Nor'west arch

As Canterbury North Wester ( Māori parera, in everyday language often Nor'Wester or nor'west arch of English arch = " arch " ), is referred to a special weather conditions on the east coast of New Zealand's South Island. It is characterized by a wide strip of clouds on the otherwise cloudless sky which is accompanied by strong wind coming from the northwest currents.

The North Wester is a typical foehn wind. Warm and moist air from the Tasman Sea meets the north-west of the mountain range of the Southern Alps. The wind backs off the mountain from higher altitudes, where it cools very quickly. Shortly before the mountain range, in the West Coast, the wind currents lose much of their moisture in the form of high rainfall, leading to the formation of the local temperate rainforests. The remaining water molecules of the then relatively dry Nor'Wester during and after crossing the Southern Alps can be seen as an impressive clouds, which are particularly visible in the Canterbury region as a band at the top of each air thrust. This waveform occurs when the moisture - similar to a standing wave - condensed at the top of the arches, and thus as a cloud is visible and re-condensed at the lowest point of the wave arc.

The cloud formations and the Föhnwind extend across the entire southern Canterbury starting at Amberley in the north all the way to Central Otago deep in the Otago Region to the south and is particularly striking, especially in the flat Canterbury Plains. The largest settlement within the control of the Nor'Wester is Christchurch, the largest city on the South Island.

The dry, warm foehn wind from the northwest caused not only between seasonal droughts in the normally very fertile region, but has been shown to have an effect on the human psyche: Sun rise during the billowing gusts suicide rates and provide for headaches, depression, and increased domestic violence. With particularly strong gusts of wind in gale force again lead to significant damage to buildings. In the late winter of Nor'Wester for mild temperatures makes and announces a coming spring.