British Met Office drops long range forecasts

Seasonal weather forecasts have been abandoned as dismal failures by the British Meteorological Office, but New Zealand weather and climate agencies say they will continue with such predictions.

The National Institute of Water and Atmospheric Research (Niwa) says its three-month climate outlooks of temperature and rainfall are right about half the time, which will be about as good as it gets.

MetService defends its four to six-week seasonal weather outlooks as valuable in a country so dependent on agriculture.

The British Met Office announced at the weekend that it would stop issuing seasonal forecasts publicly and instead put out monthly predictions.

A spokesman said polling showed the public were not interested in seasonal forecasts.

The change came after two seasonal predictions went badly wrong.

The 2009 British summer was marketed as likely to be "a barbecue summer'', but instead was largely a washout.

Then the office said there was only a one in five chance of the 2009-10 winter being colder than normal.

It turned out to be the coldest winter for 31 years.

Niwa principal climate scientist James Renwick said that beyond the tropics, the predictability and the skill forecasters could achieve on long-term predictions was modest.

"Over New Zealand, we do better than a coin toss, but we don't do an awful lot better. I'm not sure of the statistics for the UK, but in the mid-latitudes such as New Zealand and the UK, it is difficult.

Our accuracy varies. We keep an eye on it.

We're producing forecasts for dry, average [rainfall] or wet, or cold, average [temperatures] or warm.

"If you were flipping a three-sided coin you'd get it right 33 per cent of the time and we get it right 40 to 50 per cent of the time.

"Because of the chaos in the atmosphere, even if they were as good as they could possibly be, you would still only get it up to about 60 per cent right. Seasonal forecasting is never going to be perfect.''

MetService spokesman Bob McDavitt said the interpolation of patterns and observations was carried out the same here as in Britain.

"With interpretation and guidance, there is value in them,'' he said.

"The value to an agricultural county like New Zealand is in terms of knowing whether to stock more or stock less.

I'm surprised the UK has pulled out.''

- © Fairfax NZ News