Behavior of Thermals

[jhamilton1123]

So thermals rise as the sun heats up the valley floor. They fall in the evening when the air cools after the sun drops. I understand the basic concepts. However, I want to get some more in depth information.

How do thermals act around points and draws:

- Do they come straight up the point only from below the end of the point? Or do they rise from the draws on each side of the point, collide on the center line with the thermals coming straight up the point, blending and rising up the point? Or do they slide along the side of the point to the end of the draw and rise up the head of the draw to the ridge?

- What do the thermals do in the draws that are on either side of the point? Do they just rise to the head of the draw and up the head ridge ? Or do some rise up the head of the draw while others rise up the sides of the points?

- What do they do after the draw or point, when they get to the top of the ridge, if there is no or very little wind? Do they just float up and away?

- What about on rainy and/or cloudy, gloomy days? Do they rise like normal if the sun doesn't come out and heat the valley floor? Are they falling all day? Is there a thermal current on a rainy day? What about a cloudy day? What about if its one of those kinda "brighter" overcast days?

- Has anybody noticed the shady side of a ridge presenting a falling thermal earlier in the day?

I went on a hunt a week or so ago. I traveled in along the main access road where deer would expect to hear, see, or smell me. This path is along the top of a ridge. My destination was a big ridge on the other side of a deep valley. These ridges run almost parallel on a SW to NE line. The wind was said to be SSW to SSE, but I'd say it was really light or not even blowing. The first interesting thing to note was that as I dropped milkweed during entry about 3.5 hours before dark, heading NE on top of this ridge, my milkweed mostly pulled to the right to the steep valley. I found this odd as I would think thermals should've been rising up that slope and the wind was from across that valley. Fast forward, I got straight across from the draw I would climb on the destination ridge, then dropped down into the valley, across and up my target draw. As I climbed the draw it was around 4:45. I dropped milkweed as I went up, and after I got to the top, but it was falling back behind me. I would've thought that the thermals would be rising, but I had wondered if the shaded draw would affect the currents. It would appear that they did. I dropped milkweed as I sat on stand, when I couldn't feel any wind whatsoever, and it still dropped all the way up until I got down. Anybody else had any experience with shaded draws seeming to have some sort of affect?

[headgear]

Your best bet is to burn through a lot of milkweed in your spots to see what the thermals are doing, we can all take a guess as to how they might flow but there is nothing better than doing it in those locations you hunt near bedding. Every location can be different so while in general they might do similar things there can be unique characteristics that come into play in every spot.

[Brandonkinchen]

YouTube hunting thermals.

[dan]

https://www.youtube.com/watch?v=7RF5QsFSd70

[<DK>]

Get on google earth and use time of day tool. You can see what spots are shaded and sunny at what times of the day.

[trapperjay]

Ithat video and Gary’s animation are excellent. Is the spot where they meet at the military crest oftentimes?

[DaveT1963]

Your best bet is to burn through a lot of milkweed in your spots to see what the thermals are doing, we can all take a guess as to how they might flow but there is nothing better than doing it in those locations you hunt near bedding. Every location can be different so while in general they might do similar things there can be unique characteristics that come into play in every spot.

x2 and five yards further away they might do somethingtotally different.


The first thing to understanding thermals is to ackowledge it is not wind. It is actually a vacum pulling air in a direction. Just remember for every action there is an opposite reaction. If wind is vacating someplace then there is also air moving in to occupy that space. That is thermal effect. Kind of like a riptide in the ocean only air can also move vertically. Bottom line is that hot air rises and sucks in surrounding air and objects create "eddies"

[mheichelbech]

Assuming your sitting in a sunny location in the morning, is it most likely that your scent will rise with the rising thermals?

How does it impact a thermal tunnel when the wind is at an angle to the ridge line? I doubt that wind blows exactly perpendicular to ridges the majority of the time??