Long-lived mesoscale convective systems (MCSs) generate a significant fraction of warm season rainfall in the central United States. Much of the heavy rain falls from nocturnal systems that form under weakly forced conditions. Flash floods usually occur at night in the eastern two thirds of the United States, a hazard of nocturnal MCSs. Despite the importance of these systems, operational models have little skill predicting the propagation of nocturnal convection over the central U.S. or producing accurate quantitative precipitation forecasts. The Plains Elevated Convection At Night (PECAN) campaign was a large, intensive field project to collect data before and during nighttime thunderstorms in the arid western Great Plains from June 1 to July 15, 2015. We were part of a large group of scientists participating in the experiment that hope to learn what triggers these storms, how the atmosphere supports their lifecycle, and how they impact lives, property, agriculture and the water budget in the region.
A key goal of PECAN is to determine how the nocturnal thunderstorms within elevated MCSs maintain their structure and intensity over long time periods in the absence of surface-based CAPE and a balance between cold pool generated vorticity and vorticity associated with environmental shear. Our overarching hypothesis motivating our research is that elevated convection is maintained by bore and gravity wave forcing. Specifically, we are studying how microphysical cooling processes in developing and mature stratiform regions of MCSs force downdraft circulations that create bore and mesoscale gravity wave features on the stable nocturnal boundary layer that in turn focus, organize and maintain future convective activity. We came out of the field in July and have been focusing our research on analysis of microphysical and radar data from the P-3 research aircraft, and well as conducting WRF modeling studies.
Publications
- Stechman, D.M., R. M. Rauber, G. M. McFarquhar, B. F. Jewett, and D. P. Jorgensen, 2016: Interaction of an Upper-Tropospheric Jet with a Squall Line Originating Along a Cold Frontal Boundary. Mon. Wea. Rev., 144, 4197-4219.
- Geerts, B., D. Parsons, C. Ziegler, T. Weckwerth, D. Turner, J. Wurman, K. Kosiba, R. Rauber, G. McFarquhar, M. Parker, R. Schumacher, M. Coniglio, K. Haghi, M. Biggerstaff, P. Klein, W. Gallus, B. Demoz, K. Knupp, R. Ferrare, A. Nehrir, R. Clark, X. Wang, J. Hanesiak, J. Pinto, and J. Moore, 2017: The 2015 Plains Elevated Convection at Night (PECAN) field project. Bull. Amer. Meteor. Soc., 98, 767-786.
- Stechman, D.M., G.M. McFarquhar, R.M. Rauber, M.M. Bell, B.F. Jewett, and J. Martinez, 2020: Spatiotemporal Evolution of the Microphysical and Thermodynamic Characteristics of the 20 June 2015 PECAN MCS. Mon. Wea. Rev., in press, https://doi.org/10.1175/MWR-D-19-0293.1
- Stechman, D.M., G.M. McFarquhar, R.M. Rauber, B.F. Jewett, and R.A. Black, 2020: Composite In Situ Microphysical Analysis of all Spiral Vertical Profiles Executed within BAMEX and PECAN Mesoscale Convective Systems. J. Atmos. Sci., 148, 1363-1388.