Arcus cloud Arcus cloud An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two main types of arcus. Arcus clouds most frequently form along the leading edge or "gust fronts" of thunderstorm outflow; some of the most dramatic arcus formations mark the gust fronts of derecho-producing convective systems. Roll clouds also may arise in the absence of thunderstorms, forming along the shallow cold air currents of some sea breeze boundaries and cold fronts. A shelf cloud is a low, horizontal, wedge-shaped arcus cloud. A shelf cloud
Ordinary Thunderstorms Ordinary Thunderstorms Ordinary Thunderstorms is a novel by William Boyd. It explores the dark side of London's underworld and the international pharmaceutical industry. Adam Kindred is a recently divorced climatologist who has moved back to England. After attending an interview for a Senior Research Fellowship position at Imperial College, London, he goes into an Italian restaurant in Chelsea and briefly encounters Dr Philip Wang, who accidentally leaves a file behind. Adam takes it to Wang's hotel, only to discover that Wang has been murdered and still has the knife in his body. Before Wang dies, he asks Adam to remove