A Storyline Approach to the June 2021 Northwestern North American Heatwave

Northwestern North America has experienced an exceptional heatwave in late June 2021 with many new temperature records across western Canada, Oregon and Washington states. Here we use a recent atmospheric reanalysis conditional approach based on dynamical adjustment to assess quantify the influence of circulation other driving factors magnitude during 28–30 period. A blocking anticyclone, enhanced low-level moisture clear-sky downward long-wave radiation are shown be main persistence magnitude. The is mainly attributable internal variability climate change being additional factor (10%). Consequences similar anomaly different phases Pacific Decadal Oscillations warmer world at global warming levels (1, 2, 3, 4°C) explored single model initial-condition large ensemble.