Alignment of Forces

A simple way to view the fire ground and to explain how the fire will change in intensity.

A segment of a wildland fire will gain intensity and speed where it finds a time or place of more favorable alignment. To communicate this change say; “The fire is going into better alignment with —” (naming the force of change.)

There are three primary causative forces present which influence the variations in intensity and rate of spread of a wildland fire. As the fire burns over the topography, the forces change independently. Each force can aid or retard the spread. The forces can work together or cancel each others effects out. The three forces usually associated with fire behavior are Weather, Topography and Fuel, AKA the fire triangle.

There are many ways to interpret information about weather, topography and fuel and this can make a fire behavior prediction complex. How can it be made simple? The CPS isolates causative elements that change fire intensities. This reduces the data that needs to be considered to make predictions of change. The primary forces that cause wildland fires to change are wind, slope, and fuel temperature variations. Observations of how these forces vary in the path of the fire are the first step in predicting changes in the fire behavior potential. A very good rule to start with is to fight fire where it is out of alignment.



A device that uses candles to demonstrate the phenomenon of how extreme fire behavior can occur. This candle board demonstrates the variability of fire intensity while all factors are the same except the arrangement of fire on the board. A line of fire has one signature flame length while a zone of fire has another. The difference is caused by the preheating differences each arrangement produces. The flame length of the line of fire can be induced to factors of ten. Watch out for sprinklers in the room when demonstrating this effect.

The idea is to understand that how fire is arranged makes a vast difference in the production of flame. The next step is to be able to foresee it happening on the fireground and to move out of the way.

Following that, it paves the way to understanding how to manage intensities and the amount of fuel consumption on prescribed burning operations to the maximum degree.


Fire Behavior Information

Variations of wind, slope, solar heating of fuels ( fuel temperature) are fire behavior information. The variations in these forces are the direct cause of fire behavior change. These variations are observable.

Fire behavior information excludes generalizations made to express conditions in the area of the fire such as air temperature, relative humidity, fuel moisture content, live fuel moisture content, and wind speed at 20 feet.

In order to make predictions of fire intensity change and to determine when and where they might occur certain select information is relevant. Identifying the kind of information needed for that task is important to enable proper focus. Fire behavior information reduces the amount of data commonly associated with fire behavior prediction. It simplifies prediction by using the fewest number of inputs that are actually causing fire speed and intensity variations on a particular segment of the fire.

The intensities and rates of spread observed on a free burning fire adequately describe the affects the fire danger is having on the fire. To be able to predict a place or time of fire intensity change, the observer must identify what is different ahead of the fire.

When conditions are such that only part of the fire behavior variable can be dealt with successfully, the fire officer needs to determine the fire’s weak spots and attack the fire at those points. The tactician can accomplish this using only the fire behavior information.


Fire Behavior Tactics Statement

A statement that directs resources on a segment of a fire. Used each time incoming resources report they are “on scene”.

Assignments to engage a wildland fire and accomplish a control objective should be thoughtfully planned. If all you hear is the order to engage the fire the plan may not thought out. If the officer cannot explain how the tactic selection was decided then the officer may not know the risks. It should be imperative to implement a tactic that is viable under the fire behavior condition. In order for the engaging fire officer to know the plan is well thought out the commanding officer must communicate the logic before the order to engage the fire.

The tactic needs to have a basis of logic and contain the cause of fire intensity change or contain the basis for the logic that the fire will not change for the duration of the engagement. The CPS language gives the supervisor the ability to communicate the logic behind the tactic that is selected.

After a size-up is made instructions must be given to firefighters who arrive on scene. The CPS teaches how to communicate the whole situation that exists, the potential for change and the tactic selected. The following is an example of a complete fire behavior tactics statement. This is not a report on conditions and a request for additional resources.

A complete statement includes:

A description of the fire scene which includes the type of fire, the segment of the fire on the topography and how it is aligned with the forces of slope, wind and preheat as well as when and where it may change.

An example:

“This fire is a topography fire. The fire is running up slope in hot fuel, aligned with the wind and is generating 40 foot flame lengths which is beyond our threshold of control. The fire is going over the ridge and will be out of alignment with wind, slope and in cool fuel within the hour and it will then be within our capabilities. Use your resources to attack the fire directly where and when it goes out of alignment.”


Fire Danger Information

Information that is useful in planning but not so useful in fire behavior predictions.

Fire danger information is useful in anticipating resource needs because it is an indicator of the difficulty of control of a wildland fire. The values of the air mass and the fuel moisture content are fire danger information. The values are combined in a formula and when calculated, result in a point on a scale of fire danger from low to extreme. The fire intensity variances become greater as fire danger increases. The fluctuations in the air temperature, relative humidity, fine fuel and 10 hour fuel stick moisture content are generalized to represent the conditions in the area of the fire. Micro climate variations in these values are not usually measured and are not easily observed.

The CPS does not use this data to make predictions of fire intensity change. Fire danger numbers nor the ingredients which are air temperature and humidity to name my favorites, do not explain the variations going on at a single point in time on a fire perimeter because they are one value and are not meant to describe the degree of variation occurring under any fire danger condition.


Fire Ground Logic

Logic to explain the basis of opinions.

Fire Ground Logic includes valuable input in solving tactical problems while intuition rejects disagreement. The primary issue is to realize that it is changes in the fire’s rate of spread or intensity that makes a fire dangerous.

There are two ways used to deal with the fire changing.

  • One is to post a lookout and react to the change. This is the primeval, tried and failed method, thought to provide sufficient margins of safety by many at all levels in the fire service. Much is made of posting a lookout and little of what the lookout is to do except to warn when something happens.
  • The second way to deal with the fire changing and becoming dangerous is to design the engagement tactic from the knowledge of fire behavior potential. When the potential reaches a danger threshold the engagement is stopped and firefighter evacuation is accomplished. This gets the troops out of the way in time but may look bad if the fire doesn’t make the run. Nevertheless, this is the only way that some of the burnover accidents could have been avoided.

Logical use of basic causative information (fire behavior information) enables one to predict differences in fire intensity by matching observed fire behavior and the alignment of forces to the alignment of forces on the ground in the fire’s path.

The intensity observed in various alignments is predictably what will reoccur when the fireground and fire are in similar alignments. Forecast weather changes may or may not be significant and can be included or rejected as useful information for prediction of changes.


Suddenly a spotfire is detected. Take action or make predictions? Will there be another spotfire? Which way is the condition going? Let us say the spotfire came from a fire burning on an east aspect and it spotted to a west aspect at 1600 hours. Compared to the fire intensity on the east aspect, will the fire behavior be worse or easier? Will there be more spotfires?

The tactics should be determined from the answer. The tactics should be defensive in this case. The tactical communication should include the reasoning behind the opinion.


Fire Prediction Map

A display of fire behavior variation potential used for briefing the fire overhead personnel.

The base map is the standard contour map that shows the fire perimeter. If the map includes the fire spread history that is better yet. Add the wind direction to the map to display the force and direction of the wind. Add the hot aspect for the afternoon layer to the map coloring the South, West and Flats with the Yellowometer.

The map now shows the alignment of forces for the afternoon, the most dangerous period for extreme fire behavior. Identify the alignments when past runs occurred. Identify where the fire edge will go into alignment on the next work shift and draw an arrow where the forces are aligned. This is a track for another potential fire run. This will be the basis for setting the time tag tactic.

Describe the potential and review the tactical deployment of the suppression force to assure no one is in front of the potential run during the time period forecast for the run.

You may recall the video made of the Butte Fire burnover when 73 firefighters were forced to deploy fire shelters. This entrapment was due to a poorly devised tactical plan assuming burnout could widen a line in timber by firing it out of alignment during the time the fire would have the advantage of full alignment and that the safety areas would be outside the fire’s environment and be safe.

The location of the fire perimeter must be known and accurately depicted on the map. The aerial GPS system is the technology that assures fireline locations are accurate.

This CPS prediction map has been used on a number of large complex fires and has had great acceptance by planning and line personnel.


Forces of Wind, Slope, and Preheat

Fire that is moving across the variations of topography will change speed and direction as dictated by the combination of steepness of slope, wind speed and direction, and fuel preheat/flammability. Predictions of fire behavior changes can be made by observing the alignment and strength of these forces in the fire’s path. Where the forces are more aligned, the fire intensity will increase. Where the forces are less agreeably aligned, the fire intensity will decrease.



AKA, an Infrared Thermometer. An electronic sensor which scans the difference in temperature between solar heated fuel and shaded fuel.

This tool is used to gather data in order to make fire behavior predictions. When the fuel temperature is above 120 degrees f. sagebrush will burn when the humidity is above 70% and air temperature is below 65 degrees f. How can that be? It was proven on the 1996 Sexton II prescribed burn by Ventura County Fire Department.

Yogi Berra put it this way, “They said it couldn’t be done, but that doesn’t always work.”



Wonderful to have but a poor command tool for firefighting. Differences in intuitive based opinions between people are often not resolved. The ranking officer’s intuition directs the operation.

The division Chief, the crew supervisor as well as some members of the crew may disagree on tactics. Who is right? Is it important to act on the opinion of who is right? Why are they right?

Ranking officers are not privileged to superior knowledge, intelligence nor experience in situations. The ranking officer may not act on the opinion of a lower ranking officer even though the persons intuition may be more correct for the situation. Many crew supervisors have more experience than do the commanding officer in the situation that may be facing them. Intuition is the direct perception of information independent of any reasoning process, an untaught predictive skill. Differences in intuitive opinions between people can not be resolved except by the use of rank. Rank is responsible and accountable for the decisions made. The ranking officer will not usually use a lower ranked individual’s opinion without giving up command.


“Going Up” or “Going Down” the Curve

A phrase which identifies the time period of peak fuel flammability on various aspects. Where is the fuel on the flammability curve? Fuel flammability is greater as it’s temperature rises. Sunlit fuel temperature can increase 80 degrees above shaded fuels. Each aspect has a peak heating period as well as a time of warming and a time of cooling. As the fuel on these aspects is warming, it is said to be going up the flammability curve. As the fuel is getting less sun and cooling with time, the fuel is going down the flammability curve. This phrase facilitates communication of the reason for the situation getting worse or easier.

Another good rule to observe is not to have unburned fuel between you and the fire during the peak hours of the aspect’s flammability curve. One exception is a north aspect. Many have paid the highest price for ignoring that basic safety rule.


Hot Fuel or Cold Fuel

A phrase which tells of potential changes in the fire’s intensity caused by the fire entering a fuel bed with a higher or lower fuel temperature than the one it is presently in. Fuel temperature is much more variable than air temperature and it is the fuel’s temperature that determines its moisture content and flammability.

Even though the air temperature and relative humidity are at a stable point over the fuel bed, the fuel bed can be highly variable in surface temperature and therefore highly variable in flammability.

Fuel in daylight hours is constantly changing from cool to hot and back to cool. You should know which way it is going. Describe the sunlit fuel as hot fuel and describe the shaded fuel as cold fuel.

Sunlit fuel is often heated to 180 degrees by solar radiation and becomes many times more flammable than cool, shaded fuels. Fuel beds subject to the solar heating variations are not a stable element. They are a highly variable element in the fire triangle. Air temperature and relative humidity readings do not reveal this variation of fuel temperature. Air temperature and relative humidity are merely a reaction to surface heating conditions and not a cause of variation of fuel flammability.

When a part of a fire is headed toward hot fuel, where it has greater potential, explain; the fire is headed toward hot fuel, and make the prediction, “it’s going to get worse.”


Opportunity Tactics or Fire Behavior Tactics

Two tactics used on wildland fires.

Opportunity tactics are tactics based upon the opportunity to engage the fire. Opportunity tactics are acceptable tactics when the fire behavior is not a factor in the fireground situation. Whenever the fire is changing, the tactics need to recognize and be based upon the fire behavior in order to be safe and effective. A drill proficient fire officer can do opportunity tactics very well.

Fire behavior tactics are tactics determined from the observations made of the fire behavior — how to engage the fire is more dependent upon prediction of when and where there are variations in the fire. Only an experienced fire officer can implement fire behavior tactics. The CPS is designed to teach this skill to shorten the learning curve.


Situation is Either Getting Easier or Getting Worse

Learn how to make this key phrase prediction before determining the tactic to employ.

Firefighting safety depends on knowing and communicating this simple prediction of the fire’s potential. It is the middle portion of a complete size-up statement.

“The fire is going into alignment, it is getting worse, we need to adjust the tactics to match the condition.”

This simple prediction puts you mentally ahead of the dangers of fire intensity changes. Acting on this prediction is far safer than reacting after the fire intensity changes.

The most basic question to ask is, which way is the fire behavior going, is it getting worse or easier with time? If this question isn’t answered, actions cannot be based on expected fire behavior, which is one of the 10 standard orders.



A tool that uses a shadow as an indicator much like a sundial, to indicate the time period each aspect which is heating.

It comes in two sizes, large, for teaching and use in the base camp and a small pocket size model for use on the fireline.

With this small tool you can amaze your friends with your predictive capability on the fireline. When the shadow points to the compass direction that aspect is at the peak of the flammability curve. That is not the only way to identify hot aspects but it is a visual aid.


Signature Predictors

There are four (4) types of fires that have different causes for the observed fire signature.  Wind driven, where the dominate force is wind; fuels fires where the dominate cause of the behavior is the available fuel; fire on fire where the fire and the radiation output becomes the dominate force causing the behavior and the topography fire.  The alignment signature is derived from the fire intensity and rate of spread due to the various alignments of wind, slope and solar preheating, fuel flammability level for topography fires.

These signatures are used in predicting fire behavior in the path of the fire. The logic is that the fire behavior will replicate when the cause of the past behavior is understood, and the fire is approaching the same alignment of wind, slope and pre-heat values.  The accuracy need only be the threshold of control level and not rate-of-spread or flame length.

The predictions can be displayed on maps for strategy and tactical uses.


Time Tagged Tactics

A phrase which predicts the time period during which a tactic becomes potentially dangerous and must be altered.

Using CPS it is possible to predict when and where a fire behavior event will be most likely to occur, when and where the fire will gain full alignment of forces. This occurred on the Dillon Incident on the 13th of August in 1994, refer to page 120. The indirect holding and firing tactic was time tagged to halt at 1100 hours. The firefighters were moved off the line before the fire made a high intensity run from below. This becomes an example of how to do it right.

Had this been done on many of the past fires, burnovers could have been avoided. Examples are the Griffith Park fire which critically burned 100 firefighters and killed 33, the Mann Gulch fire of 1949 which killed 14 firefighters, the Loop fire of 1966 which killed 13, the Spanish Ranch fire that killed four firefighters in 1979, the 1994 South Canyon fire that took 14 lives, the 1994 fatality Glenn Allen fire that burned over a small crew killing two, and the Calabasas fire of 1996 which injured 10 firefighters.


Types of Fires: Wind Driven, Fuels, Topography

Identify the fire’s type to alert people of the necessity to select an appropriate tactic.

There are certain tactics that seem to work better on one type of fire. Sometimes tactics become dangerous because the tactic was wrong for the type of fire at the outset. Another twist in the situation happens when a fire changes from one type to another in the middle of your shift and the tactic suddenly does not match the situation.

Each type fire has a matching tactic that is appropriate.

  • Tactics for wind driven fires are to anchor the heel and direct attack the flanks, avoiding frontal attack except for use of defensible space to protect structures.
  • Tactics for fuel driven fires too hot for direct attack are to go indirect, burning out the area.
  • Tactics for topography fires must consider the variations on the fire ground. These tactics must be based on reasoned prediction and change before the fire changes.

Another basic idea is to view time as an important factor on topography fires because of the aspect’s variation in solar heating. This variation caused by time change is where the time tag came from.

Tactical time tags should be considered when assigning crews to open line on all topography fires.


Threshold of Control

The level of fire intensity and rate of spread that is about to go into or beyond the firefighters capability to contain.


What is the Fire Telling You?

What it did yesterday may repeat today. What does the fire history tell you about the South Canyon fire on page 123? The fire burned for three days moving downhill, out of alignment. What can we make of that? It isn’t going out by itself. The fire will continue to burn while it is out of alignment even at night. What does that mean? The fire will continue to travel until it gains a position to come into alignment and then it will change its rate of spread and intensity for the worse.

The suppression effort failed to contain the fire while it is out of alignment. What does that mean? It means that the fire is resistant to present control efforts. None of what the fire told us is good news and reason would presume a “getting worse” situation.

The fire is moving while it is out of alignment and under-burning the oak brush. The tops of the under-burned brush are now cooked and dry much like frost killed Gamble Oak. The fuel is fire prepared and ready to re-burn.

The fire is located below the highly flammable canopy and is in alignment to burn the crowns. The fire crept out of alignment from July 2nd to July 6th backing down off a hilltop. When the fire made its first run July 6th, 1994 it re-burned a strip of oak canopy that was in full alignment. That run should have told us what the potential of the fire was while it was in full alignment. We should have understood the fire was in full alignment to burn overstory and was about to cross the canyon and get in position of full alignment to run the hot slopes to northeast. The fire behavior told enough about the potential for change from a creeping fire into an inferno to serve adequate warning for those with the observation skills to understand what the fire was telling us. Only by perceiving the fire behavior potential and altering the tactics before the fire went into alignment could this tragedy have been avoided.

Learn how to use what the fire is telling you to plan successful tactics. Is it starting to spot, torch or make small runs? Which way is the fire behavior going? Is it getting worse or easier? When the fire moves or the sun moves, you need to know which way fire behavior is going and adjust tactics to match the potential.



A big yellow highlighter used to delineate the variation in fuel flammability on a contour map. The map is called a hot slope map and the area of hot fuel by aspect and time is identified. Usually an afternoon hot slope map is used to identify the topography that is facing South, West and the flats, where there is higher solar preheating during the afternoon.


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