Winter 2012 / 2013 Part 2

[gottolovethisweather]

Agreed. The fact that it is not even October and that it is in the depths of FI, which we all know to be unreliable, means there is a minimal chance that what we are seeing will win hands down and will dominate the coming winter.

The best indicator of how strong the PV will be is by looking at the NAO. The NAO measures the difference in strength between the Icelandic Low and the Azores High. If it is forecast to be positive, you can expect above average heights to South (i.e. the Azores High), and below average heights to the North (i.e. the Icelandic Low), and as a result, you see a strong polar vortex, as the difference in pressure between the two pressure systems becomes larger, and thus the Jet Stream becomes more powerful and westerlies prevail. Basically, in a period of positive NAO, our normal zonal pattern prevails as a result of the strong PV.

At the moment, the NAO is forecast to stabilise at around neutral, which is why the GFS might be seeing this.

A very strong PV isn't likely to happen unless we see a strongly positive NAO. Apparently the GFS tends to naturally bring in milder air at the end of its runs anyway, or so I've heard.

Many Thanks for this post, snowstorm, a true breath of fresh air.

Aside from your post and a couple of others, the last twenty posts almost had me bored to tears.

Please, no more name calling, let's discuss what could be the build up to the infamous 2012/2013 winter. The only problem being, thanks to the Daily Express, the truth is out there, just a shame they're eight weeks early.

Edited September 30, 2012 by gottolovethisweather

[Methuselah]

Agreed. The fact that it is not even October and that it is in the depths of FI, which we all know to be unreliable, means there is a minimal chance that what we are seeing will win hands down and will dominate the coming winter.

The best indicator of how strong the PV will be is by looking at the NAO. The NAO measures the difference in strength between the Icelandic Low and the Azores High. If it is forecast to be positive, you can expect above average heights to South (i.e. the Azores High), and below average heights to the North (i.e. the Icelandic Low), and as a result, you see a strong polar vortex, as the difference in pressure between the two pressure systems becomes larger, and thus the Jet Stream becomes more powerful and westerlies prevail. Basically, in a period of positive NAO, our normal zonal pattern prevails as a result of the strong PV.

At the moment, the NAO is forecast to stabilise at around neutral, which is why the GFS might be seeing this.

A very strong PV isn't likely to happen unless we see a strongly positive NAO. Apparently the GFS tends to naturally bring in milder air at the end of its runs anyway, or so I've heard.

But what's the cause and what's the effect? Could it not be said that the NAO is only a statistical reflection of the relative, respective strengths of the PV and the AHPZ?

[snowstorm445]

But what's the cause and what's the effect? Could it not be said that the NAO is only a statistical reflection of the relative, respective strengths of the PV and the AHPZ?

That's what I meant. The NAO is only supposedly a reflection of this, and it is only really an indicator of the difference in pressure between the Azores High and the Icelandic Low. And since it is predicting a neutral NAO for the coming fortnight (its predictions tend to be quite accurate), we can expect fairly normal westerly patterns but not very strong ones. If it was negative, we would be seeing a weak JS, and blocking highs could build in. In a positive NAO, the JS would be very strong, and there would be little if any chance of anything beyond a strong zonal pattern. If its neutral, however, it is highly doubtful that there would be either a very strong polar vortex or very weak vortex; more likely normal conditions for this time of year.

[gottolovethisweather]

But what's the cause and what's the effect? Could it not be said that the NAO is only a statistical reflection of the relative, respective strengths of the PV and the AHPZ?

I don't know, but taken alone as one of the stepping stones, it does provide us with right ingredients. Of course, that is where my own knowledge ends. The expertise comes from where an individual can link together all these factors and then produce an accurate forecast. Until I pick up the textbooks or read the many papers out there, my head hurts at the prospect of learning............................................................ STRATOSPHERIC WARMINGS, SOLAR CYCLES, MOUNTAIN TORQUES, ENSO'S, NAO'S, AO'S. MJO'S, J-LO'S. the list is endless.

Anyway Rybris, after all my rambling, what do you think about it all? For now, I'll have a Magners on ice and chill before the real chill begins.

[Methuselah]

I don't know, but taken alone as one of the stepping stones, it does provide us with right ingredients. Of course, that is where my own knowledge ends. The expertise comes from where an individual can link together all these factors and then produce an accurate forecast. Until I pick up the textbooks or read the many papers out there, my head hurts at the prospect of learning............................................................ STRATOSPHERIC WARMINGS, SOLAR CYCLES, MOUNTAIN TORQUES, ENSO'S, NAO'S, AO'S. MJO'S, J-LO'S. the list is endless.

Anyway Rybris, after all my rambling, what do you think about it all? For now, I'll have a Magners on ice and chill before the real chill begins.

What do I think, G? Perhaps I should stick to the vodka!

[Excitable_Weatherwatcher]

20 days of the winter tread and soon we will be on the 2nd overflow. winter is a very popular subject.

[gottolovethisweather]

What do I think, G? Perhaps I should stick to the vodka!

Vodka and cider enduced weather forecasts might be the way to go. Perhaps that's how the Arctic Blast forecast for early October made it into the papers.

Back to lurking for me, as I could be derailing the thread.

Edited September 30, 2012 by gottolovethisweather

[gottolovethisweather]

20 days of the winter tread and soon we will be on the 2nd overflow. winter is a very popular subject.

It always gets people talking.

Edited September 30, 2012 by gottolovethisweather

[bobbydog]

That's what I meant. The NAO is only supposedly a reflection of this, and it is only really an indicator of the difference in pressure between the Azores High and the Icelandic Low. And since it is predicting a neutral NAO for the coming fortnight (its predictions tend to be quite accurate), we can expect fairly normal westerly patterns but not very strong ones. If it was negative, we would be seeing a weak JS, and blocking highs could build in. In a positive NAO, the JS would be very strong, and there would be little if any chance of anything beyond a strong zonal pattern. If its neutral, however, it is highly doubtful that there would be either a very strong polar vortex or very weak vortex; more likely normal conditions for this time of year.

the NAO is, as you say a reflection of the overall pattern. a negative NAO is what we get in the classic 'greeny high' situation. myself and BFTV have been looking at trends and causes of colder winters and have come up with a few ideas, built upon the findings of others, by trying to find links between various and alternative teleconnections (all credit goes to BFTV for the hard work and technical stuff)

an interesting link, still in research, is the link between polar ice extent and ozone levels. - they seem to correspond. as in the fall in ozone seems to match the timing of the fall in arctic ice levels. (it has been mentioned that less arctic ice, under favourable conditions, can lead to more snow in the N hemisphere) ozone levels have been on the rise again for the past few years. as chionomaniac has explained in the strat thread, more ozone leads to warming of the arctic strat, leading to a disrupted polar vortex. - a main ingredient for colder winters here. add this to the negative PDO (the coldest winters have generally occurred during the neg phase) and we have a few of the major 'building blocks' in place already. G.P. has said that the early signs are favourable for northern blocking this winter, i.e. negative NAO. there are many other factors which need to fall into place and there are never any guarantees. however, as of now, things are looking favourable for a cold (snowy??.....) winter. we shall see.....

Edited September 30, 2012 by bobbydog

[Barry12]

I have faith that the met are right when they say it will be a colder than average winter

http://www.metoffice.gov.uk/media/pdf/n/3/A3-plots-temp-OND.pdf

Edited September 30, 2012 by Barry95

[Skyraker]

Thinking out loud.. When is the last time we had a *really* good polar low ?

[snowstorm445]

the NAO is, as you say a reflection of the overall pattern. a negative NAO is what we get in the classic 'greeny high' situation. myself and BFTV have been looking at trends and causes of colder winters and have come up with a few ideas, built upon the findings of others, by trying to find links between various and alternative teleconnections (all credit goes to BFTV for the hard work and technical stuff)

an interesting link, still in research, is the link between polar ice extent and ozone levels. - they seem to correspond. as in the fall in ozone seems to match the timing of the fall in arctic ice levels. (it has been mentioned that less arctic ice, under favourable conditions, can lead to more snow in the N hemisphere) ozone levels have been on the rise again for the past few years. as chionomaniac has explained in the strat thread, more ozone leads to warming of the arctic strat, leading to a disrupted polar vortex. - a main ingredient for colder winters here. add this to the negative PDO (the coldest winters have generally occurred during the neg phase) and we have a few of the major 'building blocks' in place already. G.P. has said that the early signs are favourable for northern blocking this winter, i.e. negative NAO. there are many other factors which need to fall into place and there are never any guarantees. however, as of now, things are looking favourable for a cold (snowy??.....) winter. we shall see.....

Very interesting stuff. There really are so many factors to consider in meteorology, particularly in long-range forecasting. Certainly there are a huge range of things to consider when trying to even predict weather for this part of the world.

[I remember Atlantic 252]

Thinking out loud.. When is the last time we had a *really* good polar low ?

cool, another member from my snowless location, I cant remember a true polar low, 28 Dec 00 was good but not technically a polar low

[Skyraker]

I did PM you a while back , pointing out we were within a mile of each other.I was in Essex during 2009-2011 and did 'OK' out of those, but if i'm honest I remember much , much snowier scenarios leaving Barnfields or Walton High (I'm sure you know what I mean).Des.

cool, another member from my snowless location, I cant remember a true polar low, 28 Dec 00 was good but not technically a polar low

[Skyraker]

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/gif/pole30_nh.gif

Strat Temps... early I know , but the stall against the mean gives hope...

.. and there is always hope.

[The watcher]

Nobody can really say a forecast for winter is tripe, because what winter will bring is still up for grabs (being 2 months away), it could be mild, cold, worst for years, warmest on record.....nobody actually full heartedly knows at this point in time, it's all an educated guess. What is tripe is someone putting in a paper that an icelandic blast will bring Ice and snow to the UK in less than 7 days. That is quite a reliable timeframe (synoptically) and there is no signs of this at all happening.

[TEITS]

No, of course not, it's still something worth watching out for over the next few weeks though, same goes for the opposite scenario i.e blocking

Whatever the GFS is predicting over the next few weeks has no bearing on what may happen over this coming winter. Look at November 1981 as an example because this was a generally mild, unsettled month prior to the bitter cold spell in Dec.

[SMU]

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

first -5 scale this year

S

[gottolovethisweather]

http://www.knmi.nl/e...agse/index.html

first -5 scale this year

S

You've lost me on that one Steve, but I'm assuming its the first sign of something cooler. To which chart on that link are you referring to.

[feb1991blizzard]

You've lost me on that one Steve, but I'm assuming its the first sign of something cooler. To which chart on that link are you referring to.

On the bottom of the temperature chart the scale goes down to -5c for the first time, the temperature does not go that far but far enough for another notch on the scale to appear on the chart, least i think thats what he means anyway. Obviously in summer even the 0c would not appear on the chart.

[snowking]

GTLTW

Take a look at the graph at the bottom left of the image

It's the first time the minus 5 has been shown on the scale

[gottolovethisweather]

GTLTW

Take a look at the graph at the bottom left of the image

It's the first time the minus 5 has been shown on the scale

Thanks but, to be fair, I personally don't think that means much at this stage. Nevertheless, the trend is there to see and my eyes are already fixed to pints due North and East. For early signs as to what is developing longer-term, all peeps should also keep tabs on the following links.

http://forum.netweat...re#entry2375508

http://forum.netweat...re#entry2370466

http://forum.netweat...re#entry2375695

All links take you to the latest postings in each case.

Edited October 1, 2012 by gottolovethisweather

[Thundery wintry showers]

I'm going to make some extremely bold predictions for the upcoming winter:

• Daylight will steadily decrease, reaching a minimum around 21st/22nd December, and will then increase afterwards.
  
• Each of the three main winter months will be colder than this upcoming October.
  
• The sun will shine for less than 50% of the possible total in all parts of the country.
  
• Somewhere at low levels will see a covering of snow at some point.
  
• If we get snow in November, the winter will feature repeated posts referring to the old saying, "Ice in November to bear a duck, the rest of the winter will be slush and muck", referring to the 2010/11 season as proof of the amazing accuracy of the saying.
  
• Hastings will have more than twice as much sunshine as Lerwick.
  
• The mean global temperature will be above the twentieth-century average in all three months.
  
• Penzance will have very little snow.
  

[BornFromTheVoid]

I'm going to make some extremely bold predictions for the upcoming winter:

• Daylight will steadily decrease, reaching a minimum around 21st/22nd December, and will then increase afterwards.
  
• Each of the three main winter months will be colder than this upcoming October.
  
• The sun will shine for less than 50% of the possible total in all parts of the country.
  
• Somewhere at low levels will see a covering of snow at some point.
  
• If we get snow in November, the winter will feature repeated posts referring to the old saying, "Ice in November to bear a duck, the rest of the winter will be slush and muck", referring to the 2010/11 season as proof of the amazing accuracy of the saying.
  
• Hastings will have more than twice as much sunshine as Lerwick.
  
• The mean global temperature will be above the twentieth-century average in all three months.
  
• Penzance will have very little snow.
  

Nope, that's one for the bin. Didn't even release your methods

[gottolovethisweather]

I'm going to make some extremely bold predictions for the upcoming winter:

• Daylight will steadily decrease, reaching a minimum around 21st/22nd December, and will then increase afterwards. AGREED
  
• Each of the three main winter months will be colder than this upcoming October. AGREED
  
• The sun will shine for less than 50% of the possible total in all parts of the country. ??????
  
• Somewhere at low levels will see a covering of snow at some point. I BLOODY HOPE SO.
  
• If we get snow in November, the winter will feature repeated posts referring to the old saying, "Ice in November to bear a duck, the rest of the winter will be slush and muck", referring to the 2010/11 season as proof of the amazing accuracy of the saying. WHAT ABOUT OCTOBER SNOW?
  
• Hastings will have more than twice as much sunshine as Lerwick. I ASSUME SO.
  
• The mean global temperature will be above the twentieth-century average in all three months. POSSIBLY
  
• Penzance will have very little snow. DEFINITELY
  

I know we are being naughty, but the gist of all this, is that it is far too early to predict the forthcoming winter guys and gals.

I will say however, good on you, to all those that haven't yet issued their winter LRFs and to all those folk, attempting to educate us dunces.

Edited October 1, 2012 by gottolovethisweather