Siberian Snow Cover a Big Factor In Winter Predictions

I briefly mentioned in a post last week that there has been extensive research at MIT by a individual named Judah Cohan that suggests the amount of snow cover over Siberia in the fall months especially October is usually a precursor to the temperatures of the United States during winter. The main reason being that the increased snow cover strengthens the Siberian High pressure which results in high level warming over the stratosphere which ultimately breaks up the polar vortex (coldest weather in the Northern Hemisphere) and displaces it further to the south near the US. 

Looking at current snow conditions over Siberia we are running above normal. In fact September snow cover was 9th most recorded on record for Eurasia. Here is a graphic showing current snow cover..

As you can see most of Siberia is covered in snow which is a good sign if you want cold air for winter. To take it a step further Cohan developed a model to project what the winter temps would look like based on Snow Cover, here was last years forecast..

Here were actual temps for last year..

Pretty impressive accuracy and the main component as i mentioned is snow cover. 

With all of this being said there is a factor that needs to be mentioned that can counteract this above average snow cover and it is a pattern called the quasi-biennial oscillation (QBO). In simple forms this is a weather pattern that represents easterly and westerly zonal winds over the extreme altitudes of the equator.  When the westerly's propagate downward from the stratosphere it tends to favor less high pressure over Greenland and the Arctic. When this is in its opposite easterly phase more blocking is favored.

Right now we are in a westerly QBO which does not favor blocking to the north which is essential for an active winter. Here is what westerly QBO years have looked like..This graphic shows the correlation. Blue and purple colors are a negative correlation meaning a west QBO results in low pressure not high pressure over the Arctic. 

As you can see a west or positive phase QBO results in a negative pressure correlation to the north (low pressure) and a positive correlation to the south (high pressure, warm conditions.) However, with above normal snow cover, low solar activity, very weak warming in the El Nino region and model projections for this winter, which all favor blocking, there are a lot of moving parts to look at. Before I release my final winter forecast (coming within a week) I want to figure out which of these factors have been most dominate over the last few decades.