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What's the most important thing to know about thermals??? Thanks for any input. Leo
Cold goes down warm goes up.
I prefer the merino wool ones.
Wind should be sucking downhill pretty hard in the morning. In my experience it will last to about 9 or 10. Then switch uphill for a little while. Then things get totally unpredictable until about an hour before dark. Then it will start going downhill hard again.
Your specific area it may behave differently. Your gonna have to hunt and see what happens. Storms will screw everything up.
Good luck.
Good one Mule Power!
I have found that uphill and downhill air currents are easier to read about and predict in theory than to understand and use in actual hunting environments. Like patdel says every area may be different. On calm days I just keep that wind checker bottle handy.
I have some fiber material that floats like you wouldn't believe. It's possible to watch the fiber float for up to around 50 yards from my location. I don't think that is possible with powders? I just used it on a dall sheep hunt and it saved my butt!
Milk weed does an excellent job of telling what the wind. Is really doing.
If it's straight up thermals with no prevailing winds it can trip you up cresting a hill. I checked wind direction one morning on a saddle once, moved a little ways and actually passed center line of the saddle and didn't realize it and sat up for some elk we could see in the distance and called them right in only to get winded. Good luck!
Great tip jims. I've been using fibers from cotton balls for years. I put a fresh cotton ball in the chest pocket of each of my shirts and jackets. A few fibers will tell you more about thermals and wind direction than powders ever will. Polyfill from aspirin and other over the counter meds works well too. On my last elk hunt the guide's powder showed the wind moving straight uphill. I released some cotton and we both watched in amazement as the cotton went uphill about 20 yards, moved vertically for several feet and then u-turned back over our heads and went straight downhill.
Not to turn this into a wind checking thread, but I always used a powder bottle to check the wind until one of my hunting partners showed me a trick where he ties a small 14-18in piece of thin, thin thread to the bottom limb of his bow. then you just hold your bow out and the thread will hang vertically up and down and show you which way the wind blows. Then you never have to worry about pulling out a bottle and all that jazz. Just another option. I found bright green thread at the local craft store and it works great.
OK a serious answer. Air is like water. It rolls around stuff creating slackwater eddies etc. It breaks like a wave and rolls under itself at the crest of a hill.
AND.... even on sunny south slopes there are shady chutes where the air drops all day. The only way to find spots like that is by being there and knowing your area.
There is actually a lot more to it than hot air rises and cool air drops.
+1 on the milkweed pods. I swear by them.
An open sunny hillside that heat the air well can pull the air from another place or side that has dark timber on it. Even 1 or 2 pm and the currents can still be going down.
Every place is different. And thermals rarely overcome the prevailing winds in an area. Mostly in effect when very light to no wind.
You are actually talking about up slope and down slope winds. Cold down, warm up. The heating of air in the morning shifts the direction as does the reverse in evening with cooling.
Thermals are somewhat different in that they can occur on flat ground too.
Many years ago on this forum we had a very good discussion about this. The best input came from one poster that was a glider pilot.
At major changes in geography, ridgetops, valley bottoms, saddles, bowls, basins, outcroppings eddy currents form as the air flows in, around and swirls over these features. The prevailing wind and the thermals air interaction is relative to their relative strength in relation to geographical features. Less dense warm air rises while more dense cool air settles, damp air is lighter than dry air. For a wind air movement indicator I get a crew cut prior to hunting season and stop shaving. I then leave the back of neck, the sides of my head and face exposed while hunting so I can feel air move over my face, neck and head. I know what the air is doing without looking. The main concern is the air blowing directly over my body and where the air is taking my scent. Second concern that I keep in mind when setting up an ambush is the residual scent that sticks to the ground, shrubs and trees I walk on or touch. If the prey crosses your path on their way to your planned rondevu you will more than likely be stood up.
Dey go up..dey go down...and dey swirl and change when within 80 yards of elk.
A spray bottle isn't going to tell you much more than thermal direction within an arms reach of your location. Floating fibers or something like milkweed (when available) will give you a lot better feel for thermals as far as you can see them floating. I always put a few of the fibers in a spot where they are available quick and easy. The small can I bought has lasted me around 10 years and I use it a lot. The fibers I use are super bright and I can see them for a long ways! You would be amazed at the thermal directional changes that take place once a few yards from your position.
Thermals should not be confused with Wind. Thermals are driven mostly by the heating/cooling of the earth surface
Thermals are very gentle movements of the air, sometimes almost imperceptible. Cold air sinking below the rising thermal causes a downdraft. That's why you can feel thermals in your face in one spot, then feel it on your neck in another.
Typically the thermals move DOWNSLOPE in the mornings until the air heats. When the air heats up, it mixes. After the air heats up and stabilizes, the thermals will be UPSLOPE during the day. Later in the day, as the air starts to cool, the thermals will mix again and then just before dark, they will be predominately DOWNSLOPE again
Thermals are weather dependent. You wont have any consistent thermals if a weather front is moving thru.
Slope direction definitely has an impact. The sun or prevailing wind will warm one side or mix it before the other.
Here's some more info regarding thermals... Downslope wind—
1. A wind directed down a slope, often used to describe winds produced by processes larger in scale than the slope. Because this flow produces subsidence, downslope winds experience warming, drying, increasing stability, and clearing if clouds are present.
2. Flow directed down a mountain slope and driven by cooling at the earth's surface: a component of the mountain–valley or mountain–plains wind systems; same as katabatic wind.
The many synonyms for downslope flow are sometimes used interchangeably, and this gives rise to ambiguity and confusion. Downslope can be used generically to denote any wind flow blowing down a slope, or it is used specifically for katabatic flows on any scale, such as the nocturnal slope-wind component of mountain–valley wind systems or mountain–plains wind systems.
See katabatic wind, gravity wind, drainage wind, fall wind, bora, foehn, chinook.
I have to agree that it does no good to know what the thermals or wind for that matter is doing right where you are sitting. The thread on the end of your bow or a puff bottle does you no good. You need something that tells you what the wind is doing quite a distance from your stand. I always carry a film vial full of milkweed puffs. I had a good buck coming last year and the wind seemed perfect, right oi my face. He buggared and left at about 35 yards. I than took out my milkweed and released a few they blew directly behind me, hit an up slope and swirled around and can back past me right to where the buck was standing when he buggared. The wind was bouncing off the hill behind me and swirling my scent in the wrong direction. Shawn
