"Ask ATC" Blog

Thunderstorms and Deviations

It is the summer season in the Northern Hemisphere.  Here in Alberta, Canada, we usually get some great summer thunderstorms late in the day. 

Thunderstorms pose a unique challenge to aviation.  The biggest risks are turbulence, icing, lightning and hail.  While pilots are cautioned to avoid them, managing traffic flows in complex airspace can be a strain on the air traffic controller, and put extra workload on pilots.

Here are some tips for working with ATC to avoid thunderstorms: 

1)   Request deviations early.  If you think a cell may be a problem, let ATC know sooner rather than later.  This allows the controller to plan to keep other aircraft out of the way.

2)   Request block altitudes for turbulence.  If you are having difficulty maintaining altitude, a block altitude will afford some flexibility while searching for smooth air.

3)   Give and request PIREPS.  Let the controller know if you experience something out of the ordinary, like turbulence or hail, which other aircraft will want to know about.

4)   Always ask before deviating.  Even if you think it will be a small deviation, controllers often run minimum lateral separation between yourself and another aircraft that you may not be aware of.  A loss of separation could occur.

5)   Plan descent early.  When numerous aircraft are deviating, a controller may not be able to accommodate requests for descent or direct routings in as timely a manner as normal.

6)   Err on the side of caution.  The best way to avoid a thunderstorm is to plan around them.  Either file clear of the weather, or wait for it to improve.

Safe flying.