Some in South Carolina were pelted with hail ranging from marble to tennis-ball sized during a series of thunderstorms last Friday. But it just so happened that an ER-2 NASA aircraft was conducting atmospheric research over S.C. at 65,000 feet as part of the IPHEX project and pilot Stu Broce had a front row seat to the storms from quite the unique perspective.
He snapped a series of photos showing the towering thunderstorms that were estimated as high as 50,000-55,000 feet! To compare, typical thunderstorms in the Puget Sound region reach 10,000-15,000 feet tall, maybe 20,000 in our strongest events.
Meteorologist Ed Piotrowski with WPDE-TV in Myrtle Beach, S.C. originally posted the photos and had this excellent description of how what you're seeing:
"Notice how the the clouds spread out creating a saucer shape at the top of the storm," he wrote. "This is the anvil and it normally forms at the tropopause ( boundary between the troposphere and the stratosphere) where the surrounding air is warmer. The tropopause acts like a lid, deflecting the rising air and causing it to spread outward. Often jet stream winds will carry the anvil (cirrus clouds) far downwind."
And as far as the bubbling clouds that seem to shoot through the anvil? "Sometimes the updraft is so strong/fast that the momentum of the rising air can break through the lid and carry clouds above the anvil. Overshooting tops are often indicative of severe storms," he wrote.
It's those intense updrafts and the altitude of the storms that help the hailstones grow so large. The updrafts push raindrops up into the higher reaches of the cloud where it's well below freezing and the raindrops freeze into an ice pellet.
The pellet eventually gets too heavy for the tip of the updraft and falls back toward the Earth, getting wet again as it falls through more raindrops. It encounters the stronger updraft at the base of the cloud and gets shot upward again into the sub-freezing temperatures where the water on the pellet freezes again, adding another layer of ice. That pellet falls, gets wet, hits the updraft, goes back up, and grows again with another layer of ice.
This process repeats until the hail stone is heavier than the updraft can support it and it finally falls to the ground. The stronger the updraft, the larger the hailstone can grow. It's said a 56 mph updraft will support a golf-ball-sized hailstone, so the updrafts in these particular hailstorms featured above were even stronger!