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Extreme Fire Behavior – II

 

Fire managers make decisions throughout the day on how to suppress fires and best use resources while protecting life and property. This Standard Firefighting Order depicts a firefighter observing increased fire behavior during a time of day when temperatures are high and relative humidity is low.

3. Base all actions on current and expected behavior of the fire. A firefighter looks at his watch, which reads 2 PM, while a fire actively grows in steep terrain and heavy timber.

3. Base all actions on current and expected behavior of the fire.

Read about all 10 Standard Firefighting Orders.

Changes in fire behavior are always present in incidences of shelter deployment. Firefighters need to maintain situation awareness of live and dead fuel moisture conditions, as well as predicted and current weather conditions. As fire behavior moves from mild to moderate to extreme, it is critical to respond correctly to the changing situation.

Discuss how the following factors can contribute or lead to extreme fire behavior:

  • Frost kill: late or unusually extensive freezes, high loading of frost-killed fuels.
  • Drought Conditions: Live Fuel Moistures Index, Keetch-Byram Drought Index (KBDI), Soil Moisture Index, low humidity, high temperatures.
  • Slope: increases fire spread uphill, preheats fuels by convection; may channel winds.
  • Sea Breeze/Foehn: wind direction may vary throughout the day; humidity changes may occur; strong wind velocities may drive fire behavior.

To aid situation awareness:

  • Track National Fire Danger Rating System (NFDRS) live and dead fuel moisture outputs.
  • Take hourly weather observations and track the hourly changes. By tracking fuel moisture and weather observations and using the Fire Severity Related to Fuel Moisture Chart, firefighters can be alerted to conditions leading to situations where there is a high potential for extreme fire behavior.

 

Category
Weather Fire Behavior
References
National Fire Danger Rating System Information
10 Standard Firefighting Orders, PMS 110
10 and 18 Poster, PMS 110-18
18 Watch Out Situations, PMS 118
Extreme Fire Behavior 1 6MFS Topic

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PMS 412 provides guidance for wildland fire investigations. This guide outlines recommended procedures, practices, techniques, and methods to promote a systematic approach. The last update to this publication was in 2016.

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NWCG Guide to Wildland Fire Origin and Cause Determination PMS 412

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Date: March 31, 2025
Questions?  Please contact:
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