But when it comes to a long-term prediction about the amount of rainfall to expect, Earth Sciences New Zealand has made a rare admission of uncertainty.
Earth Sciences New Zealand forecasting principal scientist Chris Brandolino said at this stage rainfall totals and the related soil moisture levels and river flows were also most likely to be near normal, but the ‘‘near even spread of probabilities’’ meant there was significant ‘‘uncertainty’’ about the long-term forecast.
It meant rainfall could also be below average or above average.
‘‘Nationally, the risk of drier-than-normal conditions is expected to increase as the season progresses,’’ he said.
There was more certainty in the three-month outlook for the West Coast, Southern Alps and foothills, inland Otago and Southland.
Mr Brandolino said temperatures were about equally likely to be near average or above average; and rainfall totals, soil moisture levels and river flows were equally likely to be near normal or below normal.
Average temperatures for April are between 3°C and 16°C in Otago, and 7°C and 14°C in Southland.
Nearer to June, the average temperatures drop to between -3°C and 11°C in Otago, and between 4°C and 10°C in Southland.
‘‘Neutral El Nino-Southern Oscillation [Enso] conditions are currently present in the tropical Pacific, although the atmosphere continues to exhibit lingering influences from the weak La Nina conditions experienced during summer,’’ he said.
‘‘The next three-month period is expected to reflect ongoing weakening of La Nina influence, with a gradual shift toward more El Nino-like conditions.’’
During winter, El Nino conditions typically bring colder, more frequent southerly winds and increased snowfall to Otago and Southland.
This pattern often results in higher rainfall on the West Coast, while eastern areas, such as coastal Otago, can experience drier conditions.
‘‘Subsurface ocean temperature anomalies in the Pacific are increasingly supportive of the development of a potentially significant El Nino event later this year.
‘‘El Nino conditions become increasingly likely, with the probability of emergence rising to around 80%, for June-August,’’ Mr Brandolino said.
If El Nino continues into summer later this year, it is likely to bring stronger westerly winds and higher pressure to southern New Zealand, resulting in hotter, drier conditions for eastern areas such as Otago and Canterbury, while increasing rainfall in the west.
The climate pattern raises the risks of drought, water scarcity and fire hazards.
