Could a group of large flying creatures cause a tornado?

Question

In the world I am making their is a species of wyvern like monsters that hunt in groups of 10 to 20 in the aftermath of the storms they make and have wingspans that range from 20 ft to 36 ft.
Other relevant information

• A wyvern's average body temperature when hunting exceeds that of 110 degrees Fahrenheit.
• The average wyvern has a large amount of heat shed during hunting.

The Question

Could a flock of these creatures realistically cause a the forming of a EF0 tornado or greater just from them flying in a formation and the body heat they are giving off?

Answer 1

A small group of large flying creatures, no.

...but a large group of small flying creatures, yes.

The photo below is not a tornado, but a "bugnato" caused by a massive swarm of mosquitoes. As animals flap their wings, they make the air around them move faster which slightly reduces the ambient air pressure. Amongst a small group of flying animals like your typical flock of birds, this effect is not a super big deal because each member of the flock is much stronger than the over all pressure gradient caused by their flapping, but when you get millions or billions of insects flying in close formation the ambient pressure difference can become stronger than any individual member's flying power. When this happens, the insects get sucked into flying in a circle instead of straight. As they get sucked in they are forced to fly closer together which makes the vortex even stronger; so, only once your flock/swarm size gets big enough that no individual member is strong enough to resist the overall vortex does a tornado like phenomenon happen.

The biggest problem with your wyvrens is that it does not matter how strong any one of their wing flaps are, without enough of them they can not create a tornado. Their wing flaps could make a lot of turbulence, but not give that turbulence enough structure to turn into a vortex.

In some settings, Wyvrens are basically treated as plague dragons breathing some sort of toxic or disease carrying breath weapon instead of fire; so, if you were to take this general concept but make them breath swarms insects as their breath weapon, then perhaps enough wyvrens working together could breath a bugnato into existence.

FYI: Windspeeds in a bugnato are much lower than a tornado so while they look a lot like a tornado, they do not move nearly fast enough to cause structural damage.

... but if they breath fire, they could make a fire tornado

When you create a circle of fire, it consumes the oxygen in the middle of the circle much faster than around the outside of the circle. This creates a vacuum that pulls the surrounding flames inward forming a fire vortex. So if your Wyverns were to breath fire in a circle around a target, their flames would come together and consume whatever is in the middle in a tornado made out fire.

Answer 2

No, they don't use enough energy.

A bald eagle has around 650 joules of kinetic energy to fly at full speed.

A tornado contains around 10,000 kilowatt hours or around 36 billion joules.

Lets assume ten birds fly for an hour, and constantly use the amount of energy a bald eagle uses to stop from full speed in a second every second.

650 * 3600 * 10= 20 million joules.

That's nowhere close to the amount of energy. You're a thousand times off. Even if the animals got larger, or they got more numerous you'd be nowhere close.

Answer 3

Maybe a smaller vortex than a tornado?

https://www.livescience.com/bubble-net-whales-video.html

Tornados are freaking powerful. They would be tough on fliers of the size you describe. But maybe they could make smaller vortices? These whales make nets of bubbles and so not actual swirling vortices. But I could imagine your creatures making smaller vortices.

https://www.boldmethod.com/blog/lists/2017/02/5-factors-that-affect-vortex-strength/

Your fliers cruise through a flock of their prey. The trailing vortex concentrates the prey animals and knockes them off balance. Following wyverns go through the center of the vortex and scoop up a number of animals.

Answer 4

Here is an picture of a F5 tornado that struck Moore in 1997.

And here's daddy

That's right, you are looking at a supercell, gigantic behemoths of thunderstorms that extend as high as 70,000 ft, and the father of hail, torrential rain and (of course) tornadoes. Although you requested for an "EF0" tornado, I still described the F5 tornado. Because, tornadoes are notoriously difficult to produce.

Let's see how tornadoes are formed-

-Hot, humid air- In order to have even a decent garden-variety thunderstorm (forget supercells) you need massive amounts of hot, humid air. Sure, 43°C sounds pretty balmy, but there is a reason why you can't make tornadoes with a few flying creatures shedding off body heat.

Try out this activity at home.

Take some boiling water, and pour it into a bucket of water at ,let's say, 40°C). The bucket gets just lukewarm, or maybe not even warm up at all. Heat does not just depend on energy, it also depends on the mass of the object. A bucket of water at 40°C contains more overall heat than a cup containing water at 100°. This also applies to gases (including air) as well.

When you get warm air, it creates updrafts, often containing moisture. This moisture, when it contacts the cooler, upper atmosphere, it condenses to form clouds. Just normal fluffy or wispy clouds. End of story.

But, if you have a lot, on the order of thousands or even millions of tons (yes, tons) of warm air, then as it cools down, it rapidly transfers its latent heat to the surrounding air, causing it to suck up even more air, and this air also releases its latent heat. This chain reaction goes till you end up with a rather tall and hefty anvil cloud. The latent heat released is immense, on the order of millions or even billions of joules.

-Wind shear- Wind speeds and directions can vary with altitude. I doubt whether your 40ft wyverns can change wind direction just by flying. Have you ever noticed (in an apartment) how the terrace is windy, whereas the air is still at ground level?

When you get two horizontal air currents that have different directions and speeds, they form a horizontal air vortex, which is basically the parent vortex of the tornado, or the mesocyclone.

Image of an mesocyclone:

-What goes up, must come down-Updrafts do not last forever. Especially if you lift air to freezing altitudes, then it will rapidly cool and sink back to the surface. These are what meteorologists call downdrafts, and these are the key features that drive microbursts and heat bursts (caused due to adiabatic heating of rapidly sinking air parcels)

Updrafts and downdrafts, when combined, have a notorious knack for rubbing hail against smaller ice pellets, this friction is basically what causes lightning in thunderstorms. (Of course, don't go to your refridgerator and rub ice cubes against frost to create electricity, you need a tad lot more to generate lightning)

So, your downdrafts are gonna tilt your horizontal air vortex downwards, and well, there you have it, a tornado is born.

So, coming back to the question:

-You need a lot more wyverns in your flock, think on the order of millions of wyverns. The best that a flock of 20 flying creatures can do it to stir up a dust devil (albeit very weak and short lived).

-If you want your wyverns to create a massive warm-air parcel, for a flock of 20 creatures, you would need to have body temperatures on the order of hundreds or even thousands of degrees (Rip wyvern).

The best case scenario I can think for your novel is that an entire kingdom of wyverns have gone fishing for a festival (use story license), and while hunting, they create a lot of hot air over the lake where they are fishing, and accidentally trigger a supercell. And maybe trigger wind shear from the sheer amount of wyverns that are fleeing in different directions and trigger a small tornado.

You just need a lot of wyverns to do the job.