Plains Elevated Convection At Night

Over the Great Plains, summertime thunderstorms and convective precipitation frequently occur after sunset, not during the afternoon. Much of this nighttime rainfall is caused by mesoscale convective systems (MCSs) and is critical to the hydrology and agriculture of the region, especially over the more arid western Great Plains. Unfortunately, MCSs also cause severe weather, including flash floods, intense damaging winds, and large hail. These are particularly hazardous at night due to the lack of visibility and awareness. While forecasting the initiation, location, duration, and severity of these nighttime storms is difficult, targeted observations in critical locations, at critical times, can help improve forecasts.

What is PECAN?

PECAN is a large meteorology experiment sponsored by the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), National Aeronautical and Space Administration (NASA), and the Department Of Energy (DOE). The scientific goal of the project is to collect data before and during nighttime severe storms in order to learn how they form, why some become severe, and how to predict them better.

PECAN will use 8 mobile radars, 3 research aircraft, dozens of mobile weather balloon launching systems, mobile and deployable weather instruments, laser systems, and other cutting-edge targetable instruments to “chase” severe nighttime storms.

Major scientific questions include:

- How do small-scale features in the atmosphere cause and maintain convection after sunset?

- What processes control the intensity and severity of nighttime MCSs?

- What observations are needed to improve forecasts of the formation and evolution of nighttime storms?

PECAN will be conducted at night in the central Great Plains between 1 June and 15 July 2015, with an operations domain encompassing central and western Kansas, as well as adjacent parts of Nebraska, Texas and Oklahoma, a region climatologically favorable for summertime nocturnal thunderstorms. Specifically, PECAN will focus on storms that form in environments with a stable boundary layer (SBL), a nocturnal low-level jet (NLLJ), and the largest CAPE (Convectively Available Potential Energy) located above the SBL.

This the first time there has been a large, coordinated effort to study the interrelationship between (1) the initiation of elevated deep convection, (2) the dynamics and microphysics of nocturnal MCSs, and (3) the properties of high-amplitude SBL disturbances. PECAN’s focus on elevated nocturnal convection and on stable layer disturbances distinguishes it from other field campaigns that have studied deep convection in the central USA.

The PECAN campaign will utilize many mobile and stationary research assets, including: three aircraft (NSF University of Wyoming King Air, NASA DC-8 ,and the NOAA P-3), eight mobile Doppler radars (2 SMART-Rs, NOXP, 3 DOWs, MAX, RaxPol), a deployable radar (S-POL), a mobile lidar (TWOLF), several mobile mesonets, several mobile and stationary radiosonde systems, and profiling sensors such as DIfferential Absorption Lidars (DIAL) & Raman lidars, multi-channel microwave radiometers, infrared spectrometers, and acoustic systems. Existing observational facilities, such as the DOE/ARM Southern Great Plains site and National Weather Service WSR-88D radars, will provide additional data to aid in the analysis and understanding of these nighttime thunderstorms.

PECAN scientists and crew will hit the road in late May, and the project will run from 1 June through 15 July 2015.

PECAN Domain