El Nino still climate driver

"Over the past few weeks we have had some rainfall over the northern and eastern part of the North Island which has certainly alleviated the situation with soil moisture - it has improved things," he told Rural News.

"There has been some rainfall over northern and eastern Canterbury which has certainly helped.

"But the El Nino is very strong – it has peaked out. But even though it will be weakening, it will still be weakening from a very higher intensity. The analogy for that is if you have $100 million and you lose $10 million in the stock market over a week – you will still be pretty rich. You do lose 10% but you coming down from a very high level.

"Because it is at such a higher level, even if it is easing and losing its "giddy up" it will still be a major climate driver for the next few months."

Brandolino says the most likely outcome for the north of the North Island is for drier than normal conditions for the rest of summer into the early autumn; for the rest of the North Island there is an equal chance for rainfall to be either near normal or below normal.

For the northern and eastern part of the South Island there is about an equal chance for rainfall to be near normal or below normal. For the western part of the South Island it is most likely to be above normal.

"In summary we still expect El Nino to be the main climate driver. What has happened over the past couple of weeks – I wouldn't latch onto that too much.

"We have been describing what we think will happen with El Nino and that is based on long term computer models that try to project what will happen but it is also based on what has happened with the three previous very strong El Ninos.

"We know the average outcome in New Zealand of El Nino especially with the strong ones. But each El Nino has its own uniqueness – you can have a family of children and they all look alike but they all have their own unique set of characteristics. Each El Nino has its own set of unique traits."

It never follows the script exactly – modelling is more for guidance purposes, Brandolino says.

"I think it is important to know as we head into the rest of summer and early autumn we are still calling a dryness risk for the eastern and northern parts of the South Island, the eastern and northern part of the North Island.

"By the time autumn comes around there will be some differences and subtleties to that statement."

As of yesterday, the driest soils are over the interior of Otago, especially west and north-west of Dunedin, he says. South central and central Southland have the most abnormally dry soils for this time of year.

The soils are quite dry still in mid and southern Canterbury, east of the divide. About mid and northern Canterbury the soils are moistening up - relative to this time of the year, they are pretty average.

For Kaikoura and Marlborough the soils are near average.

"It is important to remember that during this time the soil loses about 3mm a day to the atmosphere. So even though an area can be in decent shape in terms of soil moisture, it only takes about a couple of weeks of dry weather for things to turn south pretty quickly."

In the North Island the soils are unusually dry for the Kapiti Coast but nothing exceptional or severe.

"Central Waikato is pretty dry now – if you exclude the Coromandel, west of the Coromandel from Thames to Lake Taupo that stripe is pretty dry right now. Also the far western part of Northland is quite dry for this time of year.

"I expect soil moistures to deteriorate in Gisborne over the next week or two – particularly Gisborne to Hawkes Bay as there is not much rain forecast in that region.

"If you lose 3mm a day on average in the summer time, if computer models are predicting 25mls over 10 days, you are going to be in deficit."

In summary Brandolino says it is too early for farmers to let down their guard. Even though they will hear that El Nino is weakening, it is if from a very high intensity.

"The impacts of El Nino don't go away because it is weakening," he says. "People hear it is weakening and think we will let our guard down, or we've had a bit of rain here in Northland or the Coromandel or parts of Canterbury we can let our guard down. That is not the case.

"We need to watch the tropics – that can be a wild card. We are expecting a pretty active tropical season in the tropics near the dateline. That is a breeding ground for tropical cyclones especially in the second half of the year which we are entering. If it is busy up there, there could be an extra ex-tropical cyclone or two dropping towards New Zealand.

That could be a wild card for the northern and eastern parts of the North Island. It is not a guarantee but something that could come into play and impact soil moisture, certainly weather conditions going forward.

"But for the northern part of the North Island the most likely outcome for the rest of summer into the first month of autumn is for drier than normal conditions."