KEY POINTS:
Kiwis can expect a little bit of everything when it comes to the weather this summer. Conditions are usually determined by the dominant weather in spring, but MetService weather ambassador Bob McDavitt said the pattern until November would be neutral, between El Nino and La Nina.
"There will
be more variety. Not one weather system - hot or cold - will dominate. They will share it," McDavitt said.
"El Nino and La Nina will take turns taking over the main weather theme. All the weather patterns will dominate - but they are not going to fight over it."
McDavitt compared weather patterns to an orchestra.
When El Nino is the composer, we get "marching music", La Nina is more "more romantic", and a neutral pattern is like jazz - everyone gets a turn being the boss.
During an El Nino pattern New Zealand tends to experience stronger or more frequent winds from the west in summer, typically leading to drought in east coast areas and more rain in the west.
A La Nina summer was usually characterised by more northeasterly winds, which tend to bring rainy conditions to the northeast of the North Island, and reduced rainfall to the south and southwest of the South Island.
Warmer than normal temperatures typically occur over much of the country during La Nina, although there are regional and seasonal exceptions.
"Each pattern will hang on for a week or two, so we'll get hot then cold, wet then dry," said McDavitt. "We'll get a variety of weather but it won't be erratic."
National Institute of Water and Atmospheric Research senior climate scientist Dr Jim Salinger said the official summer seasonal forecast would be released in November.
"It's too early to predict what that forecast will be but it might be a bit warmer than normal," he said.
Weather Watch analyst Philip Duncan said neutral periods could be hard to forecast and spring was not an indication of what we would get in summer.
He said there were further difficulties with predictions because of the range of "micro climates" in New Zealand and its size.
"We are two small islands stuck bang in the middle of the southwest Pacific."
Duncan said that in the short term, the neutral spring would bring more westerly winds, meaning warmer weather for the east coast but cooler spells in the west of the country.
But if the neutral system continued into summer Duncan predicted Auckland, Bay of Plenty and Hamilton would have a wetter, but warmer, summer than the last.
Humidity levels would be high, increasing the chance of more showers.
In Northland there was always the chance of a tropical cyclone brushing the region in cyclone season between November and April, he said.
One weather analyst preferred to use the cycles of the moon rather than satellites for long-range weather predictions.
Ken Ring has been using the technique for 35 years and said it gave him an edge over mainstream weather experts.
"We have alternative medicine and alternative music, I like to think this is just alternative weather."
He is predicting a sudden rise in temperature around mid-November before rain in the month's last 10 days.
Ring also predicted heavy rain in the first week of December but mid-December to February would be mainly dry for Northland, Auckland, Canterbury, Hawke's Bay and the Bay of Plenty.
For Christmas Day Ring predicts the best weather in the top half of the North Island and east of the South Island, but says it will be cloudy through inland Otago and Southland.
The hottest places may be Gisborne and Hawke's Bay in the North Island and Canterbury and South Canterbury in the South Island.
Wellington was Ring's pick for the best New Year weather, while Christchurch would be cloudy and Auckland could have rough weather in the Hauraki Gulf.
