APPLY WEATHER INFORMATION

1
APPLY WEATHER INFORMATION

• The weather cannot be controlled, only prepared
  for

2
Assessment criteria

• Identify sources of weather information
• Obtain interpret meteorological data
• Synoptic charts satellite images
• Daily 4 day forecasts
• Max min temperatures
• Rainfall, snowfall, pressure
• warnings

3
Weather maps and charts
Atmospheric pressure map
Visible satellite image
Infra red satellite image
Other types?
Source Images from Japan Meteorological Agency
satellite MTSAT-1R via Bureau of Meteorology.
4
Assessment criteria

• Access area-specific information
• Interpret BoM forecasts warnings assess
  appropriateness of activities in planning
• Access additional weather information as
  necessary for planning
• River heights, tides, snow cover
• Estimated water release from dams

5
(No Transcript)
6
Assessment criteria

• Evaluate current predicted weather conditions
  in terms of their effect on a planned outdoor
  activity
• Modify activity plans, if necessary, following
  consideration of weather information

7
BACKGROUND WEATHER INFORMATION

• SEASONS
• UNIQUE AUSTRALIAN WEATHER
• PRESSURE SYSTEMS
• AIR MASSES FRONTS
• COLD WARM FRONTS
• INTERPRETING SYNOPTIC CHARTS
• CLOUD FORMATION RAINFALL
• 4 DAY FORCASTS
• SATELLITE IMAGES

8
Seasons

• As the Earth revolves
• around the Sun, it is tilted
• on its axis at an angle of
• 23.5 degrees.
• In December when the
• southern hemisphere is tipped
• towards the sun, more direct
• sunlight and long hours of daylight cause
• warmer weather in June, when the southern
  hemisphere
• is tipped away from the Sun.

9
Australian Weather

• In terms of weather, Australias long coastline
  is unique in the world. It stretches more than
  3000km roughly along the 35th parallel of
  latitude.
• To the south, the southern Ocean extends 3000km
  to the Antarctic continent. From there, outbreaks
  of very cold polar air move northwards, warming
  somewhat as they pass over the ocean. The air is
  still cool when it reaches Australia.

10

• Inland from the southern coast, a large
  proportion of the country is arid or semi-arid,
  with low rainfall and very hot summers.
• Air coming from the hot interior to the coast
  meets the cold air from Antarctica, giving
  southern Australia highly variable weather.

11
Pressure systems

• Atmospheric pressure varies with both height
  above mean sea level, and from place to place at
  mean sea level.
• Mean sea level pressure (MSLP) is measured in
  units called hectopascals (hPa).
• Lines on a weather map joining places of equal
  MSLP are called isobars.

12

• On a daily weather map there will be patterns of
  relatively high and low pressure systems over
  Australia.
• It is these systems that generate variations in
  wind, temperature and rainfall.

13

• In the southern hemisphere the wind flows
  clockwise around low pressure systems and
  anti-clockwise around high pressure systems.
• The strength or speed of the wind is closely
  related to the spacing of isobars.
• Closer spacing means stronger winds.

14
Air masses

• A large body of air originating in a particular
  place is called an air mass.
• The boundary
• line that
• separates
• 2 air masses
• is a front.

15
Air masses weather maps

• The main features of a weather map are
• Isobars generally drawn at intervals of 2 or 4
  hPa, depending on the scale of the map.
• Cold and warm fronts major boundaries between
  air masses. Shown as a bold line with triangles
  for a cold fronts or semi-circles for warm
  fronts.
• Troughs of low pressure shown as dashed lines.

16
(No Transcript)
17

• 4. Areas where rain has fallen in the past 12 or
  24 hours, shown by hatching.
• 5. Surface wind direction and speed at spot
  locations the direction from which the wind is
  blowing is designated by the arrow shaft and the
  speed by the barbs along the shaft.
• ( a long barb 20km/h, 2 long and 1 short
  barb 50km/h)

18

• There are 2 main types of fronts
• COLD FRONTS, and
• WARM FRONTS

19
Cold Fronts

• In a cold front, an active wedge of cold air
  undercuts a mass of warmer air. It moves under it
  because it is colder more dense.
• Cold fronts move at different speeds and form a
  range of shapes.
• They also produce many variations in weather
  depending on whether the warm air was dry or
  moist.

20
Summer cold front map
Cold front storm cloud
21
Warm Fronts

• Warm air is the more active part of the system.
• It moves in on the cooler air but because it is
  less dense it is lighter and rides over it.
• The retreating cool air is replaced by the warm
  air.
• Warm fronts move much slower and the slope of the
  front is much less than in a cold front.

22
(No Transcript)
23

• The temperature, moisture content and other
  properties of an air mass reflect the region
  where it originated.
• As it moves its properties are modified by the
  surfaces it passes over.

24
Weather systems

• Australias weather systems arrive from and move
  across the continent West to East
• As a general rule in summer there are more high
  pressure systems and in winter there are more low
  pressure systems

25
Weather chart

• High pressure system
• generally calmer conditions
• Warmer
• wind flows anti-clockwise around high pressure
  system (red arrows) and spiralling slightly
  outwards

26
Weather chart

• Low pressure system
• - stronger winds, more unsettled conditions
• Colder
• - wind travels in a clockwise direction around
  low pressure system and slightly inwards
• very deep low pressure systems may form into
  cyclones

27

• Inflowing air associated with lows result in
  convergence ascent of air often resulting in
  deep cloud formation and rainfall.
• Outflowing air associated with highs result in
  divergence and descent of air and more stable
  weather.
• BOM_Air pressure

28
Typical Summer Weather Map

• Northerly winds over eastern Australia
• Moist, easterly flow
• Cold front passing South Australia

29
Typical Winter Weather Map

• Deep low pressure system (972 hectopascals) south
  of Tasmania
• Very cold south westerly air traveling northwards
  across Tas, Vic and SE NSW

30
Cool changes

• With a high pressure system over eastern
  Australia, the anti-clockwise air movement brings
  an air mass from the hot dry interior over the
  southeast coastline. Temperatures under these
  north wind conditions are typically around 40
  degrees for several days.
• At these fronts, the hot northerly wind is
  abruptly replaced by a cold south-westerly wind.
  Clockwise-flowing air moves towards the front
  from the west. The arrival of the front can drop
  the temperature by 10 15 degrees in half an
  hour or less, with a further decrease in the next
  day or so.

31
Monitoring the weather

• Air pressure is probably the most important
  weather element, because pressure variations
  drive the winds.
• Daily weather map sequences show a series of high
  and low pressure systems moving across the
  continent.

32
(No Transcript)
33
Cloud formation rainfall

• Convective rainfall when the earths surface is
  heated, air evaporates. As it rises it cools and
  condenses.
• Eg. Rain on a hot summer afternoon, especially in
  the tropics. Often associated with huge
  anvil-topped clouds.

34

• Orographic rainfall air is forced to rise when
  land barriers such as mountain ranges lie in the
  path of air masses.
• On the leeward side of the mountains, descending
  air is depleted of its moisture, sometimes
  causing desert conditions.

35

• Frontal rainfall when moist air moves into a
  low pressure area or a front, clouds and rain may
  develop.
• This type of rainfall is less violent that in
  thunderstorms because the air rises more slowly
  and is cooled more gently.
• It is also usually more widespread and protracted
  eg. Dull grey overcast skies and drizzly rain.

36
Satellite patterns to watch for

• Cold front long sweeping cloud, sometimes with
  a spiral hook cloud shape.

37

• Severe thunderstorms large blobs of cloud.

38

• Stratocumulus large areas of uniform, lighter,
  low level clouds indicate overcast and persistent
  drizzle.

39

• Air pressure is measured
• with a barometer.
• Temperature is measured
• with a thermometer.
• Humidity is the mass of water vapour in a unit
  volume of air and is measured by a wet-bulb
  thermometer (the warmer the air the higher the
  humidity because the more water vapour it can
  hold.)
• Wind speed is measured with an anomometer.

40
YOUR TASK