Fire Behavior & Weather Flashcards

What is the 'mixing height' in meteorology and how does it affect wildland fire smoke and fire behavior?

Answer: The height to which the atmosphere mixes vertically; a low mixing height traps smoke and limits convective column development

Mixing height is the depth of the atmosphere available for vertical mixing; low mixing heights trap smoke near the surface and suppress the convective column that drives fire behavior.

Which situation best illustrates the danger of a 'saddle' or 'notch' in terrain for firefighters?

Answer: Saddles act as chimneys that funnel and accelerate winds, causing fire to rapidly intensify and change direction

Saddles and notches concentrate and accelerate wind flow, acting like chimneys that can cause fire to explode in intensity and change direction rapidly, creating deadly traps for firefighters.

What does 'spotting distance' indicate in terms of wildland fire behavior, and what factors increase it?

Answer: The distance firebrands are carried ahead of the main fire front; increased by higher winds and taller flame heights

Spotting distance is how far embers are carried ahead of the fire front; it increases with wind speed, flame height, and atmospheric instability, creating the potential for new ignitions far from the main fire.

How does 'atmospheric instability' differ from 'atmospheric stability' in terms of wildland fire behavior?

Answer: Unstable air allows convective columns to develop and carry fire upward, while stable air suppresses vertical development and limits fire activity

Atmospheric instability allows air to rise freely, supporting tall convective columns that can produce erratic fire behavior and long-range spotting; stability suppresses vertical development and limits these phenomena.

What is the primary purpose of a 'Red Flag Warning' issued by the National Weather Service?

Answer: To alert fire agencies that critical fire weather conditions (high winds, low humidity, dry fuels) are imminent or occurring

A Red Flag Warning alerts fire agencies and the public that a combination of critical fire weather — typically high winds, low relative humidity, and dry fuels — creates conditions for extreme fire behavior.

In S-130 training, what is the significance of the 'point of origin' in understanding fire behavior?

Answer: Studying the point of origin helps investigators determine weather, fuel, and terrain conditions that allowed the fire to start and spread

Examining the point of origin reveals the fuel, weather, and terrain conditions present when the fire started, providing critical insight into initial fire behavior and how it may continue to develop.

Which combination of factors from the fire environment triad is most likely to produce extreme fire behavior requiring immediate crew withdrawal?

Answer: Dry cured fuels, unstable atmosphere, and strong aligned winds on steep south-facing slopes

Dry fuels, atmospheric instability, strong winds, and steep south-facing slopes reinforce each other across all three legs of the fire environment triad (fuels, weather, topography) to produce extreme fire behavior.