Wednesday, December 6, 2023

Drier trend emerges for Fieldays – and fields

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But with an El Niño likely forming this winter, it’s moderation we need.
Weatherwatch director Phil Duncan says New Zealand is something of a traffic island this summer, for weather systems to either hit or dodge.
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By Phil Duncan, WeatherWatch Senior Analyst

The chance of El Niño forming later this winter or spring has risen from 50% to 70%, according to the Bureau of Meteorology. The latest Climate Driver update from BoM has shifted the El Niño “Watch” to an official “Alert” – meaning it’s looking very likely to form in the coming months. 

Last week we mentioned the atmosphere was slow to respond to the developing El Niño, but in recent weeks it has started to appear in the weather pattern over Australia, bringing a series of large highs to them – some of which are drifting towards New Zealand.

The eastern side of the North Island – mainly Gisborne and Hawke’s Bay – have had an exceptionally wet 2023 made far worse by the flash flooding brought by Cyclone Gabrielle. Despite some rain last week from a weak sub-tropical low, these regions are generally heading in a drier direction. 

In fact the general trend is to see drier weather emerging, which it gradually has been doing lately. Of course, the ground is so sodden that it doesn’t take much rain to create more mud. But long range data does support a drying out of eastern parts of NZ with El Niño more likely to create windy westerlies than wet easterlies. Still, we’re in a neutral period for now, so the weather pattern is still chaotic.

Temperature-wise, frosty weather last week was widespread for the first time this year across the South Island – and there were even a few light frosts into the windier North Island. Our long range data still supports June leaning warmer than average. 

El Niño does inject more south to southwest winds over NZ, which increases the chances of cold shots of air from the Southern Ocean – but the windy westerlies can also push temperatures up at night. The difference in overnight lows between a high parked over the top of you with clear skies and light winds, vs a windy westerly from Tasmania, could be as much as 10 to 15degC warmer. 

There have been quite a few alarming headlines about El Niño from various outlets around the globe. It’s important to remember La Niña and El Niño are natural climate drivers and are important to help balance the books. 

South America has had significant drought lately, whereas our side of the Pacific Ocean has had rainmakers. To shift that dynamic would be helpful in bringing rain relief to dry parts of South America and dry relief to sodden parts of NZ. 

But as with anything, moderation is key. If this next El Niño event lingers too long into 2024 it could cause dry complications here in NZ – so if you want dry weather, perhaps don’t wish for it too hard.

Upcoming Highlights:

• Mild nights for northern NZ with a lack of frosts for many

• Temperatures closer to normal in the lower South Island

• Most regions lean drier than average 

• Our Mystery Creek forecast at shows a dry start to Fieldays – but maybe some wet weather late week

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