Updated: Oct 7, 2021
There's no doubt that a pilot weather report (PIREP) for extreme turbulence should get your attention. Here's an urgent report from the crew of an Embraer E175 flying over northeastern Alabama at flight level 290.
Fortunately there were no injuries or damages, but what might have been causing this kind of turbulence and to what extent could that possibly extend to higher or lower altitudes? Well, let's drill down using the Skew-T log (p) diagram to find out.
Below is the sounding analysis nearby the location of the PIREP. The image is below is zoomed on the upper troposphere in order to see details of the winds and temperature...both are important to assess the potential for turbulent mixing. There are a lot of changes in wind speed, wind direction and lapse rate going on within about a span of a few thousand feet.
Notice the winds at FL290 are 134° at 15 knots. That's the flight level of the aircraft. But also take a look at the blue wind speed trace on the right. The winds rapidly decrease and then rapidly increase. They also have a rapid shift in wind direction from 007° at 20 knots to 036° at 7 knots to 134° at 47 knots. Just in the span of 3,000 feet the winds shift direction from north to southeas