What Makes up the Weather To understand what factors make up the weather. To understand how to read a synoptic chart.

Air Pressure The pressure exerted by the weight of the atmosphere. When air cools its molecules become packed more tightly, this means colder air is heavier and sinks giving high pressure. When air is warmed the molecules move further apart. Because they are lighter they rise giving low pressure ISOBARS are lines of equal pressure value on a map.

remember to add the degrees Temperature The measurement of the heat of the atmosphere. Temperature of air is measured in the shade. Remember when writing a temperature down, remember to add the degrees Celsius symbol.

Precipitation This includes snow, hail, sleet etc… Air contains water vapour picked up from the sea or other bodies of water. Cold air can not hold as much water as warm air so as air cools, (by being forced upwards, or by contact with cold ground) it reaches the dew point where the vapour turns to moisture, i.e. it condenses. Condensation may be in the form of dew, mist, fog or clouds. Further condensation gives rain.

Cloud Cover The amount in 1/8ths, that the sky is covered by cloud. Clouds have a blanket effect, they reduce the amount of heat coming from the sun during the day and keep in the heat at night.

Wind Direction The wind moves from areas of high pressure to areas of low pressure. Winds are always described by the direction from which the wind is blowing. West East The wind above is described as a Westerly wind.

Wind Speed Winds are strong if the pressure gradient is high. Pressure gradient is the difference in value between high and low pressure. The closer the isobars are together the stronger the winds will be. Strong winds Calm winds

Sunshine The number of hours the sun shines a day. .

Synoptic Charts Synoptic charts are weather maps produced by the Meteorological Office. They use official symbols to represent the weather conditions at specific stations. 5 weather elements are shown by symbols. But atmospheric pressure is obtained by looking at the isobars.