Tornado

A tornado is a rotating column of air, extending from the base of a cumuliform cloud, and often visible as a condensation funnel in contact with the ground, and/or attendant circulating dust or debris at the ground (WMO, 2017).

The strength of a tornado can be estimated from the degree of damage caused using the Enhanced Fujita scale (Wind Science and Engineering Center, 2004; National Weather Service, no date).

Tornadoes kill fewer than 100 per year on average but they can be very destructive and cause huge economic losses. The United States is a major hotspot with about 1,000 tornadoes every year, causing 80 deaths and more than 1,500 injuries on average (National Geographic, 2019).

Owing to the unpredictable nature of tornados, protecting the public is focused on education and outreach which provide information on the tornado as a threat, how to identify a tornado and practical measures on how individuals can protect themselves, and how to find and watch warning systems that alert the public (CDC, 2020).

Since the advent of Doppler Radar, lead times for tornado warnings have increased from when a tornado first touches the ground to upwards of 14 to 20 minutes or more beforehand (WMO, 2017b; National Geographic, 2019).

Risk factors

  • Lack of early warning systems and preparedness programmes.
  • Even when warning systems are in place, the aged and children have higher mortality rates.
  • Populations living in mobile homes are at greater tornado risk. The rate of serious injury for mobile homes occupants is 85.1 per 1,000 compared to 3 per 1,000 for occupants in standard homes.

Vulnerable areas

  • The most tornado-prone areas in the world are in North America, in particular the Great Plains in the United States and south-central Canada.
  • Tornado Alley, a region that includes eastern South Dakota, Nebraska, Kansas, Oklahoma, northern Texas and eastern Colorado, is home to the most powerful and destructive of these storms.
  • The United States gets 75 per cent of all the world’s tornadoes, followed by Canada and Bangladesh.
  • Australia, New Zealand, South Africa, India, Argentina and the Russian Federation are also prone to strong tornadoes.
  • Communities living in poorly built houses close to potential flying objects are in particular danger. People outdoors when tornadoes occur are at higher risk of mortality.

The Enhanced Fujita Tornado Scale

The Fujita Scale is named for Dr TT (Ted) Fujita, who made the first systematic study of tornado forces; it was replaced by the Enhanced Fujita (EF) Scale in February 2007.

Risk reduction measures

  • Monitoring systems to observe thunderstorms with radar and receive reports on tornadoes.
  • A hazard map to identify risk and vulnerability.
  • A warning/communication system to alert people in the path of a tornado.
  • Underground shelters to protect people.
  • Avoiding mobile home settlements in risky zones.
  • Education and awareness about tornadoes, warnings and safe action.

Latest Tornado additions in the Knowledge Base

Cover
This study investigates how the inclusion and presentation of protective action guidance affects participant perceptions of a tornado warning message and their perceived ability to act upon the information (i.e., self- and response efficacy).
On May 22, 2011, a tornado rated as the most intense on the Enhanced Fujita (EF) Scale, an EF5, cut a 6-mile-long (9.7-kilometer) gash through the densely populated Joplin metro area, home to more than 50,000 people.
National Institute of Standards and Technology
In any windstorm, tornadoes included, the roof needs to be secured — this is due to the uplift, the same physics that allows an aircraft to fly.
Conversation Media Group, the

This report discusses losses from natural hazards are escalating dramatically, with more properties and critical infrastructure affected each year. Although the magnitude, intensity and/or frequency of certain hazards has increased, development

Rising temperatures and risky development contribute to heightened exposure to earthquakes, flooding, tornadoes, hurricanes and wildfire.
AGU Advancing Earth and Space Science
A series of maps developed by NIST indicates the wind speeds from tornadoes that certain buildings should be designed to withstand, in miles per hour.
National Institute of Standards and Technology
Ten years ago today - on April 27, 2011 - Alabama suffered the largest and costliest tornado outbreak in state history.
Advance Local

This paper proposes a methodology based on a multi-layer Monte Carlo simulation to model a two-stage recovery process for residential buildings: functional downtime due to delay and functional downtime due to repair. The delay portion of the model was

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