New Zealand Climate Update 157 – July 2012

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

Current Climate - June 2012

Lower pressures than usual affected the area to the southeast of New Zealand during June 2012, resulting in more southwest winds than normal over the country. The month was notable due to several rapidly deepening, intense weather systems in the New Zealand region. In particular, a rapidly deepening low over the Tasman Sea on 5 and 6 June produced heavy precipitation in Tasman and Buller, and snow to sea level in Canterbury, whilst intense lows on 18 and 25/26 June resulted in severe winds across the South Island (and heavy rainfall in some areas). 

Global Setting – June 2012

Neutral ENSO conditions presently exist in the tropical Pacific, but an El Niño is likely by spring if present warming rates continue. Over the July to September period, circulation in the New Zealand region is likely to show a transition from the more 'blocked' north-easterly anomalies persisting from the recent La Niña towards a zonal westerly flow at the end of the season as El Niño conditions settle in. 

Outlook - July to September 2012

Neutral ENSO conditions presently exist in the tropical Pacific, but an El Niño is likely by spring if present warming rates continue. For late winter, there is inconsistency in the predicted pressure patterns, and it appears likely that there will be a transition from the more 'blocked' north-easterly anomalies persisting from the recent La Niña towards a zonal westerly flow at the end of the season as El Niño conditions settle in. Sea temperatures around New Zealand are likely to be near normal for the season as a whole. Late winter temperatures are likely to be near average overall for all regions except the west and south of the South Island, where average or above average temperatures are likely. Frosts and snowfalls typical of winter and early spring will occur from time to time. Rainfall is likely to be normal in the North Island, and normal or below in the South Island.

Retrospective - April to June Outlook

ENSO-neutral conditions were (correctly) predicted to return to the tropical Pacific during the season. Lower pressures than normal were expected to persist north of the country during the April to June period, with more high pressure systems and ridges over and east of southern New Zealand. This mean sea level pressure pattern was indeed observed.

Predicted rainfall: Rainfall totals are likely to be normal or above normal in the north and east of the North Island, and near normal in all other regions.