Violent nighttime thunderstorms have sent generations of terrified children scurrying into their parents' beds over the booming sounds of thunder and brilliant flashes of lightning.
Now, for the first time, dozens of scientists are fanning out across the central USA this summer to unlock the mysteries of how these nocturnal storms form and improve forecasts for when they might strike.
The massive field campaign "PECAN" (Plains Elevated Convection at Night) has been underway since June 1 and will continue until mid-July.
"One thing that has been striking to me is that we always see something interesting in the data," Tammy Weckwerth, a PECAN principal investigator with the National Center for Atmospheric Research, said in an email this week. "No matter when we collect data or what the conditions are, there is always something intriguing going on in the atmosphere."
The big nighttime thunderstorms are both a blessing and a curse for the Plains region, where tornadoes often make the most news.
"Nighttime thunderstorms are an essential source of summer rain for crops but are also a potential hazard through excessive rainfall, flash flooding and dangerous cloud-to-ground lightning," said Ed Bensman of the National Science Foundation.
The storms — which typically form in huge clusters — can also be rather challenging to predict. Unlike their daytime counterparts that rely on the sun's heat to form, the development of thunderstorms at night is not well understood.
The field research is allowing scientists to get an up-close look at weather phenomena such as the low-level jet stream (a speedy flow of air about a mile up) and little-understood bores (atmospheric ripples or waves), both of which help stir up the atmosphere to create nighttime storms.
PECAN uses eight mobile radars, three research aircraft, dozens of mobile weather balloon launching systems and more than 100 weather instruments to "chase" severe nighttime storms.
"The sheer number of instruments being coordinated is unprecedented," said Weckwerth, who has been involved in more than 15 other field expeditions.
Other well-known summer field campaigns in the central USA were VORTEX, which studied tornadoes, and MPEX, which looked at storms from above.
"Previous severe weather campaigns have focused mostly on daytime storms, for largely practical reasons, as it is more difficult to set up instruments in the dark," said Bart Geerts, a PECAN principal investigator with the University of Wyoming. "The large thunderstorm complexes traveling across the Great Plains at night really are a different beast."
The scientists on the project are confident the detailed observations will lead to more knowledge about nighttime storms and how they form. "That improved understanding will help us to improve our forecast models, which should lead us to improved forecasting skill," Weckwerth said.
PECAN is a $13.5 million multi-agency project sponsored by the National Science Foundation, NOAA, NASA, and the Department of Energy with participants from eight research laboratories and 14 universities.
