Atmospheric science

Hail the size of grapefruit shattered car windows in Johnson City, Texas. In June, 2024, a storm chaser found a hailstone almost as big as a pineapple. Even larger hailstones have been documented in South Dakota, Kansas and Nebraska. Hail has damaged airplanes and even crashed through the roofs of houses. How do hailstones get so large, and are hailstorms getting worse? As an atmospheric scientist, I study and teach about extreme weather and its risks. Here’s how hail forms, how hailstorms may be changing, and some tips for staying safe. How does hail get so big? Hail begins as tiny crystals of ice that are swept into a thunderstorm’s updraft. As these ice embryos collide with supercooled water – liquid water that has a temperature below freezing – the water freezes around each embryo, causing the embryo to grow. A hailstone cut in half, which reveals layers of clear and cloudy ice formed as the hailstone journe...

As the weather warms, people spend more time outdoors, going to barbecues, beaches and ballgames. But summer isn’t just the season of baseball and outdoor festivals – it’s also lightning season. Each year in the United States, lightning strikes around 37 million times. It kills 21 people a year in the U.S. on average. For as often as lightning occurs – there are only a few days each year nationwide without lightning – there are still a lot of misunderstandings about nature’s largest spark. Because of this, a lot of people take unnecessary risks when thunderstorms are nearby. I am a meteorologist who studies lightning and lightning safety, and a member of the National Lightning Safety Council. Here are some fast facts to keep your family and friends safe this summer. What is lightning, and where does it come from? Lightning is a giant electric spark in the atmosphere and is classified based on whether it hits the ground or not. In-cloud li...

Dozens of tornadoes hit the central U.S. April 26-28, 2024, tearing through suburbs and small towns and damaging hundreds of homes from Oklahoma to Nebraska and Iowa. Spring is tornado season in the U.S., but the tornadoes in Nebraska and Iowa were quite a bit farther north and east of what would be typical for tornadoes in late April, when tornado activity is more common in Oklahoma and Texas. The outbreak did fit another pattern for severe weather events, however, that occur as the atmosphere transitions out of El Niño. And this is exactly what was happening in late April. I study tornadoes and the conditions under which they form. Here’s how these storm systems develop and what El Niño has to do with it. Preliminary reports of tornadoes and hail during severe storms on April 26, 2024, collected by the National Oceanic and Atmospheric Administration’s Storm Prediction Center. NOAA...

Meteorologists have been talking for weeks about a snowy season ahead in the southern Rockies and the Sierra Nevada. They anticipate more storms in the U.S. South and Northeast, and warmer, drier conditions across the already dry Pacific Northwest and the upper Midwest. One phrase comes up repeatedly with these projections: a strong El Niño is coming. It sounds ominous. But what does that actually mean? We asked Aaron Levine, an atmospheric scientist at the University of Washington whose research focuses on El Niño. NOAA explains in animations how El Niño forms. What is a strong El Niño? During a normal year, the warmest sea surface temperatures are in the western Pacific and the Indian Ocean, in what’s known as the Indo-Western Pacific warm pool. But every few years, the trade winds that blow from east to west weaken, allowing that warm water to slosh eastward and pile up along the equator. The warm water causes...

Torrential downpours sent muddy water racing through streets in Libya, Greece and Spain and flooded parts of Hong Kong and New York City in September 2023. Thousands of people died in the city of Derna, Libya. Zagora, Greece, saw a record 30 inches of rain, the equivalent of a year and a half of rain falling in 24 hours. A few weeks earlier, monsoon rains triggered deadly landslides and flooding in the Himalayas that killed dozens of people in India. After severe flooding on almost every continent this year, including mudslides and flooding in California in early 2023 and devastating floods in Vermont and New York in July, it can seem like extreme rainfall is becoming more common. So, what role does global warming play in this? And importantly, what can we do to adapt to this new reality? A powerful storm system in 2023 flooded communities across Vermont and left large parts of the capital, Montpelier, underwater. John Tul...