When a strong cyclone centered in the Middle West extends its influence to the Atlantic coast a small secondary low-pressure area is often formed just inland from the coast. The southerly wind readily establishes itself at the surface along the low, flat coast, and therefore brings about a rapid fall in pressure not only by blowing away the dense, cold air, but also by bringing much warmer air soon from over the Gulf Stream. Perhaps a hundred miles inland, on the other hand, the relative roughness of the land tends to retain the cold surface air for some time, while the southerly wind rides over it. Once the pressure along the coast has become lower than that inland, a secondary cyclone develops and survives for the short time till the relatively mall volume of cold air becomes mixed with the warm and blown away.