Here's a dilemna I'm currently having, and that what I call trying to RNG for a tornados with a jolly nature and a physical spread. I'm having no problem reaching frame 19 for 31/31/31/23/31/31 and oh I wish it was a flawless spread, but it seems I have now seen every other nature at least twice except for this jolly nature. I tried almost every pattern, and still no match after like over 100 attempts when hitting seed. If this continues after 30 more attempts, I will have to reluctantly try a different seed. Times like these I wish natures were more predictable.
I saw in Brag About My Pokemon that you already got yours, but at least in my experience going for a Modest Tornelos, I found something that helped me a whole lot. After saving inside the cabin, resetting to hit my seed, and advancing my IVs through walking, I would begin by not saving at all, and as soon as I started to walk out the door I would spam A like crazy, not stopping until Tornelos was gone and the weather cleared a bit. I would then capture (masterball), and check the IVs and nature, writing it down if I hit my seed (IVs). I would then repeat it, but save one time, and spam A like crazy till Tornelos was gone, then capture, and write the nature down if I hit my seed. Then 2 saves, then 3 saves, etc, etc. Until I ran into the nature I wanted. At least in my case, I had "acceptably consistent" natures when doing it this way. They would vary some times, but about 70% of the time, if I got say Timid with 5 saves, I would get Timid with 5 saves when I did it again (I tested that several times).
In the case of the Modest one, it took like 14 or so saves before I stumbled upon a Modest one. I could have just kept it, but I wanted it in a Dusk Ball. So I reset, and saved 14 (or whatever it was) times again and this time spent the time whittling it's health down and putting it to sleep. Sure enough, it was Modest again.
I know EE's already got his, but this might possibly help anybody else going after roamers.