Page History

At inception around 2010, the extratropical extra-tropical cyclone diagrams (= "cyclone database" products) were generated using bitmap manipulation. As a result the products had a somewhat noisy/jagged visual appearance relative to many NWP products available nowadays (2021). In addition the software was proving costly to maintain. So in May 2021, and in close collaboration with the UK Met Office, ECMWF upgraded to a Python-based code suite, which applies the same graphical processing principles, but which saves the frontal objects in vector form and recreates fronts from those vectors wherever they are needed on a product. For these products this provides an aesthetically pleasing visual appearance, clearer rendering of details and a capacity to use transparency settings. In future this software change will also facilitate greater platform portability (e.g. for ecCharts, commensurate with user requests) and easier development of other product variants. During the upgrade a few other minor changes were applied, including correction of a pre-existing bug that affected the strike probability products. The main differences in output that resulted from these various changes are highlighted below, for user reference:

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Comparing the spots (=cyclonic features) between the two renderings on Fig8.1.15.1-1 we see some differences. In general the substantial features (large dots) are the same, whilst the other (small dot) features, that are innately weaker, are more liable to differ slightly. Differences are essentially random and relate to identification algorithm sensitivities. These algorithms can respond one way or another when one of the identifying thresholds required for feature acceptance is on the borderline of being met. Most thresholds relate to field values (e.g. computed thermal gradient), although one defines a minimum separation distance between features. One cannot say that one plot is better than the other. When looking at an ensemble (e.g. on dalmatian Dalmatian charts) such random differences will tend to cancel, and so are unlikely to change user interpretation (e.g. see Fig8.1.15.1-3)

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The look of the cyclone plume diagrams, and the track animations, accessible by clicking on a cyclone at T+0, have also changed in the new version, but the content and functionality are the same. The entry point for the cyclone database web products has also been upgraded, whilst retaining the same functionalities. Output images are now all in "png" format; previously most were "gif".

See the new Cyclone Database Products.

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