New Zealand will experience a week of clear, calm weather, with many places still dry since summer. Photo / Hayden Woodward
Weeks of calm weather have left much of New Zealand dry – and the driest pockets are expected to worsen amid a warm, sunny week ahead.
Niwa’s latest monitoring report shows hotspots – places where soil conditions are very dry to very dry than normal ground conditions – are now forming in many parts of the country.
They include parts of Northland, Auckland, Waikato and the East Cape, the stretch from Hawke’s Bay to Wairarapa, the city of Wellington, most of eastern Marlborough and northern Canterbury, and the Otago coast south of Dunedin.
And New Zealand’s most recent Drought Index map shows widespread “dry to very dry” conditions over much of the central and eastern North Island, along with the northeastern South Island and parts of Otago and Southland.
The fire hazard is currently heightened in northern places such as Whangārei, Dargaville, Kaipara and Woodhill, along with much of Marlborough, central Canterbury and northern Otago.
Rainfall has been modest recently – most places on the North Island received less than 10mm last week, thanks to the dominant high pressure system – and is expected to improve slightly next week.
MetService predicts less than 2mm of rainfall over much of New Zealand over the next six days.
Niwa astrologer Ben Noll said some places, such as the east of the Bay of Plenty and East Cape, now have a rainfall deficit of about 50mm.
“That’s the kind of amount it would probably take maybe two or three good rainmakers to get this land close to normal.”
While little is expected in the short term, Noll said April could provide some assistance.
“We may not have one, but potentially two Madden-Julian Oscillation (MJO) pulses arriving in the Australasia region – one in the first 10 days of this month and the other in the last 10 days.”
MJO is the greatest element of intra-seasonal variability in the tropical atmosphere, and in certain phases it can cause heavy rainfall.
“So that might give us some chances for decent rainfall during April. After all, this month is sure to have a lot more potential for rain than we’ve seen lately.”
Noll said New Zealand’s post-summer drought could be partly explained by the fact that the “coercive patterns” that affect weather in tropical atmospheres have centered on the Indian Ocean, thousands of kilometers away, rather than in the central Pacific.
“As this pulse gets closer to us, at the end of March and into April, we might expect to see things change in the neck of our forest,” he said.
“But what we’re seeing now is really part of the overall pattern we’ve been through over the summer.”
What is the main driver of background weather – the “non-traditional” La Nina climate system – is rapidly fading and is likely to disappear completely by mid-year.
Monday: Good, apart from cloudy areas in the morning and evening, from Auckland to Kāpiti, including the Coromandel Peninsula, Bay of Plenty, Taupō and Taumarunui. Mostly cloudy in Gisborne and Hawke’s Bay, with little rain north of Napier and a possibility or two further south. Especially good across the South Island, with cloudy areas morning and night. Clouds are getting stronger around Canterbury and the Marlborough coast with uneven drizzling mornings and nights.
Tuesday: Periods of cloudy and heavy rain around Hawke’s Bay, Gisborne and Northland, and great elsewhere on the North Island. Cloud area morning and evening on the South Island, but otherwise fine.
Wednesday: Periods of cloudy and heavy rain around Hawke’s Bay, Gisborne and Northland, and great elsewhere on the North Island. Cloudy periods to the south and east of the South Island, accompanied by a morning drizzle. A bit of a downpour in the interior about Nelson and Buller in the late afternoon.
Thursday: Cloudy periods and heavy rain around Hawke’s Bay, Gisborne and Northland, but mostly fine elsewhere.
Friday: Cloudy periods and torrential rain around Hawke’s Bay, Gisborne and Northland, accompanied by rain developing around Fiordland, but mostly fine elsewhere.