S-244 Field Observer & Fire Effects Monitor ENVIRONMENTAL OBSERVATIONS

LESSON 1 FIRE WEATHER & EXTREME ATMOSPHERIC CONDITIONS

Objectives  Demonstrate the ability to observe and document fire weather factors.  Demonstrate the ability to recognize and report atmospheric characteristics that influence critical fire behavior.

Tasks from FEMO/FOBS Taskbook 16. Monitor, obtain, and record weather data.  Identify, observe and record appropriate weather data such as mid-flame wind speed, wind direction, relative humidity and other characteristics that influence fire behavior. 20. Recognize and report atmospheric characteristics that influence fire behavior.  Fire whirls, their causes, and associated fire control problems.  Winds associated with thunderstorm cells and their effect on fire behavior.  Wind speed changes and direction shifts associated with cold front passage and the effects on fire behavior.  Other indications of an unstable atmosphere.

Observing Fire Weather Accurate weather observations improve spot weather forecasts, fire behavior predictions, and firefighter safety!

Fuel Conditions

Observing Fire Weather Time & Location:  At least every hour  In a representative location

Observing Fire Weather Unrepresentative Sites:  In the black  Too near the fire

Observing Fire Weather Wind Observations:  Eye-level wind speed measurement requires at least one full minute of sampling

Observing Fire Weather Temperature & Relative Humidity  Avoid direct sunlight during temperature and humidity observation

Observing Fire Weather Temperature & Relative Humidity  Swing the psychrometer until the wet bulb temperature stops decreasing

Observing Fire Weather Temperature & Relative Humidity  Calibrate electronic sensors against reliable instruments regularly

Observing Fire Weather Cloud Cover:  Estimate within 10%

Observing Fire Weather Canopy Cover:  Estimate within 10%

Observing Fire Weather Exposed or Shaded:  More or less than 50 percent?

Calculating:  Fine Dead Fuel Moisture (FDFM) and  Probability of Ignition (PIg) Observing Fire Weather

Gather information: Time? Month? Where’s the fire?  If the fire is BELOW you, use B  If the fire is ABOVE you, use A Observing Fire Weather

Step 1: Determine Reference Fuel Moisture Observing Fire Weather

Step 1: Determine Reference Fuel Moisture Observing Fire Weather 4

Step 2: Add Dead Fuel Moisture Correction Observing Fire Weather 3

Step 3: Calculating Probability of Ignition Observing Fire Weather 50

Ensure that you are proficient in observing the weather and calculating FDFM and PIg. Observing Fire Weather

Observing Fire Weather Record Keeping Double check:  Values in correct column  Obvious discrepancies

 Communicate observations with direction and magnitude of changes since last observation.  Immediately report weather conditions that could be hazardous. Observing Fire Weather

Indicators of Instability:  Good visibility  Gusty winds  Dust devils  Cumulus clouds  Castellatus clouds  Smoke rising straight up Extreme Atmospheric Conditions

Indicators of Stability:  Poor visibility  Steady winds  Stratus clouds  No defined smoke column Extreme Atmospheric Conditions

Inversions:  Strong indicator of a stable atmosphere  Breaking inversions signal a transition from stable to unstable conditions Extreme Atmospheric Conditions

Unstable Atmosphere Expect:  Increased fire behavior  Rapid growth  Vertical fire development Extreme Atmospheric Conditions

Thunderstorms Expect:  Lightning  Gusty turbulent winds

Extreme Atmospheric Conditions Cold Front Winds Expect:  Strong winds shifting direction clockwise.  Spotting

Extreme Atmospheric Conditions Fire Whirls Expect:  Unpredictable direction of spread  Tornado- strength winds  Increased spotting in all directions

Johnson Fire, 2002

 Accurate weather observations improve spot weather forecasts, fire behavior predications, and firefighter safety.  Document observations clearly; double-check for mistakes.  Immediately report: – Thunderstorm activity – Cold front wind shifts – Signs of increasing atmospheric instability Summary