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Please refer to the handout showing the storm tracks labelled 'ens_oper' during this exercise. It is provided for reference and may assist interpreting the plots. Each page shows 4 plots, one for each starting forecast lead time. The position of the symbols represents the centre of the storm valid 28th Oct 2013 12UTC. The colour of the symbols is the central pressure. The actual track of the storm from the analysis is show shown as the red curve with the position at 28th 12Z highlighted as the hour glass symbol. The control HRES forecast for the ensemble is shown as the green curve and square symbol. The lines show the 12hr track of the storm; 6hrs either side of the symbol. Note the propagation speed and direction of the storm tracks. The plot also shows the centres of the barotropic low to the North. Q. What can be deduced about the forecast from these plots?
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So far we have been looking at reducing the information in some way to visualise the ensemble.
To visualise all the ensemble members as normal maps, we can use stamp maps. These are small, stamp sized contour maps plotted for each ensemble member using a small set of contours.
There are two icons to use, stamp.mv and stamp_diff.mv. Plot the MSLP parameter for the ensemble. Repeat for wind field.
Q. Using the stamp and stamp difference maps, study the ensemble. Identify which ensembles produce "better" forecasts.
Q. Can you see any distinctive patterns in the difference maps? Are the differences similar in some way?
If time:
Use the macros to see how the perturbations are evolving; use ens_to_an_diff.mv to compare individual members to the analyses.
Find An additional exercise is to find ensemble members that appear to produce a better forecast and look for where the initial forecast differences are significant.to see how the initial development in these members differs. Start by using a single lead time and examine the forecast on the 28th.
- Select 'better' forecasts using the stamp plots and use ens_to_an.mv to modify the list of ensembles plots. Can you tell which area is more sensitive in the formation of the storm?
- use the pf_to_cf_diff macro to take the difference between these perturbed ensemble member forecasts from the control to also look at this.
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Use 'mapType=1' to see the larger geographical area (please note that due to data volume restrictions, this mapType only works for the MSLP parameter). |
Task 5: Cumulative distribution function at different locations
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