It’s time for another storm-chasing timelapse from photographer Mike Olbinski! “Vorticity 6” focuses on supercell thunderstorms and their tornadoes. There’s billowing turbulent convection, undulating asperitas, bulging mammatus, microbursts, and more. There’s nothing like timelapse to highlight the growth, rotation, and shear involved in these storms. (Video and image credit: M. Olbinski)
Storm-chasing photographer Mike Olbinski (previously) returns with another stunning timelapse of summer thunderstorms in the western U.S. I never tire of watching the turbulent convection, microbursts, billowing haboobs, and undulating clouds Olbinski captures. His work is always a reminder of the incredible power and energy contained in our atmosphere and unleashed in cycles of warming and cooling, evaporation and condensation. (Video and image credit: M. Olbinski)
Conventional wisdom suggests that hailstones form over the course of repeated trips up and down through a storm, but a new study suggests that formation method is less common than assumed. Researchers studied the isotope signatures in the layers of 27 hailstones to work out each stone’s formation history. They found that most hailstones (N = 16) grew without any reversal in direction. Another 7 only saw a single period when upwinds lifted them, and only 1 of the hailstones had cycled down-and-up more than once. They did find, however, that hailstones larger than 25mm (1 inch) in diameter had at least one period of growth during lifting.
So smaller hailstones likely don’t cycle up and down in a storm, but the largest (and most destructive) hailstones will climb at least once before their final descent. (Image credit: D. Trinks; research credit: X. Lin et al.; via Gizmodo)
In spring and summer, major thunderstorms can include dangerous and destructive hailstones. In Catalonia, a group of scientists collected hailstones after a record-breaking 2022 storm, finding some as large as 12 centimeters across. Using a dentist’s CT scanner, they looked at the interior of the hailstones, uncovering layers that reveal how the hail grew. In the past, researchers have studied hail by slicing the ice; that method gives them only a single cross-section through the hailstone, which gets destroyed in the process. In contrast, a CT scan revealed the full interior of the ice.
The scientists found that, even though hail often appears spherical, the nucleus of the hail is not always located in the center. They saw that the hail grew in uneven layers that varied in density, depending on the storm conditions the hail experienced. To get to the enormous sizes seen here, hailstones have to travel up and down repeatedly through a storm, building up layer by layer. From the hail’s interior structure, the team could also tell what orientation the hail took its final fall in; the ice along the bottom of the hailstone was bubble-free, indicating that it collected as water drops hit the surface and froze. (Image credit: T. Ribas; research credit: C. BarquΓ© et al.; via New Scientist)
The intense heat from wildfires fuels updrafts, lifting smoke and vapor into the atmosphere. As the plume rises, water vapor cools and condenses around particles (including ash particles) to form cloud droplets. Eventually, that creates the billowing clouds we see atop the smoke. These pyrocumulus clouds, like this one over California’s Line fire in early September 2024, can develop further into full thunderstorms, known in this case as pyrocumulonimbus. The storm from this cloud included rain, strong winds, lightning, and hail. Unfortunately, storms like these can generate thousands of lightning strikes, feeding into the wildfire rather than countering it. (Image credit: L. Dauphin; via NASA Earth Observatory)
It’s wild that we’re still discovering new weather phenomena, but the gigantic jets seen here were only identified in 2002. This uncommon type of lightning shoots up from the tops of thunderstorms into the ionosphere. The video/image above was caught by cameras normally used to monitor meteors. The jets themselves are red in color, a result of the electrical discharge interacting with nitrogen in the atmosphere. (Video and image credits: b/w – Caribbean Astronomy Society, color – F. Lucena; via Gizmodo)
Stormy skies feature much more than the forked cloud-to-ground lightning we’re used to seeing. This composite image shows a rare and recently-recognized type of lightning known as a gigantic jets. This type of lightning travels from the top of thunderclouds, around 16 km in altitude, up to the ionosphere at about 90 km. Their bottoms look a bit like blue jets, while their upper reaches look like red sprites, two other types of unusual lightning. The mechanism behind gigantic jets is a topic of ongoing research, but your best chance at seeing them is watching a distant thunderstorm from a clear vantage. (Image credit: Li X.; via APOD)
Growing up in northwest Arkansas, I spent my share of summer nights sheltering from tornadoes. Central North America — colloquially known as Tornado Alley — is especially prone to violent thunderstorms and accompanying tornadoes. That’s due, in part, to two geographical features: the Rocky Mountains and the Gulf of Mexico. Trade winds hitting the eastern slope of the Rockies get turned northward, imparting a counterclockwise vorticity. At the same time, warm moist air carried from the Gulf feeds into the atmosphere, creating perfect conditions for powerful thunderstorms. By this logic, though, South America should see lots of tornadoes, too, courtesy of the Andes Mountains and the moist environs of the Amazon Basin. To understand why South America doesn’t have a Tornado Alley, researchers used global weather models to investigate alternate North and South Americas.
They found that smoothness is a key ingredient for the upstream, moisture-generating region. Compared to the Amazon, the Gulf of Mexico is incredibly flat. With a flat Gulf, tornadoes abounded in North America, but their numbers dropped once that area was roughened to mimic the Amazon. The opposite held true, too: a smoothed-out Amazon Basin resulted in more simulated South American tornadoes.
For those in Tornado Alley, the results don’t offer much hope for mitigating our summer storms — we can’t exactly roughen the ocean. But the study does sound a word for warning for South America; the smoother the Amazon region becomes — due to mass deforestation — the more likely tornadoes become in parts of South America. (Image credit: G. Johnson; research credit: F. Li et al.; via Physics World)
A calm, sunny day erupted into a thunderstorm off the coast of Scotland for photographer Brian Matthews. Turbulent clouds streak the sky, and a downpour on the left releases a stream of precipitation. Storms like these were once uncommon in the United Kingdom, but with increasingly hot weather due to climate change, more water vapor and more energy in the atmosphere create conditions for storms like these. (Image credit: B. Matthews; via Wildlife POTY)
Summertime in the middle U.S. means thunderstorms, many of which can form long lines of storms known as squall lines. Complex convective dynamics feed such storms. Here is an illustration of one part of a squall’s lifecycle:
As it falls, rain evaporates, cooling air near the ground and forming a cold pool. If incoming winds block the cold pool from spreading, the pool will act instead as a ramp that redirects the wind upward, carrying any warmth and moisture up into the storm cloud. Wind shear — a vertical variation in wind strength with altitude — creates positve vorticity that opposes the negative vorticity inherent to the cold pool. Together these two regions of opposing vorticity lift more air and moisture into the squall, generating more clouds and more rainfall. (Image credit: top – J. Witkowski, illustration – C. Muller and S. Abramian; see also C. Muller and S. Abramian)