The Mechanics of Fire Tornadoes

A tornado may very well be one of nature's most stunning displays. A small one leaves onlookers in awe. A larger one sends people scrambling for cover in basements and shelters. But when a massive tornado strikes—one that’s rated EF-5 on the enhanced Fujita scale—its destructive power is often called "the finger of God." Such a storm leaves behind devastation as if an angry deity were punishing humanity for its misdeeds.

Now imagine injecting heat, ash, and flames into a swirling vortex of air. Witness a column of fire rising from the earth, stretching toward the sky, and then surging forward, consuming everything in its path. Could such a phenomenon actually occur? And if it does, could it burn with the same ferocity as an EF-5 storm, perhaps earning the title of "the finger of the devil"?

You might be surprised to learn that the answer to both questions is affirmative, and the storm in question is commonly called a fire tornado, fire whirl, or fire devil. The latter two names may sound familiar because they reflect the same colloquial terms we use for other similar meteorological phenomena, such as whirlwinds and dust devils. In fact, fire tornadoes are more akin to whirlwinds than to full-blown tornadoes. However, all these storms share one thing in common: they involve a mass of air rapidly rotating around a central axis.

So, why don’t we hear more about fire tornadoes? It’s not because they’re rare, but because they typically form in situations most people prefer to avoid. These include wildfires, large fires ignited by natural disasters, and occasionally, house fires. As you would expect, firefighters often encounter fire tornadoes. Scientists wanting to study these unique storms must either go into the heart of infernos or bring the inferno to their laboratories. Consider it storm chasing—with a fiery twist.

Would You Like to Supercell That Tornado?

To the average person, any funnel-shaped column of air is a tornado, but meteorologists are more precise. They categorize twisters into two main types: supercell and nonsupercell, based on their formation and the degree of destruction they cause. For a tornado to be classified as a supercell tornado, it must meet three specific conditions [source: Williams]:

Many people believe that a tornado must take the classic shape of a funnel twisting through the sky, but that's not always the case. Tornadoes that lack a funnel often appear as broad cylinders or cones, sometimes stretching up to a mile wide, swirling just above the ground. Regardless of their shape, these massive tornadoes are capable of causing significant destruction, tearing down homes and buildings, tossing vehicles, and uprooting trees.

Tornadoes that don't meet the supercell criteria fall into the nonsupercell category. For instance, waterspouts are nonsupercell tornadoes that develop over water. While they may seem similar to their larger, land-based counterparts, they form differently, arising from cumulus clouds that never become thunderstorms, and may not evolve into them. Consequently, they have shorter lifespans and typically produce wind speeds between 33 and 45 mph (53 to 72 kph), which is much less intense than their more powerful tornado relatives.

The same principle applies to landspouts and gustnadoes. Landspouts form over land, yet they resemble and behave like waterspouts. As a result, they inflict far less damage than supercell tornadoes. Similarly, gustnadoes are brief, weak (though impressively named) tornadoes that form at the boundary between cold descending air and warm air at the surface. This boundary, known as a gust front, is often a precursor to a thunderstorm and potential supercell activity, but the winds themselves don't qualify as full tornadoes.

Meteorologists also recognize a third category of tornado-like storms called whirlwinds. These are common atmospheric phenomena that occur when the sun heats dry land, causing a column of warm air to rise quickly. As it ascends, the air begins to rotate around a vertical axis, much like water swirling down a drain. When the rising column of air picks up debris, it becomes visible, and is often named based on the type of debris it collects, such as dust whirls (or dust devils), sand whirls, snow whirls, and even hay whirls.

Fire tornadoes form when a fire, rather than the sun, heats the air above the Earth's surface. While not technically tornadoes, they are a special kind of whirlwind (which explains why they’re also called fire whirls or fire devils in many regions). Although less common than dust devils, fire tornadoes can easily develop over large fires, and they follow many of the same principles as real tornadoes in terms of their formation.

Vertical Vortex: The Science of Fire Tornadoes and Updrafts

Tornadoes, whirlwinds, and spouts all share a common feature: they are all types of atmospheric vortices—air currents that rotate around either a vertical or horizontal axis. These vortices can vary in scale, from small eddies around buildings to massive mesocyclones forming within thunderstorms. Regardless of size, most atmospheric vortices emerge when the air near the Earth's surface is heated, whether by sunlight or by fires on the ground.

Imagine a vortex forming on a hot day over dry land. The air close to the ground absorbs more sunlight, heating up faster than the air higher in the sky. As the temperature of the ground-level air rises, it becomes lighter and rises more easily. This hot air ascends in columns, creating powerful updrafts that can reach thousands of feet. Often, an upward-spiraling movement, similar to the whirlpool effect seen when water drains from a bathtub, begins within the air column. Some of these vortices are weak and invisible, while others, formed from stronger updrafts, spin with significant force as more air is sucked into the rising column. When dust or sand is pulled in, the vortex becomes a visible whirlwind.

Now consider a wildfire raging across hundreds of acres of brush or forest. In this scenario, it's not the sun but the fire itself that heats the air near the Earth's surface. However, the outcome is the same. The hot air above the fire rises quickly in columns, or plumes, as they are called by firefighters. As the air ascends, it begins to spin, drawing in more air and pulling the flames upward in a tight spiral. Most fire whirls remain small, only a foot or two wide, but some can grow as tall as 400 feet (122 meters) and reach a width of 50 feet (15 meters), resembling a small tornado.

In the examples above, the axis of rotation is perpendicular to the ground. This is common when intense heating causes strong updrafts. However, not all vortices form in this way. Some begin with their axis parallel to the ground, either lying on their sides or backs. An upward force eventually tilts the vortex, causing it to stand upright. Scientists now believe this is how many fire whirls begin. This process may also explain the formation of the vortex at the center of a supercell tornado, the mesocyclone. Next, we will explore the conditions that contribute to this unique aspect of vorticity and how they can lead to a massive firestorm.

Rockin' Roll: Fire Tornadoes and Horizontal Vorticity

We are accustomed to seeing tornadoes and fire whirls spinning in a vertical orientation. It might be surprising to consider them positioned differently. However, scientists have recently proposed a new model to explain how vertical vortices form. This is how the model works:

The fire whirl that emerges from this process might seem like an unusual event, but many scientists classify it as an example of microweather: a small-scale weather system triggered by a localized event. In the case of fire tornadoes, that event is typically a wildfire, although it could also be caused by a house fire, an urban firestorm from firebombing, nuclear explosions, or natural disasters. The key ingredients are a large amount of dry fuel and an intense fire concentrated in a small area. When these conditions align, fire tornadoes are likely to form.

As you can imagine, firefighters encounter these rare meteorological events much more frequently than the general public. And they must exercise extreme caution. Fire tornadoes have been known to ignite new fires by spreading into untouched areas. They can also perform dangerous feats, such as picking up burning logs and tossing them over great distances. Not surprisingly, many state forestry services incorporate fire whirl training into their programs. The California Department of Forestry and Fire Protection, for instance, shows its firefighters a 1989 video of a fire whirl that developed during a massive wildfire and proceeded to consume three parked fire trucks and a news crew filming the scene.

Thankfully, fire tornadoes rarely cause widespread casualties. In fact, most of us will never witness one in our lifetimes. However, on rare occasions, thousands of people face the terrifying fury of a raging firestorm, with flames, smoke, and harmful gases engulfing the area. In the next section, we’ll revisit some notable fire tornadoes that continue to leave their mark in history.

Famous Fire Tornadoes

While wildfires typically occur in rural or wilderness regions, where most people never experience the blaze firsthand, there have been instances where fire tornadoes have emerged in urban areas. These fire tornadoes have caused massive damage and loss of life. Below are three notorious cases of fire tornadoes during urban fires, listed in chronological order:

On October 8, 1871, the Great Peshtigo Fire, which ravaged the town of Peshtigo, Wisconsin, and parts of Michigan, became one of the deadliest fires in U.S. history. The blaze started on the same day as the infamous Chicago fire, triggered by similar conditions: a dry summer, slash-and-burn farming, and a strong cold front that intensified prairie fires. The town, filled with wooden buildings and lumberyards, quickly became an inferno when the fire reached it. In mere moments, a massive fire tornado spiraled through the town, with winds up to 100 mph (161 km/h) and temperatures reaching 700°F (371°C). The fire claimed the lives of those who could not reach the river, and Peshtigo still holds the record for the worst fire disaster in U.S. history, with a death toll of 2,000.

The Great Kanto Earthquake struck on September 1, 1923, causing widespread devastation across Tokyo and Yokohama. The earthquake, followed by a tsunami, led to a loss of thousands of lives. However, it was the subsequent fire that consumed entire neighborhoods of wooden homes, forcing people to flee. Thousands rushed to the Sumida River in search of safety, only to be trapped by a towering fire tornado, called a 'dragon twist' by locals. Nearly 45,000 people perished in the firestorm, contributing to a total death toll of 140,000. The devastation left 45 percent of Tokyo in ruins, as described by Hammer.

April 7, 1926 – The San Luis Obispo Fire. On the morning of April 7, 1926, during a moderate thunderstorm over San Luis Obispo, California, lightning struck oil storage tanks at a Union Oil Company facility situated 2.5 miles (4 kilometers) south of the city's center. This spark ignited either the oil itself or the vapors hovering above it, resulting in a catastrophic five-day blaze that consumed around 6 million barrels of oil. As the fire raged, onlookers reported seeing hundreds of tornadoes created by the inferno.

In the April edition of Monthly Weather Review, J.E. Hissong published an article about the unusual meteorological event, marking the first scientific exploration of fire whirls and how they form. In his paper, Hissong emphasized the fire whirls' direct role in causing property damage and loss of life.

One of the whirling fires left the area around the reservoirs and moved east-northeast for about 1,000 yards, picking up the Seeber cottage, located just outside the tank farm. The whirlwind lifted the house several feet into the air before carrying it roughly 150 feet to the north, where it was dropped, completely destroyed. Both Mr. A.H. Seeber and his son, who were inside, tragically lost their lives.

Hissong's article also included several photographs of the fire tornadoes – some of the earliest ever documented. Nowadays, thanks to widespread access to video cameras and platforms like YouTube, fire tornadoes are being captured on film more frequently. A 2012 video shot by filmmaker Chris Tangey in the Australian outback has garnered over 2.5 million views. The footage showcases a red-orange spiral of flames twisting nearly 100 feet (31 meters) into the sky. It is a mesmerizing spectacle, though it's always advisable to observe fire tornadoes from a safe distance – part beauty, part danger.