Help me understand thermals. Where I hunt in NW Tennessee the topography is very flat. I mean flat, as in over 1,000 acres maybe 3 feet difference in elevation, except for man made levees. My question is do thermals still play a role in an area like this or should I not worry about it?
Hunting Thermals
- Thread starter beefydeer
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BSK
Well-Known Member
Thermals in flat terrain are driven by differences in land use. Open fields warm faster than forested areas in the morning. Air will rise over these fields and air will be drawn from the forested areas to replace that rising air. So you can see light thermals flowing from the woods towards the fields once sunlight is fully on the fields. Of course, this requires very calm winds to be seen.
Think about it like the first rule of plumbing, water flows downhill. Its the same with cold air. If you have open areas, when the sun hits them they are going to warm up first creating rising warm air. I don't remember the numbers but the further away from the ground you get the colder the air gets. So as the surface warms, the colder denser aur above it falls
All else being equal, what happens if you're hunting in a woods stand, situated between a field in one direction and a creek in the woods on the other?
I typically go very deep in the woods sometimes a mile or more from any open areas. Mainly because I find patches of oak trees in the middle of the cypress swamp. If I am this far from the fields should I worry about the thermals?
BSK
Well-Known Member
I doubt it. The only thermals in those type locations will be driven by the different surface temperatures over swamp versus dry ground.
Depends on the size of the creek, flow, and water temp. If it's a dry creek bed then it isn't going to move the air. If it's a cold spring fed, flowing stream then it'll absolutely suck wind into it.
I was sitting on the porch of my parents' cabin yesterday morning watching the sun come up. Zero wind but as the warm morning sun heated up the ground as its beams crept up the hollow, there was a fairly stiff breeze pushing up into the head of the hollow. My dad pointed out that the canopy wasn't moving. The tops of the trees were dead still. The wind was only rushing across the ground as it warmed up. That's thermals.
As for flat ground, BSK nailed it. If you're not on a field edge there's probably not much to worry about. In the morning as the ground warms up, the air rises. In the evening it falls. The trickiest I've ever experienced on flat ground was a 30 acre island of mature timber in the middle of a huge cattle pasture. I learned to only go in after sun up and as long as I could get in a tree undetected I was fine. Deer would be all around me & never know the better. But it's impossible to hunt it in the evening. Doesn't matter which tree I'm in or where the deer are. If they enter the woodlot as the sun is dropping, I'm busted. It's like a pool that contains all of my stink. No exaggeration I could hear deer sorting from 100yds upwind of me. First time or two I dismissed it as they were spooked by something else but eventually I realized it was me. When evening thermals dropped, those cool dark woods contained every bit of my stink. Once I quit hunting it in the evenings and only after sun up mornings, I began doing really well. I still don't understand exactly what's going on in there in the evening but the deer sure seem to know it. Thermals can be weird. Every spot is unique.
It makes sense that thermals would basically throw your scent every which way from your tree stand, as if the scent of the hunter in the stand was a bottle of water suspended over a flat sidewalk, and the thermals simply screwed the cap off.
Did you ever get to hunt it in the evening with a strong prevailing wind? Wonder if there's a threshold past which flat land evening thermals get overwhelmed, even in the woods.
BSK
Well-Known Member
Yes, over 5 MPH.
Probably but I haven't tried it. However I have hunted dark gloomy cold days and noticed a remarkable difference. They still act a bit hesitant and shy like they know something isn't right, but they still meander around. On a normal sunny day they freak out from way off. That's how I realized it was thermals spreading my scent all over the place. That stand of timber is predominantly white oak with a mix of willow oaks and beech, so it's akin to a giant acorn food plot in an otherwise desert of pasture grass. Great place to hunt but it's hard not to get busted.
And yeah it makes sense. The thermals pull my odor straight to the ground, which is warmer than the air so it wooshes outward suspended above the ground. I think???
I'm used to hunting the mountains and the thermals are hard to read in that type of terrain. 25' in a one direction could make a difference in getting winded or not. I would say thermals in flat terrain would be harder to play than mountainous terrain.
BSK
Well-Known Member
Agreed. I hunt ridge-and-hollow country and the thermals are quite predictable there. On a sunny morning, the sun is going to hit the ridge-tops first. The air will warm just above the ground, rise, and draw in cooler air from the valleys. On a calm morning, it's pretty hard to get winded by a deer on the ridge-tops because the air is rising straight up. On the flip side, afternoon hunting is tough, as the air flows down the hillsides and runs down the valleys like water.
deerhunter10
Well-Known Member
Great question and great answers. Thermals ruin more people's hunt then most people realize. Also winds swirling around points and corners of ridges. A good snow falling with the wind blowing will help a lot understanding wind.
Though before the sun hits, it's still going downhill. So I try to not work my way up too high up the ridge before it gets light.
Guess that's what the fancy kids call a "two-stage setup," these days.
BSK
Well-Known Member
Good points younggun308. I'm just too lazy to get that fancy with my set-ups!
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I never really had any issues with thermals when I hunted in Indiana, but I have a VERY difficult time in Tennessee. Many hunts ruined because of thermals like you say.
