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 'mixing height' and how does it influence fire behavior?
Answer: The altitude up to which the atmosphere is well-mixed, affecting convective column development and smoke transport
Mixing height defines how high convective air can rise; a low mixing height suppresses fire convection while a high mixing height allows strong fire columns and spotting.
Which factor best explains why fires in steep canyon terrain can suddenly 'blow up' in the afternoon?
Answer: Afternoon heating creates strong upslope winds that align with fire spread direction
Afternoon solar heating intensifies upslope (anabatic) winds in canyons, which can align with fire spread direction and cause rapid rate-of-spread increases.
What information is NOT typically required when requesting a spot weather forecast from the National Weather Service?
Answer: Names of firefighters on the incident
Spot weather forecast requests require topographic and environmental data; individual firefighter names are not part of the meteorological information needed.
A psychrometer is used to measure which weather variable critical to fire behavior?
Answer: Relative humidity and dew point
A psychrometer uses wet-bulb and dry-bulb thermometers to determine relative humidity and dew point, key variables for assessing fuel moisture and fire danger.
What is the significance of the 'critical fire weather pattern' involving an upper-level ridge of high pressure?
Answer: Upper ridges cause atmospheric subsidence, suppressing cloud formation and creating hot, dry, and increasingly windy conditions
An upper-level ridge produces subsidence that warms and dries air as it descends, suppresses cloud cover, allows intense solar heating, and can enhance surface winds — a classic critical fire weather pattern.
When calculating fire weather observations using the Fire Weather Index system, which parameter most directly reflects the dryness of fine fuels?
Answer: Fine Fuel Moisture Code (FFMC)
The Fine Fuel Moisture Code (FFMC) in the Fire Weather Index system reflects the moisture content of fast-drying fine fuels that respond to daily weather changes.
A weather observation notes 'temperature 95°F, relative humidity 8%, wind 25 mph gusting to 40 mph.' What action should a Division Supervisor take?
Answer: Immediately evaluate crew positioning, escape routes, and safety zones given extreme fire weather
The combination of high temperature, critically low humidity, and strong gusty winds represents extreme fire weather requiring immediate evaluation of crew safety positioning without delay.