when do cirrus clouds usually appear in the sky
Cirrus cloud On planet Earth, cirrus generally appears white or light grey in color. It forms when water vapor undergoes deposition at altitudes above 5,500 m (18,000 ft) in temperate regions and above 6,400 m (21,000 ft) in tropical regions. It also forms from the outflow of tropical cyclones or the anvils of cumulonimbus clouds. Since cirrus clouds arrive in advance of the frontal system or tropical cyclone, it indicates that weather conditions may soon deteriorate. While it indicates the arrival of precipitation (rain), cirrus clouds only produce fall streaks (falling ice crystals that evaporate before landing on the ground).
BBC Weather Forecast information is provided by MeteoGroup, who replaced the Met Office as the BBC's provider of weather services in 2018.[1]
Alonso Álvarez de Pineda
1 + 2 + 3 + 4 + ⋯ which increases without bound as n goes to infinity. Because the sequence of partial sums fails to converge to a finite limit, the series does not have a sum.