cross winds & downdrafts at 1150 & 1625

[Idaho Sawyer]

This last weekend I was killing some rocks across a canyon and had a wind situation I havn't dealt with before so I wanted to share it. I will start by saying that I shoot a lot in BIG canyon country (central ID), so I am use to shifty winds, updrafts and down drafts. Usually updrafts and downdrafts are expected with the diurnal winds or if the slope lines up with your prevailing wind. Well I set up to shoot across a canyon that was running West to East ( East being down slope), at the head of that canyon is a major ridge running North to South. I had a full value wind coming from the west (coming over that major ridge running N to S) I adjusted for a full value 10 mph wind and adjusted my dope according to the Kestrel and ipad, which have been spot on out to 1700 yds. Broke the shot and watched the shot hit 1 1/2 moa low and 1/2 to the R. I wasn't surprised by the windage being off but the elevation got my attention. readjusted accordingly and broke the second shot. Wind was good and but still 1/2 low. Adjusted accordingly and hit the mark. repeated and hit the mark, realigned on the next pile of rocks at 1625 and repeated the process. This rock required 3 1/2 moa extra elevation to anchor, plus the appropriate wind.

My conclusion, as wind travels over ridges, it creates burbles on the backside of those ridges and down air is the result of those burbles. To back that statement, I was at the same canyon the next day, no wind situation, dialed in my original dope and cold bored the 10x on my rock. Repeated that at the 1625 rock. Something to think about in canyon country.

 

[HuntFarther]

I dont think people play that much to realize what you are talking about in these distances. I know first hand and have been trying to read landscape with like winds to see what happens and I am shocked with what I find.

 

[Idaho Sawyer]

Wind mixed with topography can be a humbling endeavor!!!

 

[Broz]

Wind mixed with topography can be a humbling endeavor!!!

Amen..

Jeff

 

[M67]

As an old glider pilot having done my fair share of ridge soaring, i can fully appreciate the presence of very strong up- and downdrafts in steep valleys. To say that i utilise it when shooting would be a vast exaggeration...

I feel a lot of people miss over and under to vertical wind, and think it is due to other variables, such as ES, bad shooting, wrong V0, wrong BC, ***. In the hills and mountains, shooting these distances, a bullet is going to be blown up or down, period.

Just starting to get a sort of a grip on horisontal wind judgement, this weekend was a first for me in assessing the vertical vind, and making a first round hit on a target with a wind corrected elevation adjustment.
Just 980m out, but still.

K

 

[albertakid]

My shooting partner and I have seen this happen quite a few times. We have an area that we shoot out to 2000 plus yards alot and have seen some major changes in elevation due to up drafts makes you think twice about what you think you know?? Also angle of the shot doesn't cross alot of peoples minds, but it can really change things up if it's not accounted for.

Jordan

 

[Broz]

Those large pine trees on steep slopes in the bullet path, flapping their arms like they were trying to fly. It took me a long time before I realized they were trying to tell me something.

Jeff

 

[Idaho Sawyer]

With my occupation I get to fly a lot in the backcountry and using streamers we determine wind drift, up/down air, etc. I feel fortunate to be able to apply that knowledge to bullet flight

 

[Canadian Bushman]

You guys make me thankful to live on the plains. I drove 300 mi last weekend and elevation changed 14ft.

 

[BrentM]

When I was a student pilot and reading the wind section of the manual I remember the illistrations showing high and low pressures on the front and back sides of the ridges etc. I have a book that also targets back country flying and it addresses much of this. However, in a plane you are generally flying within areas the air is a bit more stable vs being relatively close to the ground. Not that any of this has made me a better wind reader but I have been thinking about it ever since I shot that mountain lion a month ago and how it all applies to the bullet path.

I noticed a transition from updraft, hide area, to down draft, within a relatively short distance down the slope of the finger I was on that day. I also noticed a pressure shift in kestrel. The pressure shift was not great enough at 1000 to make any difference but at 1500-2500 I do believe it needed to be accounted for. I have not shot beyond 1500 so I have no clue. ??

Back to the point, on the backside of mountain the wind tumbles in a clockwise rotation, creating up and down drafts. Have you guys noticed this and thought about how to account for bullet path relative the invisible air stream at say 100 feet off the deck?

 

[BrentM]

Illustration

 

[Idaho Sawyer]

Your photo is the down draft (I referred to them as burbles) that I am referencing in my original post. From my experience there is no updraft in the lee side, clockwise air. As far as detecting it, My first go to would be thermals, if those aren't present, your next best bet would practicing in those conditions and reconizing those lee side conditions. I will be on the lookout for them from here on out and put that mental slide in the shooting book for future situations that resemble it.

The pressure shift in the Kestrel I find interesting because it is the same air, so to speak, it is justing swirling off the ridge, I understand if your losing or gaining elevation, but if your ele. stays the same your pressure shouldn't fluctuate with moving air (unless a front is coming or going). Maybe someone else can chime in here and share

 

[BrentM]

I wonder if pressure is the wrong term. It is a differential for sure but.... since you experience with airplanes look at wing design. The air over the top of the wing has to travel faster then the air across the bottom and pressure differential is created which creates lift.

Another example might be the way sand or snow etc moves behind a wind block. To a degree the material moves toward the block, on the wind blocked side, and it lifted up, tossed around, and the cycle repeats. The turbulance created behind the block/rideridge line creates a disturbance that is unstable. I notice this area also will build and flush, in a cycle type fashion.

Thoughts? I don't mind being told I am full of crap either. I am learning and observing.

 

[BrentM]

btw- That is my picture and illustration. Feel free to modify it and use it if you wish.