Hey folks, this thread is great! Using this in combination with the topo terms and descriptions thread and the HC bedding DVDs, I've learned more in the last 24 hours than my entire 13 years out hunting, at least it feels like. Since I'm basically a rookie at this, take this post for what you will, but just my 2 cents.
So when I think of thermal hubs and converging ridges, I almost look at them as opposites. Thermal hubs is an area where you have 2 or more valleys/hollow/ravines (whatever your terminology) converging down into a small area at the valley floor, which would provide deer an excellent opportunity to use their noses to determine what is going on in all those areas above. This of course is once the thermal reverse has happened. I am also thinking that the thermal drop into this hub can occur at different times depending on the direction the slope faces (I would imagine eastern facing valleys would have thermals dropping much earlier than west and south facing valleys, just because the sun leaves them earlier). Knowing that these areas can be a nightmare to hunt due to these thermals and wind, this might provide an opportunity for an ambush - I think Dan spoke of this in the HC Bedding DVD. I'll do my best to be as clear as possible since I don't have a map or an example to show.
Say you have an East facing valley that leads down into a thermal hub. You have a west wind, so you would think a buck would be bedded on one the spurs that is making this hollow, peering down into the bottom, collecting thermals from everythign below him. Since its east facing, especially if it is rather steep, the sun will set behind this hilltop much earlier than the other areas, allowing for the cooling air to start the thermal switch. The buck is confident there is nothing below him because he's been smelling that all day. At this point, if you can hug the edge/transition on the valley floor, you may be able to make a frantic ambush in and catch the buck coming down out of his bed into the bottom and have no idea you are there. By hugging the east side, you may also be able to avoid letting any other deer know you have entered the area, even if they are bedded on the other spurs/valleys that are creating the hub. This is speculation here, but I think it's a fair assumption, because since the area you are closest is now experiencing falling thermals, I think you may be able to avoid the other areas where the thermals are still rising. The benefit here, if this is possible, is not only would you have a great chance at killing a buck bedded on that eastern slope, you may be able to catch any other bucks coming from the other valleys, if for some reason they would happen to be bedded elsewhere. Again, the 2nd part of this scenario is speculation only, and would be a secondary target, as you would be set up on the best and most likely buck bed. So that's that for thermal hubs, but switching over to converging ridge, which as I mentioned before, I feel you could treat as an exact opposite.
This time instead of valleys meeting in one area like we saw with the thermal hubs, you would have ridges or spurs all meeting close to one area. Spokes on a wheel seems to be one of the best analogies for this that I've heard. Now we talked about falling thermals for hubs, but I feel converging ridges would be a prime area for rising thermals, esp during the pre-rut for cruising bucks. It seems to me that a buck would be able to stay in that top 1/3 area of the elevation at a spot with converging ridges, and be able to smell any and everything going on in those hollows that are below him, simply by subtly moving around. This would be a morning setup I would imagine, and target the rising thermals that occur when the sun comes up. If there happened to be a hot doe anywhere on those spurs or hollows, rising thermals would bring that smell to him as he is cruising the wind tunnel. I feel like this would be a much better area to target compared to thermal hubs, simply because of access and more consistent with winds since it is up higher. But again, I would feel doing this would be primarily a pre-rut/cruising stand location, so it limits the time of year you would focus here.
I'm sure this information is in several other places here on the beast, and documented by hunters much more experienced and successful than I, and if I happen to be incorrect, someone please enlighten me, but knowing what I know about thermals and buck activity at given times of the year, it just makes sense. I am fairly new here, so I am still navigating around working my way through the best tactical threads now. Since most of my vacation will be during the first few weeks of November, I need to start focusing on rut-related information here on the beast, which would help me better understand a mature bucks movement during this time of year, esp in hill country.
Thanks to everyone who has contributed to these threads, the information is exceptional!