TY - JOUR
T1 - Using the translation speed and vertical structure of gust fronts to infer buoyancy deficits within thunderstorm outflow
AU - Hutson, Abby
AU - Weiss, Christopher
AU - Bryan, George
N1 - Funding Information:
Acknowledgments. This work was supported by NSF Grants IIS-1527183 and AGS-1824713. We would like to acknowledge support from the High Performance Computing Center at Texas Tech University. We thank the first author’s committee members, Dr. Eric Bruning and Dr. Johannes Dahl for providing helpful feedback to improve this research. We would also like to thank the editor and anonymous reviewers for their thorough review that improved this manuscript.
Publisher Copyright:
© 2019 American Meteorological Society.
PY - 2019
Y1 - 2019
N2 - This study investigates whether the thermodynamics of supercell rear-flank outflow can be inferred from the propagation speed and vertical structure of the rear-flank gust front. To quantify the relationship between outflow thermodynamic deficit and gust front structure, CM1 is applied as a two-dimensional cold pool model to assess the vertical slope of cold pools of varying strength in different configurations of ambient shear. The model was run with both free-slip and semislip lower boundary conditions and the results were compared to observations of severe thunderstorm outflow captured by the Texas Tech University Ka-band mobile radars. Simulated cold pools in the free-slip model achieve the propagation speeds predicted by cold pool theory, while cold pool speeds in the semislip model propagate slower. Density current theory is applied to the observed cold pools and predicts the cold pool speed to within about 2 m s-1. Both the free-slip and semislip model results reveal that, in the same sheared flow, the edge of a strong cold pool is less inclined than that of a weaker cold pool. Also, a cold pool in weak ambient shear has a steeper slope than the same cold pool in stronger ambient shear. Nonlinear regressions performed on data from both models capture the proper dependence of slope on buoyancy and shear, but the free-slip model does not predict observed slopes within acceptable error, and the semislip model overpredicts the cold pool slope for all observed cases, but with uncertainty due to shear estimation.
AB - This study investigates whether the thermodynamics of supercell rear-flank outflow can be inferred from the propagation speed and vertical structure of the rear-flank gust front. To quantify the relationship between outflow thermodynamic deficit and gust front structure, CM1 is applied as a two-dimensional cold pool model to assess the vertical slope of cold pools of varying strength in different configurations of ambient shear. The model was run with both free-slip and semislip lower boundary conditions and the results were compared to observations of severe thunderstorm outflow captured by the Texas Tech University Ka-band mobile radars. Simulated cold pools in the free-slip model achieve the propagation speeds predicted by cold pool theory, while cold pool speeds in the semislip model propagate slower. Density current theory is applied to the observed cold pools and predicts the cold pool speed to within about 2 m s-1. Both the free-slip and semislip model results reveal that, in the same sheared flow, the edge of a strong cold pool is less inclined than that of a weaker cold pool. Also, a cold pool in weak ambient shear has a steeper slope than the same cold pool in stronger ambient shear. Nonlinear regressions performed on data from both models capture the proper dependence of slope on buoyancy and shear, but the free-slip model does not predict observed slopes within acceptable error, and the semislip model overpredicts the cold pool slope for all observed cases, but with uncertainty due to shear estimation.
UR - http://www.scopus.com/inward/record.url?scp=85075562582&partnerID=8YFLogxK
U2 - 10.1175/MWR-D-18-0439.1
DO - 10.1175/MWR-D-18-0439.1
M3 - Review article
AN - SCOPUS:85075562582
VL - 147
SP - 3575
EP - 3594
JO - Monthly Weather Review
JF - Monthly Weather Review
SN - 0027-0644
IS - 10
ER -