Tuesday, April 23, 2024

Here’s hoping for more weather complications

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Cyclone Lola could mean ours is a broken El Niño, and that’s a good thing, says Phil Duncan.
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By Philip Duncan, WeatherWatch NZ

Spring is called spring for a reason – the weather bounces around like a cork at sea. The severe weather New Zealand has had over the past week is peak “crazy” when you’re getting a snow blast in the south and frosts, while the remnants of a former record-breaking tropical cyclone drift into northern NZ.

These two extreme weather events from both the south and north are typical of spring, though – although the cyclone aspect was unusual. 

While tropical cyclones have formed early in the South Pacific before – the record I believe was late September – Tropical Cyclone Lola last week was the earliest ever Category 5 tropical cyclone on record, not only for the South Pacific basin, but for the ENTIRE southern hemisphere. 

What made Lola even more unusual was the fact it formed north of NZ. Usually during El Niño, high pressure north of NZ keeps cyclone formation more likely to the east of the international date line (out towards Tahiti). But this storm – and the remnants coming into northern NZ to kick off the last days of October – perhaps show that El Niño’s weather pattern may be “broken” in our part of the world. And that is a good thing. 

Broken means it’s less predictable. Why is that a good thing? Because a predictable El Niño means hot and dry in the east of NZ and inland with a high risk of droughts forming. A “broken” or “complicated” El Niño means we have better chances of wild card weather systems that deliver rain. 

Rainfall accumulation over seven days starting from Sunday, October 29 through to Sunday, November 5 shows a sub-tropical low brushing northern New Zealand with some rain – but a very fine line between wet and dry. Meanwhile, the South Island has a wintry change bringing rain to the West Coast and Southern Alps.

While an El Niño spring can bring more rain to western NZ, I think it’s safe to say some eastern parts of NZ have been wetter than expected so far this spring. The warmer than average sea surface conditions in parts of the Tasman Sea and tropics mean that when a low pressure zone does happen to form there, it has the chance of rapidly deepening. 

That is what happened to Cyclone Lola – and while the historic cyclone was short lived, the remnants have made it to NZ, bringing some unexpected weather. This is what we mean by a “broken El Niño weather pattern”. 

So for now, this pattern may be driving some of us a little crazy with all the wind and up and down temperatures, but to be perfectly honest, it’s likely much better to be unsettled than to be locked into a strong westerly El Niño event. Which may well still happen. 

If you’re a conservative person then winter only ended five weeks or so ago, so it’s not surprising at all to be seeing severe weather risks around NZ and changeable weather with the odd snowy blast. But the warm energy in the Tasman Sea and southwestern Pacific gives this current El Niño a weird twist that, for now anyway, is giving NZ some relief from a too-dry weather pattern.

Upcoming highlights:

• Low pressure in the north weakens and falls apart

• Westerlies return

• Temperatures are bit more stable this week in NZ

El Niño Watch: El Niño breaks pattern, what does that mean for farmers?

In this episode WeatherWatch forecaster Phil Duncan talks about a ‘broken’ El Niño and how that is causing some unusual weather patterns, which are not necessarily a bad thing for New Zealand farmers. Phil also unpacks whether Cyclone Lola will bring rainfall to NZ shores.

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