On today’s written post I want to take a look at past sudden stratospheric warming events since we may have one on the way for next month.
Most if not ALL SSWE’s (sudden stratospheric warming events) are triggered during east QBO winters. Notice in the below chart we had a strong west QBO winter which meant no North Atlantic/Greenland blocking and so a fast flowing jet stream was unimpeded crossing due west to east into Western Europe. and we’re heading deep into one just now.
A lot of the reason for a cold US winter last year was down to warm water in the NE Pacific Ocean. That’s where we saw the strat warming and therefore all the cold got driven out of the arctic into North America.
Credit: AccuWeather Pro
Yes we did see strat warming last winter but on the other side of the pole from us hence the cold North America but warm Europe winter!
The QBO is east and since the record or near record N Asia snow cover in October, the strat warming has started off fast and earlier than usual, likely down to the vast early season snow pack.
Via Anthony Sagliani
It’s thought that this INCREASED coverage of snow, early is what’s started the early warming of the stratosphere directly above!
Not always, but in some years with all the above, the persistent pushing and pressurising of the warming on the polar vortex will break the dam AS WE HEAD INTO WINTER. Look at the below example and note the timeframe. A true SUDDEN STRATOSPHERIC WARMING EVENT doesn’t happen until winter but the warming begins during early autumn or even late summer over Siberia and this was what sparked the cold outbreaks of 1985, 2009, 2010 and even 2013.
We pretty much need an east QBO and we have it. We also need to wait 9 times out of 10 until December when the mid-latitudes cool and snow cover grows further, afterall it would appear that the snow cover itself may have started this strat warming in the first place.
We’re all jumping too fast I think (myself included) and if it does happen, which I believe there’s a good chance, it’s unlikely to occur till early or mid December and we’ll see it’s effects later December!
While I want to see more before shouting for cold here, all of the ‘build-up’ through October into November across the hemisphere and what we’re seeing with the central to west based El Nino, near perfect North Atlantic SST profile and up in the stratosphere cannot be ignored.
Pay attention to the below examples. Two major ones… 1984 into 85 and 2009 into 10. Notice how both see a ridge over the UK RETROGRADE WESTWARD out over the Atlantic and Greenland while warming strats over SIBERIA and sweeps across the northern hemisphere. Notice that it starts in N Asia and spreads east. We’re seeing the warming there now. Will be watching the modelling closely because we may all of a sudden see the appropriate warming on our side of the pole early next month and if so, look out!
That ridge retrograding from the UK (we almost have that in place NOW) backing WNW into the Atlantic and Greenland in the below examples means the Siberia high expands dramatically and pushes east to west. The dam breaks and our coldest weather which has been building over the vast snow fields of northern Asia is released.
Noteworthy sudden strat warming events of the past.
500mb perspective
1984-85
2009-10
Another nice view of the SSW back in 2009
We also saw an SSWE in December 2012 into 2013.
Graph shows the warming.
Animation of the Dec 2012 example.
CURRENT graphs show a warming trend… These suggest warming in the more crucial mid and low levels of the stratosphere!
50hpa
70hpa
Notice in both SSWE examples above that there’s two positives, one over either Scandinavia or the UK and the other over Alaska or Siberia which join by crossing the pole. These are aspects we should be watching closely for clues in the current situation.
No video today.
Next update will be Monday morning.
Have a great weekend.
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