Friday, March 29, 2024

Winter gets dry on big highs

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A winter weather pattern dominated by extreme high-pressure systems has made farming easier but raises some concerns over low moisture levels’ impact on spring growth.
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Australia is experiencing extremely dry conditions. All of New South Wales was recently declared in drought and this winter the impact is starting to drift across the Tasman.

Water restrictions imposed in NSW in May for the first time in a decade, coming after two years of below-average rainfall. Australia is import grain because of to back to back droughts.

Weather Watch forecaster Philip Duncan said almost all of New Zealand’s weather has been dominated by high pressure systems that arch across part of Australia and right across the Tasman.

“While we are only on the edges of this influence we are catching the dry bug. 

“While we are still getting a bit of rain, at least enough to keep things growing, we have certainly not received enough to replenish soil moisture levels in many places.” 

Dry conditions are particularly noticeable in Northland, eastern Waikato, Hawke’s Bay, Wairarapa and South Canterbury.

Total Ag farm adviser Aaron Baker said while the dry conditions are welcome in Northland over winter for getting work done there is real concern heading into spring in a region that can be highly variable for rainfall.

“We have just had the second driest June in five years, May was also dry and it came after a dry summer and dry autumn.” 

Kerikeri has had seven consecutive months of below-average rainfall.

Northland farmers’ concern was also exacerbated by many dry stock farms relying on surface supply, dammed water for stock supply.

Aucklanders are also being urged to cut water use as storage for the city’s water supply sits almost 30% below its historic average.

NIWA soil moisture deficit analysis shows heightened moisture anomalies along East Coast, Hawke’s Bay, Wairarapa, Nelson and South Canterbury-Otago. 

South Canterbury has the most severe moisture deficit, at 25% of field capacity.

The upside of the conditions has been particularly high use of pasture and winter feed crops, with far less loss to usually muddy, wet conditions. 

Frosts have been welcome in areas like Bay of Plenty to help deal with insect pests.

“I think this is the first year when I have never heard farmers complain about the winter weather conditions. Some are saying it’s the best winter they have ever had,” Duncan said.

But he notes an underlying wariness about where it might put spring moisture levels.

The high-pressure systems arching across the Tasman have been notable not only for the distance they cover but also their intensity.

As an ultra-intense 1040hPa high moves away to the east this week another is poised to take its place, intensifying again at over 1030hPa.

“We are being affected right now by weather patterns that are much bigger than our own country. 

“I am not sure a lot of work has been done to know why these types of pressure systems are happening at this stage of the winter. 

“You would typically expect these at the end of winter.”

Duncan said ironically Australia is reporting greater snowfalls than NZ this winter and that does not bode well for irrigation replenishment here come the thaw.

“While there is a good dump of snow on the very tops of the southern mountains, that’s quite a small surface area in terms of snow storage for water supply. That will have an effect come February-March next year.” 

He expects it could also present problems for electricity generation if there are no major shifts in weather patterns.

But Duncan cautioned there is always a degree of chaos about predicting NZ’s weather. Being a small cluster of islands in a big ocean means it takes only one major rainstorm to shift prospects.

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