Products from the upgraded system will be made available on 3 December 2010 in the following way:

• Products with an issue date of November 2010 will be removed and replaced with equivalent products from the upgraded system;
• Products for all future dates will be derived from the upgraded system until further notice;
• Forecasts issued with the former system prior to November 2010 will remain in place on the website;
• Corresponding changes will be made to the verification information.

The main changes made to the GloSea4 system are listed below:

• Improvements to the coupled-model (HadGEM3) physics, including a scheme to assimilate sea-ice concentrations: sea-ice in both forecast and hindcast mode, is now initialised from observed values rather than climatology;
• Improvements to the model resolution for both the atmosphere and ocean components: the new atmosphere resolution is ~120 km in the horizontal and 85 levels (improving resolution of the stratosphere); the new ocean resolution is 1 ° and 75 levels. The ocean-atmosphere coupling frequency is 3 hours;
• The hindcast period used has been updated to a more recent period, 1996 to 2009.