We love to talk about the weather and to complain when the weatherman gets it wrong. This is not great when you are on holiday, but how many of us know what it takes to actually create those forecasts each week? And why the weathermen and women do their best but don’t always get it just right?
Creating a forecast
Meteorology is one of those sciences that uses a lot of technology but is also about the human touch and that’s why we still have weather people, rather than just weather computers. When forecasts sit down to look at the UK weather forecast for this week, for example, there’s a lot of data involved but there is also a lot of experience and knowledge being used.
Most forecasters will start their shift by taking a look at what the weather is doing right now and what has been going on for the last 24 hours or so. They also look further afield than just their immediate area – so while they might be forecasting for the UK, they will look at the whole Western Hemisphere to look for patterns and data to help with their forecast.
What they study
Some of the factors that they will consider include the temperature, wind speed, air pressure and the precipitation – rain, hail, sleet and snow. They will use a variety of information from satellites and radar as well as from weather stations around the country that help build up a picture of what is happening at the moment and what has been going on in the immediate past.
They begin by looking at the top layer of weather, the big stuff, then work downwards to look at the layers of weather on a smaller scale. They also use surface maps that help them spot where key factors are located that can influence the forecast – things like high and low pressure, cold and warm front as well as cloud cover and wind.
Once the meteorologist has the information from the various charts and other data sources, they can then start to look at computer models. Models are used to create different scenarios as to what might happen with the weather over the next few days or week. Millions of observations from weather stations and other sources are fed into these models to help experts decide what is the most likely outcome.
Sometimes, there will be 5, 10 or even 20 different models in use to see what the likely outcome of current weather conditions is going to be and this can lead to hundreds of different possibilities, all based on data.
Working as a team
In many cases, creating that forecast is a collaborative affair between a number of meteorologists and their interpretations of the weather. One might look at a forecast and see heavy rain while another might see a light shower. Between them, they have to decide what is the most likely outcome to tell the public about.
Another approach is to have each specialise in a certain area and pull these predictions together into a forecast that has a high chance of being accurate. There’s no crystal ball involved and meteorologists can be wrong when it comes to their predictions – that’s why forecasts for the week are often made with a note of ‘likely weather’ rather than ‘definite weather’.
However, forecasters do get pretty adept at guessing what the weather will do and that’s why forecasts are usually fairly accurate. Experience and expertise combine with technology to increase the odds of accuracy and let us all know if we need that umbrella for the morning commute or not.