S-290 Final Exam

The 1 hour timelag fuel category is:

0.0 to 1/4 inch in diameter

The following statement best describes timelag fuel categories:

1 hour timelag fuels react to changes in RH mush faster than 100 hour fuels.

The five stages of vegetative development for live fuel moisture are:

300%, 200%, 100%, 50%, less 30%

Select the statement that best describes the effect of slope steepness on fuel availability.

A fire starting at the base of a slope has more fuel available for spread.

When stable air is forced over a mountain range, and then descends the leeward slopes as dry, warmed air, it is called:

A foehn wind

A ground fire has burned under a thick stand of pine reproduction. What potential problems could occur?

A return possibly involving the canopies.

A fuel model is defined as:

A set of tubers that define fuel input for use in the surface fire spread model.

Available fuels are:

All dead and live fuels that will ignite and continue to burn.

The criteria for determining a Red Flag Warning is a combination of high to extreme fire danger and a critical fire weather pattern such as:

All of the above Dry lightning Lightning following an extremely dry period Unusually low RH Very dry and unstable air

Which is an indicator of possible fire behavior problems?

All of the above Leaning, sheared, or well-developed smoke column Trees crowning Fire whirls beginning Frequent spot fires

Wild land fire behavior in the third dimension:

All of the above Presents a vertical dimension to fire suppression Exhibits crowning, spotting, and vortex phenomena. May affect the atmosphere near the fire.

What conditions will occur under a surface inversion during the morning hours?

All of the above Temperatures are cool, winds are calm or light Fire activity is decreased Pollutants can accumulate under inversions

What weather processes can and should be monitored visually?

All of the above Thunderstorm buildups Clouds Approaching cold fronts Indications of a stable or unstable air

Aspect affects fuels and their availability to burn because:

All of the above are correct Southwest slopes provide drier sites Vegetation type and fuel moisture content changes by aspect Shading on northern aspects can increase RH

Fireline intensity is dependent upon:

All of the above. Fuel size Fuel moisture Fuel temperature Fuel compactness and arrangement

En route to a fire you notice that smoke from a burning haystack rises straight up. What could this indicate on a wild land fire:

An unstable atmosphere may increase fire activity.

4 factors that are responsible for the occurrence of fire behavior in the third dimension are:

Available fuels, wind, low atmospheric moisture, and instability.

Why do dry climates usually have lower nighttime temperatures than humid climates?

Because there is less water vapor in the air to absorb and reflect heat back to the surface at night.

The least critical form of heat transfer that influences rate of spread in a running wild land fire is:

Conduction

A fire that advances through canopies of brush and trees is known as a:

Crown fire

Select the fuel complex that would reach it's moisture of extinction first during nighttime humidity recovery.

Cured cheatgrass

Initiate action based on ____ fire behavior.

Current and expected

Which of the following is an indicator of stable air?

Inversion

Fire which can generally be attacked at the head or flanks by persons using hand tools have flame lengths that are____.

Less that 4 feet

Which of the following fuel characteristics affect all 6 wild land fire behavior concerns; i.e. ignition, spread, intensity, spotting, torching, and crowning.

Moisture content

The fuel moisture at which fire will not spread is the:

Moisture of extinction

Three stages of crown fire development are:

Passive, active, and independent.

When the wild land fire environment is dominated by a ______ fire, the convection column overpowers the wind field.

Plume-dominated

The surface fire characteristics chart relates _____.

Rate of spread and flame length.

Local winds are best defined as:

Small scale convective winds of local origin caused by differences in heating and cooling.

S/U Clouds form in layers.

Stable

S/U Smoke column spreads out after limited rise.

Stable

When a cold front or thunderstorms are forecast in the vicinity of a fire, what is the most important information a security weather watch can provide?

Strong shifting winds

Foehn winds can adversely affect wild land fires because they can produce:

Strong winds, warmer temperatures, and very low RH.

Fire is burning in litter on top of the ground, but occasionally carries into the crowns of individual trees, which produces burning embers that start new fires outside the fire perimeter.

Surface fire with torching and spotting.

Fuel moisture content definition:

The amount of water in a fuel expressed as a percent of the oven dry weight of that fuel.

If the wet build is not read at it's lowest point, what will happen?

The calculated RH will be too high.

A wind is caused by:

The direction the wind is blowing from.

Wind direction is:

The direction the wind is blowing from.

Fuel loading definition:

The oven dry wight of fuel in an given area, expressed in tons/acre or pounds/acre.

Fuel chemical content definition:

The presence of volatile substances in a fuel.

Fuel moisture timelag can best be described as:

The rate at which dead fuel gains or loses moisture.

Select the correct statement regarding the shape of the country and it's effect on wild land fire behavior.

The shape of the country can influence the curing of fuels as well as the intensity and spread of wild land fires.

Fuel size and shape definition:

The surface-area-to-flume ratio.

T/F Crown fire development depends on crown flammability along with adequate surface-to-crown and crown-to-crown heat transfer.

True

T/F Dead grass reacts like a 1 hour timelag fuel.

True

T/F Effective windspeed is the mid flame windspeed increased for the effect of slope on fire spread.

True

T/F On average the RH doubles with each 20F decrease of temperature, or halves with each 20F increase in temperature.

True

T/F RH measures the amount of moisture in the air.

True

T/F Steep slopes, chutes, saddles, and narrow canyons are terrain indicators that should be monitored.

True

T/F The lowest RH occurs with the highest temperature.

True

T/F Topography can directly and indirectly affect fuels and their availability for combustion.

True

T/F Two requirements for long range spotting are wind and a well developed convection column.

True

T/F Unstable air can be formed by either heating the air near the ground or by cooling the air aloft.

True

T/F Unstable air can often be found in low pressure systems and on the leading edge of cold fronts.

True

T/F Vortices are grouped as vertical or horizontal depending on their axis of rotation.

True

S/U Clouds grow vertically

Unstable

S/U Firebrands are lifted into convection column.

Unstable

S/U Gusty winds

Unstable

A slope wind is caused by:

Warm air rising and cold air settling.

1 hour timelag fuel moisture is used in fire behavior calculations to determine:

Whether fine dead fuels are available for ignition and fire spread.

You are on a fire in the coast range of Southern California. The fire is burning above you on the slope. At 1800, you experience a sudden cal in the sea breeze. What might you next expect to occur next?

Wind may shift to downslope with possible foehn wind surfacing.

Inputs used to determine fine dead fuel moisture content are:

Time of day, month of year, dry bulb temperature, RH, aspect, percent slope, shading of surface fuels.

Of the three primary environmental factors that influence fire behavior, which is the least variable?

Topography

T/F The type of vegetation has little affect on temperature and humidity.

False

T/F Upward moving air contracts and warms.

False

What is the general effect of stable air on wild land fires?

Fire activity decreases

The factors that contribute to the spotting problem can be classified into three general areas:

Firebrand source, transportation, and the receiving fuel.

East, Mono, Santa Ana, and Chinook are all examples of:

Foehn winds

Spot weather forecasts are:

Forecasts that are issued to fit the time, topography, and weather of a specific location.

What are the different lighting processes that can lead to thunderstorm development?

Frontal, orographic, thermal, convergence

Probability of ignition is determined by:

Fuel shading, fine dead fuel moisture percent, and dry bulb temperature.

Slope affects fuel availability to burn because:

Fuels are preheated upslope through radiation and convection. Rolling firebrands ignite new fuels below.

Which fuel has the higher surface-area-to-volume ration?

Grass

T/F Bends in canyons are likely places for wind eddies to form.

True

The 4 fuel groups as defined in the Fire Behavior Prediction System are:

Grass, shrub, timer litter, and logging slash.

Fire begins burning into the crowns and spreads through the canopy. There is a sudden increase in fireline intensity where the fire controls it's environment. At one point flames can be seen carried high into the convection column with a whirling motion.

Ground fire with smoldering and flare ups.

The point to which a combustible material must be heated to produce self-sustaining combustion is known as the:

Ignition temperature

As air sinks, it.

Increases in pressure, warms and compresses.

The convection column form your fire has developed to several thousand feet as a result of intense burning. You notice the top of the column has been sheared off. What could happen next?

Expect moderate to long range spotting downwind. Strong winds aloft could surface on the fire.

Low RH and a high 1000 hour timelag fuel moisture are both critical fuel moisture indicators that should be monitored.

False

T/F Air flows clockwise around low pressure systems and counterclockwise around high pressure systems.

False

T/F Cloudiness has little affect on relative humidity and temperature.

False

T/F Continous fine fuels, heavy fuel loadings, ladder fuels, crown spacing, and special fuel situations are fuel characteristics that should NOT be monitored.

False

T/F Foehn winds always cause fuels to gain in moisture content.

False

T/F RH is usually lower on north aspects.

False

T/F Regardless of fine dead fuel moisture percentage, rate of spread is determined by the live fuel moisture.

False

T/F Strong surface winds, lenticular clouds, high fast moving clouds, approaching cold front, cumulonimbus development, and sudden calm or battling winds are all indicators of wind that are not of great concern to wild land firefighters.

False

T/F Temperature decreases with an increase in elevation when an inversion is present.

False