New Zealand Climate Update 156 – June 2012

What happened in May, how our climate outlook for the previous three months turned out, global and local sea temperatures, and our outlook for June to August. 

Current Climate - May 2012

May was characterised by higher pressures than normal to the southeast of the country.  Lower pressures than usual were observed near Tasmania and also to the east of the North Island.  This pressure pattern resulted in more easterly quarter winds than usual over New Zealand. 

Global Setting – May 2012

Neutral ENSO conditions presently exist in the tropical Pacific, but there is a likelihood of El Niño developing by spring. For winter, higher than normal mean sea level pressures are expected to the south of New Zealand (but with a weak circulation anomaly over the country itself). 

Outlook - June to August 2012

Neutral ENSO conditions presently exist in the tropical Pacific, but there is an enhanced risk of El Niño conditions developing during the second half of 2012. For winter, higher than normal mean sea level pressures are expected to the south of New Zealand (being weak over NZ itself). Sea temperatures around New Zealand are likely to be near normal for the season as a whole. Winter temperatures are likely to be near average overall for all regions, although frosts and cold snaps typical of winter will occur from time to time. Winter rainfall totals are likely to be below normal in the eastern South Island, normal to below normal in the western North Island and northern South Island, and near normal elsewhere. 

Retrospective - March to May Outlook

The mature La Niña event in place at the start of autumn 2012 was (correctly) forecast to have eased to neutral by the end of the season. A somewhat stormy Tasman Sea (with lower pressures than usual) was expected for March – May, with more frequent northeast winds than usual predicted over the country. Pressures were indeed generally below normal over the north Tasman Sea, as well as near Tasmania. Higher than normal pressures continued east of the Chatham Islands during autumn, and also extended across the South Island. More east to northeast winds affected New Zealand during autumn.