UPDATE (15 Oct 2020):

• Early in 2020 the test products described below (i.e. charts) became operational, and the charts were then replicated on the ECMWF forecasts web page.
• On 7th October 2020 ECMWF opened up all of its forecast web charts for free access, worldwide, with the aforementioned products now being accessible at the following links:
  Early warning for cold spells over Europe (Extended Range) / Trajectories (Medium Range)
  Stratospheric sudden warning
  Weather regimes extended range forecast
• The previous links, highlighted below, are now being discontinued. So please update your bookmarks to use instead the links listed above.
  
  

From time to time ECMWF develops new forecast products to help users interpret the ECMWF model outputs. As part of the development process, potential products may be made available in test mode. This allows users to provide feedback on the usefulness of the product and helps to ensure that the final product meets the users’ needs.

Please note that test products provided here are for a limited time, and are not operationally supported, although ECMWF makes best efforts to ensure they are routinely available. These products should not be relied on for operational use. Note that in general the test products are available only in graphical form and do not follow the official release time schedule of forecast data.

ECMWF welcomes feedback on these test products – please provide your feedback in the comment panel at the bottom of the relevant product page.