April ClimateWatch: La Nina ends, now here’s what NZ can expect (+11 Maps & Video)

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April ClimateWatch: La Nina ends, now here’s what NZ can expect (+11 Maps & Video)

31/03/2021 9:52pm

> From the WeatherWatch archives

La Nina has come to an end according to scientists at the Bureau of Meteorology. As WeatherWatch.co.nz and RuralWeather.co.nz said back in spring of 2020, this fairly short lived La Nina wasn’t going to be the silver bullet for the drought/dry parts of NZ and instead rather a silver lining.

While La Nina did bring some intense downpours in December, early January and again in recent weeks – the rain relief has been very “hit and miss”. Even within some close knit rural communities or within one suburb of a city some had huge downpours while others nearby got next to nothing.

The reason La Nina wasn’t going to necessarily bring a major wet summer to New Zealand was due to the fact it wasn’t overly strong or long lived and that the high pressure belts over NZ have been above normal for the past two years (and counting).

So with La Nina gone, it’s now this continuation of above normal high pressure that will continue to dominate our country. But just because La Nina is over doesn’t mean the tropics north of NZ have gone cold and quiet. A low in the second week of April may produce a rainmaker for northern or western NZ (not locked in but possible, as you will see in our ClimateWatch April video update).

HOW THE HIGHS AND LOWS ARE SHAPING UP IN APRIL:

(blue boxes indicate low air pressure, red boxes indicate high air pressure)

EXPECTED APRIL RAINFALL:
The NZ areas kicks off the first half of April with an “Air Pressure Sandwich”. This means we have a belt of low pressure across the tropics, a belt of high pressure in a line from the Indian Ocean to just south of Aussie and into the NZ area, and then south in the Southern Ocean lies another belt of low pressure. All things considered neither of these low pressure belts (in the tropics or Southern Ocean) look overly stormy at this stage.

The increased high pressure in the NZ area for two years (still yet explained by scientists in NZ) carries on into April and this will mean inland and eastern areas lean drier than average.

A low in the Tasman Sea in April’s second week has the potential to deliver heavy rain to the upper North Island and/or the West Coast – but again it will be the dominating high pressure belt that will be the decider on if this low makes it to NZ with much needed rain.