Warm, moist conditions herald spring
Warm temperatures, average to above average soil moisture levels, normal rainfall and a less-than-likely El Nino are among the revelations of Niwa's spring outlook.
Released this week, the seasonal climate outlook for September to November from the National Institute of Water and Atmospheric Research has predicted Waikato temperatures are 45 per cent likely to be above average.
The outlook said the chances of an El Nino developing later this year have further dropped since August.
Niwa forecaster Chris Brandolino described an El Nino event as a ''marriage of the ocean and the atmosphere''.
''There can be no marriage until they are both at the alter.''
Last month, the ocean was patiently waiting for her atmosphere groom, Brandolino said, but now she's moved along.
''Now we have the atmosphere saying 'I'm ready' and the ocean has given up."
International guidance has indicated that the chance for El Nino developing over spring is about 55 per cent. Brandolino said if the nuptials do go ahead during summer, ''it will be a weak to moderate El Nino''.
Rainfall totals in September to November are 45 per cent to 40 per cent likely to be above average or average in the Waikato and equally likely to be in the same range in all North Island regions.
''Regarding rainfall for the next three months, we're looking as an equal chance of above average or near average, there's only a 15 per cent chance it will be below average,'' Brandolino said.
Soil moisture and river flows are both 40 per cent likely to be above average, in Waikato, and about equally likely to be in the near normal or above normal range in all North Island regions.
''If you look at it like a pie graph, the biggest slice of pie is above or near average soil moisture.''
Brandolino said the predicted rainfall and increased soil moisture will bring relief to areas of the Waikato that are thirsty following a dry August.
Between September to November, average sea level pressures are expected to be lower than normal to the north and over most of the country.
Sea surface temperatures for the coming three months are expected to be near average around the coasts of New Zealand.MetService has predicted a low over the Tasman Sea is expected to move eastwards this week, crossing the North Island during Friday and Saturday.
This low is expected to bring periods of rain or showers to much of the North Island, especially northern and eastern areas.
There is a low risk of heavy rain in the Coromandel Peninsula and Bay of Plenty during Friday and Saturday.