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Tuesday, 6 September 2011

Weather Forecasting

Data Collection and Analysis


  • Thousands of surface stations collect data at 0000, 0600, 1200 and 1800 GMT based on weather ships and automatic buoys at sea and on land.
  • Upper atmospheric data is captured by radiosondes and aircraft.
  • Lower atmospheric data is collected through vertical wind profilers and radar.
  • Satellites orbiting the Earth including Polar Satellites (NOAA), geostationary satellites (meteosat) and geostationary and operational environmental satellites (GOES) measure and track weather systems. 
  • Data from this range of sources is then transmitted to weather centres and collated by computer models.

Methods of Forecasting

1. Synoptic weather forecasting – predict weather system movement using surface and upper air data.
2. Numerical and statistical forecasting.
3. Ensemble forecasting – inputting slightly different initial conditions into a range of computer models to predict the likelihood of certain types weather, such as rain or snow.

Synoptic pressure fields are shown as isobars (lines of equal pressure at a set height).

Synoptic Pressure Fields

The closer the isobars the greater the geostrophic wind velocity. (Geostrophic wind flows horizontally and parallel to isobars, they come about when pressure gradient force and the Coriolis force are balanced.) Wind speed is measured in knots, as shown in the table below.


Terminology

High Pressure = cool, dry air that is associated with fair weather and light winds (rotate clockwise in the northern hemisphere and anti clockwise in the southern hemisphere)
Low Pressure = warm, moist air that usually brings stormy weather and strong winds (rotate anti clockwise in the northern hemisphere and clockwise in the southern hemisphere)
Weather Front = boundary between two different air masses
Cold Front = where a cold air mass is moving to replace a warm air mass
Warm Front = where a warm air mass is moving to replace a cold air mass
Stationary Front = where two air masses merge and don’t move
Occolude Front = a combination of two fronts when a cold front ‘catches up’ with a warm front
Trough = an elongated area of low pressure associated with cloud cover and precipitation


Weather Station Symbols

Table displaying symbols used on weather charts – BBC GCSE Bitesize



Classroom Activity - Presenting The Weather

The class can be divided into small teams of meteorologists faced with different weather scenarios. Building upon prior knowledge of British weather patterns and interpretation of weather maps and synoptic charts, pupils are instructed to interpret infrared satellite imagery from the Met Office to predict the forecast for later that day. Pupils can choose to present their findings as they wish, although a strong recommendation to use ICT could be stipulated to develop their technical skills. Each weather team will be allocated 5 minutes to present their weather forecast.

The main parameters pupils need to take into account are temperature, humidity, precipitation and atmospheric pressure.


Lesson Plans/Resources


BBC Weather Lesson Plan for Key Stage 2 (could be adapted for Year 7:
 
Fantastic free resources are available to order from the Met Office. The interactive weather presenting kit looks very flashy! 





Weather For Wiz Kids is a brilliant, colourful website that uses simple language and diagrams to define pressure systems and weather fronts, ideal for Key Stage 3 and 4. 





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