From: Merlin Zener 12/11/99 16:45:28 Subject: accuracy of weather forecasts???? post id: 6922 G'day, so here I am on the Sunshine Coast, and it's raining *again* - after I distinctly remember the weather report on ABC radio yesterday saying it was going to be fine - all the way through to Monday! Does anyone ever follow up on weather predictions by the bereau, and take note of how often they actually get it right? Or is it like where they say you could get a drunk monkey to pick stocks at random, and outperform the highly paid funds managers on the percentage they actually get right???? :)) From: steve(primus) 12/11/99 16:47:38 Subject: re: accuracy of weather forecasts???? post id: 6924 The forecast for the sunshine coast for the last two days has been rain showers. It should clear overnight. I don't know which forecast you heard but it wasn't the one issued by the BoM. From: steve(primus) 12/11/99 16:50:11 Subject: re: accuracy of weather forecasts???? post id: 6927 Forecast issued for today: A few showers this afternoon and evening with some local thunder and possible small hail. Fine Saturday. Winds mostly light to mderate SE/NE. Sunday ... Fine. Monday ... Mostly fine. What are you complining about? From: oPi 13/11/99 1:57:13 Subject: re: accuracy of weather forecasts???? post id: 7034 I once heard it said that if you forcast that tomorrows weather is going to be exactly the same as todays, you would actually get it right more often than the forcasters. oPi From: The Jezois 13/11/99 4:07:40 Subject: re: accuracy of weather forecasts???? post id: 7041 Have you read the novel: "Breathing Underwater"? The protagaonist's father signs himself "The Weather Watcher" and sends the local TV Weatherman out of his tree with daily reports on his accuracy. From: steve(primus) 13/11/99 7:08:08 Subject: re: accuracy of weather forecasts???? post id: 7047 The accuracy of weather forecasts has always been a subject of some amusement to some people ever since The Times had a go at Robert Fitzroy back in the 1850s. Fitzroy's forecasts were as accurate as the limited knowledge of atmospheric processes allowed. Today, our forecasts are as accurate as our much wider knowledge allows which is very accurate indeed. We used to run a verification scheme where we would ask members of the public to assess the accuracy of the forecasts over a month. This was called the "Reasonable Person Verification Scheme". We would also have two or three people in the office doing the same thing. The members of the public consistently rated the accuracy of the forecasts higher than we did ourselves. This was a subjective system. We also run an objective system which compares the forecasts with the official observations. Weather forecasts are accurate for the most part. Very occasionally we get it wrong but it is not often. In NSW I talk to Richard Glover on 2BL and Mike Carlton on 2UE every weekday afternoon, discussing the forecast for the next few days. If I get it wrong, both of them take me to task or I admit it up front and explain why. It happens very rarely. The last time in Sydney was the weekend of the Online Internet Show where we forecast showers instead of the almost continuous rain. I go out to Agricultural shows around the State talking to farmers. For the most part they are very happy with the amount of information available and the accuracy of the forecasts. Persistence forecasting is a benchmark. If we are not more accurate than that then what are we doing? Sydney has about 60 rain events a year. That is a day or a series of days on which it rains. If you go with persistence forecasting "If it rains today it will rain tomorrow, if it's fine today it will be fine tomorrow" you will be wrong the 60 days it starts raining and wrong the 60 days it stops. The other 245 days you will be right. This has an accuracy of about 66%. Our forecasts are more acurate than that. One reason we didn't go beyond four days for a long time was that after four days the science was no better than persistence so there was no point. Better computer models have allowed us to extend it to a seven day outlook now, but the last three days are still experimental. The big problems are forecasting the extreme events. Tropical Cyclone forecasts are now very accurate and have been for many years. The forecasts for TC Tracy, for instance, were spot on, as have been all the TC warnings since then. We were quite correct with our forecasts for the Sydney/Hobart Yacht Race despite the comments of a loud mouthed radio talk-back host and five warnings had been issued to the fleet before they hit the storm. We didn't get a warning out for the April 14 hailstorm, but of 12 severe thunderstorms in Sydney last season we had warnings on 10 of them. When we get the forecast wrong, as we do on rare occasions, I am the first to admit it. But when people accuse us, wrongly, of getting the forecast wrong, as Merlin Zener did when he started this thread, expect me to defend the dedication of the meteorologists and the science of meteorology. From: Martin B 15/11/99 10:00:47 Subject: re: accuracy of weather forecasts???? post id: 7292 Haviung relatively recently moved to Melbourne - land of changable weather - I am amazed at the accuracy of the weather forecasts (and also how essential following them can be.) If Steve's mob says there's a change coming through, sure enough a change will come through. Reasonably often it's a little bit wrong - the change comes through faster, or slower than forecast, or it isn't as strong as forecast - but the basic prediction is pretty much spot on. This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.