New Zealand Climate Update 147 – September 2011

August 2011 was characterised by frequent southerly winds, and higher pressures than usual, over New Zealand. A polar outbreak affected New Zealand mid-month, bringing heavy snow to unusually low levels across eastern and alpine areas of the South Island, as well as Wellington. Snow also fell across the lower North Island, with flurries in unusual locations further north. The long-lived southerly winds between August 14 and 17 delivered extremely cold air over the country. Numerous August low temperature records were broken between the 14th and 17th.

ENSO conditions in the tropical Pacific are in the neutral range and are expected to remain neutral through the spring. Mean sea level pressures are likely to be above normal across much of New Zealand, with weaker westerlies than normal over the country, on average. Temperatures are likely to be above average in the North Island as well as for the northern South Island, and near average or above average in other regions.