Sandstorm Front (2D)

This 2D simulator shows a sandstorm the way it actually happens: as a wall of dust that has to travel across the desert before it reaches you. The map is divided into cells along the wind direction; each grain-size class — fine, medium and coarse sand — only starts lofting once the local friction velocity clears its own Bagnold threshold, so raising the wind speed changes not just how much dust lifts but which grains join first. Lofted mass advects downwind cell by cell, building a genuine moving front rather than an instant haze, and a live Koschmieder-law readout turns the concentration reaching the viewer's position into a collapsing visibility distance as the wall arrives.