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Using clustering will highlight the clusters when plotting the ensemble members in each cluster in the plots.

In this exercise you will:

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Warning

Always use the eof.mv first for a parameter and ensemble forecast (e.g. ens_oper or ens_2016) to create the cluster file. Otherwise the cluster_to_an.mv and other plots with clustering enabled will fail or plot with the wrong clustering of ensemble members.

Panel
titleCompute EOFs and clusters

Edit 'eof.mv'

Set the parameter, choice of ensemble and forecast step required for the EOF computation:

Code Block
param="z500"
expId="ens_oper"
steps=[2012-09-24 00:00]

Run the macro.

The above example will compute the EOF of geopotential height anomaly at 500hPa using the 2012 operational ensemble at forecast step 00Z on 24/09/2012.

A plot will appear showing the first two EOFs (similar to Figure 5 in Pantillon et al.)

The geographical area for the EOF computation is: 35-55N, 10W-20E (same as in Pantillon et al). If desired it can be changed in eof.mv.

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borderColorred

Q. What do the EOFs plotted by eof.mv show?
Q. Change the parameter used for the EOF (try the 'total precipitation' field). How does the cluster change?


 

Panel
titlePlot ensemble and cluster maps

As described in task 1, use the cluster definition file computed by eof.mv to the plot ensembles and maps with clusters enabled.

 

From Figure 7 in Pantillon et al. we see that cluster 1 corresponds to a cutoff low moving eastward over Europe and cluster 2 to a weak ridge over western Europe. Cluster 1 exhibits a weak interaction between Nadine and the cut-off low over Europe. In cluster 2, there is a strong interaction between the cutoff and Nadine in which Nadine makes landfall over the Iberian penisula.

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Excerpt Include
Credits
Credits
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Introduction

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. A key question is how uncertainty from the initial data and the model parametrizations impact the forecast.

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