The weather pattern known as El Nino is on its way, with whispers in some scientific circles that it could be the primary cause of the planet’s warmest ever year.
Well, you could have fooled me as I put on a woolly jumper and a ski jacket to accompany a military-level beanie before stepping outside the house the other morning. The frosty reception didn’t quite warrant a pair of gloves, but the thought certainly crossed my mind, to be perfectly honest.
Maintaining the upfront theme, I’ve never had a particularly solid grip on the differences between the El Nino and La Nina patterns because, quite frankly, they both bring the sort of extreme weather I neither want to see nor hear about. A head-in-the-sand approach, you might say.
There’s no hiding now. The facts are all too plain for all to see.
Thus, what does the National Institute of Water and Atmosphere scientists in Wellington have to say about it?
While I had my head in the sand, some of the better-informed of you may have heard about the rare ‘triple-dip’ La Nina pattern that has been in effect during the past three years.
The scientists tell us that it had an especially strong influence on our weather patterns – we experienced atmospheric rivers, ex-tropical cyclones, floods, droughts, record temperatures, high humidity, and multiple marine heatwaves. As if you didn’t already know.
But now a new driver is coming to town: El Nino. Buckle up.
El Nino and La Nina are opposite phases of a natural global climate cycle. Typically, during an El Nino pattern, there is a weakening of the trade winds that blow across the Pacific. This allows warm water to move eastwards, creating hotter-than-average ocean temperatures towards South America. The opposite happens during La Nina, with unusually warm water pooling in the western Pacific.
In 2015, an exceptionally strong El Nino took hold in the Pacific Ocean, triggering a cascade of damaging weather. Several New Zealand regions experienced an exceptionally dry spring and start to summer, prompting concerns of drought. The event also helped make 2016 the planet’s hottest year on record.
During the past three years, a significant amount of warm water built up in the western Pacific Ocean and is now sloshing eastward, so El Nino is building once again. Importantly, the closer you are to the tropical Pacific, the more immediate and likely the effects will be. We sit just outside of the tropics, so the effects of El Nino can take some time to build and often don’t set in until spring or summer.
So, what should we expect?
Niwa says we will likely get a sharp, cold snap along with strong winds reasonably soon.
Further ahead, southwesterly-to-westerly winds may become more prominent. This increases the chance for drier-than-normal conditions in our neck of the woods and tends to cause more rain in the west.
Such winds can also contribute to increased wildfire risk because of drying grounds in key agricultural regions and occasional hot air masses coming in from Australia. You could say that it’s the 501 weather pattern our neighbours are preparing to send our way.
