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Konrad Fiedler/AFP/Getty Images
Konrad Fiedler/AFP/Getty Images

Is California's Drought Finally Ending?

Konrad Fiedler/AFP/Getty Images
Konrad Fiedler/AFP/Getty Images

One of the most devastating weather disasters in the past decade wasn’t a tornado tearing through the Plains or a hurricane swirling ashore, but rather the slow-motion dehydration of the most populous state in the United States. California has spent the past five years mired in its worst drought in centuries, which devastated crops and water supplies across the state. While the adverse effects of the drought will take much longer to wear off, the state recently got some good news about its improving liquid fortunes.

The latest issue of the United States Drought Monitor (USDM) shows that just over half of California is still in a drought. More than half of an enormous state steeped in drought sounds pretty bad, but conditions have actually improved tremendously over the past couple of months.

The United States Drought Monitor for California on January 31, 2017. Image Credit: Dennis Mersereau

At the end of January 2016, 95 percent of California was in some level of drought, and 40 percent of that area was in that scale-topping "exceptional drought" category. Today, one-fifth of the state is still in a severe drought, and a tiny portion—just under 2 percent—is in an extreme drought. No part of California is experiencing an exceptional drought anymore, the most urgent level on the five-point scale used to determine drought status.

The USDM is a weekly analysis drawn by scientists who look at precipitation, groundwater, and soil data to determine how dry the ground is across the entire country. The lowest categories—abnormally dry and moderate drought—are usually transient and can come and go with unusual dry spells. But in the case of California’s water troubles, extreme and exceptional drought conditions have become commonplace over the past few years.

The worst drought in the modern history of California began at the beginning of 2012 and steadily worsened over the next five years. The intensely dry weather came to a head in 2014, leading some scientists to declare the presence of a “megadrought”—a lack of rain in the western United States so extreme and long-lasting that such conditions haven’t occurred in this region since the 12th century. But then conditions improved somewhat during the winters of 2015 and 2016, culminating with this winter’s drought-busting deluge.

The progression of California’s drought as seen through the USDM’s weekly drought analyses. Image Credit: Dennis Mersereau

 
The solution to drought is always a prolonged period of steady, soaking rainfall and, in the case of mountainous regions, decent storms with accumulating snow. Weather patterns began to shift early this winter into a configuration that let ample moisture flow over drought-stricken areas of the West Coast. A steady flow of tropical moisture, a phenomenon known as an “atmospheric river,” helped storm systems wring out as much precipitation as possible over areas that needed it the most.

The recent period of much-looked-for rain in California started in earnest around the middle of December 2016 and continued through the end of January. After just above average precipitation in December in San Francisco, the Bay Area saw nearly twice its normal January rainfall by the end of January. It’s a similar story across the rest of California.

Precipitation between November 3, 2016 and February 1, 2017, as compared to normal. Image Credit: Dennis Mersereau

There’s even better news in the mountains, where springtime runoff contributes significantly to reservoirs and groundwater in lower-lying areas of the state. The storms that brought rain to the rest of California brought even greater amounts of snow to the mountains. Some mountainous towns have snow depths taller than most houses. A ski resort near Lake Tahoe saw so much snow in one January snowstorm that their chair lifts were buried.

But the latest forecast from the Climate Prediction Center calls for a general trend of below-average rainfall during the month of February and equal chances for below- or above-average precipitation through the early spring months. It’s worth noting that another long period of dry weather could erase the gains California has seen over the past month or two. More often than not, drought begets drought, and it can be a tough cycle to break once it begins. Still, the recent rainfall is a welcome sign nonetheless, and one that will hopefully continue in rainy seasons to come.

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Weather Watch
Thanks to Desert Dust, Eastern Europe Is Covered in Orange Snow
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iStock

Certain areas of Eastern Europe are starting to look a bit like Mars. Over the last few days, snowy places like Sochi, Russia have experienced an unusual snowfall that coated mountains in orange powder, according to the BBC.

The orange snow was the result of winds blowing sand from the Sahara east to places like Moldova, Romania, Bulgaria, Ukraine, and Russia. The sand mixes with precipitation to form orange-tinted snow. According to the BBC, the phenomenon occurs semi-regularly, turning snow orange about once every five years, but this year is especially sandy. As a result, skiers are navigating slopes that look like they're from a different world, as you can see in the video below from The Guardian.

The Sahara rarely gets snow, but when it does, the landscape can look somewhat similar, as you can see in this image of the Atlas mountains in Morocco.

Instagram is currently filled with photos and videos from Eastern Europe featuring the odd-looking snow. Check out a few samples below.

[h/t BBC]

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Weather Watch
What Is Thundersnow?
Jessica Kourkounis, Getty Images
Jessica Kourkounis, Getty Images

The northeastern United States is dealing with its second major nor'easter in a week, with rain and heavy snow—and the associated power outages—cutting a path across the Mid-Atlantic and New England. But news of the adverse impacts of the snowstorm is being accompanied by an unusual buzzword: thundersnow. Thundersnow occurs during a thunderstorm that produces snow instead of rain. The mechanisms that produce rainy thunderstorms and snowy thunderstorms are largely the same, even if the air temperature is below freezing.

A band of snow can become strong enough to produce lightning through two processes known as convection and forcing. Convection occurs when an area of warm air quickly rises through cooler air above it. Convective snow is most common during lake effect snow events like those you’d find on Lake Ontario or Lake Erie, since the process requires extreme vertical temperature gradients that can result from bitterly cold air flowing over a warm body of water.

Forcing is slightly different. A strengthening low-pressure system involves fast, dynamic changes in the atmosphere, especially when one of these storm systems quickly gains strength. Such a fast-developing storm can cause large amounts of lift in the atmosphere, a process that forces air to swiftly rise like you’d see during convection. This creates intense bands of snow that can grow so strong that they produce thunder and lightning. This process is responsible for the thundersnow that occurs during blizzards and nor’easters, those powerful storms that regularly hit the eastern coast of the U.S. during the winter. Thundersnow can be pretty exciting—just ask The Weather Channel's Jim Cantore:

The name “thundersnow” can be a bit misleading. One of the most enjoyable things about a snowfall is how silent it is outside when there’s a thick blanket of snow on the ground. Snow absorbs sound waves so efficiently that you can usually only hear ambient noises immediately around where you’re standing. Snow muffles the sound of thunder for the same reason. Thunder that might be audible for many miles during a rainy thunderstorm might only be audible for a few thousand feet away from where the lightning struck. Unless the lightning strikes very close to where you are, you might only see a bright flash during thundersnow without ever hearing the thunder.

While thundersnow is a fascinating phenomenon to encounter, it does involve lightning, after all, and it’s just as dangerous as any other lightning bolt you’d see in a rainy thunderstorm. If you’re ever lucky enough to experience thundersnow, the event is best enjoyed indoors and out of harm’s way.

This piece originally ran in 2017.

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