The Particle Color gradient has been adjusted for a dirty, dusty look. The color of the particles is also animated over lifetime using the Color Mix and Life Gradient in Particle Age Effects. The settings blend the funnel to the black storm clouds in the background image. Open the Fractal Fury rollout. The Gaseous particle type, a low Density and a higher Exponential Blend value create the soft, gaseous look of the funnel.
Scale is set to a lower value.
These settings help to keep the render times very low and still offer a good effect quality. All PyroCluster helpers for the tornado use this settings. For the swirling dust clouds, where the tornado touches the ground, we're using bigger particles. The Global Particle Color is dirty and dusty like the funnel and matches the color of the ground in the background image. In Fractal Fury, we choose a higher Density and higher, negative Peak Blend value in order to give the chunks of dirt and dust clouds the right look.