Nice post long range post and analysis showing the return of some cold air late in January. I wanted to share it because it highlights a cold shift in the pattern over the next few weeks and why I have drown-on about the MJO and climate teleconnections so much... like in my previous post: https://facebook/MeteorologistOceanographerDavies/posts/630490680331703 Understanding state of large atmospheric forcing patterns like the MJO (in this instance), ENSO, or PDO can help Meteorologists figure out if the model projected pattern, like the one shown nicely here by Justin Berk, Meteorologist, make sense. In this case, I believe it does. Here is the science behind WHY: A study by Moon et al., 2012 showed back during the Snowmagedon winter that when MJO was in phases 7 or 8, there was a deep ridge in the western U.S. (+ Pacific/North American Oscillation (PNA) perhaps? ... or ... +Tropical/Northern Hemisphere Oscillation (TNH) like it appears we are in now) and trough in the eastern U.S. At low- and mid-levels. Under this scenario, cold air could be pumped in from Canada via a dipole in the pattern with a High in the West and Low in the Eastern North American continent. This is in concert with the increasingly negative Arctic Oscillation (AO). Speaking of AO, a paper by LHeureux and Higgins (2008) showed that the MJO has a statistical impact on the Arctic Oscillation (AO) when it is in phases 7 and 8. Those phases are correlated with -AO which we all know tends to result in more cold air and blocking. Ive mentioned both of these papers early this winter, but they are good and are worth continually mentioning! -- SUMMARY: In this case since the GFS Ensembles are predicting a Phase 7 MJO, the pattern the model projects makes sense to me. If this model solution verified, it would drive some really cold air into the Eastern U.S. at the end of the month/early February. An additional note: The on-going +TNH pattern (which Wxrisk has been continually noting) with a strong ridge over Alaska and western Canada will also help drive the northern jet further south... particularly if that ridge out west continues to amplify such that it can join or connect with a ridge over eastern Europe/Western Russia. This would mean the cold air associated with the polar vortex in the upper levels of the atmosphere would have no where to go except digging south... into southeastern Canada and the northern tier of the United States. This would be consistent with the amplified pattern we have seen thus far.
Posted on: Fri, 17 Jan 2014 19:11:16 +0000
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