Weather disasters

Blizzards

A blizzard is a severe winter storm condition characterized by low temperatures, strong winds, and heavy blowing snow. Blizzards are formed when a high pressure system, also known as a ridge, interacts with a low pressure system.

According to Environment Canada, a winter storm must have winds of 40 km/h or more, have snow or blowing snow, visibility less than 500 ft, a wind chill of less than −25 °C, and that all of these conditions must last for 4 hours or more before the storm can be properly called a blizzard.

Like all severe weather events, blizzards can be disruptive to local economies. In cities that do not have snow removal equipment, traffic and commerce can be brought to a stand still for days, and in some cases weeks. The economic impact ranges across industries, from lost productivity in companies because people cannot get to work, parents must stay home with children due to school closings, airport closures, product delivery delays and the actual cost of snow removal.

Cyclones

Cyclone, tropical cyclone, hurricane, and typhoon are different names for the same phenomenon of a cyclonic storm system that forms over the oceans.

A cyclone refers to an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Large-scale cyclonic circulations are almost always centred on areas of low atmospheric pressure. Warm-core cyclones such as tropical cyclones, lie within a smaller scale. Subtropical cyclones are of intermediate size. Cyclones have also been seen on other planets outside of the Earth, such as Mars and Neptune.

Droughts

A drought is an extended period of months or years when a region has a deficiency in its water supply. It can have a substantial impact on the agriculture of the affected region. Although droughts can persist for several years, even a short, intense drought can cause significant damage and harm the local economy.

Generally, rainfall is related to the amount of water vapor in the atmosphere, combined with the upward forcing of the air mass containing that water vapor. If either of these are reduced,the result is a drought. Periods of drought can have significant environmental, agricultural, health, economic and social consequences. The effect varies according to vulnerability. For example, farmers are more likely to migrate during drought because they do not have alternative food sources.

Some effects of drought are:

• Diminished crop growth or yield productions and carrying capacity for livestock
  
• Dust storms, when drought hits an area suffering from desertification and erosion
• Famine due to lack of water
  
• Habitat damage, affecting both terrestrial and aquatic wildlife
  
• Reduced electricity production due to insufficient available coolant for power stations and reduced water flow through hydroelectric dams
  
• Shortages of water for industrial users
  
• Snakes migration and increases in snakebites
  
• Social unrest
  
• War over natural resources, including water and food
  
• Wildfires, such as Australian bushfires, are more common during times of drought

As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases.

Tornados

A tornado is a violent, dangerous, rotating column of air which is in contact with the surface of the earth. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust.

A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds and rapid rotation usually causes water vapor in the air to become visible as a funnel cloud or condensation funnel.

There are different types of tornado. Here is a list of types and brief descriptions:

• A multiple vortex tornado: is a type of tornado in which two or more columns of spinning air rotate around a common center.
  
• A satellite tornado: is a term for a weaker tornado which forms very near a large, strong tornado.
  
• A waterspout: is defined simply as a tornado over water.
  
• A landspout: is a tornado which the name stems from their characterization as essentially a "waterspout on land".
  
• A dust devil: resembles a tornado in that it is a vertical swirling column of air.
  
• A fire whirl: tornado-like circulations occasionally occur near large, intense wildfires
  
• A steam devil: is a term describing a rotating updraft that involves steam or smoke.
  

Most tornadoes take on the appearance of a narrow funnel, a few hundred yards (a few hundred meters) across, with a small cloud of debris near the ground. There is an extremely wide range of tornado sizes, even for typical tornadoes. Weak tornadoes, can be exceedingly narrow, sometimes only a few feet across. On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. Tornadoes can have a wide range of colors, depending on the environment in which they form. Those which form in a dry environment can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels which pick up little or no debris can be gray to white. While traveling over a body of water as a waterspout, they can turn very white or even blue. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning brilliantly white.