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Your Storm Forecast Is Going to Get More Precise

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Just about every alert you hear before a storm creeps up on the horizon was issued by the National Weather Service (NWS). We use this federal agency's services almost every day without thinking about it. Daily forecasts, storm alerts, weather radars, and satellite images are all produced by thousands of meteorologists who work day and night to keep us safe. One part of keeping us safe is making sure we understand what they're trying to tell us. After all, what good is a warning if you don't know exactly what they're trying to say? The NWS is working to simplify the warning process to give us better information and help us make better decisions to stay safe during hazardous weather.

Right now, the NWS issues dozens of different alerts that cover all sorts of dangerous conditions. These alerts are called watches, advisories, and warnings, with each respective category carrying a greater sense of urgency. There are alerts for tornadoes, severe thunderstorms, floods, hurricanes, winter storms, and even conditions like dense fog or blowing dust.

The sheer number of alerts can be daunting, not to mention the sometimes-convoluted language forecasters use to tell us what's going on. It's easy to miss the distinction between a tornado watch and a tornado warning, for example. The Hazards Simplification Project is an ongoing effort within the National Weather Service to whittle down the number of alerts and use clearer language to give us a leg-up on dangerous weather conditions.

The first couple of changes will go into effect later in 2017. The NWS currently issues 10 different alerts for winter weather events such as blizzards, ice storms, lake effect snow, and snowstorms. In the winter, the agency will reduce the number of alerts to just six. They're getting rid of the blizzard watch, for example, merging it with the winter storm watch. Winter weather alerts will also be issued in a “what/where/when” format, outlining exactly how much snow or ice you can expect, where it's expected, and when it's expected to happen. Previously, you had to scour a few paragraphs of text to figure out what was coming your way.

The NWS will also look into changing their weather maps to display just four different colors when weather alerts are in effect—a dramatic change from the hodgepodge of colors that smear weather maps today. Each weather alert currently has its own unique color on weather maps, so these maps are almost indecipherable when there's a lot of active weather across the country. The agency may soon replace all of these colors with just four hues—yellow, orange, red, and purple—to convey the severity and urgency of the alert in effect.

improved hazardous weather map from the NOAA
A swath showing the probability of a tornado near Birmingham, Alabama, under the new FACETs project. The old tornado warning polygon is outlined in red.
NOAA/NSSL

There are also some big changes in the works for warnings in the future. Meteorologists used to issue tornado and severe thunderstorm warnings for entire counties, which didn't work out too well as some counties in the United States are enormous compared to the size of a single thunderstorm. About a decade ago, they reduced these warnings to polygons that covered just the area expected to be impacted by the storm. This greatly reduced false alarms and helped warn only the people who needed to take shelter.

In the next couple of years, the NWS will roll out a project called Forecasting a Continuum of Environmental Threats (FACETs). This project will reduce those old warning polygons even further into a swath that shows the probability that a certain area will be affected by a tornado, large hail, or damaging winds. The resulting warning area, seen above, looks similar to the cone of uncertainty forecasters use ahead of hurricanes and covers a much smaller area than the old polygons. This will allow forecasters to warn only those directly affected by the approaching hazards, reducing false-alarm rates even further and giving people greater confidence that they should take action right away instead of waiting it out.

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Britain Is in the Midst of a Rare ‘Wind Drought’
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Generating renewable energy in Britain is a little less than a breeze these days: A “wind drought” is halting the country’s wind turbines.

This month’s wind energy output is down 40 percent from the same time last year, New Scientist reports. On average, about 15 percent of Britain’s electricity comes from wind power. Data starting from July 1 of this year put the monthly average closer to 6.9 percent. Last month, turbines were producing less than 2 percent of Britain’s electricity—the lowest output in two years.

That’s with even more wind turbines being installed over the course of the past year, New Scientist says. The data aren’t entirely surprising, though. The jet stream tends to make the UK’s weather drier and calmer during the summer and wetter and stormier during the winter. But the high pressure the jet stream has brought with it this year has been unusually prolonged, scientists say.

“It’s like a lid, it keeps everything still,” UK Met Office spokesperson Grahame Madge told New Scientist. “From the forecast looking out over the next couple of weeks, there doesn’t seem to be any significant change on the way.”

The wind drought shouldn’t cause too many problems in the short term. Electricity demand is low during the summer (very few British homes have air conditioning), and the country’s been able to compensate for the lack of wind by burning more natural gas. If the wind drought continues to persist, though, UK residents may begin to see an increase in utility fees. Natural gas prices have already risen with the increased demand.

“As we continue to transition to a low-carbon energy system, managing the intermittency of renewable power an important role in balancing supply and demand,” a National Grid spokesperson told New Scientist. “However, we have planned for these changes and [are] ready to play our part.”

The wind drought comes about eight years after British politicians vowed to reduce the UK's dependence on fossil fuels. Last year was the first year that electricity generated from low-carbon energy sources like solar power, wind power, and nuclear power outpaced high-carbon energy sources like coal and natural gas. This summer’s wind drought may make it difficult to improve on last year’s numbers.

[h/t New Scientist]

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Why Does the Sky Look Green Before a Tornado?
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A common bit of folklore from tornado-prone parts of the U.S. says that when the skies start taking on an emerald hue, it's time to run inside. But why do tornadoes tend to spawn green skies in the first place? As SciShow's Michael Aranda explains, the answer has to do with the way water droplets reflect the colors of the light spectrum.

During the day, the sky is usually blue because the shorter, bluer end of the light spectrum bounces off air molecules better than than redder, longer-wavelength light. Conditions change during the sunset (and sunrise), when sunlight has to travel through more air, and when storms are forming, which means there are more water droplets around.

Tornadoes forming later in the day, around sunset, do a great job of reflecting the green part of the light spectrum that's usually hidden in a sunset because of the water droplets in the clouds, which bounce green light into our eyes. But that doesn't necessarily mean a twister is coming—it could just mean a lot of rain is in the forecast. Either way, heading inside is probably a good idea.

For the full details on how water and light conspire to turn the sky green before a storm, check out the SciShow video below.

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