Scientists discover new details of icy plumes that foreshadow deadly storms

One of the biggest hazards to people around the world are major storms that spawn flooding, tornadoes, and other disasters. Scientists from Stanford University published a new study that they believe solves a mystery having to do with plumes of ice and water vapor that sometimes appear above under storms. Researchers say these mysterious icy plumes could foreshadow potentially deadly supercell storms.

Scientists know that when plumes of ice and water vapor rise above severe thunderstorms, the chances of tornadoes, high winds, or big hail impacting land below is high. The new Stanford study has discovered the mechanism behind these plumes and its link to a phenomenon observed by Leonardo Da Vinci more than 500 years ago.

The plumes are tied to a phenomenon called "hydraulic jumps." One of the questions the study sought to answer was why the plumes were associated with the worst weather conditions. Research in the past showed that plumes of the sort are easy to spot in satellite images and often show up 30 minutes or more before severe weather impacts the ground below. Study lead author Morgan O'Neill is an assistant professor of Earth system science at Stanford.

Supercell storms have a rotating draft that can push into the sky at speeds higher than 150 miles per hour. Those updrafts have the force to punch through the troposphere, which is the lowest layer of the atmosphere. Using simulations of supercell thunderstorms, researchers discovered the downslope windstorm caused by rising air in the storms could generate wind speeds of over 240 miles per hour.

The extremely dry air coming down from the stratosphere meets moist air rising from the troposphere in a very narrow and extremely fast jet of air. Researchers note that wind speeds that high were never observed or hypothesized in the past. The new model suggests the turbulence in the atmosphere accompanying these plumed storms is created by a phenomenon called a hydraulic jump. Simulations suggest a hydraulic jump coincides with rapid water vapor injection into the stratosphere at rates of up to 7000 kilograms per second. While this phenomenon has yet to be confirmed, O'Neill says we have the technology to verify the models, something the researchers hope to do.