Ken Ring's "forecasts" have been subjected to some serious scrutiny beyond my own modest efforts. Erick Brenstrum of MetService (author of the excellent New Zealand Weather Book) writes regularly for NZ Geographic, and used his column in the May-June issue this year (#79) to look at how Ken's forecasts for 2005 performed. The piece is not available on the web, but Erick was kind enough to send me a copy, together with a letter from Ring and Erick's reply from the current issue (#81). It's a fascinating read...

Erick reveals that the weather maps that Ken prints in his almanac are those for 18 years and 10 days prior to the day in question. There is, I presume, a "lunar" reason for this. Ken has quite a few to play with...

"Weather maps will be seen to repeat on a simpler time frame, and I have used 6584 lunar days, 6726 lunar days and 6935 solar days in past almanacs. These cover 18-20 years. Anyone wishing to explore the cycles operating on their location should experiment with old rainfall or temperature data, finding a stand-out event and then checking back through their own records to find a matching standout event between 18-20 years ago. The cycle that emerges can then be used to project into the future. What works for one location will not necessarily work for another."

That may explain why they don't work at all. Erick analyses a number of common NZ weather systems - strong northwest winds preceding a front that brings heavy rain to the west coast, and lows that cross the country bringing rain to the east coast. In 2005 there were 22 of the former - none matched in Ken's maps - and 18 of the latter, of which Ken's map sequence got precisely one. Giving him his one day either side leeway doesn't make much difference.

Ken wasn't impressed with Erick's deconstruction of his forecasts. From NZ Geographic issue 81:

"Despite what he says, I can prove they work 85 per cent of the time."

And then, in what seems to be something of a meme for Ken, he accuses Brenstrum of bullying him by naming him. As Warren Judd, editor of NZ Geographic comments:

"...once you publish a book, you're fair game for public scrutiny of its content and your own competence."

I'm waiting for Ken to supply his proof of competence. I've been looking. I can't find it.

PS: Warren, could you put Erick's columns up on your site? It would be a service of national importance...