Shooting Through a Strong Updraft

[SonoranPrecision]

I was taking a shot from a rock ledge/semi cliff face, at about 370 yards, and 15 degrees down, but about 15-20mph wind coming up the cliff, almost vertical at that point. I took the shot, which would have otherwise been a chip shot, but under up missing about .7 mil high. Fortunately I was able to spot the miss and follow up with an effective hit.
Other than taking notes through trial and error, is there a way, or rule of thumb, to predict (within reason) the effect of this kind of wind?

 

[6.5SH]

If it was a full value wind at that speed did the .7ish mil miss equal what the calculator says is the wind hold?

 

[SonoranPrecision]

Oh shit… yeah it’s right about there haha didn’t even think to try that. Makes sense though

 

[smoothy8500]

about 370 yards, and 15 degrees down

15 degrees I think added .2mil elevation unless compensated for distance.

 

[ma smith]

... about 15-20mph wind coming up the cliff, almost vertical at that point...

This is an interesting obeservation, and a good question about the ballistics.

If its doing 3 different things at near/far/middle, tho... you'd have to composite the whole thing (weighted average).

 

[SonoranPrecision]

If its doing 3 different things at near/far/middle, tho... you'd have to composite the whole thing (weighted average).

Definitely. I tried what 6.5SH said, and played with it a little. The place where I was shooting was straight down for maybe 20 feet, but then sloped down for about 70% of the shot distance, then flat the rest. Basically, if you turn the wind rose on its side, and use “12 o’clock” as the direction of fire, you can estimate an average direction of the updraft, and get really close, assuming you have a good idea of the wind speed.

It was just another variable that I hadn’t experienced yet.

 

[Jackomason]

I've had the same experience but on the targets end. The crazy thing is that when you get an up draft like that, how wide is it? Maybe like 30 yards? Most of the time we are judging winds it's in 300- 500 yard increments.

 

[JustSendit]

I’ve seen some crazy upwind drafts out west. Predicting the amount of elevation change has felt like a crapshoot. Depending on the angle, the terrain, and wind speeds there’s a lot going on. Generally in the mountains I use correct kestrel data for the angle, and still quarter the target low even during calm conditions. High winds and a high angle shot, I’ll incorporate AJ and then reduce my elevation based on distance and target size. Even so, I’ve guessed completely wrong but a low miss in the mountains is easier to correct than high. At the extreme I can remember, I have shot and held an additional 2mils lower than AB corrected data for a 700m target at 20degrees in 25mph full value winds.

In my opinion, it’s a swag based on environmentals and terrain and knowledge of the shooting area.

 

[SonoranPrecision]

I’ve seen some crazy upwind drafts out west. Predicting the amount of elevation change has felt like a crapshoot. Depending on the angle, the terrain, and wind speeds there’s a lot going on. Generally in the mountains I use correct kestrel data for the angle, and still quarter the target low even during calm conditions. High winds and a high angle shot, I’ll incorporate AJ and then reduce my elevation based on distance and target size. Even so, I’ve guessed completely wrong but a low miss in the mountains is easier to correct than high. At the extreme I can remember, I have shot and held an additional 2mils lower than AB corrected data for a 700m target at 20degrees in 25mph full value winds.

In my opinion, it’s a swag based on environmentals and terrain and knowledge of the shooting area.

That’s all great info, thank you. That’s a good tip about quartering low. Missing damn near a mil high at 370 had my head spinning till I started to think about what was going on haha

I know I need to get some more practice in the mountains for this exact reason.

 

[Sheldon N]

Other than taking notes through trial and error, is there a way, or rule of thumb, to predict (within reason) the effect of this kind of wind?

The main spot I shoot and practice has a lot of valleys and vertical faces. You can get a large amount of vertical wind component depending on the wind angle.

Honestly, even at a place where I'm familiar it's tough to completely predict. My big picture approach is to consider the global wind direction (ie winds aloft, weather pattern) then try to picture how it will interact with terrain. Where does it fall down a hillside/cliff (or create turbulence), where does it updraft, look for terrain pinch points where the wind will accelerate, and look at areas where the wind direction might change as it flows around and follows the landscape. Sometimes turbulence is the toughest thing, obvious when you're shooting an known accurate rifle but getting 0.5 mil or more of vertical variability shot to shot.