Niwa’s winter climate summary had New Zealand once again breaking records. PHOTO/STOCK.ADOBE.COM
Wairarapa’s winter was certainly warmer than usual, but not as wet as we thought.
National Institute for Water and Atmospheric Research’s [Niwa] latest winter climate summary showed New Zealand had its wettest and warmest winter on record.
But, despite widespread flooding events in Wairarapa, the region recorded only average winter rainfall.
Niwa said the winter season was the warmest on record, eclipsing last year’s previous record.
It said temperatures were well above average for the North Island and parts of the West Coast, Tasman, Nelson, Marlborough, and Canterbury.
Exceptions to the wet weather included parts of Waikato, Coromandel, eastern parts of the North Island from East Cape to coastal Wairarapa, and southern Southland, where near normal rainfall was observed.
In its June stock survey, Beef and Lamb said 2021-2022 on the east coast of the North Island was a complete contrast to the previous two summers of drought.
“For the six-month period to June 30, 2022, rainfall was close to double the historical average at 182 per cent.
“This combined with elevated temperatures and reduced stocking rates following drought enabled pasture covers to build ahead of livestock demand.”
Beef and Lamb said with processing constraints livestock numbers were higher than normal.
It said the increased rain allowed farmers to graze a higher proportion of their land during summer and autumn due to the removal of stock water limitations.
“Due to good growth this season, hay sheds were full, and other supplements replenished.”
Meanwhile, Niwa said Castlepoint had its warmest winter air temperature since records began in 1972, with a mean temperature of 11.8 degrees Celcius. The record was 1.8C above average.
Further down the coast, Ngawi also had its warmest winter air temperature since records began in 1972, with a slightly higher mean temperature of 12.3C.
Inland Martinborough had a record-beating warm winter with a mean temperature of 10.1C, 1.7C higher than average. Records began in 1986.
Wairarapa didn’t make the list for rainfall records.
Niwa said several factors contributed to New Zealand’s warm and wet winter record.
“The overall air pressure pattern saw higher than normal pressures to the east of the country and was associated with more northerly quarter air flows.
“This allowed for frequent low-pressure systems to approach from the northwest, transporting warmth and moisture from the tropics.”
It said the distinctive lack of southerlies during winter was characteristic of La Nina – a key driver behind the third consecutive warm winter record.
Niwa said the influence of La Nina also contributed to the warmest winter sea surface temperatures in New Zealand’s coastal waters since 1982.
It said marine heatwave conditions happened offshore in many regions and were ongoing for more than six months in the eastern Tasman Sea.
“The source region for several of New Zealand’s atmospheric river events, the Coral Sea, also experienced a marine heatwave.
“These warm waters not only contributed to warmer temperatures on land but also provided extra moisture to low-pressure systems approaching the country.”
Niwa said the additional warmth in the southwest Pacific came in a sub-tropical jet stream that’s average position was farther south than normal, more commonly passing over the North Island.
A climate driver later in winter was the developing negative phase of the Indian Ocean Dipole, marked by warmer than average seas in the tropical eastern Indian Ocean near Sumatra and cooler seas in the west near Africa, Niwa said.
Niwa said it was likely that the extreme rainfall events of winter 2022 were more intense because of climate change.
