Welcome to March! We’re approaching the end of winter and the inevitable climb toward summer. The annual ritual of warmth flushing out the cold makes the atmosphere pretty restless, allowing dangerous storms to bubble up on a regular basis. It’s critically important for everyone to know what to do when bad weather strikes, and staying safe begins with knowing these five terms meteorologists most often use to talk about life-threatening weather.
1. SEVERE THUNDERSTORM
The defining characteristic of spring weather in the United States is severe thunderstorms. A severe thunderstorm is one that produces hail the size of quarters or larger, wind gusts that reach 58 mph or stronger, or a tornado.
Severe thunderstorms can seriously injure or kill you if you’re caught outside during one or if you’re in a building that can’t withstand the fierce winds or damaging hail. After all, the damaging wind gusts within a severe thunderstorm can cause as much damage as a tornado. Hail is no laughing matter, either—hail that seems small can easily shatter windows, especially when it falls during strong winds.
Tornadoes are the most well-known type of severe weather. These destructive forces can range in shape from a thin rope to a wedge that consumes the landscape. Most tornadoes are small and don’t cause much damage, but a handful of tornadoes every year are strong enough to level entire neighborhoods.
One of the most dangerous things about a tornado is that you can’t always see one coming. We can see tornadoes because of the condensation funnel, or the cloud that forms as a result of the low pressure within the rotating column of air. Some tornadoes—especially when they just start to form—don’t have that condensation funnel, making them hard to spot until it’s too late. To make matters worse, many tornadoes that form in humid areas are often wrapped in heavy rain, making one impossible to see until it’s right on top of you.
3. STORM PREDICTION CENTER
A severe weather outlook from February 23, 2016, showing a moderate risk of severe weather along the northern Gulf Coast. (IMAGE: SPC)
The Storm Prediction Center (SPC) is a branch of the National Weather Service that’s devoted to predicting severe thunderstorms. The agency issues thunderstorm forecasts up to seven days out. The risk for severe weather is conveyed using a five-category scale that ranges in severity from “marginal risk” to “high risk.” Days featuring a high risk—a 5 on the scale—are extremely rare, saved for the worst severe weather outbreaks that could produce widespread destruction and claim dozens if not hundreds of lives.
You should check the SPC at least once a day during severe weather season, and more often if hazardous weather is on your doorstep.
One of the most common terms you’ll hear during the spring and summer is a “watch,” either a severe thunderstorm watch or a tornado watch. A watch means that conditions are favorable for dangerous thunderstorms to develop over the next couple of hours. If you’re ever placed under a watch, it means that you should keep an eye out for urgent weather updates through the day.
Severe thunderstorm and tornado watches are issued for wide areas on a county basis, sometimes covering entire states. You should always know what county you live in and what counties surround you—it could save your life one day.
Weather radar shows a large tornado moving toward Moore, Oklahoma, on May 20, 2013. The National Weather Service issued a tornado emergency before the EF-5 tornado devastated the town south of Oklahoma City. (IMAGE: Gibson Ridge)
When a severe thunderstorm develops, meteorologists at the National Weather Service will issue a severe thunderstorm warning that alerts you to the imminent arrival of large hail or damaging winds. A tornado warning means that meteorologists detect rotation in a thunderstorm or that someone has spotted a tornado on the ground.
A warning is an urgent alert that means your immediate safety is at risk. Warnings are issued ahead of individual storms using polygons on a map that cover areas most likely to see dangerous weather. Most severe thunderstorm and tornado warnings are issued 15 to 30 minutes before the storm arrives, but sometimes there’s little or no warning ahead of time. If you’re ever placed under a warning, you have to act quickly to protect your life.
Sometimes when a large tornado is barreling toward a city, the National Weather Service will issue an extremely rare “tornado emergency” instead of a tornado warning. The enhanced language is designed to drive home the point that your safety is at grave risk.