More stuff from Larry... October 31 will be the last day for the Snow Advance Index (SAI) and were on a pace to end up maybe 3rd or 4th. Snow cover extent in Eurasia doesnt correlate as well as the snow cover advance index. The idea is that the speed/advancement of the snow cover in October can determine the AO for the winter since the snow cover creates a feedback with the polar vortex and weakens it, thus allowing the AO to be more negative, which means colder air farther south. This is only one piece of the puzzle though. Related to this: Year: Oct. highest SCE increases/DJF AO *1976: 16.75/-2.6 (2nd lowest DJF AO since 1950)(Nino) *2009: 15.5/-3.4 (lowest AO)(Nino) 2012: 14.75/-1.1 1970: 13.7/-0.5 *1968: 13.6/-2.3 (3rd lowest AO)(Nino) 2003: 13.5/-1.0 Note the top three most negative DJF AOs being among the top five (of 46) and also being Ninos. Because it is very roughly already nearing 13.5, 2014 is at a pace that could very well get it to 14-15 as of 10/31 (assuming not much meltback due to the expected continued intense cold through 10/31), which would put it in 4th place or even 3rd! Assuming we get the Nino, a top 3-4 for 2014 would seemingly favor a strong -AO for DJF based on these stats and Cohens theory behind it. These numbers suggest that another rare sub -2 DJF AO wouldnt at all be out of the realm of reasonable possibilities.
Posted on: Sun, 26 Oct 2014 11:03:39 +0000