The jet stream, an area of fast moving winds high up in the atmosphere (four to eight miles), became incredibly wavy during the heat wave, formingwhat is known as an omega block. While an omega block may sound like something straight out of a sci-fi movie, it has a much simpleratmospheric origin. When the jet stream getswavy, it can occasionally look like the Greek letter omega. Try to see it for yourself in the figure above of 300hPa (jet stream level) average winds during the heat wave.These blockages occur when a high pressure is lockedbetween two low pressures on either side. OverEurope, this high allowed hot air from the tropics to move north and essentially get trapped over Europe. Clear skies allowed for the temperaturesto rise even further, creating a stronger dome ofhigh pressure,reinforcing the already stagnant omega blockatmospheric pattern. The high pressure blocked any potential low pressure systems from movingover Europe, instead pushing them to the north,like a large boulder diverting water in a stream.The omega block over Europe eventually weakened and moved east by the end of the second week of July, allowing cooler temperatures to prevail.