Forest fires .. How do they start? And what is the role of the weather in its spread?!

2021-08-21 2021-08-21T08:53:55Z
رنا السيلاوي
رنا السيلاوي
محرر أخبار - قسم التواصل الاجتماعي

Weather of Arabia - Forest fires may ignite within seconds, spreading quickly and devouring dry plants and almost everything in their path, as forest fires can sweep thousands of hectares of surrounding land, threatening the homes and lives of many in the vicinity, even producing smaller fires by throwing Embers are miles away. In this article we'll look at wildfires, explore how they start, and how weather contributes to their spread.


Causes of fires

On a hot summer's day, when drought conditions are peaking, something as small as a spark from a train wheel hitting the track can start a wildfire. Sometimes, fires occur naturally for a variety of reasons, including the heat of the sun or lightning. However, the majority of wildfires are caused by human negligence.


Common human causes of wildfires include:

  • Deliberate or premeditated fire for sabotage purposes
  • Barbecue fires for picnics or camping trips
  • Throwing lit cigarette butts
  • Incorrectly burning debris
  • Playing with matches or fireworks
  • Make a fire for a purpose (such as getting rid of weeds)


How does a fire start?

Everything has a certain ignition point, the temperature at which wood ignites (300 degrees Celsius), when wood is heated to this temperature, it releases hydrocarbon gases that mix with oxygen in the air and ignite and create a fire.


There are three components necessary for ignition and combustion to occur, called the fire triangle, as fire requires:

  1. fuel to burn
  2. Air that supplies oxygen to combustion
  3. And a source of heat to raise the fuel to the point of ignition


Firefighters often talk about a fire triangle when they are trying to put out a fire. If they can remove any of the sides of the triangle (fuel, oxygen, or heat), then they can control the fire and eventually extinguish it.



Factors that determine how a fire spreads

After an ignition has occurred and a fire has started, there are several factors that determine how a fire will spread. These three factors include; Fuel, weather and terrain . Depending on these factors, a fire can quickly die out or turn into a raging fire that burns thousands of hectares.


The first factor: fuel for the fire (combustible substance)

Forest fires spread depending on the type and amount of fuel surrounding them. Fuels can include everything from trees, plants, and dry grass fields to homes. Here are the basic fuel properties that determine how it affects a fire:


  • Material size and shape: A small amount of fuel causes a fire to start and spread slowly and with a low intensity. If there is a lot of fuel, the fire will burn more intensely, causing it to spread faster.

Small materials such as: dry grass, pine needles, dry leaves, dead branches, etc., burn faster than large tree trunks and broad branches.


  • Moisture content: The dryness of materials can also affect the behavior of fire, when materials are dry they heat up faster and ignite faster, resulting in a fire that is difficult to contain. As the fire progresses, it dries out the materials around it directly, as heat and smoke cause the fuel's moisture to evaporate.


  • Distribution of materials: Spaced materials dry faster than closely spaced materials, and trees and plants close together retain more moisture, as moisture absorbs the heat of a fire.


The second factor: the role of weather

Weather plays a major role in the birth, growth and death of wildfires, with drought leading to very favorable conditions for wildfires, and winds helping to advance wildfires.


Weather can stimulate fire to move faster and swallow more land. It can also make the task of fighting a fire more difficult.


There are three components of weather that can affect wildfires:


1. Temperature: Temperature affects the outbreak of forest fires, because heat is one of the three corners of the fire triangle that we mentioned earlier. The remains of trees and plants on the ground receive heat from the sun, which heats and dries materials. Warmer temperatures allow the fuel to ignite and burn faster, increasing the rate of wildfires. For this reason, wildfires tend to flare up in the afternoon, when temperatures are at their highest.


2. Winds: Winds have perhaps the greatest influence on the behavior of wildfires, and are also the most unpredictable factor. Wind supplies the fire with additional oxygen, drying the materials further and pushing the fire across the earth at a faster rate.


Winds not only affect how a fire starts, but the fires themselves can develop their own wind and weather patterns. Large, violent wildfires can generate winds called fire whirlpools. Fire whirlpools, which resemble tornadoes, are caused by the heat of a fire, and fire whirlpools are known to hurl flaming tree trunks and burning debris into great distances.


The stronger the wind blew, the faster the fire spread. The fire generates its own wind ten times faster than the surrounding wind, and it can even throw embers into the air and create additional fires. Winds can also change the direction of the fire, and storms can raise fires to trees, resulting in crown fires reaching even the tops of the trees.


3. Humidity: While wind helps spread fire, moisture works against fire. Moisture (in the form of dampness or precipitation), can slow a fire and reduce its intensity. Materials can be difficult to ignite if they contain high levels of moisture, because moisture absorbs the heat of a fire. When the humidity is low, which means there is little water vapor in the air, wildfires are more likely to start. The higher the humidity, the less likely the material will dry out and catch fire.


Since humidity can reduce the chances of wildfires breaking out, precipitation has a direct impact on fire prevention.


The third factor: the terrain


This article was written originally in Arabic and is translated using a 3rd party automated service. ArabiaWeather is not responsible for any grammatical errors whatsoever.
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