The 2021 Western North American Heatwave and its Subseasonal Predictions
Abstract
Record-breaking above-normal temperatures were observed across western North America in June-July 2021. In this study, our ability to predict this heatwave 2-3 weeks in advance is assessed based on 10 Subseasonal-to-Seasonal prediction models. It is found that the above normal temperature in Western Canada during June 28-July 4 was predicted by most models as early as June 10. However, for the forecasts initialized earlier than June 17, not a single ensemble member of all the models was able to capture the magnitude of the observed temperature anomaly. We identify two important processes for this heatwave: an upper tropospheric wave train associated with the boreal summer intraseasonal oscillation in Southeast Asia and an anomalous North Pacific atmospheric river leading to high moisture conditions. Most models were able to predict the wave train across the North Pacific. A realistic representation of moisture transport and its pattern appears crucial for the extended-range forecast of this heatwave.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.A25E..01L