By Dale R. Larson
If you don’t understand it, the wind can blow your best bow shot opportunity. Knowing where your scent flows during various conditions is paramount in placing stands and choosing entrance and exit trails.
Since air is invisible, we can only imagine its flow without a marking aid, such as smoke, puff bottles or wind floaters. Imagine that a stream of water is air, and watch its reaction to obstructions in its path, observing both on and under the surface. Remember that turbulence in air is more active than turbulence in water. Air is lighter than water and responds more violently. Next, throw in the parameters of wind velocity, temperature changes, topography and vegetation, all of which affect wind currents.
Velocity affects all the reactions to all obstructions as the wind speed changes. Wind speeds are created by high and low pressure systems dictated by unbalanced barometric pressure air masses. The distance and difference of barometric pressure between the highs and lows determines wind speeds, which are hard to predict in the field. But wind direction can be forecast with the aid of a barometer.
A falling barometer with south to southeast winds indicates a storm approaching from the west to northwest. As the storm moves through, the winds change to west to northwest by way of south and southwest. This same scenario plays out with winds from the east to northeast, with the storm approaching from the south to southwest. Basically, if the wind is blowing from the east quadrants and the barometer is falling, you can predict its direction. With the computer, this information is handed to us on a silver platter along with surprisingly accurate long-range (seven days) wind directions and speed forecasts.
Temperature differential creates airflow. Every mountain bowhunter talks about the morning and evening thermals, but these are everywhere. It can be as subtle as small air movement between a shaped area to a sunny hillside or as predictable as mountain thermals. As the air drops, it seeks the lowest elevation and flows using these low terrain features. Thermal air movement is not just a mountain phenomenon.
The topography of your hunting area trains the airflow through and around its shapes. The more rugged, sharp and elevation change in the terrain, the more violent the reactions and difficult predicting the wind becomes. All terrain features will either become an obstruction and create turbulence or a drainage and train the flow. All obstructions will create back eddies of wind current, either horizontal or vertical in shape. These eddies also change size according to the increase or decrease of the wind’s velocity.
When using a back eddy to disperse your scent, make notes of how the wind speed affects its size. It might take a certain wind speed to achieve the right flow of your scent column. One back eddy scenario that I like to use takes a 15 mph wind or higher, with my stand placement near or on the top of a slope of a draw or canyon and hunting hillside travel corridors or benches.
My setup allows me to hunt with prevailing winds for the normal morning and evening hunts, but a strong wind hitting the draw perpendicular creates a back eddy, sucking my scent back out the top, and allows all-day hunting as long as the wind velocity stays high.
This back eddy effect extends down the slope, depending on wind velocity, until it collides with the main wind flow either up or down the draw. Side draws or main draws train the airflow just like water drainages. As a main draw runs past a side draw, it sucks the side draw airflow into the direction of the main draw’s airflow.
Use hillside draws to either push or pull your scent away from your stand. Just be either far enough up or down the draw to get the desired effect. It is difficult to hunt points because of all the different airflows. It’s very tempting to hunt points because they normally hold a lot of deer sign, but stands are better positioned on travel corridors that lead to these points and benches.
Vegetation is another airflow obstruction. It changes the air currents that are created by the terrain. If you have the air currents figured out for the terrain, throw some trees into the equation and then you have to interpret the wind current’s reactions to the new obstructions. I am not trying to turn this into a mind-boggling stand placement exercise, but all of us can reflect on the perfect stand that never produced a shot opportunity.
Without a strong wind, these changing currents are very subtle. They’re unnoticeable without imagination and working knowledge of air currents. I constantly use a puff bottle on my approach or while sitting in my stand. I want to know exactly where my scent column is at all times. If a buck approaches in a manner that will soon put it downwind, I want to know when I have to take the shot prior to it reaching my scent column.
By learning how air currents flow, you will be able to hunt some areas that you previously thought were unhuntable and understand why some areas never produced the anticipated bow shot.
This article was published in the August 2004 edition of Buckmasters Whitetail Magazine. Join today to have Buckmasters delivered to your home.