Last summer we were told it would be hot and sunny – it was wet and cloudy for most. The late and great Augie Auer used to say seasonal forecasts were as accurate as a flip of a coin due to their 50% accuracy rate. I’m unsure if the folk at NIWA would quite agree however the public might. Perception is often reality and that is always the case in the weather and climate forecasting industries.

Those who defend their forecasts when the public clearly know you’re wrong only service to crush their own credibility. That’s why when last summer panned out to be a disaster you had NIWA quickly setting the record straight from their earlier predictions, as did WeatherWatch.co.nz.

So what is the deal with this summer?

There is talk of a weak El Nino – that’s the opposite of what we had last summer, La Nina. (let’s be honest, most people would probably enjoy the opposite of last summer weatherwise, with perhaps the exception of dairy farmers who loved the rain).

Generally speaking El Nino brings cooler waters to our beaches but more high pressure systems. It increases our chances of 30 to 40 degree days in the east of the country due to more westerlies, but can also bring more cloud and more sou’westers to the west of New Zealand, including Auckland.

Farmers don’t like El Nino as it can bring droughts – and our worst droughts have been associated with El Nino over the past few decades.

Personally I don’t like predictions more than a month out however sometimes common sense can make it easier and more reliable to do so.

In March this year I predicted an increased chance of big southerlies, especially at the start of winter. This was before the government owned forecast agencies had their predictions and was based entirely on the weather patterns that had been affecting NZ for the past 6 months and then working out what is most likely to happen over the coming months.

This is part of the formula we have used successfully for years and is why we continue to grow our client base.

You can’t plan your holiday with these predictions though. For example, if NIWA said this summer we can expect very dry weather, well that might be the case over those three months – but your 10 days at the beach may well be the time we have a week of rain and colder winds.

To me these long range predictions are simply indicators.

So a weak El Nino may actually have little to no impact on NZ. We’re certainly not seeing any weather patterns lingering – and this has been the case all year. The weather across 2012 has been very changeable – in other words – average and normal. Hot and dry one day, wet and cold the next. Winter started off cold, ended warm. Spring has been all over the place. Last summer, however, was consistently wet – why? Because we had La Nina that dominated our weather. So when we remove a dominating feature like El Nino or La Nina the weather tends to become more chaotic – and we get a better variety of weather.

This summer may see drier weather in the east and inland areas – it’s certainly expected to be sunnier and hotter than last summer for most of our top holiday spots. That’s based on evidence of El Nino forming but also on the fact that a ‘normal’ or ‘average’ summer tends to see drier weather in the east too.

“Average” isn’t a bad word when you’re talking about seasons – for most of us anyway. When the weather is average it means we get healthier portions of weather – rather than pigging out on a winter of solid rain or fasting in a summer of drought. We get a bit of everything – so everything, you guessed it, “averages” out.

I’m optimistic of a good summer for both holidaymakers and farmers – but as I said back in August, farmers in the east especially should be at least mentally preparing themselves for a tougher summer than last.

As for holidaymakers – no credible forecaster can give you a concrete prediction for summer this far out. All I say is look at the facts:

• A weak El Nino appears to be forming, this more often than not favours dry, hotter, weather in the east. But keep in mind the predictions at this stage are only for a “weak” El Nino.
• NZ’s weather pattern has been chaotic/changeable since Autumn (If this continues it reduces the risk of droughts)
• Highs and lows are moving through quickly (granted it is Spring, but they have had this trend all year).

If this continues I think we can expect a hotter, drier, summer in the east, a cloudier but drier summer in the west, but still the odd rainstorm.

That may not sound as detailed as you like, but that’s the nature of the business we’re in.

Finally – it’s important to note that a seasonal forecast isn’t a “weather forecast”. It’s a “climate prediction”. The difference? Well ‘climate’ is a bit like predicting the tides – we look for patterns, trends etc. ‘Weather’ is like predicting the size of the swells on those tides. So clearly we can predict climate information more long term – but the specifics of the weather still remain in the 6 to 10 day area if you want real accuracy.

– Homepage image / Foehn Mackenzie

 

– By Head weather analyst Philip Duncan – follow him on Twitter