The document provides information about weather maps and weather concepts. It discusses key elements of weather maps including isobars, pressure cells, wind direction and speed. It explains that high pressure cells bring clear skies while low pressure cells bring cloud and rain. It also summarizes different types of rainfall including convectional, orographic and frontal rainfall. Seasons are determined by the positioning of pressure systems with lows over northern Australia in summer and highs in winter.

1. WEATHER MAPS/SYNOPTIC
CHARTS
GEOGRAPHY SKILLS

2. WEATHER AND CLIMATE
Weather is the state of the atmosphere at any one place or
time. This includes: humidity, temperature, sunshine hours,
cloud cover, precipitation (any moisture reaching the earth’s
surface). This includes rain, sleet, snow, hail, dew and frost.
Climate is the average or long term weather
conditions of a region. It is the result of years
of research into data.

4. WEATHER OR CLIMATE
Hot and dry conditions, together with strong winds, led to
Bushfires near Wagga.
At this time of year Darwin usually experiences hot and wet
weather.
The maximum temperature in Moscow today is -23oC
On Monday night a southerly change arrived about 10:30pm
Climate Weather

5. WEATHER OR CLIMATE
Tully in Queensland is Australia’s wettest town.
September was chosen for the 2000 Olympics because that month
usually has the best weather.
On New Year’s Day the temperature in
Sydney was 45oC
Sydney receives more rain per year than London
Climate Weather

6. • Synoptic charts or weather maps provide a snapshot
of the weather experienced at a particular place at a
certain time.
• They show information relating to air pressure, air
masses and fronts, cloud cover, wind speed, wind
direction and rainfall.
• This information allows us to make predictions
relating to temperature, humidity, ocean conditions
and the likely weather for the next few days.
SYNOPTIC CHARTS

7. SYNOPTIC CHARTSSynoptic Charts
What is this feature?
What does the shading
refer to?
What is the wind speed and direction?
What is the air pressure?

8. • Atmospheric pressure or barometric pressure is the
pressure exerted by the weight of the air on the
earth’s surface.
• Atmospheric pressure is measured in hectopascals
(hPa).
• Atmospheric pressure is mapped to form isobars.
• http://www.juicygeography.co.uk/
animations.htm#downloads/flash/highpressure.swf
ATMOSPHERIC PRESSURE

10. ISOBARS
• Are lines on a synoptic
chart joining places of
equal atmospheric
pressure.
• To estimate atmospheric
pressure you need to
refer to the two nearest
isobars. e.g. if point “A” is
situated half way between
1020 hPa and 1024 hPa,
“A” would be > 1020 but <
1024 hPa.

11. ISOBARS
How do you work out
which are high pressure
cells and which are low
pressure cells?
An isobar is a line on a
map joining places of
equal atmospheric pressure

12. PRESSURE CELLS - ARE DEFINED BY THE PATTERNS FORMED BY ISOBARS.
•Are these high
pressure cell s
or a low pressure
cells?
•How can you tell?

13. HIGH PRESSURE SYSTEM
• occur where atmospheric pressure increases towards the
centre of the system. High pressure systems are
characterised by light winds, clear skies, dry weather and a
high diurnal (daily) temperature range.
• A ridge is an extension of high pressure from a high
pressure system.
• http://www.bom.gov.au/weather/national/charts/
synoptic.shtml

14. HIGH PRESSURE CELLS
•Why does the air descend?
•Why does the air moves outwards?

15. TYPICAL WEATHER ASSOCIATED
WITH HIGH PRESSURE
• light winds
• clear skies, dry weather
• higher diurnal (daily) temperature
range i.e. hot days (sun rays
maximum effect)
• cool nights (because of lack of cloud
cover).
• Frosts are likely in winter.

16. HIGHS CAN BRING RAIN FROM ONSHORE WARM WATERS

17. LOW PRESSURE CELLS (CYCLONES OR DEPRESSIONS)
• occur where atmospheric pressure decreases towards the
centre of the system.
• Low pressure systems are associated with stronger winds,
cloudy skies, rain
• a lower diurnal temperature range.
• A trough is an extension of low pressure from a low pressure
system.

18. LOW PRESSURE CELLS
Ascending air
•Why does the air rise?
•Why does the air moves inwards?

19. TYPICAL WEATHER ASSOCIATED WITH LOW PRESSURE
• strong winds, cloudy skies, rain and a lower diurnal
(daily) temperature range i.e. mild temperatures (sun
does not have maximum effect because of cloud
cover, heat trapped in at night).
• Frosts are unlikely.

21. • http://www.bom.gov.au/lam/Students_Teachers/
pressure.shtml
• http://www.bom.gov.au/lam/Students_Teachers/
Worksheet23.shtml

22. WHAT IS WIND?
• Wind is the movement of air masses
(common bodies of air) from high pressure
areas (highs) to low pressure areas (lows).
The effect of this movement of air is to
rebalance the pressure in the atmosphere.
• Note that:
• the greater the difference between the
high and the low pressure, the greater
the wind speed will be, and
• the closer together the isobars are on
the weather map, the stronger the
winds will be.

23. WIND SPEED
• is determined by the closeness of the isobars.
The closer the isobars the stronger the winds.
• A steep pressure gradient exists where isobars
are close together.
• If isobars are far apart a place will generally
experience light winds. This is called a slight
pressure gradient.

24. NOTE THE CLOSENESS OF THE
ISOBARS
Note the spaced isobars

25. READING WIND DIRECTION ON A WEATHER MAP
Sydney
N
Close up of a map
Easterly √(Remember that we
name our wind direction
on where the wind came
from)
Not where its
going too
x

26. HOW TO READ WIND SPEED ON A WEATHER MAP
Legend- Wind Speed
5 km/hr
10 km/hr
20 km/hr
To work out the
wind speed of an
area, all you need
to do is match up
the wind speed
symbol found on
the map with the
symbol found in
the key
The wind speed at
point A is 5 km/hr
A
30 km/
hr
Calm

27. WIND DIRECTION
• Wind is named according to
the direction the wind is
coming from, e.g. south =
southerly.
• Wind direction is largely
determined by the location
of pressure systems.

28. WIND DIRECTION
Remember we always refer to where the wind is coming from!
Where has the wind come from?
1
2

29. WIND DIRECTION – ANTICYCLONES (HIGH PRESSURE
CELLS)
• In the southern hemisphere winds blow
outwards in an anticlockwise direction from
areas of high pressure.
ANTICYCLONE = ANTICLOCKWISE WINDS.

30. TROPICAL CYCLONES (T.C.)
• Are a very intense low pressure system.
They generate very strong winds, produce
rough seas and heavy rains
• Wide spread damage occurs if they make
landfall (contact with land).

31. A CROSS SECTION OF A TROPICAL CYCLONE

32. WIND BLOWS OUTWARDS IN AN
ANTICLOCKWISE DIRECTION IN AREAS OF
HIGH PRESSURE.
ANTICYCLONE = ANTICLOCKWISE WINDS.

33. WIND DIRECTION – DEPRESSIONS
(LOW PRESSURE CELLS)
• In the southern hemisphere winds
associated with low pressure systems blow
in a clockwise direction towards the centre of
the system.
LOW T. C. = CYCLONE = CLOCKWISE WINDS.

34. WINDS BLOW TOWARDS THE CENTRE OF A LOW
PRESSURE SYSTEM AND IN A CLOCKWISE
DIRECTION
LOW P. C. = CYCLONE = CLOCKWISE WINDS.

35. WIND INDICATORS
• Wind indicators show wind speed and direction.
• The feather indicates wind speed
• The shaft indicates the direction from which the wind is coming
• The black dot is the place that is experiencing the windy conditions

36. IDENTIFYING WIND DIRECTION
• First - Identify the type of pressure system.
• Southern Hemisphere
LOW =clockwise
HIGH = anticlockwise.
• (the reverse is true in the northern hemisphere)
• Wind, generally speaking, moves across the isobars

37. FRONTS
• A front is the leading edge of change. They are the
border zone between warm and cold air. There are
two types of fronts:
• Warm fronts occur when warm air is pushed into a
cold air mass. These are very rare in Australia. They
result in drizzle and light rain over a few days.

38. A WARM FRONT

39. COLD FRONTS ARE FAR MORE COMMON IN
AUSTRALIA AND OCCUR WHEN COLD AIR IS
PUSHED INTO A WARM AIR MASS. THIS FORCES
THE WARM AIR TO RISE CAUSING A NUMBER
OF CHANGES:
(A) DECREASE IN TEMPERATURE: COLD AIR
REPLACES WARM AIR.
(B) CHANGE IN WIND DIRECTION AND
SOMETIMES SPEED.
(C) BUILD UP OF CUMULONIMBUS OR RAIN
BEARING CLOUDS.
(D) INCREASE IN HUMIDITY: CORRESPONDING
TO A BUILD UP OF CLOUDS.
(E) PROBABILITY OF RAIN.
Make up an acronym to remember these changes.

40. A COLD FRONT

42. TEMPERATURE AND HUMIDITY:
• are related to the wind. Winds pick up the
characteristics of where they form – sea or land – these
are called source regions
Remember:
• Winds off the land are generally hotter and drier.
• Winds off the sea tend to be cooler and wetter (greater
moisture = greater humidity).

43. HUMIDITY
• Humidity is the amount of water vapour in the
atmosphere
• A high humidity means there is a lot of water
vapour, and a low humidity means a little.
• The humidity level varies with temperature. The
warmer air is, the more moisture the air can hold
as vapour. The colder the air is, the less moisture
the air can hold.
• Humidity is measured as a percentage, relative
to the saturation point where the air can hold no
more water vapour (i.e. 100 percent humidity).

44. TYPES OF RAINFALL:
CONVECTION
http://www.youtube.com/watch?v=RkgThul2El8
http://www.bbc.co.uk/schools/gcsebitesize/geography/weather/elementsofweatherrev6.shtml

45. TYPES OF RAINFALL:
OROGRAPHIC
http://www.youtube.com/watch?v=BVykQfRC_aI
http://www.bbc.co.uk/schools/gcsebitesize/geography/weather/elementsofweatherrev6.shtml
http://www.radioblogclub.com/open/51998/elevation_u2/U2_-_Elevation
Elevation U2.url

46. OROGRAPHIC RAINFALL
The dry air mass becomes warmer, with little
chance of rain. Deserts are often found on the
leeward side of large mountain ranges
Warm moist air
approaches a
mountain barrier
The air mass is
forced to rise as it
hits the mountain and
condenses into
clouds
Orographic
rainfall occurs on
the windward
side of the
mountains
The air mass, now
drier, flows down the
leeward side of the
mountains

47. TYPES OF RAINFALL:
FRONTAL
http://www.youtube.com/watch?v=D88dYNFyBq8
http://www.bbc.co.uk/schools/gcsebitesize/geography/weather/elementsofweatherrev6.shtml

48. FLASH VIDEO ON TYPES OF RAINFALL
Show Weather Rainfall wmv
http://blip.tv/scripts/flash/blipplayer.swf?
autoStart=false&file=http://blip.tv/file/get/Gatm-
Rainfall922.flv?source=3

49. SEASONS
• are determined by the location of various pressure
systems.
Remember:
• Summer = Lows over Northern Australia and
Highs over Southern Australia.
• Winter = Highs over Northern Australia and Lows
over Southern Australia.

50. SUMMER WEATHER MAP
Where are the different cells located?

51. WINTER WEATHER MAP
Where are the different cells located?

52. CLEAR SKIES ALLOW THE
SUN’S RAYS TO HAVE MAXIMUM
EFFECT. DAYTIME
TEMPERATURES ARE USUALLY
HIGH.
At night, clear skies
allow heat to be lost
causing temperatures
to fall. In winter frosts
are likely.

53. WHY DO CLIMATES VARY?

54. FACTORS AFFECTING THE CLIMATE
What makes a certain place hot, cold, wet,
dry, windy…?

55. YOUR IDEAS
On the A4 paper provided
and working in pairs:
Quickly sketch as many ideas as
you can as what might cause
temperature and rainfall to be
different at various places.
You have 3 minutes

56. WORLD PATTERN OF CLIMATE
The climate of a particular place on the earth’s
surface depends on 5 main factors.
Latitude:
radiation from the sun is stronger and more direct
at the equator. Places at the equator are therefore
generally hotter than the places near the poles.
Also seasonal differences are more obvious away
from the equator.

57. LATITUDE
HTTP://PEOPLE.CAS.SC.EDU/CARBONE/MODULES/MODS4CAR/CCONTROL/
CONTROLS/LATITUDE.HTML
• The sun’s rays are
concentrated at the
equator but spread out at
the poles.

59. ALTITUDE (ELEVATION):
• The air is generally thinner and therefore colder
higher up in the mountains than it is at sea level.
Also precipitation (rainfall and snowfall) is generally
affected by mountain ranges as moist air will be
forced to rise over the mountains (orographic
rainfall). This will cause the air to cool and then
condense into cloud.

60. DISTANCE FROM THE SEA:
• The ocean acts as a stabilising influence on
temperatures as the sea heats and cools more
slowly than the land. Thus diurnal (daily) and
annual (yearly) ranges of temperature are smaller
near the coast and greater in inland areas. This
means that inland areas generally have hotter
summers and colder winters than coastal areas.
Also moist air near the coast may result in more
rainfall in coastal areas than places inland.

61. DISTANCE FROM THE SEA
• In the summer, the sun heats
the land quickly but it takes
longer to heat up the water
which is large and deep.
http://people.cas.sc.edu/carbone/
modules/mods4car/ccontrol/
controls/landwater1.html
• However, the water stores heat
for longer and so in winter, the
temperature of the sea is
warmer relative to the land and
so keeps coastal places warmer.

62. OCEAN CURRENTS:
• Cold ocean currents cool the air and generally cause
dry conditions along the coastline. Warm ocean
currents will warm the air and cause warmer, wetter
conditions.
• http://people.cas.sc.edu/carbone/modules/
mods4car/ccontrol/controls/ocean.html

64. PREVAILING WINDS
• These are the winds that
blow most often.
• Winds can affect
temperature and
precipitation.
• Winds blowing over
tropical oceans bring
warm and wet weather.
• Winds blowing from the
poles and over land bring
cold and dry weather.