Wildland fire behavior chapter 4

Torching

Fire burning on the surface, but periodically igniting the crown of a single or small group of trees or shrubs before returning to the surface. Not as serious as a crown fire

Smoldering

Fire burning without flame and spreading very slowly

Three factors that control the development of the vertical dimension are

Fire intensity, stability of the air, and wind aloft ( strong upper-level wind tend to limit the vertical development of a fire)

Backing

Fire moving away from the head down hill or against the wind

Running

Fire spreading rapidly with a well-defined head

Crowning

Fire that advances across tops of trees or shrubs more or less independent of surface fire. High fire intensity and high for rate of speed

Flames of 4 to 8 feet mean what

Fire too intense . The use of bulldozers, engines and retardant drops can be used

Fine fuels are usually the carrier of what

Fire, even in timber

Flame length less than 4 feet means what

Fires can't be attacked at the head or flanks using hand tools Handlines should hold fire

The larger attend our fields are less reactive to what

Relative humidity, but they can be tested by bending them

What are crown fires

They begin as an individual torching tree or bush if conditions are right the torching fuels will cause other trees a torch

Blowup

Sudden increase in fire intensity our rate of speed significant to preclude direct control or to upset existing suppression plans.

The weather related factors that influence fire behavior are

Temperature, relative humidity, atmospheric stability, wind speed and direction, and precipitation

Fuel moisture and temperature

The most important fuel components

The intensity of a fire increases what else will Increase

The rate at which the fuel is preheated

The probability of spotting is directly related to the intensity of what

The surface fire, burning conditions, overstory species, and crown spacing

Active crown fire

This fire is dependent on the surface fire, but there is much more transfer of heat from one bringing crown to the unburned grounds of other trees.

Flames of 8 to 11 feet mean what

Torching, crowning and spotting major fire runs. Control efforts at the head will probably be ineffective

When does a wind fire become a plume fire

When the energy released by the fire takes the convective column to such Heights that it's force becomes greater then the wind.

What three factors influence direction of fire

Wind, slope, condition of fuel

A relative humidity of 25% or less will allow fine feels to burn what

With considerable intensity

Crown level winds

of 20 miles per hour or more will permit and sustain convective and radiant heat transfer

Spotting occurs when

Burning material is carried ahead of the fire and deposited and unburned material.

The windspeed at 15 mph will

Have considerable movement in the brush and timber, and dust will be stirred up

Spotting

Sparks or embers produced by the main fire and carried by when our conviction columns across the control line

Short range spoting

Spotting that can be over ran by the existing fire

The windspeed at 10 mph will cause trees to

Standing single trees to sway from side to side

Plume driven fires

Sudden increase in Intensity Spotting occurs in all areas, The direction of spread is difficult to determine Downdraft should be a concern

Spotting in wind driven fires is

Downwind, and is a major contributer to its spread

Crown fires

Fastest spreading of all fires. Moves about 5mph or more

Creeping

Fire burning was low flame and spreading slowly

Indrafts winds

Are winds that move in to replace heated air that is lifted by the convective action of the fire. Provide oxygen to fire. It's a circle, increase in wind, increases the intensity of the fire, which in turn increases the wind

A vertical fire with the fire intensity being hot what happens

As the hot air rises cooler air from the surrounding areas will be drawn inward toward the fire to fill the void. These in drafts can actually found the fire increasing the intensity even more. Which in turn can cause it's own environment i.e. thunderclouds with lightning and strong winds.

0400 to 0800 hrs is that time of day when a fire can be when

Be easily controlled

Fine fuels moisture changes

Constantly and quickly,

What factors cause firebrands to be lifted and ignite a spot fire.

Convective lifting(the hotter the fire the higher the lift) Wind Fuel bed (where they land, High fuel) environmental conditions(moisture, slope, wind)

Flames Over 11 feet mean

Crowning, spotting and major fire runs are probable, Control at head ineffective

The Topographic factors that contribute to fire behavior are

Elevation, position on the slope, aspect, shape of the terrain, most important is steepness of slope

At 1800 to 0400 hrs factors are

Favorable

Fire intensity is affected by what four factors

Feel loading, compactness our arrangement of fuels, fuel moisture content, slope and wind speed

The fuel components that affect fire behavior are

Feel loading, size and shape of the fuel, compactness, horizontal and vertical continuity,chemical content, fuel moisture, Fuel temperature

What six factors influence the fire rate of spread and burn pattern

Fire intensity, wind speed, slope, feel type changes, natural or man-made barriers that stop or slow spread, and spotting

In the Beauford scale to estimate the windspeed a 5 mph wind will cause what

The leaves of a tree to flutter and move

Indrafts winds usually drop off just before what

The downdraft hits

Continuous fine fuels provide the potential for what

Rapid rates of spread

Long range spotting

Causes it's own fire

The vertical dimension should be considered when

When I fire develops and size or intensity

Wind driven fires

usually large and know what direction they are. The wind drives the heat to the unburned areas. A crown fire is very likely. Fast, long range spotting, direction is predictable, attack fire from flank, wind shifts are a concern

What are large dead fuels usually called

1000 hour fuels

What percentage will 1000 hour fuels burn

20%

Ten-hour feels with a few moisture content below what percentage are indicators of dry conditions

7%

What are the seven factors that constitute the fire environment

Fuel characteristics, fuel moisture, fuel temperature, topography, atmospheric stability, wind, fire behavior.

Where do crown fires occurs

Heavy timber fuels, canopies of tall shrubs, brush, plantations

At 1000 to 1800 hrs fire intensity is at its

Highest

Fast-moving clouds indicate what

Highwinds and may be signaling a Windshift. Be alert if the clouds are moving in a direction different from the surface winds.

Spot fires my hide and smolder for

Hours or days

Fuel moisture determines

If fuels Will be available to burn

Wind and convection are a problem. In the northern hemisphere what happens

In the northern hemisphere there is normally a counterclockwise movement of air as it rises. This means that there will be a higher percentage of spot fires on the left side of the fires head

1000 hour fuels are usually where there is considerable snowfall these feels big into influenced by her behavior when

In the summer after they have had time to dry out, if there's a drought, or there was an early spring

Oh 600 to 1000 hours fire in Intensity begins to

Increase making fire control more difficult

What four ways can spotting occur

Popping, convection, winds, gravity. Convective heating is the biggest problem dropping some distance

Crown spacing

Is 20 feet or less will permit convection and radiant heat transfer to occur at a level of intensity they can maintain a fire spread.

Passive crown fire

Is usually confined to one tree or a small group of trees

Independent crown fire

It is not dependent on the surface fire for its energy. This fire is developed in the crowns as the fire moves from one ground to another

For a crown fire to sustain its run it needs 6 factors

Low fuel moisture, relatively close crown spacing, intense surface fire, strong winds and steep slopes, ability to spot ahead

Downdraft occure

Occurs below the convective column. When heated air is lifted, cooled in the upper atmosphere, then back to the surface. Wind is spread everywhere.

Area ignition

Occurs when hundred of spot fires start influencing each other, and an area explodes in fire

What are the three progressive stages that crown fires developing

Passive, active, and independent