Normally, weather systems are transported from west to east by the jet stream in a pattern of four upper-atmosphere waves that extend southward from the polar region.
This is known as a “progressive” pattern in which weather conditions at any given location change on a regular or irregular basis.
But this summer, the upper atmosphere in the northern hemisphere has mainly been configured with five main waves, which is known as a “stable” or “blocked” pattern that locks the same conditions over the same areas of the middle latitudes.
Producing either hot and dry conditions or abnormally high rainfall in some areas, this pattern can be linked to the Russian heat and fires, Eastern European floods, heat in America’s Heartland and even the disastrous monsoon rains in Pakistan and Kashmir.
The image to the upper right was created by Jesse Allen of NASA’s Earth Observatory.
Based on satellite observations, it shows how expansive the abnormally hot conditions in western Russia were in late July. The heat actually became noticeable in early July. The blocked weather pattern allowed the heat to linger for weeks, resulting in the firestorms and chocking clouds of smoke.
Full story and image: NASA