I was reading about some inflight upset incidents, some of them with several passengers seriously injured, and there are some things in common ( almost ) in all of the cases : planes flying at cruise ( usually FL 330 or higher ), clear skies with no evidence of any atmospheric disturbance, and sudden "impact" of the plane with severe turbulence in clear air, prompting the undesirable consequence of people being hurt. I personally NEVER unlock my seat belt, but is understandable that, in long flights, with the seat belt sign off, many people think is totally safe ( and even healthy ) to take a walk in the aisle, or go to the bathroom, or to change the dipper of the baby... and then you find your self smashed into the roof of the cabin...

Can anyone explain how the CAT occurs ?
Are more common in some places ( like in the vicinity of high mountains for example ) ? Why ?

Thanks in advance !!

Rgds.
G.

it can occur anywhere it´s usually the limits of jet streams or a 2 different Masses of air, it can happen in mountain areas os course. usually pilots have in the forecast areas where it may happen, in the weather report and in the flight plan it´s called Shear rate, from 0 to 5, you´d better avoid 5 areas. It´s very easy to see in the SIGMET charts.

This is a link for a forecast.... http://www.turbulenceforecast.com/clear_air_turbulence.php

Now check out this one, http://www.turbulenceforecast.com/weather12.php

You can see the relationship between both?? different masses of air and on the top right you can see the Low pressure and the isobars close by indicating a fast reduction on the pressure and check also the air temperature map and you will also the relationship between the cold and warm masses of air.

Usually a very dangerous one it´s one you can observe over a mountain with a altocumulus lenticularis... that´s really dangerous, you can even pass 10.000 feet above, it doesn´t matter you will get CAT.

http://en.wikipedia.org/wiki/Clear-air_turbulence

After many years flying as a pilot and pax I never ever release my seat belt, even when sleeping in business class i put my seat belt over the blanket so the cabin crew can see it. I´ve seen catering trucks hitting the ceiling and pax landing in the row behind and cabin doing like spiderman on the lockers and ceiling.

Quoting migair54 (Reply 1): After many years flying as a pilot and pax I never ever release my seat belt, even when sleeping in business class i put my seat belt over the blanket so the cabin crew can see it. I´ve seen catering trucks hitting the ceiling and pax landing in the row behind and cabin doing like spiderman on the lockers and ceiling.

Wow...!!

Many thanks for all the info provided !!

Rgds.
G.

I can only provide a simple answer based on personal experience, but the stronger the headwind, usually there is turbulence. I flew B6 JFK-PBI last February and it was as clear as can be, but due to the headwind, we had over three hours of the seatbelt sign illuminated 90% of the time and the plane bouncing around like a truck with bad shocks. I though it was kinda fun, but a bit unnerving. This was the only time my family said I looked white and very happy to be getting off the plane.