New Zealand looks set to head into summer under El Nino conditions, which are warmer and drier in eastern regions, but Niwa scientists say it is ''unlikely'' to be anything like last summer.
A Niwa report shows the consensus from international models is for the tropical Pacific to transition toward El Nino over the next three-month period.
''The probability for El Nino conditions increases as we reach into and beyond the southern hemisphere summer, with a 78% chance for El Nino conditions over the February-April 2019 period.
''The strength and characteristics of this event - if it eventuates - remain uncertain at this point, but indications so far are that it is unlikely to be in the strong category.''
The atmospheric circulation around New Zealand for August-October 2018 is forecast to be characterised by mixed air flow patterns, the report showed.
The emergence of El Nino conditions, especially during the second half of the season, may influence periods of enhanced southwesterly wind flows.
As a result, warmer than average conditions during the first part of the season may give way to spells of cooler conditions later on.
During the next three months, temperatures are forecast to be above or near average in the South Island.
Rainfall totals are forecast to be near normal for the southern region.
Soil moisture levels and river flows are forecast to be below normal in the east of the South Island, and near or above normal in Southland and the west of the South Island.
