Potential Future Changes of the Severe Weather Environment in Western Canada

Severe convective storms are a common atmospheric phenomenon in North America that can produce high impact weather such as hail, destructive winds, tornadoes, and torrential rainfall. As such, they pose a significant threat to society and can lead to major economic losses. There are concerns over the impact of global climate variability on severe convective storms in the future. Though they still have too coarse of spatial resolution to directly resolve severe convective storms, regional climate models (RCMs) forced by global climate models (GCMs) have the ability to assess regional severe weather environments. The North American Regional Climate Change Assessment Program (NARCCAP) provides such dynamically downscaled RCM simulations at a 50 km resolution for the 1971 to 2000 and 2041 to 2070 periods. The objective of this work is to examine how the severe weather environment may change in the future based on three well-behaved NARCCAP model pairs, focused on western Canada and the northern U.S. Plains. Very preliminary results suggest that the seasonal progression of the supercell composite parameter (SCP) and significant tornado parameter (STP) appear to follow a natural seasonal progression (north and south) for HRM3-HadCM3 and MM5-CCSM but is not so apparent for MM5-HadCM3. Most of the Canadian Prairies (particularly Saskatchewan and Manitoba) have increases in SCP in June and July (mostly due to higher CAPE) with only some regions having increased STP; although most areas also have increased CIN (capping). However, increases in future convective precipitation seem to suggest that CIN will broadly be overcome, thus, there may be the potential for more frequent and/or more intense supercells and tornadoes, in the future over some regions. Further analysis is ongoing with this study, however, a more diverse set of regional climate model projections are required to increase confidence in the results.