How do meteorologists create forecasts?
Meteorologists use a variety of tools including weather satellites and radars to forecast the weather. They spend years studying how different elements in nature affect each other and about how the different types of weather are created. They study high and low pressure and learn how that can change the types of weather that will occur.
Weather Satellites
Weather satellites watch the world from space, and have been taking pictures from there since the first one was launched in 1959. Some of these pictures are exactly like photographs, taken by cameras that are sensitive to light, and these are great when the sun is high in the sky. These are called Visible Satellite Pictures.
But the weather doesn't stop at night, so we also need "cameras" that can "see in the dark". Because the land, the sea and the clouds radiate warmth, day and night, they can be "seen" by heat-sensing devices, even when the sun has gone down. With the information collected by the heat sensors, scientists can build up a very detailed picture of the Earth and its atmosphere. These pictures are called Infrared Satellite Images.
Weather Radar
Weather radar uses microwaves and their echoes to detect anything that falls from the sky, like rain, hail or snow. Some radars can even pick up moisture that hangs in the air, like mist and fog.
When you think of "microwaves", you probably picture an oven, but microwave energy does much more than just cook food. It carries information like telephone calls and computer data from place to place, and it's also very useful for weather forecasters. When you shout straight at a wall, you hear an echo, as the sound waves bounce back at you. In much the same way, a radar station sends out "shouts" of microwave energy, and "listens" to see if they'll return. When the microwaves hit off rain (or hail, sleet or snow), they bounce back to the radar station; the heavier the rain, the "louder" the echo, as the microwaves bounce back off lots of different "walls".
The radar then converts the echoes into picture form; the weakest ones appear blue or green, the stronger ones are yellow, and the red or purple ones are the strongest of the lot. By measuring the amount of time it took the microwaves to return, the radar can also calculate how close the rain is.
High and low pressure
A high pressure system is a whirling mass of cool, dry air that generally brings fair weather and light winds. When viewed from above, winds spiral out of a high-pressure center in a clockwise rotation in the Northern Hemisphere. These bring sunny skies.
A low pressure system is a whirling mass of warm, moist air that generally brings stormy weather with strong winds. When viewed from above, winds spiral into a low-pressure center in a counterclockwise rotation in the Northern Hemisphere.
Making a forecast
The atmosphere is being measured all the time at weather stations around Ireland, Europe and even at sea. Those measurements for pressure, wind speed, temperature, rainfall etc. are put into big, long mathematical equations, so complicated that they have to be done by computers. This happens four times everyday - at midnight, 6 a.m., midday and 6 p.m. The number crunching takes quite a while - it can last up to 4 hours.
The equations produce lots of weather charts that give a forecast for about ten days ahead. The meteorologists look at what the computer has to say. They examine the satellite and radar pictures to see where the cloud and rain are, and how quickly they are moving. Then, using their knowledge and experience of the Irish weather, they make predictions of their own.
These predictions are what you see on the RTÉ weather forecast during the day and after the news. They let us know what the weather will be like for the next few days, so we can plan picnics or days out. It also lets farmers know what the weather will be like for their crops and informs them whether the grass will grow and their cows will get enough to eat to help them produce lots of milk.
Presenting the weather
Weather presenters have an important job in telling people what the weather will be like for the next few days. In order to do their job well, meteorologists must gather all the facts, work out what the forecast is and then present it on the television. It's a big job and meteorologists work very hard. We've already seen how they create a forecast, but here are some things they must remember about presenting.
- Speak clearly, if a presenter mumbles the viewers at home won't hear them
- Look at the camera, so the viewers know you are talking to them
- Be tidy, presenters are professionals and must look neat and tidy at all times.
- Smile. Even if the forecast is for rain presenters must smile for the viewers at home.
Why not put these tips to good use by presenting the weather on RTÉ Two. For a chance to prove your presenting skills click onto our competition page.
