Farmers and growers across New Zealand and Australia have the same problem – where is May’s rain?
The dry weather pattern engulfing both nations is being caused by the same enormous area of high pressure. The main high has been dominating south Australia and much of NZ for the entire first fortnight of May and will likely last well into the third week of the month.
With so much of NZ’s weather coming from this part of the globe it’s worth noting that in the states of Victoria, Tasmania and South Australia, many people are screaming out for rain.
In NZ it’s a bit more subdued because we have had pockets of rain relief over the past month or two, but for some it’s still not enough and with winter almost upon us, time is running out as the nights get colder and longer for at least another month and a half.
Frosts have returned to NZ after being absent on a widespread scale so far this year. Some regions only had their first frost in the past few days. However, it’s fair to say some of you had a doozy, with minus fives, sixes and even below that.
The frosty weather is also thanks to these powerfully stubborn high pressure zones anchoring themselves around the Tasmania area. The anticyclonic flow means these highs can have great “reach” over the Southern Ocean area, scooping up much colder air then dredging it up over NZ as a south to southwesterly flow.
NZ has had several warmer than average winters in a row. When I use the word “average”, I’m thinking of the past 40 years or so. In recent years, roughly the past seven, NZ has had much milder winters.
In previous years high pressure was parked further north of NZ and this kept northern NZ in a rainfall deficit for several years, and encouraged plenty of mild westerlies, which dried out the east and kept many places milder.
This year, the high pressure zones are both further south and further over towards Aussie. This encourages more south to southwest flows from the Southern Ocean area.
In saying that, we might be going into a colder-than-average phase at the moment but compared to 10 to 40 years ago I think most people might still consider this milder than usual overall.
The last major snow events into NZ were over a decade ago, in 2011 and 2012. Since then it’s been significantly milder due to the placement of highs and lows around us. The joy of living on two mountainous large rocks partially in the Roaring Forties – we’re always at the whim of single highs and lows.
Upcoming Highlights:
• The high that’s affected NZ since the end of April is finally centred over NZ on Monday May 13.
• Windier westerlies cover the South Island by Wednesday, with West Coast rain
• The next cold southerly is pencilled in for the weekend of May 18/19 – might be some northern rain too (not locked in)
