Weather Observation Flashcards
7 cards from real S-130 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Weather Observation flashcards as text
What is the relative humidity level generally considered critically low, significantly increasing fire danger in wildland firefighting?
Answer: Below 25%
Relative humidity below 25% is typically considered critically low, causing rapid drying of fine fuels and sharply increasing fire danger and spread rates.
A firefighter notes the wind direction has shifted 180 degrees and speed has increased. This is MOST likely associated with:
Answer: Passage of a frontal system
A sudden 180-degree wind shift combined with increasing speed is a classic indicator of frontal passage, which can cause extreme fire behavior.
What does the term 'fine fuel moisture content' refer to in fire weather observation?
Answer: The moisture percentage in 1-hour timelag fuels like grass and dead needles
Fine fuel moisture refers to the moisture content of small-diameter, fast-drying fuels such as grasses and dead needles that respond quickly to atmospheric changes.
Which cloud type is most associated with stable atmospheric conditions and generally lower fire danger from wind?
Answer: Stratus
Stratus clouds form in stable, layered air with little vertical mixing, indicating calm conditions less likely to produce erratic fire-driving winds.
How does increasing elevation generally affect temperature and relative humidity in mountainous fire environments?
Answer: Temperature decreases and humidity generally increases
As elevation increases, air temperature typically decreases at the environmental lapse rate while relative humidity tends to increase, affecting fuel drying rates.
What is the purpose of using a Kestrel weather meter or similar handheld device on a wildland fire?
Answer: To take on-site measurements of wind speed, temperature, humidity, and dew point
Handheld weather meters allow firefighters to take real-time, on-site measurements of critical weather variables to assess current and anticipated fire behavior.
What is the dew point temperature and why is it important in fire weather?
Answer: The temperature at which air becomes saturated and moisture condenses; low dew points mean dry air
Dew point is the temperature at which air reaches 100% relative humidity; a large spread between air temperature and dew point indicates very dry air and high fire danger.