How Tornadoes Form: It’s Not Really Understood

Yesterday, I was reminded that the NOAA (National Oceanic and Atmospheric Administration) admits that atmospheric scientists are still mystified by tornadoes.

  1. Why is it, for instance, that not every thunderstorm generates a tornado, even when you have all the necessary conditions of shear, lift, instability and moisture?
  2. Most destructive tornadoes spout out of supercells, rotating thunderstorms with well-radar-defined circulation called mesocyclones. But what does it take for the mesocyclone to give birth to a tornado? Only 20% do. Is there something that spontaneously aborts the formation of such a storm, or is there a key ingredient that seeds it?

Observations from VORTEX (Verification of the Origins of Rotation in Tornadoes Experiment) suggested that temperature changes across the edge of downdrafts (see blue arrows in the diagram from my notes) were a key prerequisite to tornado-formation. But some of the most destructive tornadoes like the May 3, 1999 Oklahoma one ( Bridge Creek–Moore tornado with wind speeds of 486 ± 35 km/h) and many of the 71 other ones that formed that day emerged without such variation.

Source: Daphne Zaras – Source for picture of supercell ( to the right of my diagram of a mesocyclone, Stefan Klein )

Here’s a list of noteworthy facts about tornadoes from a National Geographic Special and from Wikipedia’s article on tornado records.

  1. The United States is currently living through the longest span without a tornado rated F5/EF5 ( as of June 7 2022), which is now at 9 years. An F5 tornado ( scale from 0 to 5) is estimated to have maximum winds between 261 mph (420 km/h) and 318 mph (512 km/h).
  2. It’s hard to imagine the strength of a tornado if you haven’t experienced it. Pieces of debris become deadly weapons. A piece of wood can gain enough potential energy to pierce a car door or move through a home’s front door and then carry enough momentum to stick itself into a fridge door. It’s why you should head for a basement and not seek shelter in a car or indoors on a main floor. Whereas a strong wind is difficult to walk against, a tornado can carry you away into the distance. A Missouri man holds the record for being carried 1,307 feet (398 m), according to National Weather Service measurements.
  3. The small town of Dolores, Uruguay has been hit multiple times by intense tornadoes, most recently on April 15, 2016, when an EF3 tornado destroyed large portions of the city. The Enhanced Fujita Scale or EF Scale, which became operational on February 1, 2007, is used to assign a tornado a ‘rating’ based on both estimated wind speeds and related damage. The F scale only uses the former.
  4. It’s hard enough to understand how a single tornado forms, let alone why and when so many will form in a short time span. 104 tornadoes formed over 5 hours and 26 minutes, during the 1981 United Kingdom tornado outbreak on 23 November 1981, the highest rate ever.
Destruction from the 2016 EF3 tornado in Dolores, Uruguay

The Illusion of More Glitter in the Distance

On the surface of a lake or other body of water, there can be a wonderful pattern formed by points of light that almost seem to be dancing. Each of these points is a reflection of the sun, and the reason there are many is because the surface is not perfectly still. The gentlest wind can ripple the top of the water, creating a variety of sloped surfaces, collectively causing a multitude of distorted reflections, which we call glitter.

Now consider the following view of a glittering lake.

I’ve drawn two boxes. Due to perspective, to the eye they seem to be of equal area, and of course the one further away seems to contain far more glitter. Assuming that the two areas are being equally perturbed by the wind, the extra concentration of glitter in the first box is an illusion. In reality, the area of the lake enclosed by the top box is larger than what is contained in the lower box. And though a larger area will contain more glitter, throughout the lake there will be an approximately equal concentration of point-like reflections.

This reminds me of how we assume we have to travel away to see more glitter, when in reality there is just as much beauty close to our homes. When I worked in Hawaii many years ago, I had to get a hepatitis shot before beginning to work. I told a nurse who had lived in Oahu all of her life that I had moved there from Canada, “How can you leave such a beautiful country to come to Hawaii?” In Canada people rarely take a vacation within their own borders, and if they do, they feel as if they are settling for some thing cheaper and sacrificing a more intense pleasure than they would get by going to places like Hawaii, Arizona, Iceland or Europe. In Hawaii, affluent high school students go to Colorado during their Christmas vacations and to California or New England for college. Otherwise, they feel trapped on the island—what they describe as “a rock”. Many adult residents who are not surfers rarely go to the beach after their children are grown up. Most Hawaiians, like Canadians, have forgotten how to appreciate the glitter under their noses.

Last week, we accidentally stumbled upon such glitter. Less than two hours from Canada’s largest city, in the waters of Lake Ontario at Presqu’ile, we saw stunning shades of turquoise that we mistakenly believed could only be witnessed in the seas of the Caribbean or Mediterranean.

But where is the glitter, you may ask? Well, the stillness of the water is one of the prerequisites for seeing the beautiful shades of blue, a reminder that glitter is only one manifestation of a lake’s beauty— at any distance.