By "this turbulence" the examiner refers to the turbulence associated with the jet stream - Clear Air Turbulence.
Clear Air Turbulence associated with Jet Streams is strongest on the cold side of the jet stream where the wind shear is greatest. In the vicinity of a jet stream, CAT can be encountered anywhere from 7 000 ft below to about 3 000 ft above the tropopause.
- In this case, the jet core is at FL310, you are flying at FL270 => 4000 ft below the jet core. The best way to avoid CAT would be to descend further to a lower flight level, as at FL270 you still might experience clear air turbulence. Descending to FL240 should be enough to avoid the CAT area.
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