  0.4  0.5  0.6  0.6  0.7  0.8 
Slash Pine  0  0.1  0.2  0.3  0.3  0.4  0.5  0.6  0.7  0.8  0.8 
Longleaf Pine  0  0.1  0.2  0.3  0.3  0.4  0.5  0.6  0.7  0.8  0.8 
Pond Pine  0  0.1  0.2  0.2  0.3  0.4  0.5  0.6  0.6  0.7  0.8 
Loblolly Pine  0  0.1  0.2  0.2  0.3  0.4  0.5  0.6  0.6  0.7  0.8 
Nomogram Instructions
This process and the nomograms that integrate the factors do not factor in terrain features as discussed above.
Inputs Required:
Torching Tree: Species, Height, DBH.
Open 20 ft Windspeed.
Downwind Average Tree Height (Divide by 2 for open stands).
Nomogram 1 (Flame Height) & Nomogram 2 (Flame Duration)
Start with input DBH, draw a vertical line to interest curve for input torching tree species, turn and draw a horizontal line to determine flame height in Nomogram 1 and flame duration in Nomogram 2.
Nomogram 3 (Firebrand Lofting):
Divide Flame Height (Nom 1) by the input torching tree height and use that value to select the curve in Nom 3. Using the flame duration (Nom 2), draw a vertical line from the bottom axis to intersect the selected curve. From that intersection, draw a horizontal line to determine the ratio for calculating firebrand height. Multiply ratio from Nom 3 by flame height to determine firebrand height.
Nomogram 4 (Maximum Spotting Distance):
Using the estimated firebrand height, draw a vertical line from the bottom axis on right to intersect curve for selected downwind tree height. From intersection draw a horizontal line to line for input windspeed, then down to spot distance.
Nomogram Worksheet
Follow 1 to 5, left to right on each line.
NOM 1. Maximum Spotting Distance (Flame Height)
NOM 2. Maximum Spotting Distance (Flame Duration)
NOM 3. Maximum Spotting Distance (Firebrand Lofting)
NOM 4. Maximum Spotting Distance (Maximum Spotting Distance)
Spotting Likelihood/Probability
Though tables for Probability of Ignition are provided in the Fuel Moisture section, they describe only the likelihood that an ember will ignite a fire in receptive fuels. Wildland Fire Decision Support System (WFDSS) spatial analyses integrate the potential frequency and distance for spotting fire behavior, but frequency information is hard to isolate.
Combining Maximum Spotting Distance with Probability of Ignition
Integrating Spotting Spread into Fire Growth Projections
FARSITE, FLAMMAP, and FSPro attempt to integrate the estimate of the number of embers and the distribution of distances they travel into the fire growth projection. Estimating maximum spotting distance from nomograms or BehavePlus only suggests an outer perimeter for spotting potential.
Isolating Spotting Spread Potential with FSPro
A suggested method for applying the WFDSS spotting models is to isolate the potential probability of spotting across significant barriers using FSPro analysis. FSPro is normally used to apply probabilities associated with windspeed and direction combined with day to day variability in fuel moisture scenarios. The MTT spotting spread model includes monte carlo probability assessments associated with embers lofted from crown fires.
Consider these adaptations to the FSPro Inputs:
 Assume a oneday analysis with forecasted ERC, Windspeed and direction favorable to spotting spread.
 Assume a number of fires (several hundred to several thousand) using the oneday scenario from above.
This method assumes that the scenario is favorable for torching and spotting behavior. Ensure that the analysis will produce at least passive crown fire. The number of fires assumed for the analysis will drive the variability in:
 Ember source location from user applied probabilities.
 Ember size and, therefore, distance.
Probability contours produced by the analysis reflect the locations for possible spotting and the relative probabilities for their occurrence. Tonja Opperman demonstrated this technique on the Chakina fire near McCarthy, Alaska in 2010. Output map is shown here.
Comparing Spotting Estimation Tools
Tonja Opperman, Fire Applications Specialist, Wildland Fire Management RD&A, assembled these tables based on contributions and discussions among many fire behavior researchers, programmers, and practitioners, including: Pat Andrews, Mark Finney, and Chuck McHugh at the Missoula Fire Lab; Brian Sorbel from the Alaska Region of the NPS; Mitch Burgard and Erin NoonanWright from the Wildland Fire Management RD&A; Stu Brittain with Systems for Environmental Management in Missoula; Joe Scott with Pyrologix in Missoula; and Rick Stratton from the Pacific Northwest Region of the USFS. Corrections can be forwarded to Tonja Opperman at tonja_opperman@firenet.gov.
Maximum Spotting Distance (NonSpatial)
System  Maximum Spotting Distance from Torching Trees Nomograms  BehavePlus v.5.0.5 

Inputs 


Spotting Process 


Outputs 


Assumptions & Limitations 


WFDSS Spotting Spread (Spatial)
In all geospatial systems, embers are only generated from passive and active crown fires, not from surface fires, fire whirls, burning piles, or structures. Spotting can be turned off or set to zero in all tools.
System 
Short Term Fire Behavior (STFB) FLAMMAP MTT similar 
Near Term Fire Behavior (NTFB) FARSITE similar 
Fire Spread Probability (FSPro) 

Inputs 



Spotting Process 



Outputs 



Limitations & Assumptions 


