A developing La Nina climate system has been partly blamed for the wildfire that just devastated Lake Ohau Village this month. Photo / Andy Winneke
A La Nina climate system - partly blamed for the wildfire that just devastated Lake Ohau Village - could spell a busy summer for fire crews in some parts of the country.
The fire that razed nearly 50 buildings at the idyllic South Island spot came at a time the arriving, moderate-strength La Nina was bringing stronger westerly to north-westerly winds, instead of south-westerly winds usually seen at this time of year.
As summer neared, that pattern was expected to change to more north-easterlies, bringing classic La Nina patterns.
"When it arrives, La Nina will have different impacts on fire conditions in different areas of the country," said Darrin Woods, a a wildfire specialist with Fire and Emergency NZ.
"These north-easterly air flows could bring wetter conditions for the north and east of the country, and potentially drier conditions for the lower and western locations of both islands.
"We regularly monitor the weather forecasts and how these conditions will affect the fire danger and potential fire behaviour in different areas of the country."
The latest fire danger outlooks, issued by Scion and Fire and Emergency NZ, noted how several large wildfires have already broken out in the south - largely driven by dry soils, frost-cured grasslands and strong, gusty winds.
The risk of further big wildfires over coming months would depend on factors like dryness, rainfall, winds and how much "fine fuels", such as dead grass and pine litter, there'd be.
"A notable dryness in the east and north of the South Island is a concern," the report noted.
The report looked back to fire seasons during previous moderate-strength La Nina systems.
Over January in two recent events, in 2011/12 and 2007-08, fire danger reached high to extreme levels across broad swathes of the south and east of the South Island.
But in the North Island, the widespread high fire risk seen over 2007/08 stood in stark contrast to the largely greener conditions of 2011/12.
This time round, the report indicated that while the threat of outbreaks would be low for much of the South Island, danger was expected to increase along its east coast.
With warmer and drier than normal conditions forecast over this month and November, landscapes could dry out easily and become more susceptible to fires starting and spreading.
"Specific areas to watch over the next three months are Marlborough, Canterbury and Otago."
In the North Island, where fire danger typically peaked in February and March, fire risk was placed as generally low this month.
But that fire danger would increase for the east coast if forecast warmth and dryness played out over coming weeks.
"Locations that could develop an elevated risk of high fire danger dangers over the next three months include Gisborne, Hawke's Bay, and Wairarapa," the report said.
"Expect periodic increases in fire potential and activity if dry, warm and windy conditions occur."
Woods said local fire teams prepared for a range of scenarios - including the impact of weather patterns like La Nina.
"This information also helps us determine when to put in place a prohibited or restricted fire season," he said.
"We do have the ability to use additional resources and move resources around the country if required."
Today, rural fires cost the economy about $67m each year. But thanks to climate change, that figure would swell as fire seasons lengthen by an average 70 per cent in a mere 20 years.
Projections suggest that, by 2040, fire risk in many regions - even wetter places like Taranaki, Manawatu and the South Island's West Coast - would shift from one end of the scale to the other.
Wellington could experience a doubling to 30 fire risk days a year - and coastal Otago a tripling to 20 days a year.