Tuesday, April 23, 2024

November brings some order to NZ’s chaotic weather patterns

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More high pressure will encourage more westerlies over NZ, says Phil Duncan.
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By Phil Duncan, WeatherWatch

November is usually the month that sees the “crazy” part of spring start to ease and traditionally New Zealand has plenty of westerlies and an uptick in high pressure during this month. 

With the exception of November 2022, most other years have been fairly westerly driven with high pressure to the north. Over the next couple of weeks we see more high pressure crossing NZ or to our north. This will also encourage more westerlies over NZ – which will be warmer than the uptick in southerly flows we’ve had recently. 

This also means eastern areas will continue to see lower rainfall totals with the usual regions, like Hawke’s Bay, Wairarapa and Canterbury, looking driest.  

However, Canterbury may have some good spillover from the West Coast where a few hundred millimetres are coming over the next 10 days or so. It’s actually quite a classic El Niño setup, after a month or so of colder than usual weather. 

There have been a number of southerly events lately, and these really dropped temperatures. Even those in the upper North Island were lighting fires and heaters in the first week of November – which in my 45 years isn’t a normal thing. 

Our recent FMG El Niño Watch podcast episodes have been focusing on what to do if you’re farming but it doesn’t feel like El Niño. The consensus from our experienced farming guests so far is to plan for the worst but hope for the best. 

NZ’s location on Earth does mean we get surprise weather events thrown at us. El Niño makes for more westerlies into NZ, but it only takes a slight twist from being a westerly to more of a sou’westerly and suddenly colder air comes in. 

Places like Wellington and southern Wairarapa can shift from a westerly (mild) to a southerly (colder) very easily. Lately we’ve even had sou’easters in the mix and they can be bleak for eastern NZ.  

So the uptick in westerly winds should bring a more traditional setup to the country as we go through November. 

The tropics directly north of NZ is active too, with a tropical storm (or depression) dominating this week around Vanuatu. 

However, unlike Lola, which saw the remnants regroup with another low north of NZ to bring severe weather into North Island for a few days, we’re expecting more high pressure between NZ and this tropical low to keep it north of us. This is usually what El Niño does – but didn’t do last month with Lola. But any low near Vanuatu is worth monitoring from a NZ perspective.  

And finally, Australia has had some significant downpours over the past week in southern Queensland and New South Wales – and more this week for some dry eastern areas, but it is hit and miss.

Rainfall accumulation over seven days starting from 7am on Sunday, November 12, through to 7am Sunday, November 19 shows West Coast wettest and eastern areas driest.

Upcoming Highlights 

• Big jump in temperatures back into the 20s for eastern areas

• High pressure around northern NZ for the start of this week

• Windy westerlies off and on this week

• Wettest on the West

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