Ntxw wrote:Being that winter is only 5 more months away, I'm sure others here are anxious to know what to look for the next few months that could give us the slightest inkling of what may be. For today, I'm going to start with the EPO or East Pacific Oscillation.
Last winter we were privileged to witness this oscillation at it's best. Ignored for years we finally came into conclusion that it has a tremendous influence. Back in October and November we saw the signs of this signal telling us what it would do the whole winter even at the face of a strong +AO/NAO and unfavorable PNA. For years we have come to think the AO releases cold air and used to far too deeply on determining outbreaks. While this is a good start it does not always direct it towards our neck of the woods (Texas) for this you need the -EPO. Without it the -NAO that usually accompanies -AO (the two are closely related) will flush it across to Europe and Asia while the Pacific sends in mild air.
Here are some examples for two decades that were very different from other, AO/NAO that are not too much of influence long scale but the EPO has glaring differences.
1980s were a very cold decade dominated by anomalous -EPO
1990s were a much warmer decade with predominately +EPO
And then even on a seasonal scale the differences are drastic
Winter of 2011/12's +EPO dominance
Last winter -EPO dominance
As the days grow shorter, I'm sure all of us will be keeping a close eye on the Pacific Ocean and what it may do, McFarland gave us a good standard to this oscillation but more is needed to understand it, most severe Arctic outbreaks in Texas can be traced back to the EPO. One eye will be on the tropical Pacific for El Nino the other on the North Pacific for blocking. Of course unless you are a certain met heat miser from Houston.
The January/February 1951, December 1983, February 1989, and most recent ones occurred in negative EPO or North Pacific Oscillation (NPO). The 1951, 1983, 1989, and 2014 had mostly positive NAO. It shows that negative NAO is not necessary to have freeze. EPO is just as an important factor. I think EPO is overlooked a lot and NAO gets more attention. NAO is closer to America than EPO is, as it is over Alaska. EPO is the Pacific version of NAO.