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Based on Earth Science, Tarbuck and Lutegns Chapter 20:

Tornadoes are violent windstorms that take the form of a rotation column of air called a vortex.

The vortex extends downward from a cumulonimbus cloud.

Most tornadoes form in association with severe thunderstorms.

A mesocyclone is a vertical cylinder of rotating air that develops in the updraft of a thunderstorm.

fig. 20-18 Tarbuck Lutgens

fig. 20-18 Tarbuck Lutgens

From eSchoollToday

Supercell tornadoes – more powerful than those that do not come from supercells.

A supercell storm is a thunderstorm characterized by powerful updrafts.

Example of non-supercell tornadoes are ‘gustnadoes’ and ‘landspouts’.


tornado tipsStep 1: Like all winds and storms, tornadoes begin when the sun heats up the surface of the land. As the warm, less heavy air begins to rise, it meets the colder, heavier air above it.

Note that wind shears make it even easier to set them off. A wind shear is when two winds at different levels and speeds above the ground blow together in a location.

tornado tipsStep 2: The faster moving air begins to spin and roll over the slower wind. As it rolls on,  it gathers pace and grow in size.

tornado tipsStep 3: At this stage, it is an invisible, horizontal wind spinning and rolling like a cylinder. As the winds continue to build up, stronger and more powerful warm air forces the spinning winds vertically upward, causing an updraft.

tornado tipsStep 4: With more warm air rising, the spinning air encounters more updraft. The winds spin faster, vertically upwards, and gains more momentum.

tornado tipsStep 5: At this stage, the spinning winds, creates a vortex and the the wind has enough energy to fuel itself.

tornado tipsStep 6: The tornado is fully formed now and moving in the direction of the thunderstorm winds. When the pointed part of the tornado touched the ground from the cloud, it is often referred to as ‘touch down’.


The Fujita scale

rates tornado intensity, based on the damage tornadoes inflict on human-built structures and vegetation.

The intensity is determined by meteorologists and engineers after a ground or aerial damage survey; and depending on the circumstances, ground-swirl patterns (cycloidal marks), radar tracking, eyewitness testimonies, media reports and damage imagery, etc.

{ adapted, https://en.wikipedia.org/wiki/Fujita_scale }

Chap 20, Table 1, Tarbuck & Lutgens Earth Science

Chap 20, Table 1, Tarbuck & Lutgens Earth Science

The Enhanced Fujita scale (EF-Scale) rates the strength of tornadoes in the United States and Canada based on the damage they cause….it began use in the United States in 2007.

The scale has the same basic design as the original Fujita scale—six categories from zero to five, representing increasing degrees of damage. It was revised to reflect better examinations of tornado damage surveys, so as to align wind speeds more closely with associated storm damage.

Better standardizing and elucidating what was previously subjective and ambiguous, it also adds more types of structures and vegetation, expands degrees of damage, and better accounts for variables such as differences in construction quality.

{ adapted from https://en.wikipedia.org/wiki/Enhanced_Fujita_scale }


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