I'm convinced that if you were to design a tornado specifically to attack and kill storm chasers, you'd be hard-pressed to do better than El Reno 2013. Perhaps the most you could do is change the setting (hilly and forested terrain instead of open plains to reduce visibility further) and the time of day (have it occur at night to even further reduce visibility), but outside of that, I doubt that much could be changed regarding the tornado itself (unless someone else has some ideas about that, in which case please share with the rest of us!).