![]() ![]() Subsequently, this closed feature expanded to the east, extended along the west coast of North America with a region of higher heights over the PNW, and persisted for three days: 26–28 June 2021 ( Figure 2, right). Also seen in this early figure is a development of a Rossby wave meander over the Sea of Japan. The 100 hPa level geopotential heights over the Bering Sea rapidly formed a closed feature on 17 June 2021 ( Figure 2, left). ![]() The severe weather event of June 2021 in the Pacific Northwest (PNW) started mid-month with the split in the polar vortex into two centers. This mandates improved understanding on how the weather is changing as the planet warms, because weather has a large impact on humans and ecosystems. The heatwave that occurred in the Pacific Northwest (Oregon, Washington, southern British Columbia) during late June 2021 is an example. ![]() What are the interpretations and implications for further climate change? It is possible that there are additional interactions between shifts in the climate system and tipping elements occurring simultaneously. This raises the philosophical question of: what does it mean when an event is well beyond a previous record? This does not seem to be, necessarily, part of a long tail distribution of previous observations from historical data, but is rather a result of new, and perhaps unknown, processes. There appears to have been an increase of extreme events over the previous few years of various types, locations, seasonal timings and durations many such events have been well beyond previous records. Both the Pacific Northwest event in 2021 and the Siberian heatwave climax in June 2020 may be examples of crossing a critical state in large-scale atmospheric circulation variability. The seasonal transition at the end of spring suggests the possibility of a southern excursion of a polar vortex/jet stream pair. Warming was sustained in the region due to subsidence/adiabatic heating and solar radiation, which were the main reasons for such large temperature extremes. The associated tropospheric trough (low geopotential heights) established a multi-day synoptic scale Omega Block (west-east oriented low/high/low geopotential heights) centered over the Pacific Northwest. A polar vortex instability center formed over the Bering Sea and then extended southward along the west coast of North America. At the large scale prior to the event, the polar vortex was split over the Arctic. There were hundreds of deaths over the region and loss of marine life and forests. The extreme heat event that hit the Pacific Northwest (Oregon, Washington, southern British Columbia) at the end of June 2021 was 3 ☌ greater than the previous Seattle record of 39 ☌ larger extremes of 49 ☌ were observed further inland that were 6 ☌ above previous record. ![]()
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