Large parts of the US have been battered by severe weather this week, as low pressure developed over the north-west coast. The weather system intensified into a phenomenon known as a bomb cyclone, which rapidly intensified to an estimated central pressure of 942 hectopascals (hPa) – close to the lowest pressure recorded in that area.
To be classified as a bomb cyclone, the central pressure of a low pressure system must fall by at least 24hPa in 24 hours. Wind speeds exceeded 70mph (113km/h) near Seattle, while Canada had the strongest winds with gusts of about 100mph. There were two deaths and almost 500,000 people in the region were left without power.
