El Nino to return with both rain and drought

In drought-prone areas such as Canterbury and eastern North Island, El Nino brought drier conditions as the country headed into summer. Photo / NZME

Climate scientists are warning that a large, ocean-driven El Nino system could bring unwelcome weather extremes this year, making the east coast drier and the west coast wetter.

Models have changed so much in the past fortnight that the Australian Government's Bureau of Meteorology this week confirmed El Nino thresholds had been reached in the tropical Pacific for the first time since March 2010.

The latest climate predictions indicated a solid chance - about 70 per cent - that El Nino conditions would continue through the southern winter and spring.

"The chances of a relatively dry winter increase during El Nino for the western North Island - Northland, Auckland, Waikato, Waitomo, Taumarunui and Taranaki - as well as for Nelson and Marlborough," said MetService meteorologist Georgina Griffiths.

"But in the North Island, we may not notice this effect very much from day to day, since winter usually yields more than enough rain."

Spring was when El Nino really started to flex its muscle here, she said, and typically it made the season stormy, windy and extremely cold.

While the chances of a wet spring were increased during El Nino in the west and south of the South Island, the western North Island, Nelson and Marlborough, tended to be drier than usual.

In drought-prone areas such as Canterbury and eastern North Island, El Nino brought drier conditions as the country headed into summer.

"These regions are impacted by El Nino towards Christmas, in fact during the driest time of year."

Federated Farmers Northland president Roger Ludbrook said he was already preparing his beef farm by ensuring he could offload cattle without affecting the budget.

El Nino

• The trade winds weaken, leading to a rise in sea surface temperature in the eastern equatorial Pacific and less "up-welling" off South America.

• In New Zealand, farmers in the western, wetter areas often face significant damage to pastures from too much rain, while those in the east have to deal with extremely dry conditions.

• The last severe El Nino in 1997-8 caused a drought that cost New Zealand hundreds of millions of dollars.