S-130 Weather Observation 4 — Questions and Answers
Question 1: What is a 'Red Flag Warning' and what conditions typically trigger it?
- A warning issued when a fire exceeds 100 acres
- A National Weather Service alert for critical fire weather combining low humidity, high winds, and dry fuels (Correct answer)
- A local fire agency alert for high public use of recreational areas
- A warning specific to prescribed burn operations only
Correct answer: A National Weather Service alert for critical fire weather combining low humidity, high winds, and dry fuels
Red Flag Warnings are issued by the National Weather Service when a combination of low relative humidity, strong winds, and dry fuels create extreme fire danger.
Question 2: Which topographic feature causes a 'saddle' or 'notch' effect that dramatically accelerates wind speed through it?
- A broad ridge top
- A col or gap between two peaks (Correct answer)
- A wide valley floor
- A convex slope
Correct answer: A col or gap between two peaks
Cols, saddles, and notches between terrain features act as funnels that compress and accelerate wind, creating locally extreme and dangerous conditions for firefighters.
Question 3: A fire weather forecast states 'winds become erratic after 1400.' What should incident commanders do with this information?
- Plan to increase suppression activity after 1400 to take advantage of wind
- Ensure all crews are in safe zones or have escape routes identified before 1400 (Correct answer)
- Wait until erratic winds begin before repositioning crews
- Request the weather forecast be revised because erratic winds are unpredictable
Correct answer: Ensure all crews are in safe zones or have escape routes identified before 1400
Predicted erratic winds are a critical trigger: all crews must be in defensible positions with clear escape routes before the forecasted time.
Question 4: What is meant by 'fuel moisture recovery' during nighttime hours?
- The process of airdropping water on fuels overnight
- The reabsorption of atmospheric moisture by dead fuels as temperature drops and humidity rises at night (Correct answer)
- The rate at which heavy fuels dry after rain
- Prescribed burning done at night when fuels are safer
Correct answer: The reabsorption of atmospheric moisture by dead fuels as temperature drops and humidity rises at night
Overnight, dropping temperatures and rising relative humidity allow dead fine fuels to absorb moisture from the air, temporarily reducing their flammability.
Question 5: What does the acronym 'RAWS' stand for in the context of fire weather data collection?
- Remote Automated Weather Station (Correct answer)
- Regional Air Weather Survey
- Rapid Assessment of Wind Speed
- Resource and Weather System
Correct answer: Remote Automated Weather Station
RAWS (Remote Automated Weather Stations) are unmanned weather monitoring stations that continuously collect and transmit fire-weather data from remote locations.
Question 6: How does a Foehn wind (or its North American equivalent, the Chinook) affect fire danger?
- It brings moist maritime air that reduces fire danger
- It is a warm, dry downslope wind that rapidly dries fuels and increases fire danger (Correct answer)
- It is a cold polar wind that lowers temperatures and suppresses fire activity
- It creates stable conditions with no significant wind shift hazard
Correct answer: It is a warm, dry downslope wind that rapidly dries fuels and increases fire danger
Foehn/Chinook winds descend and compress on the lee side of mountains, warming and drying dramatically, which can critically lower fuel moisture and drive extreme fire behavior.
Question 7: When observing smoke column behavior, what does a smoke column that leans and then 'mushrooms' at a low level indicate?
- A strong, stable fire with good upward convective column
- An inversion layer capping the convection at a low altitude, indicating atmospheric stability (Correct answer)
- Very high fire intensity with spotting risk
- A cold front approaching from the west
Correct answer: An inversion layer capping the convection at a low altitude, indicating atmospheric stability
Smoke that rises then spreads laterally at a low level is hitting a temperature inversion, indicating atmospheric stability and reduced convective column strength.
S-130 Weather Observation 4
What is a 'Red Flag Warning' and what conditions typically trigger it?