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Two tropical cyclones orbiting around each other in the northwestern Pacific Ocean on July 25, 2017.
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The Coolest Meteorological Term You'll Learn This Week

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Two tropical cyclones orbiting around each other in the northwestern Pacific Ocean on July 25, 2017.
RAMMB/CIRA

What happens when two hurricanes start to invade each other's personal space? It's easy to picture the two hurricanes merging into one megastorm that tears across the ocean with twice the fury of a normal storm, but what really happens is less dramatic (although it is a beautiful sight to spy on with satellites). Two cyclones that get too close to one another start to feel the pull of a force called the Fujiwhara Effect, a term that's all the rage in weather news these days.

The Fujiwhara Effect occurs when two cyclones track close enough to each other that the storms begin orbiting around one another. The counterclockwise winds spiraling around each cyclone force them to participate in what amounts to the world's largest game of Ring Around the Rosie. The effect is named after Sakuhai Fujiwhara, a meteorologist who studied this phenomenon back in the early 1900s.

The extent to which storms are affected by the Fujiwhara Effect depends on the strength and size of each system. The effect will be more pronounced in storms of equal size and strength; when a large and small storm get too close, the bigger storm takes over and sometimes even absorbs its lesser counterpart. The effect can have a major impact on track forecasts for each cyclone. The future of a storm completely depends on its new track and the environment it suddenly finds itself swirling into once the storms break up and go their separate ways.

We've seen some pretty incredible examples of the Fujiwhara Effect over the years. Hurricane Sandy's unusual track was in large part the result of the Fujiwhara Effect; the hurricane was pulled west into New Jersey by a low-pressure system over the southeastern United States. The process is especially common in the northwestern Pacific Ocean, where typhoons fire up in rapid succession during the warmer months. We saw a great example of the effect just this summer when two tropical cyclones interacted with each other a few thousand miles off the coast of Japan.

Weather Channel meteorologist Stu Ostro pulled a fantastic animated loop of two tropical cyclones named Noru and Kulap swirling around each other at the end of July 2017 a few thousand miles off the coast of Japan.

Typhoon Noru was a small but powerful storm that formed at about the same latitude as Kulap, a larger but much weaker storm off to Noru's east. While both storms were moving west in the general direction of Japan, Kulap moved much faster than Noru and eventually caught up with the latter storm. The Fujiwhara Effect caused Typhoon Noru to stop dead in its tracks, completely reverse its course and eventually perform a giant loop over the ocean. Typhoon Noru quickly strengthened and became the dominant cyclone; the storm absorbed Kulap and went on to become a super typhoon with maximum winds equivalent to a category 5 hurricane.

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Two tropical cyclones orbiting around each other in the northwestern Pacific Ocean on July 25, 2017.
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science
Geological Map Shows the Massive Reservoir Bubbling Beneath Old Faithful
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Yellowstone National Park is home to rivers, waterfalls, and hot springs, but Old Faithful is easily its most iconic landmark. Every 45 to 125 minutes, visitors gather around the geyser to watch it shoot streams of water reaching up to 100 feet in the air. The punctual show is one of nature’s greatest spectacles, but new research from scientists at the University of Utah suggests that what’s going on at the geyser’s surface is just the tip of the iceberg.

The study, published in the journal Geophysical Research Letters, features a map of the geological plumbing system beneath Old Faithful. Geologists have long known that the eruptions are caused by water heated by volcanic rocks beneath the ground reaching the boiling point and bubbling upwards through cracks in the earth. But the place where this water simmers between appearances has remained mysterious to scientists until now.

Using 133 seismometers scattered around Old Faithful and the surrounding area, the researchers were able to record the tiny tremors caused by pressure build-up in the hydrothermal reservoir. Two weeks of gathering data helped them determine just how large the well is. The team found that the web of cracks and fissures beneath Old Faithful is roughly 650 feet in diameter and capable of holding more than 79 million gallons of water. When the geyser erupts, it releases just 8000 gallons. You can get an idea of how the reservoir fits into the surrounding geology from the diagram below.

Geological map of geyser.
Sin-Mei Wu, University of Utah

After making the surprising discovery, the study authors plan to return to the area when park roads close for the winter to conduct further research. Next time, they hope to get even more detailed images of the volatile geology beneath this popular part of Yellowstone.

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Two tropical cyclones orbiting around each other in the northwestern Pacific Ocean on July 25, 2017.
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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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YouTube

At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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