We've already have a few decent snow events this winter. The first was on December 1st. The second was Christmas Eve and Christmas Day, the snowiest Christmas Eve/Day since 1995. The National Weather Service here in Cleveland has a great summary HERE .
Now that we are a few days into January 2021, what does the current pattern tell us?
If you remember back on December 8th on my post, I mentioned the possibility of a GREENLAND BLOCK (red color) which would increase the possibility of cold and snow to finish out December.
MODEL animation from December 8 showing potential Greenland Block
It was too early at that point to say for certain that the mid-late December pattern would be a harbinger of what was to come in January. Now look at the animation below. See how the block (red color) near Greenland is staying in place. Also see how the western North America ridge (red colors) is starting to develop. This is a bigtime one-two punch: Ridge west (potential block) and a ridge (Greenland block) east.
The jet stream is trending MUCH stronger. Look at the warmer colors across the eastern US. East coast snow lovers will love this!
Top years with similar pattern shows below normal temperatures the 3rd week of January
So after watching the pattern over the last month becoming more persistent, as of this writing (January 4) all this seems to be foreshadowing more cold and deeper southern storm systems!
Some projections are starting to show this idea.
First 2 weeks of January snowfall
3rd week of January snowfall projection
What about the Polar Vortex? Are there indications this become more unstable in the weeks ahead? Absolutely.
Look at the surface map over Asia and the large surface high pressure.
Meteorologist Mike Adcock noted this on Twitter on December 28th: "Looking at 2100 UTC obs in Mongolia, Tosontsengel is reporting 1089.5 hPa. This station is the record-holder from 2001 (1084.8 hPa). Further, Tsetsen Uul (labelled w/ H) is reporting 1093.5 hPa (32.29"). These, along with other reports, if verified, would break the world record."
This Siberian high pressure ridge is very large. Its been locked in since last month.
Climate specialist Rick Thoman also noticed the abnormally low pressure near the dateline on December 30th: "The GFS is all in for the deepest cyclone in a long time in or near Alaska waters. I've listed the four storms since 1975 that I know of with an analyzed minimum pressure below 930hPa".
The jet stream has been extremely strong off of Asia east into the northern Pacific which probably enhanced the storm above around New Years Eve. Notice the up and down jet across North America.
What does this have to do with the Polar Vortex and the potential for cold for the eastern US?
The super-high pressure center over Mongolia if located just right creates friction along the Mongolian Mountains. This process creates atmospheric waves that propagate into the stratosphere! The mountains change the pathway so that these waves can significantly weaken the stratospheric jet stream. This can cause warming events at the top of the atmosphere called Sudden Stratospheric Warming events. When these occur, its just a matter of time before the "top-of-atmosphere warming" creates a weakening of the jet stream closer to the surface in the northern latitudes along with expansion of cold around the north pole. A weaker polar jet stream means the Polar Vortex can move south easier.
See how the temperatures have jumped recently in the stratosphere
Also notice how the wind direction made a big directional change
Here is great tutorial on how this all fits together.
It doesn't happen overnight. Its usually weeks down the road.
See how the cold reloads across western Canada and then drains into the central US by the 20th?
Expect our chances for MORE wetter snows second half of January!
