Warmer winter but more cold snaps and rain

New Zealand is in for a warmer winter, as one of our hottest years on record rolls on, but the forecaster also warns more cold snaps and big rain events are likely.

According to Niwa’s just-released climate outlook for the next three months, temperatures between now and the start of August were forecast to be above average in the north of the North Island: that included Northland, Auckland, Waikato and the Bay of Plenty.

Elsewhere, temperatures would likely be above average or average.

However, Niwa reported frosts and cold snaps would still become more common, with some cold snaps “possibly quite sharp” and perhaps an early ski season.

There was also a warning of big rain events.

“The combination of lower than normal sea level pressure over the New Zealand region and warmer than average Tasman Sea temperatures over the coming months will result in an elevated chance for significant rainfall events,” Niwa reported.

Rainfall levels in general were forecast to be above normal in the north of the North Island, and near or above normal for the rest of the North Island as well as the east and north of the South Island.

Normal or below normal levels were expected for the west of the South Island.

Soil moisture levels and river flows were expected to be near normal or above normal for all North Island regions and for the north of the South Island.

For the east of the South Island, river flows are also expected to be near normal or above normal, but with soil moisture levels forecast to be above normal.

For the west of the South Island, soil moisture levels and river flows are forecast to be normal or below normal.

“The atmospheric circulation around New Zealand is forecast to be characterised by lower than normal atmospheric pressure through to July,” Niwa reported.

“This will result in mixed and changeable air flows across the country.

“Warmer than average ocean waters that are present around the country are also expected to persist through the next three months, though forecasts suggest they will gradually weaken to the west of New Zealand.”

Over the past month, weak La Nina conditions had given way to an ENSO-neutral state, and while sea surface temperatures around the country had warmed over April, they remained slightly colder than average in the eastern equatorial Pacific Ocean.

Models indicated that this state would persist until early spring, until the tropical Pacific swung toward an El Nino.

Niwa was due to release its climate report on April in the coming days.

The balmy first three months of 2018 has given New Zealand its hottest recorded start to a year, with mean temperatures soaring to 1.75degC above average over the period.

The scorching start came amid our hottest summer on record and the influence of a record-beating marine heatwave, and also included the sixth-warmest March ever observed in the country.

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