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How Do Tornadoes Form?

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More than 1100 tornadoes tear through the U.S. every year, causing serious damage to lives and property—such as the one in North Dakota, whose 120 mile-per-hour winds injured nine people and destroyed 13 homes on Monday night. Or the April 2014 outbreak where, over a period of just three days, 75 tornadoes battered the swath of land between Nebraska and North Carolina.

The timing of these severe storms isn’t a coincidence. Tornado activity peaks in April, May, and June, especially in “Tornado Alley”—the area around Texas, Oklahoma, Kansas and Nebraska, where conditions are just right for brewing up a twister.

Unfortunately, weather systems are extremely complicated and scientists don’t fully understand how or why tornadoes form. What they do know is that there are three basic ingredients: moisture, atmospheric instability (which tends to lift air upward rapidly), and clashing air fronts.

The process starts when warm, low-lying air from the Gulf of Mexico crashes into cooler, higher-elevation air coming off of the Rocky Mountains. The clashing fronts create a swirling thunderstorm called a supercell.

What comes next isn’t exactly clear. The leading hypothesis suggests that as the cool air flows over the top of the warm air mass, it creates a horizontal spinning vortex. The horizontal vortex gets tipped into a vertical orientation as the warm air mass rises, pushing one end upwards, and as rain or hail drags the tail downwards.

Another hypothesis posits that the twister actually starts out in a vertical orientation. As the air masses crash into each other, the warm air rises, hollowing out a column in the supercell where winds spiral upwards in a clockwise direction. The rotating column is called a mesocyclone, and it occurs a few miles up in the atmosphere. Here, again, the vortex is pulled down to the ground as warm air moves upward and cool air drags the tail downwards.

When the vortex touches ground, that’s when it is officially designated as a tornado. The National Weather Service issues a tornado warning, and local residents run for cover.

The twister begins to die down when the cold downdraft chokes off the supply of warm air that feeds it. The funnel contracts in size but—like an ice skater who pulls her arms in during a spin—the winds speed up and the tail may still whip around violently. Eventually, the storm fizzles.

Scientists have measured tornado wind speeds of up 318 mph. To date, the U.S.’s deadliest twister was the Tri-State tornado of 1925, which rampaged through Missouri, Illinois and Indiana, killing 700 people and destroying 15,000 homes.

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Big Questions
Why Does the Queen Have Two Birthdays?
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CHRIS JACKSON, AFP/Getty Images

On April 21, Her Majesty Queen Elizabeth II will turn 92 years old. To mark the occasion, there are usually a series of gun salutes around London: a 41 gun salute in Hyde Park, a 21 gun salute in Windsor Great Park, and a 62 gun salute at the Tower of London. For the most part, the monarch celebrates her big day privately. But on June 9, 2018, Her Majesty will parade through London as part of an opulent birthday celebration known as Trooping the Colour.

Queen Elizabeth, like many British monarchs before her, has two birthdays: the actual anniversary of the day she was born, and a separate day that is labeled her "official" birthday (usually the second Saturday in June). Why? Because April 21 is usually too cold for a proper parade.

The tradition started in 1748, with King George II, who had the misfortune of being born in chilly November. Rather than have his subjects risk catching colds, he combined his birthday celebration with the Trooping the Colour.

The parade itself had been part of British culture for almost a century by that time. At first it was strictly a military event, at which regiments displayed their flags—or "colours"—so that soldiers could familiarize themselves. But George was known as a formidable general after having led troops at the Battle of Dettingen in 1743, so the military celebration seemed a fitting occasion onto which to graft his warm-weather birthday. Edward VII, who also had a November birthday, was the first to standardize the June Trooping the Colour and launched a tradition of a monarchical review of the troops that drew crowds of onlookers.

Even now, the date of the "official" birthday varies year to year. For the first seven years of her reign, Elizabeth II held her official birthday on a Thursday but has since switched over to Saturdays. And while the date is tied to the Trooping the Colour in the UK, Commonwealth nations around the world have their own criteria, which generally involve recognizing it as a public holiday.

Australia started recognizing an official birthday back in 1788, and all the provinces (save one) observe the Queen's Birthday on the second Monday in June, with Western Australia holding its celebrations on the last Monday of September or the first Monday of October.

In Canada, the official birthday has been set to align with the actual birth date of Queen Victoria—May 24, 1819—since 1845, and as such they celebrate so-called Victoria Day on May 24 or the Monday before.

In New Zealand, it's the first Monday in June, and in the Falkland Islands the actual day of the Queen's birth is celebrated publicly.

All in all, just another reason it's great to be Queen.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
What Is the Meaning Behind "420"?
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Whether or not you’re a marijuana enthusiast, you’re probably aware that today is an unofficial holiday for those who are. April 20—4/20—is a day when pot smokers around the world come together to, well, smoke pot. Others use the day to push for legalization, holding marches and rallies.

But why the code 420? There are a lot of theories as to why that particular number was chosen, but most of them are wrong. You may have heard that 420 is police code for possession, or maybe it’s the penal code for marijuana use. Both are false. There is a California Senate Bill 420 that refers to the use of medical marijuana, but the bill was named for the code, not the other way around.

As far as anyone can tell, the phrase started with a bunch of high school students. Back in 1971, a group of kids at San Rafael High School in San Rafael, California, got in the habit of meeting at 4:20 to smoke after school. When they’d see each other in the hallways during the day, their shorthand was “420 Louis,” meaning, “Let’s meet at the Louis Pasteur statue at 4:20 to smoke.”

Somehow, the phrase caught on—and when the Grateful Dead eventually picked it up, "420" spread through the greater community like wildfire. What began as a silly code passed between classes is now a worldwide event for smokers and legalization activists everywhere—not a bad accomplishment for a bunch of high school stoners.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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