Next week kicks off with an Antarctic blast for some, but for the rest of August a new pattern is forming – a spring weather pattern. This is different to the astronomical seasons, which are evenly spread around the year as the earth rotates around the sun.
Instead, a spring weather pattern is when we as weather forecasters start to both see and feel a shift from the “dark and dormant” winter to the “windy westerlies and injections of warmth” that spring brings.
In previous years we have declared the spring weather pattern to be here by late July. This year we’re running a few weeks later, which, to southerners especially, won’t come as much surprise.
One of the biggest pushbacks we get to any early spring weather declaration is that any snow or frost is “proof we’re still in winter”. But that’s not proof of winter. Winter is defined as a season with death and decay and the coldest weather … spring is defined as “moving, rising, life beginning, blossoms, buds, newborn animals”.
In the northern hemisphere some of the biggest snowstorms in places like Canada or Russia or northern Europe can occur in early spring. This is due to the coldest air of the year now meeting longer hours of daylight and more warmth. After all, we’re now officially out of the solar winter – the three months of the year with the least amount of available sunlight. No wonder you’re noticing the longer, brighter, early evenings now.
As Reserve Bank Governor Adrian Orr said this week, “it’s darkest before dawn … and it’s dawn now”. That sums up the current weather pattern. We’re still in winter technically, but we’re seeing hints of spring’s weather arriving.
So what is a “spring weather pattern”? I define it as being dominated by more westerlies, more injections of Australian and/or subtropical airflows, and still stormy at times. In winter we tend to have more southerlies, more injections of sub-Antarctic air.
It does feel a bit weird to be writing about spring weather when, at the time of writing this, a significant Antarctica blast is possible on Monday. But to anyone who says “so much for spring” when you get a frost or heavy snow, that is PART of spring!
If spring was warm, dry and sunny it would be summer. If it was snowy, cold, and had little plant life or growth, then we’re in winter. But I think many of you will see over the rest of August that we do have a more westerly-driven, milder at times, weather pattern – but spring brings that added risk of moisture + cold, which can lead to snowstorms and sudden severe weather events.
We generally usually see New Zealand’s weather pattern calm down in two months from now, by late October.
So we’re in a moderate to high risk for frost and snow events until then – but the weather is likely to have more of a spring in its step moving forward.
