How many times does a commercial pilot have moderate/severe/extreme turbulences?

Question

I have read that moderator turbulence is actually 1 in 20 flights, severe turbulence is about 1 in 200, and extreme actually does occur VERY very rare (because, at this level of turbulence, structural damage can happen)...

So, are these numbers ok? And if yes, when and where are these turbulence faced most (like near T-storm, low-level-turbulence etc.)?!

Answer 1

That depends on the aircraft though.  A Cessna 152's light chop would be nothing for a 777 or 747, whereas light chop of the latter may be enough to keep the Cessna on the ground!  In general, I'd go with light chop maybe every few flights or so.  It's really just the tiniest bump.  Moderate, about what you said.  Severe, maybe a 1 in 200 chance of getting into it as a pilot AT BEST but as an airline passenger, it's less likely.  Extreme, like you said, is almost a non-issue.

Thunderstorms are big causes of turbulence, as are frontal passages, places where the isobars (lines of equal atmospheric pressure) are close together, and when flying between pressure systems like highs or lows when they're close together as well.  Also on the leeward side of mountains (called mountain wave turb) when the winds are kicking, so on a crosscountry flight expect something around the Rockies, like over Denver, Colorado Springs, Phoenix, etc.

Answer 2

Moderate?  Every other day.  

Severe?  Once a month or two.

Extreme?  Never experienced it yet.

Answer 3

Weather is unpredictable.....there's no rates in turbulence Jeez.