So, for the first views post, I thought I’d go with something that most people will have seen. Over the weekend, you may well have seen an article in the Daily Express about the British winter. It’s the third such article in the last month, starting with one claiming that Britain will have the coldest and snowiest winter in 50 years, due to a strong El Nino in the Pacific Ocean. We’ll ignore the science at the moment, but if you want more information on the link between UK weather and El Nino, the Met Office Blog has a helpful article.
Now, it is important I put this here first: I am not going to say this is/is not going to happen. Partially this is because I am not a forecaster, despite what my family may think, but also, because there is a chance it may happen. And the word chance is the key one.
The Daily Express’s first of many weather stories of 2015. In the last month, 3 other stories with similar headlines have been in the paper.
Numerical Weather Prediction models have the ability to accurately forecast, at most, about a few days in advance. These are run at higher resolution and in doing so, can compute the smaller effects that affect where rain will fall, where winds will be strongest and where clouds will form more accurately. Climate models, which run with lower resolution, typically are used to run months/years into the future. Often this work is used for academic research and not released as a public announcement, but in academic papers.
When NWP’s are run, they are run several times with very small perturbations in the initial conditions. Due to the Butterfly Effect, these cause a divergence in the forecasts which grows over time. After a few days, the simulations will differ from each other significantly. What it leaves for the couple of days ahead is a probabilistic forecast, where they have a range of possibilities for what the weather will do, but also a sense of the probability of how likely each option is.
A set of ECMWF ensemble simulations showing the differences in attempting to track a the formation of a storm in the Mid Atlantic. (Source – Dr Ryan Maue, ECMWF)
The same is done with lower resolution models for further into the future. This can give a general probability of less specific statements. Normally these are used with the words “most probable scenario is a drier than average/warmer than average/windier than average” guise. And that’s it. That’s all they can say.
More and more often, forecasts are now given with a probability, and the BBC have started to include more about these uncertainties in their forecasts. The forecast of a storm which didn’t hit a couple of weeks ago was predicted almost a week in advance, but up until 2 days before there was still uncertainty with where it would make landfall. And the BBC actually showed this in the forecasts. Some other weather companies around the world have included some elements of uncertainty for a while now.
NOAA have been representing uncertainty on storms for a number of years now.
The issue I have with the Daily Express headline is that it shows no uncertainty. The general public read it, take it as truth, and then when it doesn’t happen, blame the weatherman. It’s something that is becoming more and more infuriating for meteorologists and climate scientists all over the world. Maybe it’s the scientists fault for not focusing on the uncertainty and attempting to make a result seem more certain, more important. Or maybe it’s the media’s manipulation of the message to sell more papers and gain more clicks online.
The media’s relationship with weather and climate is another story for another day. But it is certainly worth remembering that the Daily Express led with the headline “Winter 2014 set to be coldest for a century” last year, and went with “Britain facing worst winter in 60 years” in 2013. And predicted a coldest winter in 100 years in 2012 too. And 2011. And 2010…