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Clear weather - which options to try when the ride gets bumpy

It happened yesterday when I flew back yesterday from Haguenau (LFSH) towards Stuttgart. I wasn’t expecting any bumpy ride as the temperature was still around 8 C on the ground and clear skies. It got worse over the hilly area after the border. I was flying at FL060. The last time I experienced similar situation was in the summer last year when my wife was with me and I needed to get back home early afternoon. She was really bothered and I resolved not ever to make a flight with her in warm afternoons.

When should we expect a bumpy ride in low temperatures and clear skies? What are the options to avoid or lessen the lurch in stomach? I ascended higher, but another 1000’ didn’t help much. It helped a bit to slow down. Is there anything else one could do?

EDMB, Germany

I know of two sources of predictable low-level turbulence:

  • thermals: clear skies, large diurnal temperature variation, sun heats ground which heats low air which rises
  • wind on topography and obstacles: medium-to-strong wind, encountering obstacles and orographic features (mountains, hills, …)

Both get worse over typical rock, because usually rock will be bare (better heated by the sun) and a relief (will “push up” the wind air, and then it makes rotors, etc).

ELLX

Mid-day tend to have strong thermals
- If cumulus is around, avoid flying bellow if you can, if you can’t fly mid of cloud bases (thermals are rough on top and lower side of the ascent)
- If clear sky, fly high but avoid on top of dark terrain, forests, big cities…
- If you have no clue on sky or ground, just fly downwind it should be smoother

If you fly around high terrain on windy days,
- Fly 3*times higher than hills on the lee side of the wind/hill or on the up side
- If you have no clue on hills/winds, just fly downwind it should be smoother

Alternatively, with sensitive pax I fly early mornings or late afternoons and probably by night when I get a rating
Also do some gliding it helps but remember it when flying power, my worst turbulence experience with pax happened when I tried to “impress them” with a Gatwick Zone transit on 30kts westerly winds but I forgot that VFR transits ared 1500ft and Biggin Hill is 600ft (I wasn’t ready for it let alone the pax, I find that full power only delivered 80kts that day but lesson learned)

Paris/Essex, France/UK, United Kingdom

That is interesting indeed. Generally, of course, during summer, below cumulus clouds, it is often bumpy. If possible, one should climb up above the base of the cumulus clouds. If that is not possible, yes, then the only thing to lessen the turbulence is to slow down.

In winter (in the wider sense), when there is no discernable cumulus cloud around, the question is more interesting. Of course, when in the big mountains, you can get huge turbulence in case of Foehn.
And even in the less mountainous terrain, there can be effects of Foehn. In the absence of Foehn, the only thing you can do is watch the winds aloft, and if the winds aloft are strong (30-40 knots), then turbulence is more likely. But the fact is there will be days when the wind is thus strong, yet there will be no turbulence. Would be great if there were a better way to find out if a particular winter day will be bumpy or not…

Mainz (EDFZ) & Egelsbach (EDFE), Germany

boscomantico wrote:

Would be great if there were a better way to find out if a particular winter day will be bumpy or not…

In winter I can see that in the vertical profile of the wind, for strong windy days if “Airgram – wind barbs” show discontinuities then I expect turbulence but the data is not highly reliable neither for actual or forecast (sometimes just noise from weather numerics), then “clear air turbulence” from sheer waves in winter is difficult (or even impossible) to predict without lenticular cloud markers and can heppen at all heights for no reason

But yes the best indicator is wind strength and vertical gradient…

Last Edited by Ibra at 21 Mar 14:02
Paris/Essex, France/UK, United Kingdom

Arun wrote:

I ascended higher, but another 1000’ didn’t help much

Keep climbing is my strategy. You rarely find smoother air below you

EGTR

I see some hills between the two places. Peaks around 1000m. With wind perpendicular to the ridge, they might create a mountain wave effect. Maybe next time try flying north of the hills if there’s strong wind in east-west direction.

Last Edited by loco at 21 Mar 18:01
LPFR, Poland

loco wrote:

Peaks around 1000m

Yes, with 1000m peak and 30kts wind (on a typical 20 degrees hill slop) it will ring at up to FL060 and 20nm downwind

Another reason in clam wind/flat terrain is an inversion at F060? but I doubt those are that turbulence will be uncomfortable as much as the low visibility you get there…

Paris/Essex, France/UK, United Kingdom
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