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In these exercises we will look at a case study of a severe storm using a forecast ensemble. During the course of the exercise, we will explore the scientific rationale for using ensembles, how they are constructed and how ensemble forecasts can be visualised.

You will start by studying the evolution of the ECMWF HIRES forecast analyses and ensemble forecast forecasts for this event. Then you You will then run your own OpenIFS forecast for a single ensemble member at lower resolutions and work in groups to study the OpenIFS ensemble forecasts.

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titleCaveat

In practise many cases are aggregated in order to evalute evaluate the forecast behaviour of the ensemble. However, it is always useful to complement such assessments with case studies of extreme events, like the one in this exercise, to get a more complete picture of IFS performance and identify weaker aspects that need further exploration.

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Recap

Key points

  • Sources of forecast uncertainty: initial analysis and model error.
  • Initial analysis uncertainty: sampled by use of Singular Vectors (SV) and Ensemble Data Assimilation (EDA).
  • Model uncertainty: sampled by use of stochastic processes. In IFS this means Stochastically Perturbed Physical Tendencies (SPPT) and the spectral backscatter scheme (SKEB)

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titlePlot analyses in various layouts

Icon 'an_1x1.mv' produces a single plot on the page.

Icon 'an_2x2.mv' can produce up to 4 plots per page.

 

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titleChange plot contentsfields

For the 'an_1x1.mv' icon, the plot contents can be changed by editing the plot1 variable in the macro. By default the 10m wind is shown.

To alter the plotted field, right-click and choose 'Edit'.

It is possible to overlay multiple fields like this:

You will find a list of available parameters in the macro.

After editing the macro text, you can optionally save using the 'File' menu and 'Save'.

Display the plot by clicking:

Animate the plots in the display window by clicking

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titleChange plot layoutappearance

 The number of maps appearing in the plot layout can be 1, 2, 3 or 4.

Macro an_2x2.mv demonstrates how to plot a four-map layout in a similar fashion to the one-map layout. The only difference here is that you need to define four plots instead of one, .

Right-click on the icon and select 'Edit'. Change the plot layout like this:

Two map types are available covering a different area.

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With mapType=0, the map will cover a smaller geographical area centred on the UK.

With mapType=1, the map will cover most of the North Atlantic

 

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Task 2: Visualise operational HIRES forecast

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