New fire in the Tasman region – Expert Reaction

A new bush fire has broken out near Nelson, as warm and extremely dry conditions persist in the region.

Police have told residents living on a stretch of Moutere Highway to evacuate and the following up with evacuation patrols. Today was the day the State of Civil Defence Emergency expired in the region, following the fire that began in nearby Pigeon Valley three weeks ago.

This new fire is understood to be outside the original wildfire zone and moving in an easterly direction. A front is approaching the region tonight, but experts say it will not bring much relief.

The SMC asked experts to comment on conditions that may affect the fire – please feel free to use these comments in your reporting. 

Grant Pearce, fire scientist, Scion Rural Fire Research Group, comments:

“Unfortunately, a new fire has been reported in the Tasman region. This fire again appears to be burning in pine forest near Redwood Valley, some 5-6 km north of the existing Pigeon Valley fire, which is still actively being extinguished.

“The Nelson/Tasman region has continued to experience dry, windy conditions since the original fire outbreak, with only minimal rainfall being recorded over the past few weeks. Only around 3-8 mm has been recorded at weather stations close to the fire area. The effects of this have been very short-lived. Fire danger levels remain extremely high and among some of the worst ever recorded, indicating the potential for fires to start very easily, and spread quickly to become large fires that are very difficult to put out – as shown by this most recent fire ignition.

“In the 22 days since the outbreak of the Pigeon Valley fire on February 5th, the Nelson Aero weather station has recorded a further 13 days of Very High forest fire danger and 1 day of Extreme forest fire danger, meaning a total of 29 days (20 days of Very High and 9 days of Extreme) since January 1st. Long term records indicate the region averages around 9-10 days of Very High and Extreme each year, with the previous record being 17 days for the entire fire season.

“The current value for the Buildup Index (BUI), which indicates the overall fuel dryness and amount of fuel available for consumption, is 114 (with a value of 60 being very high, and 80 extreme). However, prior to the 7 mm of rain on Sun. 24th, it had reached 163 at Nelson Aero, and 171 at Dovedale closer to the Pigeon Valley fire area. The highest value for the BUI recorded at Nelson Aero was 166, in March 2001.

“The hot, dry and windy weather over the past month has continued to dry out the forest fuels, which include forestry slash and prunings, understorey scrub vegetation such as gorse, pine needle litter on the ground and organic material in the soil, that all contribute to the amount of vegetation fuel available to burn. These dry, elevated fuel loads contribute to easy fire ignition and spread, and to high fire intensities including crown fires that are very difficult, if not impossible to control, especially in steeper terrain often favoured for forestry plantings. Combined with very dry soils, the dry fuels also contribute to very difficult and prolonged fire mop-up before smouldering, deep burning ground fuels are fully extinguished.

“Surrounding grass fuels are also very dry and fully cured (dead), meaning that embers thrown from burning forest can easily ignite new spot fires and spread even more rapidly through these fine, flashy grass fuels.

“Weather forecasts for the next few days include the possibility of some rain for the Nelson/Tasman region; however this is likely to be only minor (less than 1 mm), if any. Unfortunately, in the absence of further significant rain, fire dangers will remain elevated It is estimated around 30-40 mm is required to reduce fuel dryness to below extreme levels (below a BUI value of 80), and around 100 mm to below high levels (below a BUI of 60). Previous bad fire seasons (such as 2000/01 and 2007/08) have lasted into April, so the risk of further fire outbreaks unfortunately remains extremely high.

“Scion’s Rural Fire Research team will be producing new fire climate outlooks describing likely fire danger conditions across the country for the next 3 months (Mar-May) within the next week. These are available here.

Conflicts of interest statement: Scion’s Rural Fire Research programme is funded by the Ministry of Business, Innovation and Employment (MBIE), and receives co-funding from Fire and Emergency New Zealand, NZ Forest Owners Association/Forest Growers Levy Trust, Department of Conservation and NZ Defence Force.

Georgina Griffiths, meteorologist, MetService, comments:

“This evening’s front produces very little for Nelson. Some in the Nelson region will get a sprinkle but it will be so little.

“Basically in the next five days, there’s virtually nothing of note for Nelson in terms of rain. It looks very dry.

“In the longer term, it looks like if we look at the broad range heading into March that drier expectation continues. New Zealand is suffering from high pressure in that region.

“The coming fortnight looks to be relatively dry for Nelson and doesn’t look likely to yield decent rainfall.

“I did run the numbers and, according to the airport record which dates back to 1941, we are currently on track for Nelson to have the driest January and February on record with a total of 14mm of rainfall.

“It’s a bit unusual that we have seen these dry months back-to-back.

“There was 8mm for the region last month and currently 6mm for February, and that’s really notable and obviously contributing to the fire.”

No conflicts of interest.

Ben Noll, meteorologist, Niwa, comments:

“According to the New Zealand Drought Index, parts of the Tasman District are now experiencing severe drought conditions. Drought conditions are present in and around the new Redwood Valley fire.

“Richmond has recorded just 2.4 millimetres of rain so far this February.

“Since the start of 2019, Richmond has had only two days where daily rainfall exceeded 1mm and one day where daily rainfall exceeded 5mm.

“Between the January 16 and February 24, a 40 day dry spell occurred, which is, preliminarily, the 4th-equal longest dry spell on record. A dry spell is defined as a day with less than 1mm of rain.

“For the summer season as a whole, Nelson is tracking toward its third driest summer on record with just 64 mm. Appleby is also tracking toward its third driest summer on record.

“Nelson is tracking for its third warmest summer on record.

“Gusty winds have occurred in the Nelson area today (Wednesday), up to 46 km/h so far, and forecast to gust up to 60-70 km/h upon a frontal passage during the afternoon and evening.”

Conflict of interest statement: None declared

Rob Kerr, meteorologist, MetService, comments:

“Between 4pm and 7pm there might be a few spots of rain across the area where we think the fire is.

“Their best chance of any precipitation is between 4pm and 7pm tonight, but I would not be surprised if they got nothing.

“There was only 3-4 millimetres of rain across the region when we had strong southerlies on Sunday morning. That was the best chance of rain they had and they got very little. Nelson got 0.6mm.”

Conflict of interest statement: None declared