Wednesday, February 8, 2012

Busted by the Wind!


Rough country like this can cause big wind problems

Every hunters dream situation...6:15 AM, about 45 minutes before sunrise and you have managed to find your way over the ridge, through the trees, and down to the perfect vantage point in the dark of night.  This was no problem, you have walked the path a dozen times as you have scouted this bull off and on for the past few months.  You know he will be there, he was there yesterday.  Yes, this is the spot, it will offer a perfect shot.  Right now the wind is perfect...nothing can go wrong!  As the sun begins to crest the ridge you hear him bugle below!  Wait!  No, the wind can't change direction, not right now!

If you have been hunting very long, you have experienced the frustration of being busted by the wind!  Many of us now carry tools to aid us in determining the direction.  Even so, that doesn't always take all of the challenge out of the wind.  How long will you sit on that particular spot?  Will you need to move?  Will an approaching storm switch the winds?  We try to plan by forecasts, and by what we have seen on past days in the area.  Planning is a great idea, that is exactly what I will talk about today. 

Effects heating from the sun has on slope winds

In September I sat on a ridge on Utah's Mt. Dutton range, similar to the situation I described at the beginning of this post.  We made it in before first light, and we were sure we would get set up in the right spot to look around, with the wind on our favor.  Within minutes of the sun coming up all of that changed as the wind shifted on us, carrying our scent in the direction we didn't want it to go.  Five months later I find myself sitting in a wildland fire behavior class in Boise, Idaho.  As a meteorologist is going over "diurnal" wind patters (slope winds that occur in mornings and evenings) it dawns on me that in all my 12 years fighting fire, and learning weather, I had never really applied those weather lessons to my hunting techniques.  So, sit back and let me give you a little crash course in slope winds.  For my firefighting buddies reading this, I apologize if this is basic stuff you already know.  Still, I hope you think about these things as you get out hunting.

Warm, rising air.  Upslope daytime heating

First, a simple concept: as the surface heats with the sun hitting it, that air will rise, and "flow" up the slope.  It's pretty simple, this is an upslope wind, it will begin slowly in the mornings, and can intensify throughout the day.  In the evening, the surface and air will cool, the air will flow downslope, down the canyons, and eventually to the valleys below...downslope winds. 

Now, that seems pretty simple.  However, I think about our situation on Mt. Dutton.  I had figured the winds would change and start to move upslope after sunrise.  What I didn't take in to account is that even though the sun was coming up, our side of the canyon would be shaded for some time to come!  It would be this way until the sun rose high enough in the sky to hit the slope.  Across the canyon, on the opposite aspect the air may have begun to rise.  On our side, in the shade, it would be a few hours.  So, in the tops of canyons, bowls, saddles, and other such features, it is very possible that light winds may be blowing in several different directions based on the sun hitting the slope.  It can take some time for the sun to work it's magic that will cause these little wind battles to cease, allowing the winds to balance to the point that all the wind will be pretty much upslope later in the morning, and through the afternoon. 

Evening downslope winds caused by cooling surface/air
So, as far as planning to beat the wind, look at your aspect.  When will the sun hit it?  If I am at a ridge top or in a saddle will the wind "swirl" as it is effected from various slopes?  Also, on ridge tops winds often tend to be stronger.  Afternoons can be very tricky.  Daytime upslope winds can be strong, and as the sun begins to set and the land and air cool, the wind switch from upslope to downslope can often be very abrupt.  My wife and I observed this in October as we got set up on a canyon rim.  We did anticipate this, and the wind played right to our favor.  Arriving at our spot around 3:30 PM the wind shifted quickly an hour later.  Wouldn't you know it, just minutes later a good sized group of deer appeared from the direction that the wind was now blowing from.  I have to wonder if at first they could smell us, but after the shift in wind they no longer had this advantage.  They came within 20 yards of us.  This was a light breeze, probably from 4-8 mph. 


Virga.  This is an indicator of strond downdraft winds
approaching.  Photo by Chuck Doswell http://www.cdoswell.com/

Terrain can really effect the winds.  Where canyons converge, winds from the two canyons can mix and swirl, causing an "eddy" effect.  As winds hit a peak this eddy effect can also occur on the opposite side of the peak that is being hit by the wind.  Bottom line: think of wind as you would water.  If water hits an object it will move around it.  Winds in a gap or canyon are a lot like a river that gets squeezed into a tighter area; the air will speed up as the water would.  Wind will follow the path of least resistance as water would.  As it passes through mountains, the landscape will cause winds to bend, curve up and over, strengthen through narrow areas, or be absorbed as it hits larger features head on.  Vegetation will also effect wind, as stands of trees can absorb wind, and open areas can intensify it.  It's a lot to keep in mind!
   

A bull I called in during a fierce hail storm.  This storm
aided me to call in a lot of bulls that day!

Now this is all quick and dirty, and I encourage comments here if I need to explain further or clear things up.  This is weather, and we all know things can change.  Storm systems will blow all of this out of the water.  The conditions I have mentioned about slope winds will generally apply to normal sunny days, void of storm or greater wind events.  If a storm system is on the way it is quite normal around here to experience a strong southwest wind until the storm arrives, switching to out of the northwest after the front passes.  These winds will over ride the slope winds.  Thunderstorms produce strong gusts that will cancel out slope wind.  Check your forecasts and try to understand them!  If the weatherman isn't mentioning storms or strong winds these simple slope rules will help you greatly.  As you go out and hunt keep a journal with you.  Write down what your weather is doing each time you go into an area to scout that buck or bull.  Write it down every time so you can establish patterns.  What time of day does that wind shift occur?  Where does the wind switch to?  Does the wind effect what the animals do or where they go?  People talk about patterning big game, and I find that weather is usually that driver to their patterns.  As the weather changes, so can those patterns.  Keep a log so you can learn and adjust!  Go out and give it a try, and remember to check back in to let us know how it's going!

No comments: