Weather forecasting

[Synoptic weather map weather forecatsing]

Climatology weather forecasting
General weather in summerInterior
· hot
· moist
· with thunder showers
Exterior
· East coast
o Humid
o Hot
o Weather temperature doesn’t vary between night and day
o Windy
· West coast
o Dry
o Windy


Discussion of weather systems/ patterns
· Synoptic weather mapo Shows the weather at a particular time and place
o Isobars show the air pressure
o A synoptic weather map will also show weather patterns, and weather systems

· Isobarso Is a line joining places with the same air pressure

· Mid latitude cycloneso Has  cold and warm front
o Low pressure system
o Moves from South West to North East to South East (Southern Hemisphere)
o Location 30 - 60° Latitude
o Life span of 5 – 6 days
o Warm front brings warm weather
o Cold front brings cold air
o Comes in families (family of depressions)

· Tropical cycloneso Comes in late summer early winter
o Develops between 5-30° Latitude (Latitude are the imaginary lines that run vertically along the earth, they run parallel to each other)
o It moves from North East to South West to East in direction
o Bring heat
o Only occur over oceans with a minimum temperature of 27°C

· Coastal lowo Small and weak
o Move South East along the coast
o Wind is hot and dry – is known as berg wind
o In front of the coastal low you get an offshore flow (wind from the land moving towards the sea)
o Behind a coastal low you get an on-shore flow (wind from the sea moving towards the land.
o Cool air, drizzle




· Blocking higho Often situated south of South Africa
o Forced east ward moving weather systems (mid latitude cyclones and coastal lows) to the south, away from South Africa
o Has a North South axis
o Usually occur in summer

· Isobaric patterns
o There are patterns shown by isobars that we see on the map
o There are 3 categories that fall under this heading

§ Low pressure trough· Is when the isobars bend away (southwards) from a low pressure cell
· The low pressure has to be between 2 high pressures, otherwise it is not a low pressure trough
· Rain may follow

§ High pressure ridge
· Is when the isobars bend away from a high pressure cell (eastward/ westward)
· The high pressure has to be between two low pressures.
· If air is coming from the South Atlantic ocean it may bring cool dry weather to South Africa.
· If the air is coming from the Indian ocean it will bring humidity and hot weather
§ Saddle area
· Is an area with constant or the same pressure.
· There are no isobars in this area.
· There is no wind in this area

· South Atlantic high
o Part of the pressure systems
o Situated in the west of South Africa

· South Indian high
o Situated to the east of South Africa
o In the summer it is further south
o It brings moisture into South Africa

· Kalahari higho Over South Africa in the winter
o Has strong descending air, which leads to clear skies and moderate air
o Heating in summer makes it disappear

Making our prediction using the synoptic weather map

Our unstable atmosphere

Climate and weather have intrigued people for 1000’s of years. Mankind has seen droughts, floods and ice bringing many species into extinction and mankind on the brink of extinction.
Before we can even start looking at any aspect of climate and weather its important to define these concepts. Climate refers to the long-term average weather of a geographical region taken over 30 years or more. Weather can be describes as the day-to-day atmospheric conditions of a particular place. Aspects of weather include hat and cold, humidity, wind, clouds, fog, hail, sleet and rain. The last three aspects are also known as precipitation. Climate is very unstable over time. Currently the earth is going through a warming period which is intensified by global warming. Climate has a huge impact on population growth and human activities.
Weather in life occurs in he lowest part of our atmosphere and it is here where people have the greatest impact. The earth’s atmosphere consists out of different layers with its own unique characteristics.
i) The troposphere
The troposphere reaches up to a height of approximately 16km above the earth’s surface at the equator and 9km over the poles. It contains more than 80% of all the gases in the atmosphere. The temperature decreases from an average of 22˚C to -50˚C. This temperature decrease takes place at a specific lapse rate known as the environmental lapse rate.

ii) Tropopause
The tropopause is not a layer but rather a transition zone between the troposphere and the stratosphere. The tropopause is characterized by a temperature increase with increase in altitude known as temperature inversion. This temperature increase is the result of a high concentration of ozone (O3) which absorbs harmful ultraviolet sun rays. Natural holes in the ozone exist over the poles but chlorofluorocarbons (cfc’s) released by humans into the atmosphere destroy ozone, allowing dangerous levels of radiation to pass.

iii) Stratosphere
The temperature increases from -60˚C to just below 0˚C. The increase in temperature is due to the presence of ozone.

iv) Stratopause
The stratopause forms the transition zone between the stratosphere and mesosphere.

v) Mesosphere
In the mesosphere the lack of gases results in very little absorption of solar heat energy.

vi) Mesopause
The mesosphere forms the transition zone between the mesosphere and the thermosphere.

vii) Thermosphere
The thermosphere has virtually no gases although the temperature increases sharply. In this layer you are completely expose to the full force of solar radiation.