Earth System Science Center and Department of Atmospheric Science at The University of Alabama in Huntsville

PECAN storm studies in Nebraska

Inside the MIPS command vehicle, UAH’s Kevin Knupp and Ashley
Ravenscraft, a senior at UAH, monitor the storm passing overhead.

McCOOK, Neb. – It is Wednesday and the students in UAH’s weather research team are unhappy with the weather here:  It’s much too nice, all blue skies, comfortable breezes and puffy clouds.

They were happier the night before, with one set of their instruments set up in the school parking lot of a small community north of here and the other scanning the sky from several miles away as waves of powerful thunderstorms roiled and crackled overhead, dumping from two to five inches of rain on Nebraska farms and prairies.

That’s why the UAH team is here, to collect data and learn more about some little understood weather systems, including why storms such as the one Tuesday night -- which started earlier in the day northwest of here -- often intensify after the sun goes down.

“Around sunset (which in southwestern Nebraska is after 9 o’clock this time of year) those storms started to take on severe characteristics,” said Kevin Knupp, a professor of atmospheric science and the leader of UAH’s team in this field study. “We caught the  uilding blocks of the MCS (Mesoscale Convective System), and we were right in the middle of that.” 

But that storm was gone by 1:30 a.m., so it was time to pack the instruments and drive back to McCook for a few hours of sleep. Wednesday was spent hanging out and waiting for weather that never got ... interesting.

MCS systems, which are thunderstorms so large they sometimes begin to turn like acyclone, are central to much of the research being done through this field campaign, the Plains Elevated Convection At Night or PECAN study.

While there are four official weather phenomenon being studied this summer, nighttime MCS development is one and two of the others are related.

“The MCS is kind of the key to PECAN,” Knupp said.

One of the reasons so little is known about these storms is that they generally happen after a cool, still layer of nighttime air forms near the ground. That boundary layer isolates the interesting things that are happening in the atmosphere from weather instruments on the surface, "so weather stations are largely useless," said Knupp. "The atmosphere is decoupled from the surface by this cool and stable boundary layer."

That's where PECAN fills in. Using several mobile radars and other instruments that can probe up into the boundary layer and the atmosphere above it, most nights during the campaign PECAN spreads scientists across western Kansas, and parts of Colorado, Nebraska and Oklahoma. UAH is providing five vehicles, including two mobile Doppler radars — one that makes traditional weather sweeps and another that is fixed looking upward, to give detailed information about what is happening at multiple altitudes above the instrument.

With instruments and scientists from eight national laboratories and 14 universities, the PECAN network is large enough and sophisticated enough to collect useful data from any weather events that occur over the study area. The various participants are also expected to launch more than 1,200 weather balloons during the six week campaign.

“We really have the biggest collection of remote sensing instruments, specifically profiling systems that has been brought together to date,” Knupp said. "With aircraft and lots of radars and lots of balloons going into the air, you begin to gather enough data to understand what's going on."

In addition to trying to learn more about what and how nighttime storms start, PECAN will also look for data on how large storm systems build and spread, the effects of gravity waves and bores on nighttime weather conditions, and at the effects fast-moving, low-level winds above the boundary layer have on weather conditions on the Great Plains.

UAH's PECAN preparations and participation — including data analysis after the field campaign — are supported by a 3-year, $730,000 grant from the National Science Foundation (NSF).

PECAN is a $13.5 million project largely funded by the NSF, with additional support from NASA, NOAA and the U.S. Department of Energy.
UAH's Mobile Integrated Profiling Systems collect data while a storm rolls over Maywood, Neb.

UAH’s Mobile Integrated Profiling Systems collect data while
a storm rolls over Maywood, Neb.

Inside the MIPS command vehicle, UAH's Kevin Knupp and Ashley Ravenscraft, a senior at UAH, monitor the storm passing overhead.

Inside the MIPS command vehicle, UAH’s Kevin Knupp and Ashley
Ravenscraft, a senior at UAH, monitor the storm passing overhead.

UAH's Kevin Knupp and graduate student Tony Lyza set up the computers needed to monitor weather instruments as a powerful storm approaches.

UAH’s Kevin Knupp and graduate student Tony Lyza set up the
computers needed to monitor weather instruments as a powerful storm
approaches.

Ashley Ravenscraft, a senior at UAH, secures the instrument payload to a helium balloon about to be launched in front of a powerful storm.

Ashley Ravenscraft, a senior at UAH, secures the instrument
payload to a helium balloon about to be launched in front of a powerful
storm.

0356 and Sonde2_0374: UAH students launch a weather balloon into the heart of a powerful thunderstorm over Maywood, Nebraska.

0356 and Sonde2_0374: UAH students launch a weather balloon into
the heart of a powerful thunderstorm over Maywood, Nebraska.

Sonde2_0374

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