Activity 4 - Decision time!

To be prepared, the experts at the Centre for Emergency Situations now want to know what might happen if the volcano erupts sometime over the next few days.

Take a look at the ensemble weather forecast for three days time. If FitzRoy's Peak erupts then, draw where do you think the volcanic ash might go on each of the maps on page 4 of your worksheet.

Colour ensembles map

If people have to be evacuated from the island, which sea port do you think is most likely to be operational? Circle the answer on page 1 of your worksheet.

What is an ensemble weather forecast?

Weather forecasters run a computer model a number of times making small changes to the weather conditions at the start of the analysis. This is called an ensemble of forecasts. By comparing these different possible outcomes the forecaster can decide how likely a particular weather event will be. If the forecasts vary a lot then the forecaster knows that there is a lot of uncertainty about what the weather will actually do, but if the forecasts are all very similar they will have more confidence in predicting a particular event.

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Last updated: 14 March 2013