[Winter 2017 2018 General Discussion]

Someone on TWO mentioning that active hurricane season years are more likely to see significantly colder Decembers. Interesting. Here's hoping. 

[Winter 2017 2018 General Discussion]

6 minutes ago, Catacol said:

Yep - I dont understand his logic there at all. Background warmth may well modify cold airstreams a bit, but it will mean absolutely nothing if we get a long fetch easterly or trough dropping in from the north. It will still be cold, and cold enough for snow. As far as I am aware potential for vortex disruption and a meridional jet shape is unaffected by "background warmth" so his argument is nonsense.

Also what I thought - 1 degree or so ain't gonna do much to an ice day. Unless he's more refering to the Arctic being warmer the last few years, and even then, as you say continental shouldn't be affected. 

[Greenland Blocking Temperatures in winter]

A true greenland block that we haven't seen for a while, I was wondering what are the rough maximum temperatures (with Arctic temperatures at normal) you'd expect in each month of the year they happen? In, say, Manchester, roughly middle of country.  

To start, I'd guess 8-9 degrees in late October, 6 degrees in early-mid November, 2 degrees in Early December (was that the rough maxima in December 2010? And mainly ice days from mid December to Mid February?

I guess, the main point, I'm making through this, is at what point does extensive northern blocking become "useful". No longer what some would call a waste. That which will give a decent week long snow event, not a morning of wet snow like in late October 2008 (I think it was 08). Can anyone remember a week long snow event in Mid November from extensive northern blocking centred on Greenland?

 

[Model Output Discussion 01/09/17]

2 minutes ago, Mucka said:

Let's see if we can get the block into Greenland as programmed.

4-6 degrees projected in this far out scenario. What would such a block give a month later, ice days?

[Will This Winter be like 1947 / 1963 ?]

I was struggling to find stratospheric archives, but from what I could see the only really good match on the other conditions is 1996-1997. A winter with a cold December (2.9), and a cold January (2.5). 1956-1957 seems to have been after the solar minimum, not before. For what it's worth, that winter was mild. Though there was a white christmas in places. 

[Will This Winter be like 1947 / 1963 ?]

The state of the Arctic accepted, there are some potentially interesting parallels to 1962-1963.Adding to what has already been written.

ENSO 1963: ENSO neutral in 1963 verging on weak La Nina. http://ggweather.com/enso/oni.htm

ENSO 2017: Uncertain. Forecasts range from ENSO neutral verging on weak La Nina, to Moderate La Nina

QBO 1963/2017: Both easterly QBO.

Solar activity 1963/2017: Both winters taking place in the low part of the solar cycle

Stratosphere 1963: From my understanding Canadian warming and subsequent weakening of vortex in early winter 1962.

Stratosphere 2017: Zonal wind plot forecasts suggesting polar vortex may start the season weaker than average. http://www.atmos.albany.edu/student/hattard/realtime.php

So, there you have it, La Nina could go moderate and render the parallels to 1963 obsolete, the polar vortex could suddenly ramp up strength after a promising start like last year, but interesting nevertheless. How many winters in the last 100 years have met 1963 on all the above conditions?

I am a believer in nature "balancing itself out", as it were, and with our recent mild winters streak, and drought in Spain,  feel perhaps a winter with lower pressure over Europe is due. I think 1962/1963 gave something like 300% of usual rainfall to parts of the Iberian Peninsula (as did 2009/2010)  

[Climate change study at Cambridge Bay, Resolute and Eureka, NU, Canada (1940 to 2022)]

so if causes are like soot are a big contributor, would the amount of soot eventually hit a ceiling, and the rate of arctic ice decrease start to slow down, as "just AGW" becomes the main forcing contributing to further ice loss? Assuming industrialisation, coal etc, in Asia has hit a plateau, and feedbacks don't cause runaway melting.

[Model output discussion - 5th December 2016 - Into Winter we go]

15 minutes ago, Nouska said:

For anybody not sure what a negative EPO ridge is, an illustration.

https://www.theweathernetwork.com/news/articles/epo-what-you-need-to-know/43796/0

Similar to the PNA pattern but more focus on the EPAC rather than CONUS.

Add a strong wave2 from Eurasia and the vortex is squeezed down over us - in theory.

In practice - a good example December 2010.

Very interesting. Thanks for that. So if the scandi heights can hold on... Plus what has been mentioned about possible MJO activity, and angular momentum, then I guess potentially interesting times. I  recall someone with a lot more knowledge than me - I think Tamara? - saying as well what happens if a spike is put into a vortex which has rapidly intensified in a short period of time. Something about the higher they go, the higher they fall perhaps. Here's hoping - from a cold perspective. Also those composites from Gp earlier. hmmm...

Edit: If angular momentum can just stay around neutral, that could help make things more interesting. As Singualrity has pointed out its not falling as quickly as predicted. I suppose the current models are conditioned on the fall in angualr momentum occuring as predicted. 

[Model output discussion - 5th December 2016 - Into Winter we go]

9 minutes ago, Geordiesnow said:

Chances for such deep lows is definately a possibility and one to keep an eye on, ignoring any potential impacts regarding xmas, as a weather enthusiast, I would love if a deep low does occur, it is winter after all, deep lows are common and lets be frank, snow impacts looks very unlikely.

Got to say though, I am very dissapointed what the models are hinting at regarding the strengthening of the Northern arm of the jet which in turn looks like it will push away that cold PV over Western Russia and we get mild SW'lies blasting right through there. What we are seeing is by far the worse possible weather pattern you can get if your hoping for cold because its going to be well above average well to both our North and East and you get a situation where there is barely anything significant cold air on our side of the Arctic.

So its a case of looking North and West for any cold air to head our way and have some more in the way of moderated chilly airmass whereever we are on the cold side of the jet. In summery, significant snow looks a very long way from heading this way.

Though some may disagree, if the russian high can cling on a little bit, warm 850s can get pushed into the arctic, then that can be a trigger for the wave 2 action, as mentioned by GP in strat thread. Hopefully such wave 2 action could push back against the downward propagation of insanely high zonal winds. Also of note Anthony Masiello on twitter mentioned that we're in a - EPO state? Which apparently couples well with wave 2 action when it comes to impacts. Seeing the insane push of "green" 850s into the arctic could lead to colder impacts down the line. 

Edit: The more directly that warm air can go into the arctic, the less the siberian cold pool will be pushed back - I think.

[The Seasonal Forecast Thread]

I think Roger Smith deserves a few kudos for his winter forecast. Not entirely accurate, but certainly predicted after new year storminess, along with mid January cold spell. Will the super cold February materialize?