I posted this before
I think the turning point came in March 2008, when northerly blocking started to become prevalent than it had been for a long time.
17 below 1971-2000 average months before March 2008 in 7 years but 37 in less than 6 years from March 2008
Months below the 1971-2000 average since January 2001
Jun 2013: 13.6 (-0.5)
May 2013: 10.4 (-0.9)
Apr 2013: 7.5 (-0.6)
Mar 2013: 2.7 (-3.6)
Feb 2013: 3.2 (-1.0)
Jan 2013: 3.5 (-0.7)
Dec 2012: 4.8 (-0.3)
Nov 2012: 6.8 (-0.1)
Oct 2012: 9.7 (-0.7)
Sep 2012: 13.0 (-0.6)
Jul 2012: 15.5 (-1.0)
Jun 2012: 13.5 (-0.6)
Apr 2012: 7.2 (-0.9)
Feb 2012: 3.8 (-0.4)
Aug 2011: 15.4 (-0.8]
July 2011: 15.2 (-1.3)
June 2011: 13.8 (-0.3)
Jan 2011: 3.7 (-0.5)
Dec 2010: -0.7 (-5.8]
Nov 2010: 5.2 (-1.7)
Oct 2010: 10.3 (-0.1)
Aug 2010: 15.3 (-0.9)
May 2010: 10.7 (-0.6)
Mar 2010: 6.1 (-0.2)
Feb 2010: 2.8 (-1.4)
Jan 2010: 1.4 (-2.8]
Dec 2009: 3.1 (-2.0)
Jul 2009: 16.1 (-0.4)
Feb 2009: 4.1 [-0.1]
Jan 2009: 3.0 [-1.2]
Dec 2008: 3.5 (-1.6)
Oct 2008: 9.7 (-0.7)
Sep 2008: 13.5 (-0.2)
Jul 2008: 16.2 (-0.3)
Jun 2008: 13.9 (-0.2)
Apr 2008: 7.9 (-0.2)
Mar 2008: 6.1 (-0.2)
------------------------------------ a turning point
Dec 2007: 4.9 (-0.2)
Aug 2007: 15.4 (-0.8]
July 2007: 15.2 (-1.3)
Aug 2006: 16.1 (-0.1)
Mar 2006: 4.9 (-1.4)
Feb 2006: 3.7 (-0.5)
Dec 2005: 4.4 (-0.7)
Nov 2005: 6.2 (-0.7)
July 2004: 15.8 (-0.7)
Dec 2003: 4.8 (-0.3)
Oct 2003: 9.2 (-1.2)
Feb 2003: 3.9 (-0.3)
Oct 2002: 10.1 (-0.3)
Jul 2002: 16.0 (-0.5)
Dec 2001: 3.6 (-1.5)
Sep 2001: 13.4 (-0.3)
Apr 2001: 7.7 (-0.4)
Mar 2001: 5.2 (-1.1)
Jan 2001: 3.2 (-1.0)