What is an atmospheric river anyway? Or an inside slider? Here's a glossary of SoCal weather terms

Atmospheric river. Pineapple express. Inside slider.

The weather terminology in SoCal can be a lot to keep up with, so we put together a mini glossary of terms that seem to come up in our region — with the help of some real meteorologists.

Atmospheric river

These can be thought of as long, narrow rivers of condensed water vapor in the sky. They can hold twice the water of the Amazon, according to the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography at UC San Diego. These stringy hoses bring California up to half of its annual precipitation.

Atmospheric rivers form when water evaporates up from the warm Pacific Ocean and then snakes into the West Coast, sometimes causing flooding and heavy snow.

And if you feel like you’ve been hearing a lot more about them lately, you’re probably not alone.

“There’s been a lot of science dedicated to categorizing and understanding [atmospheric rivers] better as of recently. So that’s probably how it ended up taking off a little more in terms of the usage,” Rose Schoenfeld, a National Weather Service meteorologist, told LAist.

Pineapple express

No, it’s not just a strain of weed, but yes, it is a stoner film from 2008. In weather terminology, a pineapple express is basically the old school term for a strong atmospheric river that’s capable of bringing moisture from down south in the tropics. Where they grow pineapples. Get it?

Tropical storm

Think of them as something that can look like a hurricane, but less severe, said Schoenfeld. She added that tropical storms can affect SoCal in a variety of ways.

“Most notable... by heading towards us and making rainfall, like Hurricane Hilary,” Schoenfeld said. “They can also impact us by being far away from us but they can send us some large swell from the south, they can send us some big waves."

Tropical storms are characterized by warm water temperatures providing energy.

Graupel (pronounced GRAW-pull)

It kind of looks like snow, but it's technically something else. Sometimes we see it in Southern California during especially cold storms.

Schoenfeld said it can kind of look like hail, but messier and it’s formed in a “process called riming, which is when ice supercools... onto the snow particle.”

In Los Angeles at least, one area man was seen losing himself upon the arrival of this rare delight. Behold our former education reporter, Kyle Stokes.

Former LAist education reporter Kyle Stokes enjoys the graupel falling on Pasadena in 2019.

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Kristen Muller

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LAist

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Inside slider

It’s not a secret menu bar food, but it is a weather term Schoenfeld said she hears a lot at the office.

These low pressure systems come at us from over the land.

“An inside slider is going to come at us from a little bit northeast direction. And so it’s going to be pretty dry because it would have been over land before. So inside sliders would generally just strum up a lot of winds for us and colder temperatures,” Schoenfeld said.

ARkStorm

No, it’s not a metal band. Or is it? And if you’re thinking of sneaking it into your disaster movie screenplay, we’ve got dibs.

ARkStorm (AKA Atmospheric River 1,000 year storm) is basically a doomsday scenario imagined by researchers at the U.S. Geological Survey. In this weather apocalypse, multiple large atmospheric rivers slam into California with “the fury rivaling that of hurricanes.”

The researchers of the “large, scientifically realistic meteorological event” imagined a scenario where as much as 10 feet of rain falls and hundreds of billions of dollars in damage is done after almost a month of continuous rain.

“The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years,” according to a USGS summary.

While the ARkStorm may be fuel for nightmares, Schoenfeld said she and her colleagues aren’t forecasting it at the moment.

But when they do, you'll at least know what it means.