I've been analysing today's 0Z GFS and ECM ensembles to see what they show for the 850mb temperature for SE England for 31st January. The GFS ensemble has 32 members if you include the Op and Control. The ECM ensemble has 51 including the Op (discounting Control, as it seems to be broken, the 850mb temp. being shown as identical to the Op throughout the run).
GFS: Op -9.1 Avg. -5.2 >0 2 -5 to 0 16 -10 to -5 10 -15 to -10 4
ECM: Op -6.0 Avg. -3.6 >0 8 -5 to 0 27 -10 to -5 13 -15 to -10 3
So the ECM ensemble for 31st Jan is a good deal warmer than the GFS. But for both ensembles, around 50% of the members are in the -5 to 0 range: 16 out of 32 for the GFS and 27 out of 51 for the ECM. The GFS has 14 members (almost 50%) being colder than -5, but the ECM has only 16, so only about one-third.
Originally Posted by: jhall