9/11/09 BNA to LAX

[skadanks]

My southwest airlines nonstop flight from Nashville to Los Angeles was pretty much uneventful for the first couple hours. There was frequent light turbulence, the type you get when flying through clouds, but nothing beyond class 1 turbulence. The sky had variable level cloudiness and much of the time you couldn't see the ground.

Then at 40,000ft somewhere around northern New Mexico, we approaching what looked like cirrostratus clouds. I think it was the flattened top of anvil thunderhead. I saw what looked like an "overshoot top" above, like this:

http://upload.wikimedia.org/wikipedia/commons/6/66/Overshooting_Top.jpg

I was hoping we'd fly around that overshoot top, but we were heading right for it. I started getting nervous because it's not normal to see cumulus top clouds that high up unless there are some violent winds causing them to be that high up. So we approached what I thought was the overshoot top of a thundercloud and entered it and the plane started shaking so violently that people started screaming. I'd say it was probably category 4 turbulence. Luckily, it only lasted for about 10 seconds and as soon as we came out the other side of this cloud, it was smooth again.

[pinworm]

I flew STL to PHX that same day..similar experience all around. Light turb all the way..then rougher over NM. Nothing too horrible..that I remember..Lorazepam pretty much took care of that!

[astrodeb]

That's a perfect example of what you don't want to fly into or over - convective overshoot. I get nervous seeing clouds like that even if we are not headed into them because the violent updraft causing the overshoot can make clear air turbulence near the CB. The turbulence can be bad up to 5000 feet above the actual cloud, and the cloud can easily outclimb your plane. Your pilot chose his/her route through the weather poorly on your trip, IMHO. He/she probably counted on the updraft collapsing before the plane reached the cloud. This sort of goof is what causes fear of flying in passengers and overconfidence about thunderstorms in young pilots. However, it is possible that Air Traffic Control refused permission for a diversion (in which case they should have diverted anyway...). You are lucky to have just gotten a 10 sec jolt. Kick those pilots in the pants for me!

[skadanks]

That's a perfect example of what you don't want to fly into or over - convective overshoot. I get nervous seeing clouds like that even if we are not headed into them because the violent updraft causing the overshoot can make clear air turbulence near the CB. The turbulence can be bad up to 5000 feet above the actual cloud, and the cloud can easily outclimb your plane. Your pilot chose his/her route through the weather poorly on your trip, IMHO. He/she probably counted on the updraft collapsing before the plane reached the cloud. This sort of goof is what causes fear of flying in passengers and overconfidence about thunderstorms in young pilots. However, it is possible that Air Traffic Control refused permission for a diversion (in which case they should have diverted anyway...). You are lucky to have just gotten a 10 sec jolt. Kick those pilots in the pants for me!

The pilot apologized for any "mess" the turbulence might have caused in the cabin as the flight attendants had recently made their beverage round. He then said, "that's why we always ask you to keep your seatbelt on even if we turn the light off." What's funny is that they didn't even hit the seatbelt light until we were well into the turbulence.

[astrodeb]

He/she was right, of course. Everyone needs to have their seat belts on constantly unless there is dire need to visit the lavatory or have a quick lap to help circulation on the long haul flights. However, if you saw the convective overshoot ahead, it's pretty clear that he/she could have seen it as well and deviated unless there was an ATC traffic jam in the area. The more typical (and justifiable) "caught by surprise" situation is clear air turbulence caused by long lasting wakes or the beginning of a mountain wave. Sometimes, Southwest (and United) seem a tad cavalier about CB for my taste! I just had two United flights back east which kept turning the seatbelt sign off and on in thick cloud conditions when other flights nearby were reporting moderate bumps (courtesy of Channel 9 - one the good things about United). I wonder if there are airlines which get substantially more flight attendant injuries from "unexpected" turbulence (normalized by number of flights). I just don't know. In any case, we pay to be safe, not spared from the occasional E-ticket ride...:eek: