Meteorology Tips And Information: All About Forecasting Weather

Learn how the forecasters manage to forecast the next days weather and why they don't always get it right.

Did you hear the weather forecast this morning? More than likely, you listen out for it every day. After all, the state of the weather affects most things we do. No point planning that hike, if it's gonna' rain. But, hold on - the forecast said showers and, yet, the day's brilliantly fine. Who got it wrong? Blame it on the weatherman.

Yet, just how does the weatherman manage to forecast something as changeable as weather? And why does he so often get it wrong? To answer these questions we need to get a basic understanding of how the weather works.

It is the bottom layer of the earth's atmosphere - which is six to nine miles thick that is involved in our weather. Within this area, called the troposphere, the three main factors affecting our weather are temperature, pressure and humidity. Let's consider them one at a time.

Temperature: Unequal heating by the sun's rays causes differences in temperature. The sun's rays penetrate the earth's atmosphere and go through to the surface where they are either reflected or absorbed. If the surface absorbs a lot of rays, it heats up, if it reflects the majority of them, it gets cold. In equatorial areas of the earth the sun's rays hit the earth vertically, whereas at the poles, they make contact on an oblique angle. Temperature differences caused by these differences put in motion the processes that lead the great variation in the weather around the globe.

Pressure: Air over warmer areas is less dense than that over cold areas. This causes it to rise and it is this which causes differences in air pressure. The pressure differences at the surface causes a wind to blow from the region of higher to pressure to that of lower pressure. The greater the pressure difference, the stronger the wind.

Humidity: As air moves across the earth, it picks up water. Warm air picks up moisture more readily, so air masses in low pressure areas are more humid. When humid air rises, pressure on it decreases, it expands and cools. When the temperature falls to the level where the air becomes saturated, water begins to condense in droplets or ice crystals. These then form into clouds, from which rain or snow may fall. The air, now dried, will rise to high pressure areas, bringing fine weather with it.

The meteorologist studies the pattern of temperature, pressure and humidity in the skies. He then plots a chart in a special language created by the World Meteorological Organization. Information appears as numbers rather than words, which allows the information to be relayed to ships at sea. The data is then drawn with irregular curving lines called isobars that connect places reporting the same pressure. High and low pressure areas are also identified. These charts give the weatherman a good overview of how the weather is currently. But how about forecasting?

By viewing a series of charts, a pattern of weather is able to be shown. Based on the most recent shifts of highs and lows, the weatherman is able to mark out their probable position for tomorrow. This will give him a fairly accurate indication of what will happen weather-wise tomorrow. Yet, the weatherman cannot control the weather. Many variables come into play. A low pressure center may change speed or direction. A disturbance may weaken. Which will prevail when a high and a low collide?

Weather forecasting, however, is not guesswork. It is a highly developed skill - some would say even an art. But, no matter how skilled he is, the meteorologist can never guarantee certain weather conditions. He is not a magician. So, if it rains tomorrow when the forecaster said it would be fine, don't blame it on the weatherman.

© High Speed Ventures 2011