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The SUBS-M-Climate is derived from a set of sub-seasonal range re-forecasts created using the using the same calendar start dates over several years for data times either side of the time of the sub-seasonal ensemble run itself.  The re-forecast runs are at the same resolution as the sub-seasonal medium range run (currently 36km) and run over the 46-day sub-seasonal range ensemble period. 

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Re-forecasts are made every two days during each month on 1/3/5/7/9/11/13/15/17/19/21/23/25/27/29/31 (excluding 29 February).  These are the rethe re-forecast base-dates for sub-seasonal range.

The set of re-forecasts for the SUBS-M-climate is made up from:

• a set of nine consecutive re-forecasts using the same calendar start dates for each of the last 20 years.nine consecutive re-forecasts (each covering a period of 45 days).  The middle one corresponds to the re-forecast date that is the same as, or immediately preceding, centred on the M-climate base date and covering a forecast period of 15 days.  The middle re-forecast corresponds to the closest base-date preceding the actual ensemble run date. each (If the actual ensemble run date is the 20th of the month, then the re-forecast base-date is the 19th and the other re-forecasts are for 11th, 13th, 15th, 17th, 21st, 25th, 27th, 29th). 
• re-forecasts are derived by re-running is formed from an 11-member ensemble (1 control and 10 perturbed members) .using the same calendar start date for each of the last 20 years.

Thus there are 20 years x 9 re-forecasts In total, each set of re-forecasts consists of 20 years x 9 runs x 11 ensemble members = 1980 re-forecast values.    These are available at forecast intervals of 6 hours for each forecast parameter, for each forecast lead-time and for each calendar start date and location.  They are used to define the SUBS-M-climate.  

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