A long-lived supercell over mountainous terrain

Author(s): Phillip Scheffknecht, Stefano Serafin, Vanda Grubisic
Abstract: The life cycle of a convective storm forming over highly complex topography on the northern side of the Alps is studied. Moist convection began ahead of a cold front in the late morning of 2 August 2007 in eastern Switzerland. It developed into a supercell storm that moved along the Alpine main crest for more than 8 h, passed over several 2000 m high ridges and ultimately dissipated over eastern Austria. This study analyzes the impact of topography on the pre-storm environment and on the storm development using several simulations with the Weather Research and Forecasting (WRF) model at a minimum horizontal grid spacing of 833 m. A hindcast simulation of the event features a convective system evolving in good agreement with observations. Variations in the simulated storm intensity appear to be related to the topography below the storm. Two idealized simulations help understand how the Alpine topography affected storm initiation and development. North of the Alps, relatively strong shear between southwesterly synoptic flow aloft and thermally induced plain-to-mountain flow near the ground created favourable conditions for supercell development. Small-scale terrain features supported the upward transport of moisture via slope circulations, locally reducing CIN and increasing CAPE, and ultimately enhancing the storm longevity.
Organisation(s): Department of Meteorology and Geophysics
External organisation(s): National Center for Atmospheric Research (NCAR), ZAMG
Journal: Quarterly Journal of the Royal Meteorological Society
Volume: 143
Pages: 2973-2986
No. of pages: 14
ISSN: 0035-9009
DOI: https://doi.org/10.1002/qj.3127
Publication date: 10-2017
Peer reviewed: Yes
Austrian Fields of Science 2012: 105206 Meteorology
Keywords
ASJC Scopus subject areas: Atmospheric Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/f6f654d7-7a01-466a-87f5-244b2bc4f066

Back