Why does the U.S. have so many more tornadoes than other countries?

Oklahoma's devastating tornado, which killed at least 24 people and injured more than 200 others, is drawing comparisons to past U.S. twisters today, including the massive tornado that hit the same region in 1999. And the United States has plenty of examples to draw from. According to the National Oceanic and Atmospheric Administration (NOAA), the United States, in averaging more than 1,000 tornadoes each year, is by far the global leader when it comes to number of twisters recorded. Canada finishes a distant second with roughly 100 per year.

Here's NOAA's map of the regions of the world that are most likely to experience tornadoes. In addition to the United States and Canada, the organization highlights many European countries and parts of other nations including Argentina, South Africa, Bangladesh, and Japan (click on the image below to expand):

So why is the United States so disproportionately prone to tornadoes? According to a Discovery Channel explainer on the subject, the distinction is a result of climatology, geography, and topography (the NOAA image at the top of this post shows this week's storm system over Moore, Oklahoma):

[T]he United States has an abundance of flat, low-lying geographic regions, and it also has a climate that is conducive to intense thunderstorms, and tornadoes tend to form during thunderstorms.

Turning for a moment from topography to geography, the United States has a few places that might be called tornado hotspots. Most prominent among them, of course, is "Tornado Alley," a slice of America's mid-section running horizontally from Texas up to North Dakota -- taking in portions of Oklahoma, New Mexico, Colorado, Kansas and Nebraska....

Tornado alley's tornadoes usually happen later in the spring time and sometimes into the fall. The region is considered a prime breeding ground for supercell thunderstorms, which tend to produce the strongest tornadoes. Supercell thunderstorms contain something called a mesocyclone, which has a rotating updraft -- they're very dangerous but also, when identified as supercells, can provide a good heads-up that the extreme weather they can produce, like tornadoes, is possible....

Florida, too, has lots of tornadoes. That's because the state has many thunderstorms on a daily basis, and it's also a pit stop for many tropical storms or hurricanes (the tropical storms and hurricanes don't tend to produce the kind of killer tornadoes that come about during non-tropical storms).

While the United States leads the world when it comes to sheer volume of tornadoes, the ranking changes when you apply other filters. The United Kingdom, for example, has more tornadoes relative to its land area than any other country (a fact one expert attributed to the country's position on the Atlantic seaboard, at the nexus of polar air from the North Pole and tropical air from the Equator). And factors such as high population density, ineffective warning systems, and shoddy infrastructure mean tornadoes can be particularly deadly in countries like Bangladesh, which experienced a tornado that killed 1,300 people in 1989.

Writing for PBS, Peter Tyson points out that America's tornado tally may be so high relative to the rest of the world in part because other countries aren't as diligent about recording twisters. And he adds that all nations that experience tornadoes have something in common:

They lie 20° to 50° on either side of the equator, in the mid-latitudes. "You could probably get a tornado anywhere on the planet, but there are places where they are far less frequent," says John Snow, a tornado expert at the University of Oklahoma. "For good meteorological reasons, these tend to be in the tropics and the very high latitudes."

The only continent where twisters have yet to strike? Antarctica.

NASA/NOAA GOES Project via Getty Images


GeoGuessr: Where in the (Googleable) world are you?

I'm one of the millions of people who have recently become absolutely, incurably addicted to the new online game GeoGuessr. If you're a regular reader of this blog, you probably will be too.

Here's how it works: GeoGuessr drops you in a randomly chosen location on Google Street View. You can move around, but can't zoom out. It's a bit like playing Myst, except that you're looking for clues in a real place somewhere in the world. You then have to guess where you are by clicking on a world map, with points awarded for how close you get to the actual location.

Sometimes, obvious clues like signs in the local language or geographic landmarks will make it easy. Other times you'll find yourself on a nondescript country road trying to decide if those evergreen trees look more Scandinavian or Canadian. The game's one unfortunate limitation is that it will only drop you in countries that Google Street View has mapped, which means most of Africa, the Middle East, India, and China, are immediately ruled out.  You could, however, be dropped in such locations as the base camp of Mount Everest or the Great Barrier Reef. The most exotic place I've been in the game was what looked like a jungle path somewhere in Japan's remote Ogasawara Islands.  

In addition to just being a fun way to kill time -- more time than I'd like to admit over the past week or two -- the game is also a cool way to experience visual culture and notice surprising similarities in architecture and landscape between regions. Every once in a while you can come across something weirdly beautiful or an unexpected slice-of-life moment like those documented in artist Jon Rafman's 9-Eyes project. 

GeoGuessr is the creation of a 29-year-old Swedish IT consultant named Anton Wallén. I recently spoke with Wallén via e-mail and asked him how the idea for GeoGuessr came about.

"I have always loved how Street View enables you to visit locations you would never go to in real life in such an immersive way, almost like you're there," he said. Wallén says he initially set out to build a simple "random location generator" using Street View, and only later decided to add the guessing game element to it.

According to Wallén, since the game blew up on social media last week, it's been getting 200,000 to 300,000 unique visitor per day. "To me, it's mindblowing," he says, noting that  he's "received many emails from people getting together to organize tournaments in their workplaces/schools using their own rules, parents/children and couples playing the game together as a team and also a lot of teachers allowing their students to play the game during their classes."

Initially, much of the feedback Wallén received was from readers complaining about Australia being overrepresented. (It is, after all, a pretty big country, and frankly much of the interior of it is pretty nondescript-looking from the road.) But he says he's tinkered with the algorithm and the overrepresentation complaints are now much more diverse -- which could indicate that it is, in fact, pretty random.

I asked Wallén for the hardest location he's had to guess. "The hardest probably was a very luxurious, Asian-style house somewhere in Central America (which I finally decided would have to be Japan). You could walk around in the courtyard and the garden but there was no way to leave the premises. The easiest I guess was when I was dropped right in front of a sign that said 'Welcome to Fairbanks, Alaska.'" (I had similar good fortune in Valparaíso, Chile.)

The game may even have inspired a few people to see a bit more of the world. "I got an email a few days ago from a woman who had known her husband for 12 years," Wallén says. "She had always been very fond of traveling but since he didn't like it they had never really traveled anywhere together. They both, however, liked the game very much and had been playing it for a few nights. After that, the husband had started looking up tourist locations in Japan and even bought a guidebook. That story really made me smile."