The Financial Times (via Inside Climate News) reports:

The deadly heat waves that have fueled blazes and caused transport disruptions in Europe, the U.S. and China this month have one thing in common: a peculiar shape in the jet stream dubbed “wavenumber 5.”

Scientists are racing to understand whether the band of fast-moving air that controls weather in the mid-latitudes is changing in a way that makes heat waves more frequent and persistent.

“The jet stream is the leading driver of our weather,” said Paul Williams, professor of atmospheric science at the University of Reading in the U.K. “The jet stream is like a conveyor belt, delivering storms to us one after the other.”

It can also generate heat waves when it forms into a U-bend shape, called an “omega block” because it resembles the shape of the Greek letter omega.

Right now, a global pattern of five big waves is circling the world, leading to simultaneous heat waves across continents. This pattern, known as wavenumber 5, can persist for weeks, causing hot areas to stay hot for a long time.

In China, more than 900 million people are experiencing heat waves, and more than 70 weather stations have broken records this month. In the U.S., Texas and Oklahoma are experiencing record-high daily temperatures, and more than 20 states have issued heat warnings. [Continue reading…]