Tag Archives: tornado

El Reno, OK EF-5 Tornado: Credit: Jeff Snyder.

Tornadoes form from the ground up, not the other way around as previously believed

El Reno, OK EF-5 Tornado: Credit: Jeff Snyder.

El Reno, OK EF-5 Tornado: Credit: Jeff Snyder.

Scientists used to think tornadoes originate far up in the clouds but a new evidence seems to point towards an opposite model of formation. According to new research, tornadoes may first form at ground level, generating a funnel that extends upwards. The findings could improve tornado forecasting models, which might offer precious extra time for people to get out of harm’s way during a natural disaster.

“We need to reconsider the paradigms that we have to explain tornado formation, and we especially need to communicate this to forecasters who are trying to make warnings and issue warnings,” said Jana Houser, a meteorologist at Ohio University and co-author of the new study. “You are not going to really ever be finding strong evidence of a tornado descending, so we need to stop making that a priority in our forecasting strategies.”

Houser and colleagues drove a truck-sized rapidly scanning radar through storms, hoping to catch the birth of tornadoes. The researchers eventually collected data on a couple of tornadoes of varying intensities on the Enhanced Fujita (EF), which rates the intensity of tornadoes in the United States and Canada based on the damage they cause. Two of the tornadoes were rather small (EF1) while the others varied from moderate (EF3) to extreme (EF5). The latter storm, called the El Reno tornado, formed on May 31, 2013, in central Oklahoma, shattering previous tornado records. The terrifying El Reno tornado was the widest ever recorded, peaking at 4.2 kilometers (2.6 miles) wide, and had wind speeds of more than 480 kilometers per hour (300 miles per hour), which is the second-highest wind speed recorded on Earth.

While residents fled the onslaught, the researchers drove their state-of-the-art mobile Doppler radar through the storm. This specialized radar uses the Doppler effect to produce velocity data about objects at a distance by bouncing a microwave signal off a desired target and analyzing how the object’s motion has altered the frequency of the returned signal. A tornado of such an intensity as El Reno also gathered the usual thrill-seeking storm chasers, who recorded hundreds of photos and videos from different angles and at different times, showing how the tornado was developing.

El Reno, OK Supercell – Photo courtesy Brennan Joseph.

These citizen images proved essential to the current research. The footage clearly showed a visible tornado at the ground several minutes before the researchers’ radar picked it up. This was the first hint that the currently accepted meteorological model of top-down tornadogenesis may be flawed.

When Houser and colleagues were in the lab they analyzed the data again — this time with a careful eye on data for ground-based radar. They found clear evidence of rotation at the ground before there was rotation at higher altitudes. This seemed to be the case for all five datasets that the authors analyzed — the tornado’s rotation formed at or near the ground first, rather than starting in the cloud itself.

“The coupled visual and near-surface radar observations enable an analysis of the tornadogenesis process that has never before been obtained, providing a missing link in the story of tornado formation: the rotation associated with the tornado was clearly present at the surface first. Subsequently, rotation contracted aloft nearly simultaneously over the depth of the column for which data were collected, providing distinct evidence that for this case, the tornado formed from the bottom-up. Furthermore, in the 5 datasets that were examined, NONE of the tornadoes formed following the top-down process,” the authors wrote in the study’s abstract.

Five is a pretty small sample size, which means that many more tornadoes will have to be analyzed before the new model supersedes the previous cloud-ground one. If confirmed, residents close to a high-intensity tornado could be alerted with a couple of seconds, maybe minutes in advance. In some situations, this can mean the difference between life and death.

The findings were presented on December 14 at the 2018 meeting of the American Geophysical Union.

Scientists analyze tornadoes in infrasound

Tornadoes can produce infrasounds, and those infrasounds can be used by scientists to “peak in” on the violent phenomena.

Composite of eight images shot in sequence as a tornado forming in Kansas in 2016. Image credits: Jason Weingart / Wikipedia.

A few decades ago, researchers realized that along with the very big ‘boom’, nuclear explosions also produce sounds — some of them at infrasound frequencies. Because infrasounds decay so slowly, they can travel around the Earth several times and can, therefore, be used to track nuclear tests.

Now, researchers are using the same approach to track down tornadoes, using infrasounds. During the 175th Meeting of the Acoustical Society of America, Brian Elbing, assistant professor of mechanical and aerospace engineering at Oklahoma State University, says that we can predict when and how a tornado will form, using infrasound detectors.

Tornado-producing storms can emit infrasound more than an hour before “tornadogenesis,” or tornado formation. Picking up on these waves could improve the accuracy of tornado alerts.

“By monitoring tornadoes from hundreds of miles away, we’ll be able to decrease false alarm rates and possibly even increase warning times,” Elbing said. “It also means storm chasers won’t need to get so close.”

[panel style=”panel-default” title=”Tornado formation” footer=””]No two tornadoes are the same, but all tornadoes require on specific conditions to form.

It starts when sunshine heats the ground, which causes pockets of air to rise. If the atmosphere is unstable, the pockets can rise to great heights, resulting in the development of much deep, strong currents of ascending air (updraughts) and storm clouds.

If the atmospheric winds are strong enough, the stormy updraughts can start to rotate, and tilt to become vertical.

Eventually, the rotation may become so strong that a narrow column of violently rotating air forms — thus, a tornado is born.[/panel]

An illustration of generation of infrasound in tornadoes by the Earth System Research Laboratory’s Infrasound Program.

In order to do this, Elbing and his team deployed three infrasound microphones arranged in a triangle, each spaced about 200 feet apart. The key features of these microphones are their ability to zoom in on very specific frequencies and to filter out any unwanted noise.

“First, these are larger for greater sensitivity to lower frequencies,” Elbing said. “Second, we need to get rid of wind noise. … We seal the microphone inside a container with four openings. A soaker hose — just like the ones used in gardens — is attached to each of these openings and stretched out in opposite directions.”

Of course, this would work best in areas which are prone to tornado formation, improving the alarm systems. A significant problem in such tornado-prone areas is that most tornado alarms are false — and as a result, are often ignored. With the infrasound technology, authorities could issue accurate alarm warnings and save lives. To make things even better, it can be used in tandem with existing technologies.

“Since infrasound is an independent data source, combining it with existing methods should help reduce false alarms,” said Elbing. “Today, 75% of tornado warnings are false alarms and tend to be ignored.”

Researchers already have their eyes on a particular test zone: Dixie Alley — the areas of the southern United States that are particularly vulnerable to strong or violent tornadoes. From there on, the technology could be deployed in much greater areas such as the infamous Tornado Alley.

“This is especially true for Dixie Alley, which isn’t known for the largest tornadoes but frequently has the most fatalities,” Elbing said. “Complex terrain, irregular road patterns, and nighttime tornadoes prevent storm chasers from observing these tornadoes, so long-range, passive monitoring for tornadoes will provide invaluable information about their formation processes and life cycle.”

Results have not yet been peer-reviewed.

Researchers create mesmerizing tornado simulation algorithm [with video]

It’s the mother of all computer storms. Watch it below:

The world of meteorological forecasts has changed dramatically over the years. There’s a lot more statistics and mathematical modelling than most people realize. Basically, by taking the observations from weather stations at ground level over land and from weather buoys at sea and applying the equations of fluid dynamics and thermodynamics, numerical models are created — and those numerical models are the core of weather forecasting.

Numerical models have become a core aspect of many fields of research, but rarely have they been as prevalent as in weather and climate science. It’s not just forecasts, they allow us to understand complex phenomena — such as tornadoes.

Tornado formation

No two tornadoes are the same, but generally, they do follow similar rules. It all starts when sunlight heats up bubbles of air, making them hotter and lighter. These bubbles start to rise up, forming cumulus clouds. When the atmosphere is relatively cold, they will rise even higher, forming updraught currents and generating deep cumulus and cumulonimbus clouds (i.e. thunder clouds).

In some areas, winds increase greatly with height. When this is the case, the thunderstorm updraught beings to rotate and suffers horizontal shear, kind of like a merry-go-round. This is called a supercell storm. Now, not all supercells form tornadoes. Tornadoes only form when the updraught gets coupled with an downdraught — cold masses of air coming down from the supercell — creating a violently rotating column of air. Even then, a tornado only forms when this column of air reaches the ground. All of this is almost always associated with a so-called condensation funnel a funnel-shaped cloud which forms due to the much-reduced pressure within the tornado vortex. This is why we “see” the tornado (also, due to dust and other debris trapped by the air).

This is all well-established and documented for years, but it’s hard to put figures on this process. Why do some supercells generate tornadoes and others don’t? Why do some tornadoes get bigger, and how big do they get? Can we predict that? This is where numerical models step in.

Modelling tornadoes

Image credits: University of Wisconsin-Madison.

Leigh Orf, an atmospheric scientist at the University of Wisconsin-Madison, wants to unravel the secrets of a tornado, and for that he needs much more than a laptop — he needs a supercomputer.

In order to create his simulation, the mesmerizing model you see above, he started from the powerful and long-lasting tornado that struck Oklahoma on May 24, 2011, one of the strongest tornadoes in recorded history. He basically modelled a 3D block of space measuring roughly 75 miles wide, 75 miles long, and 12.4 miles tall. He split it into cubes that are 100 feet (30 meters) on each side, ending up with 1,839,200,000 such cubes. In each of these cubes, he added parameters such as wind speed and direction, temperature, humidity, pressure, and precipitation. Then, let the simulation take its course… and as you can imagine, the required computation power is gargantuan.

“This type of work needs the world’s strongest computers just because the problem demands it,” he says. “There’s no way around it. It’s not necessarily that the weather is complex, it’s that the feature is big and it needs to be very highly resolved,” he says.

Thanks to the Blue Waters machine at the University of Illinois, he was able to complete the computation. This kind of research is pivotal in expanding our understanding of tornadoes. Over 1,000 tornadoes form every year in the US alone, and while most of these are harmless, history has taught us that sometimes, tornadoes can be devastating.

“For the first time we’ve been able to peer into the inner workings of a supercell that produces a tornado, and we’re able to see that process occur,” he says. “We have the full storm, and we can see everything going on inside of it. So just about everything is a discovery, right now, because no one’s done this before, not at this scale.”

Birds can detect approaching storm from 900km away

Some animals have extraordinary sensorial abilities; there have been scientific works documenting dogs which react to an earthquake 5 minutes before the waves reached the surface, but this is perhaps even more spectacular – some birds can sense an earthquake from 900 km away (560 miles).

A tornado in Brisco County, Texas. The birds didn’t appear to have used changes in pressure, wind speed or precipitation to warn them of the approaching storm. Photograph: Reed Timmer/Jim Reed Photography/Corbis

It seems that have avoided a devastating storm by fleeing their US breeding grounds after detecting infrasound waves from 900 km away. Researchers observed this behavior as they were studying the birds’ migration patterns. They believe it is the first documented case of birds detecting weather events based on infrared – let alone from such a big distance.

“We looked at barometric pressure, wind speeds on the ground and at low elevations, and the precipitation, but none of these things that typically trigger birds to move had changed,” said David Andersen at the University of Minnesota, explaining why they think the birds detected infrared. “What we’re left with is something that allows them to detect a storm from a long distance, and the one thing that seems to be the most obvious is infrasound from tornadoes, which travels through the ground.”

Golden Winged Warbler. Image via ABC Birds.

Golden-winged warblers breed in southeastern and south-central Canada and the Appalachian Mountains northeastern to north-central USA. The majority (~70%) of the global population breeds in Wisconsin, Minnesota, and Manitoba. The birds had just returned to their breeding grounds in the mountains of Tennessee in 2013 when a massive storm was edging closer. Although the birds had just completed a migration of more than 2,500km, they still had the energy to avoid the storm.

The storm was still 900 km away when the birds, apparently out of nowhere, decided to flee 1,500 km to Cuba, only to return after the storm has passed.

“In five to six days, they all made this big move around the storm,” Andersen said. “They all went south east in front of the storm, and then let it go by, or moved behind it. It was individual behaviour, they were several hundred kilometres away from each other most of the time.” Details are reported in the journal Current Biology.

Scientists are not really sure that the birds’ brains can pick up infrared but previous work in pigeons has suggested that birds might use infrasound to help them navigate. Infrasound waves range from about 0.5Hz to 18Hz, way below the audible range of humans. This is good news for the birds, and suggests that they may actually be more adaptable than previously though.

“With climate change increasing the frequency and severity of storms, this suggests that birds may have some ability to cope that we hadn’t previously realised. These birds seemed to be capable of making really dramatic movements at short notice, even just after returning on their northwards migration,” he said.

Sun Tornado

Solar twisters sweep the sun’s surface [INCREDIBLE VIDEO]

Exactly two years ago, NASA launched a $850 million spacecraft, called the Solar Dynamics Observatory, on a five-year long mission to record high-definition videos of the sun, which should help astronomers better understand its weather cycle and how and how it might affect life on Earth. To celebrate SDO’s 2nd anniversary, NASA has released a stunning video featuring tornado-like formations swirling across the sun’s surface. Nothing short of amazing!

Sun Tornado These aren’t quite tornadoes, though, but rather super-hot plasma eruptions. The video, shot in a 30-hour period between Feb. 7 and 8, shows a couple of such plasma fountains creeping upon the sun’s surface. Dark spots shifting back and forth represent cooler plasma, while the eerie yellow hue is simply due to the fact that the recording was made in the extreme ultraviolet range of the light spectrum.

Sun tornadoes like the ones featured in the NASA video have been known to astronomers for decades now, and although they might look fairly similar to their counterparts on Earth, they’re very much different. Tornadoes on Earth need wind to be generated; wind which doesn’t exist on the sun. Instead of temperature of pressure fluctuations, powerful competing magnetic forces, which pull the charged magnetic particles on the sun back and forth, cause the erupting plasma to eject in a swirling manner.


Deadly tornadoes continue rampage, killing over 150 people

Deadly tornadoes are rampaging the United States, killing an estimated number of 193 people in five states already, and showing people that this is just a taste of what’s to come. The majority of deaths (128) has been in Alabama, and authorities seem pretty unprepared to takek care of the situation.

Alabama Governor Robert Bentley said officials plan to tour the hardest hit areas this morning.

“There is some massive devastation out there. We have some people that are hurting. We’ll be out in just a few minutes of all Northern Alabama looking at this,” he said.

Officials states that they expect the death toll to rise, especially as the tornadoes have just begone ravaging the country.

“It’s been a devastating blow to the people of this community,” said Tuscaloosa Mayor Walt Maddox this morning. “We need men, materials and equipment. Our system is overwhelmed. The tornado took out a major nerve center of city, our environmental services department which is how we pick up debris, trash. It’s gone and the fleet that we have, the vehicles are gone,” Maddox said.

At least a dozen cities remain unpassable, and there have been reports of destroyed fire stations and communication plants.

“We have way over 100 injuries throughout the city of Tuscaloosa,” Maddox said Wednesday. “We have hundreds of homes and businesses destroyed and hundreds more damaged.”

The National Guard has already been dispatched and it’s on its way to salvage what can be salvaged from the tornadoes, but in the state of Alabama at least, the damage has already been done; but that’s not to say help is not much needed !

The tornado destruction is heading from Alabama to New York, where dozens of cities are already unrecognizable due to all the damage. The Browns Ferry nuclear power plant about 30 miles west of Huntsville lost offsite power but there is no risk of the situation escalating further, while in Huntsville, meteorologists found themselves in the path of severe tornadoes and had to take shelter from the devastating storms:

“We have to take shelter just like the rest of the people,” said meteorologist Chelly Amin, who wasn’t at the office at the time but spoke with colleagues about the situation.

You can follow a live update of the disaster at the CNN blog and we will keep you posted with the situation.