Comparisons Between November 1976 and the Present Pattern

Differences and comparisons between Nov. 1976 pattern and current predicted pattern for the 8-14 day period:

As I was doing research today during school on the ensemble forecasts for the next few weeks, as well as the analogues that the Climate Prediction Center puts out on a daily basis, I found an interesting trend. Nov. 1976 keeps appearing as one of the analog years.

So, I decided to do a comparison between the two.

First, the overall pattern for Nov. 1976 was one in which there was an enormous trough stretching from western Siberia to just south of the Aleutian islands. This is the type of trough that is currently being forecasted by ensemble guidance due to the influence of the incredible remnants of the super typhoon. Due to this influence on the global longwave pattern, I don't expect that this longwave trough will break down very quickly. And as long as this trough remains in place, the pattern will remain blocked and stuck, meaning that a mean trough will continue over Canada and the Central/Eastern United States.

THIS DOES NOT MEAN THAT THERE WON'T BE ANY PERIODS OF ABOVE NORMAL TEMPERATURES. It just means that the pattern will be dominated by bouts of Arctic air, and occasional waves of Pacific air [due to the fact that blocking won't be as prevalent as we would like it until the effects of the SSW become more prevalent].

Given that the longwave won't necessarily be locked in place across North America, I still expect quite a bit of volatility, meaning the potential for large temperature swings and major storm-systems [mainly cutters and possibly a Nor'easter].

As for other comparisons, the Western North American ridge is pretty much in the same location that it was in Nov. 1976. Given this, and holding other factors constant, I would not doubt that this will become a more permanent feature of the winter. But this is still rather uncertain [as there always with comparisons to past analogue years]. Blocking should also be slightly farther west than what occurred in 1976-1977, which may mean that the colder air may be positioned farther west than what one would normally expect in an El Nino-like pattern.

The only main difference is that the Canadian-vortex in Nov. 1976 seems to have been much stronger, but I don't doubt that the Canadian vortex that is forecast to drop into the United States sometime next week could be just as intense. I just don't expect the Canadian vortex to be as consistently strong as it was in '76.

Another difference is perhaps the fact that there was a lack of strong blocking across the poles. Based upon the mean 500 MB pattern from Nov. 1976, it appears that the PV was stronger across the poles, but this is more likely due to the fact that the Arctic regions were well below the 1981-2010 normal [average column temperatures] in comparison to today. I don't know if this will have any impact on the going forecast for late Nov. to early Dec. but it could be significant in terms of potential winter-storms, and Arctic outbreaks.