Table 1: Description of blocking events: name, date of event / longevity, and blocking intensities (BI) from observed data. BI was calculated using Eq. (1). In the name, intensity is identified as weak (W) or strong (S), season as warm (W) or cold (C), and region as Atlantic (A) or Pacific (P).

Event	Location (at onset)	Date / Longevity	Observed BI
1 (WWA)	Atlantic (50o N 20o E)	1200 UTC 23 Jun - 0000 UTC 8 Jul 2016	2.46
2 (WWP)	Pacific(50o N 165o E)	0000 UTC 27 Aug - 0000 UTC 4 Sep 2016	1.99
3 (SCA)	Atlantic (55o N 0o)	0000 UTC 3 - 0000 UTC 27 Oct 2016	3.94
4 (SCP)	Pacific (50o N 160o W)	0000 UTC 23 Feb - 0000 16 Mar 2017	4.51