Weather and Climatic Conditions

Weather and Climatic Conditions

Weather is the state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc.

Climate is generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years.

Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere). Weather occurs primarily due to density (temperature and moisture) differences between one place to another. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location.

Reading Weather Maps

The most obvious features of the media's weather maps are the patterns of high and low pressure, and the barbed lines identifying cold fronts. In the southern hemisphere, the earth's rotation causes air to flow clockwise around low pressure systems and anticlockwise around high pressure systems. (The opposite applies in the northern hemisphere.) Friction over the earth's surface causes the winds to be deflected slightly inwards towards low pressure centres, and slightly outwards from high pressure systems. Wind strength is inversely proportional to the distance between isobars -- the closer the lines, the stronger the winds. This rule does not apply in the tropics where the effect of the earth's rotation is weak. For this reason, tropical meteorologists usually replace isobars with streamline arrows which indicate wind and direction without directly relating to the pressure gradient. Shaded areas on weather maps show where there has been rain in the previous 24 hours, and wind direction is shown with arrows that have a series of barbs on their tails to indicate speed.

Sydney’s Climate

Historical Rainfall & Temperature Averages
Season / Summer / Autumn / Winter / Spring
Month / Jan / Feb / Mar / Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / Dec
Sydney Climate : Recorded at Observatory Hill 1859 - 2008
Mean Maximum Temperature / 26° / 26° / 25° / 22° / 19° / 17° / 16° / 18° / 20° / 22° / 24° / 25°
Mean Minimum Temperature / 19° / 19° / 18° / 15° / 12° / 9° / 8° / 9° / 11° / 14° / 16° / 18°
Mean Clear Sunny Days / 7 / 5 / 7 / 9 / 9 / 9 / 12 / 13 / 11 / 8 / 6 / 7
Mean Rainfall / 103 / 118 / 130 / 126 / 122 / 131 / 98 / 82 / 69 / 77 / 84 / 78
Mean Rainy Days / 9 / 9 / 10 / 9 / 9 / 9 / 8 / 7 / 7 / 8 / 8 / 8