The way the weather gets to be on TV

Dusty maps and
pocket calculators are a thing of the past  today the weather is predicted using expensive computers. We wanted to know, how the weather forecast gets to be on the television,  so we decided to see how the ZDF weathermen in Mainz work.  


 The storm approached, trees fell over, cellars flooded and drains were covered in water but  everyone knew it was going to happen before the first drop of water fell:Dr. Gunther Tiersch is the director of ZDFs weather department.He and his eight colleagues have to evaluate the  weather conditions and deliver an up to date forecast to ZDFs viewers up to 20 times per day, In addition to this they do the forecasts for ’Logo’, a program on the children's channel KIKA.

It’s 11:30pm and it’s humid at this  time Dr. tiersch is at his computer and he can already see the thunderstorm coming towards Germany. In Switzerland, a layer of dense cloud is heading towards Baden-Wuerttemberg and Bavaria. "this cloud will cause heavy rain", explains Tiersch on the basis the satellite photographs.

Every 15 minutes he gets a new satellite and radar image, in addition to this he gets the values from over 10,000 weather stations throughout the entire world . The data for Germany is updated once every hour. The rest of the world is not updated as often. Here the actualization of a storm that takes place over a three-hour time period. Lots of measurements are taken such as: temperature, air pressure, wind direction, wind speed, cloudiness, upper air flow and the duration of sunshine. These measurements are taken every six hours by weather balloons that measure at a height of 1500 meters above germany.

 40 million euro computer

Today the ZDF meteorologists began reasonably late, 9:30am, because the morning magazine this week is being produced by the ARD. Normally the meteorologists need to get up at 3:30am so they are redy fort he first weather forecast at 5:00am.


Nowadays a meteorologists job does not consist of formulating there own weather forecast. Inasted they must compare the different weather models. Gunther Tiersch says: "today weather is calculated." This means computers try to simulate the weather for the upcoming days. Since each country would like to use its own weather model, every country has its own computer. This costs an enormous amount of money, e.g. the German weather service’s computer cost 40 million euros. 

 At 12:30pm the telephone rang and the editor of "hallo deutschland" from Stuttgart asked whether the storm would hit in his area. They want to know if they can send out a team of reporters to take pictures for the news and they can only do this if they know early enough. Dr. tierschs team are also responsible for these inquiries.

Storm warning

Now the meteorologists needed to decide which weater model to use. „Most weather models have similar weather predictions, but sometimes we trust a special weather model more than the others ,“ explained Dr. tierisch.Meanwhile it is 1:30pm Dr. Tiersch began to prepare its weather forecast for the news at 5:00pm  which will be a live transmission. Today’s a special day, Instead of the usual 70 second forecast it must be over three minutes long. First he fed data into his computer which the computer put into various maps and animations. Now he adjusts the local temperatures with the other weather models and he had to insert symbols into the map. Now he puts the regional temperatures in the right maps. Because of the storms today there are two warning triangles, one over Bavaria and one over East Germany.Then he wrote his text and learnt it by heart because the weather moderators do not have Teleprompters available.

Last details

At 5:00pm Gunther Tiersch went through his text again, while the anchorman reported about the Gaza Strip and a murder in potsdam. He had a drink  just as the anchorman finished. Still in the course of the forecast the last details are clarified "how wil you actually announce me?", Tiersch asked his colleague. 
At 5:12pm it became serious. Dr. Tiersch went live on air. Looking towards the camera he welcomed the viewers. He changed the different maps using a remote. 5:40pm after the forecast Dr.Tiersch started working immediately plotting the weather report for the next forecast at 7:00pm. He then started working on the 10:15pm forecast after the "Heute Journal". At 10:30pm Gunther Tiersch finnished his work day.  
We will know if his predictions are right hours later, even if the computers and models are better, the forecasts can only be a prediction. "we will never have, technology for a 100% forecast" said Dr. Tiersch. "perhaps a 14 day prediction will be possible in the near future, but no more."


Uncalculable Weather

At the moment it is possible to workout temperatures within a three degree accuracy. Rainfall can also be predicted accuratly hours beforhand . The accuracy depends on the amount of data. The less data there is the more inaccurate the results are. When the data is incomplete the computer must guess what data is missing. This data is never exact. Nevertheless it is worthwhile to whatch the weather forecast. "we have an accuracy of 90 per cent for the next 36 hours", explained Tiersch. "nine of ten prognoses are correct."


Nevertheless the weather remains incalculable .


written by Philipp Seibt & Nicolas Werner

In 'Forum' in September 2007

new layout by Christian & Daniel
Translated by