Wind Discussion

Hello,
So with the recent "wind" influence threads I figured it might be easier to have wind influence discussion with pictures so we can have a better visual than just reading words.

So I will start....
In the below attached picture, you are target shooting and have target placed at 1800m at the "red dot" on image. (Picture and distance not to scale) Wind is blowing at constant and steady 8mph from you direct to target.
You have all the environmental data calculated and accounted for...
You have your firing position and marksmanship skills as "tight" as you can get them...
Yet you still keep hitting high then low, high then low.....WHAT "COULD" BE THE CAUSE OF THAT??
Lets see what everyone thinks on that one.



THEIS

wind coming from the valley funneling into the gorge and to your ffp?

In the environment pictured the potential for erratic winds is phenomenal. Wind is a dynamic force that affects our shooting in its simplest form by pushing the bullet sideways. But in its more complex form (Catabatic winds for example) wind can do many strange things. Catabatic winds are not reserved to winter conditions. Wind shear, which can produce vertical winds under certain conditions, will drive your shot down. You can drive yourself nuts trying to analyze the cause of every shot on target. All you can do is make sure you're not violating any basic rule and that you've taken into consideration every possible wind factor that might affect your shot. The shot will go where the shot will go ....

I'd say by looking at the steep angle of the slope the dot it on, the wind is blowing behind you, funnelling into valley then swirling as it hits the end hill, causing erratic ups and downs.

A good shooter could spend a lot of bullets randomly hitting and missing that target as wind conditions change. A slight ship to the left or right would alter everything

I don't have an answer, and my longest shots have been 1200 yards but I am working on it. All I can do is say I have trouble with a tail wind. Even at 800 I go into fits of the wind is coming from behind me. As a hunter, the wind at my back is always a disturbing feeling and that may make me uncomfortable from the start.

As a scientific mind, I need a better explanation than that. My thought is the wind catches the flat on the back of the bullet as it spins and causes a widening arc. At the specified range, it translates into an unpredictable vertical dispersion.

when in doubt, add one click down when wind from the rear and one click up when shooting into a head wind lol
i'm know im not the only one that has stupid "eh better be safe" rules when sending one off into suspect wind

Hello,
Another very often overlooked issue in regards to sporadic high/low impacts in the pictured scenario is the horizontal "floating" eddy.
As seen in the picture the firing position is slightly elevated in comparison the the base of the mountain side where target is located. You will also see a little "finger" protrusion on the left side of the mountain. So what CAN happen with a slow moving wind like the 8mph listed is that the wind "pools" up at the base of mountain and as more wind "pools" up it begins to stack then it begins to push itself up the mountain side. As it pushes itself up the mountain side it begins to form a horizontal eddy due to friction of the mountain surface, etc. This horizontal eddy then "floats" up the mountain side until enough air is pooled and stacked that it "falls" over the top which in turn releases the horizontal eddy, which in turn starts the entire process all over again.

THEIS

Much better description theis than my "it swirls".

Schnyd, I haven't ever found much difference with a direct tail wind on flat ground. The bullet is travelling too fast for wind to affect it by pushing on the butt. I have had slight shifts in wind direction ruin my shot, say a 20mph wind shifts from 6:00 to 5:00, my shot blew the snow up behind a coyotes nose.
I've also had trouble with slight 9:00 breezes, say 2 mph. It's not enough to feel, especially when I'm bundled up for -20. I've been considering tying a few strands or horse hair on my bipod to help identify slight breezes

So then how do you compensate for that? If it is constantly filling, overflowing and refilling, you can't see that turbulence because it is away from the hillside in open air.

Is it just shooting enough to recognize the terrain and pick a better firing position or is there a method to solving the problem?

Could it be that you have exceeded the limits of what your round can consistently do at that distance? It's dropped so low in velocity that the ballistics of the round have been exceeded. The limitation is so much you can not reliably recreate a consistency from shot to shot. Due to the drop in velocity, the stability of the bullet has been comprimised? So not a wind issue, but I must remember that this is a thread on wind.

I think we are assuming your bullet has not exceeded its stability in this discussion.

My solution would be to move closer to where the bc of bullet overcomes the turbulence of the hillside. Some shots just aren't tenable on game for 1st round kills, but I think practicing in such environments let's you discover your limits at making shots and push them. Rough terrain offers the hunter the ability to move closer...sometimes anyways.

It gets to the point, in my experience..whatever that's worth, that there is a point where you are making an educated guess on the wind, how well you average data and and collect that data can be completely subjective to how serious you take your shot, and how well you can collect data in that environment. With complex wind in complex terrain, sometimes I guess right, more times I guess close enough, and once in awhile...I break down the firing position and hang my head in shame.

As any paraglider or hang glider pilot knows only too well, if you try and take off on a slope with the wind at your back you will be flying into what pilots call 'rotor', which is simply put the turbulence that exists on the downwind side of an obstacle (the hill behind you). The turbulence is erratic and would be impossible to predict. This would cause exactly the sort of variances in POI described and would be almost impossible to correct for.

Let time be on your side.

I've never shot that far, but if I was thinking about it, I'd be looking down range at many different sections trying too pick-up of wind drifts, their estimated speeds, bullet trajectory from ground too above ground and it's return too ground since there is & isn't lift from below.

And example I use on cut-lines between the trees is called bullet bump drift, as the winds channel into the tree lines on both sides, this could be the same as a canyon of rocks.

We get fouled as we feel the light breeze on the left side of our face, so our mind tells us that the wind is L too R,,, "STOP" at that point.
Is this true ???


Even at 500 meters can put you off the 4" balloons.

This is where letting time be on your side.

I don't know what you folks do, but I know I start looking at many signs at ground level too see which way trees, grass, sand, flowers, and willows are moving.

Using birds that are aloft at different elevations fills me in what the winds are doing up above.

High elevation clouds might be going one direction as the low clouds going the other, fog and mist give signs drift much like sand on a dry desert floor.

Aloting time has helped me alot, learning what speeds move things even more.

I started a book for my self called winds.
In it I list objects at ground level to see what makes grass free float, bend over, and pack down flat.

Black dirt, sand and trees along with many things give us clues, it our task too take these clues and decide what they are doing.

Pal Don from Western Canada