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6 Lesser-Known Terms for Weather Phenomena

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This summer, you’re bound to hear emergency broadcasts, news reports, and videos of massive thunderstorms, with commentary and terminology you might not be familiar with. Knowing what those words mean can tell you a lot more about what’s going on than just what’s shown on the screen. Here are six lesser-known terms that are associated with the storm season.

1. Derecho


Directly translated from Spanish, “derecho” means “straight,” and, fittingly, straight-line wind damage is a defining characteristic of this weather event. Derechos, like tornados, tend to accompany massive thunderstorms, and the storms that form them are frequently preceded by low, dark “shelf clouds” (arcus, as seen above). However, unlike tornadoes, the damage they cause is not from rotating wind or vortices. They’re formed by cold wind from thunderstorms being pushed downwards (a downburst) and rapidly spreading out in all directions once it hits the ground. This blast can lead to major damage over a large area.

Straight-line wind damage is common in thunderstorms, but a derecho is defined as a wind-damage swath that extends more than 240 miles (approximately 400 km), and which has wind gusts of at least 58 mph (93 km/h) throughout most of its length. Derechos are most common along the “corn belt” in the United States, but even where they’re most prevalent, there are rarely more than two in a year (compared to 10 to 15 tornadoes a year in the most vulnerable areas). Their rarity is due to the fact that, unlike tornadoes or hurricanes, they’re not a unified and singular event, but rather an uncommon phenomenon that was considered noteworthy enough to be given a name back in 1888. The damage and top wind speed of the derecho often varies along its length because of the fact that it isn’t a unified event, but rather a long line of individual downbursts, each with their own microbursts and microclimates.

2. Squall line


Also known as multicell lines, squall lines develop from a common “lifting mechanism,” such as a cold front. Included in squall lines are multiple thunderstorm cells, all around the same stage in their lifecycle. They differ from other thunderstorm types, which are known as single cell (or pulse) storms, multicell clusters (where the storm cells are in different stages and don’t necessarily connect or move together), and supercell thunderstorms.

The greatest risk in squall lines tends to be the strong downdrafts, which can cause serious problems for aviation, and can cause major damage on the ground, such as in the case of derechos. Most derechos in North America develop from squall lines.

3. Virga

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From the Latin word meaning “rod, branch,” virgae often look like fuzzy rods or curtains hanging from clouds, and are a common meteorological phenomenon. These rods are shafts of precipitation that fall from clouds, but never reach the ground. They can be seen year-round, often over the desert or prairie, especially in temperate climates.

Precipitation often falls as ice crystals in the high atmosphere but melts as it falls. In the case of virga, this melted water eventually evaporates before hitting the ground. As one might expect, virga tends to develop from high-altitude clouds, when the atmosphere is somewhat warm and dry, allowing it to evaporate moisture easily. The evaporative cooling caused by virga can cause sometimes cause a dramatic temperature drop and strong convective surface winds or microbursts.

4. Crepuscular rays

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Like with virga, you’ve almost certainly seen crepuscular rays before, but might not have known the name. These rays are the “sunbeams” you see coming from the clouds, and the beams of light seen during the crepuscular (“twilight”—dawn or dusk) hours. They appear to converge at the sun, even though they’re actually parallel beams of light. The convergence is similar to how a train track appears to converge on the horizon, even though you know that it remains parallel.

These rays are formed due to the sunlight bouncing off of particulate matter and water vapor in the atmosphere. Since the sunlight passes through ten times the amount of atmosphere at dawn and dusk as compared to midday, there are many more particles for it to bounce off of before it reaches our eyes.

5. Haboob

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Despite its Arabic name (meaning “blasting”), haboobs are a worldwide phenomenon. In North America, “haboob” is occasionally used interchangeably with any dust storm, but it’s more frequently used in the context of a very intense dust storm wall that’s associated with the gust front of a severe thunderstorm. They can overtake a neighborhood or city in minutes, with wind speeds over 40 mph and dust so thick that there is zero visibility. As the haboobs can begin suddenly, be more intense than the average dust storm, and pick up any small particulate matter (such as infectious fungi and industrial metal waste) in their path, there is a serious risk posed to both transportation and public health when people don’t know how to react.

Protocol for haboobs is the same as other dust storms, but can be even more important, especially for those with chronic lung disease. If you’re outside, go inside if at all possible. If there are no indoor locations available nearby, cover your nose and mouth with fabric (such as a shirt). If you’re driving, pull over. Seriously, just wait out the dust; it won’t be that long. Despite the risk to lung health, nearly all deaths caused by haboobs are due to people continuing to drive through them, and getting into accidents.

Are you poetic? Do you understand the importance of waiting out a haboob? Maybe you can help out the Arizona Department of Transportation—this is the second year they’ve had a “Haboob Haiku” contest to promote dust storm safety.

6. Petrichor


The storm has passed, and the scent in the air says as much. While the smell before rain may be simple (it’s ozone, created when the atmosphere is electrified), the smell after a storm is a bit more complex, and it has a name: petrichor. Coined in 1964 by Isabel Joy Bear and R. G. Thomas of Australia’s Commonwealth Scientific and Industrial Reasearch Organization, petrichor was originally defined as airborne molecules from decomposing plant and animal matter that have settled on mineral or clay surfaces. The molecules of decay recombine with the molecules naturally on the mineral surface during dry spells, and can be smelled after a storm because the addition of water allows the mixture of fatty acids, alcohols, and hydrocarbons to be released. The term petrichor now encompasses the entirety of the smell after rain, however, not just the sharp dusty-decay scent originally described.

One of the most abundant components of petrichor gives it a musty, earthy smell. This scent is the result of the molecule geosmin. It’s a metabolic by-product of blue-green algae in water, and of Actinomyces bacteria in the soil. While it may be a beckoning call to gardeners, it’s been known for almost a century due to the problems it’s caused in winemaking—geosmin contamination leaves a wine tasting “muddy” or “moldy.”

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Nick Briggs/Comic Relief
What Happened to Jamie and Aurelia From Love Actually?
May 26, 2017
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Nick Briggs/Comic Relief

Fans of the romantic-comedy Love Actually recently got a bonus reunion in the form of Red Nose Day Actually, a short charity special that gave audiences a peek at where their favorite characters ended up almost 15 years later.

One of the most improbable pairings from the original film was between Jamie (Colin Firth) and Aurelia (Lúcia Moniz), who fell in love despite almost no shared vocabulary. Jamie is English, and Aurelia is Portuguese, and they know just enough of each other’s native tongues for Jamie to propose and Aurelia to accept.

A decade and a half on, they have both improved their knowledge of each other’s languages—if not perfectly, in Jamie’s case. But apparently, their love is much stronger than his grasp on Portuguese grammar, because they’ve got three bilingual kids and another on the way. (And still enjoy having important romantic moments in the car.)

In 2015, Love Actually script editor Emma Freud revealed via Twitter what happened between Karen and Harry (Emma Thompson and Alan Rickman, who passed away last year). Most of the other couples get happy endings in the short—even if Hugh Grant's character hasn't gotten any better at dancing.

[h/t TV Guide]