Avoiding CB’s

By Petter Hornfeldt | December 21, 2018

Good day my friends!

I hope you are all having a great time out there and that you are working towards your personal goals with grit and determination!

Yesterday I did a great flight from Girona to Billund in Denmark.

The weather, however, was not fantastic in the beginning of the first flight. It has been very warm and humid down here in Spain and in a large part of southern Europe and with those kind of conditions it is very likely that large CB cells (thunderstorms) will form if the atmosphere becomes just a little bit unstable. This normally happens towards the end of the summer season and we can start to see it happening now.

Girona is very prone to large CB’s due to its proximity to the pyrenees and the sea and as you could see in my previous blog post (click here) it can sometimes lead to diversions.

Yesterday the problem was not the weather in Girona but the weather enroute. Thunderstorms can reach very high altitudes and the higher they are, the more powerful and potentially dangerous they are.

We have very clear guidance in our operations manual about how to avoid these types of storms and, with the help of our weather radar, we can see them from miles away. 

The guidance says that we are to try and avoid all red cells that have tops (the top of the cloud, see picture below) above 35000 feet in altitude, with a minimum of 20 nm or more. We always try and avoid on the “upwind” side of the cloud if it is possible (see the wind-arrow on the picture above). 

Naturally these avoidance manoeuvres require a bit more fuel but under normal circumstances it is covered in the “contingency” fuel on the normal flightplan but if we expect a lot of weather avoidance we always carry a little bit of extra fuel to account for this. Since all aircrafts are avoiding the same thunderstorms it puts a lot of strain on the ATC units and adherence to strict RT protocol mis very important.

On the way back from Billund the storms had calmed down and we had an absolutely wonderful view over Amsterdam and Paris (see picture) on the way home.

Have a great day my friends! Now I am on my way back to the office for yet another day of flying.


  • Hello, I watched your video on the CBs which is excellent as are all your videos. Thank you very much.

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