How can meteorologists predict tomorrow’s weather?
This morning, Mika and I were invited to Sophie’s for breakfast. The radio was on and the weather forecast was playing. “Tomorrow we can expect a sunny day with temperatures of up to 25 degrees Celsius,” said the voice. I looked at Sophie questioningly and asked: “How do people actually know what the weather will be like tomorrow?”
Sophie tried to explain: “A weather forecast is like a giant puzzle: we collect lots of data about the weather and then put it together to see the picture for the next few days.”
“And what exactly is this data?” I asked curiously.
“All over the world, weather stations, satellites and weather balloons measure different values,” Sophie explained. “For example, the temperature, wind direction, air pressure and humidity. This data is then forwarded and forecasts made with the help of computers.” Weather balloons and satellites, hey! I know about them, I thought to myself.
“And what does the computer do with this data?” I wanted to know.
“The collected data is linked to weather models, as Jan Kretzchmer once explained to you, and since we humans can’t do such large and complicated calculations in our heads, we use computers for this. The models know, for example, that if the air pressure drops and humid air is added, then there is often rain or thunderstorms. But if the pressure remains high and the air is dry, the weather usually stays nice and sunny.”
“That’s exciting!” I exclaimed. “So they can tell me what the weather will be like next year for my birthday, that’s great! Then I’ll go on a scavenger hunt outside or go to the swimming pool and…”
“Unfortunately, it’s not that easy,” Sophie stopped me. “The more up-to-date data we have, the more accurately we can predict the weather for the next day or two. For the first and second day, the forecast is usually 90% accurate, but for the third day it’s already only about 75%. Unfortunately, it is more difficult to predict the weather in a week or longer because the weather can change quickly. So it’s not very likely that the exact weather predicted in the model will occur on your birthday next year.”
Now I understand it all a little better. Even though I don’t know what the weather will be like next year, there’s a very good chance that the weather forecast for tomorrow will come true. I’m already looking forward to going to the lake for a swim, and playing outside with Mika in the sun.
Text: Sophie Vliegen, Illustration: Patrizia Schoch