Upcoming winter speculation and chat - October edition

[Sir Mim]

On 16/10/2019 at 06:38, Radiating Dendrite said:

After watching gav and his winter updates over the last few weeks, the analogues (yes, I know they can be flawed and don't believe in pattern matching per se) seem to be pointing to an unsettled start before gradually getting colder towards the backend of winter. 

Sticking my neck out early:

Dec: Wet, unsettled and above average....6.5c

Jan: Wet to start and then drier and colder.....4c

Feb: Dry and Cold....2.5c

March: Continuing cold to start......5c

Average for winter months 4.3c

 

Thanks for watching his vids so I don't have to.

 

I fear, as far as "winter" is concerned we may end up defaulting to our norm again- Atlantic dominated, the occasional cold spell, frequent gales and rain...

Edited October 17, 2019 by Mr TOAD

[Kirkcaldy Weather]

Found this very in depth winter forecast from back in August and although it is a forecast for USA some sections which may be useful for UK 

 "Figure 14, above, shows 500-millibar geopotential height anomalies over the Northern Hemisphere in the same years as outlined in Figures 12 and 13, as well as over the same three-month window. Recall that negative values / cool shadings in this graphic represent negative anomalies (therefore colder and stormier weather), while positive values / warm shadings represent positive anomalies (therefore warmer and calmer weather). Per the figure, neutral-ENSO winters have historically featured high pressure ridges in the Bering Sea, as well as one positioned squarely over Greenland. A ridge positioned over the Bering Sea is identified as the negative phase of the West Pacific Oscillation (WPO), which results in cooler than normal weather over the eastern two-thirds of the United States. Similarly, a ridge over Greenland signals the negative phase of the North Atlantic Oscillation (NAO), which tends to buckle the jet stream south and provide colder weather for the Central and (especially) East U.S. That jet stream buckling also gives credibility to the above-normal precipitation anomalies in Appalachia / the Ohio Valley, as the -NAO is what tends to be the key factor to ignite big storms in the Eastern U.S., including Nor’easters. 

 

What is seen preventing those Nor’easters and pushing the above-normal precipitation track further inland as opposed to right along the East Coast is the modest ridge just offshore the Southeast, which acts as a diverting mechanism for storms traversing the Southern Plains, forcing them northeast into the Ohio Valley instead of due east towards Georgia and Alabama. Also of note in this graphic is how the -WPO ridge and -NAO ridge are strong enough to force the tropospheric polar vortex to lower latitudes. We will discuss this more later on, but it is critical to know that there are essentially two ‘versions’ of the polar vortex: the stratospheric polar vortex, and the tropospheric polar vortex. Of course, when placed on a 3D scale they are one in the same, but given that we look at slices of the atmosphere rather than 3D graphics, it is better for us to think of two polar vortices as opposed to one. Again, this will be elaborated on later in the Stratosphere section.

 

In Figure 14, it seems as though a Neutral-ENSO state will encourage the tropospheric polar vortex to split up and be forced to lower latitudes as a result of the two aforementioned ridges. Figure 15, below, illustrates what happens to the stratospheric polar vortex, at about the 50-millibar level. At the stratospheric level, it appears as though an ENSO-neutral situation provokes strong ridging over the Arctic Circle, forcing the polar vortex to lower latitudes at a weakened strength. As a consequence, it becomes far easier for below-normal temperature anomalies to flow to lower latitudes over the course of the winter. It also becomes far easier to achieve a sudden stratospheric warming (SSW), which will be discussed in detail in the Stratosphere section. For now, however, understanding that a neutral-ENSO state appears to materially disrupt both the tropospheric and stratospheric polar vortices is a key takeaway."

"Now that I’ve gotten that off my chest, we need to turn to the question of ‘what causes these splits in the polar vortex?’. You might also be wondering how the polar vortex can be present every single winter, even though it only seems to “happen” once every several years in the United States. Both of these are good questions. We’ll use the answer to the second question to also answer the first question.

 

In the winter, there is a large vortex spanning the entirety of the atmosphere relevant to weather forecasting, from the surface to the upper reaches of the stratosphere. This is the polar vortex, but it acts differently at different levels of the atmosphere. The polar vortex we’re most familiar with is what I refer to as the tropospheric polar vortex. In reality, the atmosphere is three-dimensional, so this is one big vortex, but for our purposes it’s necessary to separate them into two. The ‘other’ one is the stratospheric polar vortex. When the news talks about the polar vortex moving south into our neck of the woods, what they’re really talking about is a piece of the tropospheric polar vortex becoming detached from the main vortex and managing to be moved to lower latitudes over North America. In practice, it can be shunted to any lower latitude, including over Europe, Asia, Siberia, or the oceans. This movement of the polar vortex to lower latitudes happens quite often, but since there’s so much space on this planet and North America is only so large, the stars align only every once in a while for that piece of the tropospheric polar vortex to impact the U.S. What you won’t hear on the news, though, is how that split / disruption in the tropospheric polar vortex happened in the first place. Almost exclusively, especially in the event of a major disruption to the tropospheric polar vortex, this process begins in the stratospheric polar vortex. Usually, that involves a sudden and intense event of warm air rushing into the stratosphere and ravaging the stratospheric polar vortex, which eventually feeds down to the tropospheric polar vortex (usually with a ~2 week lag). Now, we have to identify where those sudden warm air bursts (called Sudden Stratospheric Warmings, or SSWs) come from, and that’s where the Bering Sea comes into play.

 

For reasons I’m not entirely familiar with, the Bering Sea is an incredibly fertile area for these sudden stratospheric warming events to happen. A ‘typical’ SSW event involves a ridge of high pressure and warm air blossoming over the Bering Sea and then flooding into the Arctic Circle. While this blossoming into the Arctic Circle is not a given – indeed, sometimes the warm air simply dissipates over the Bering Sea and no SSW occurs – it seems to be most likely when that warm air forms over the Bering Sea. I will discuss all of this in the Stratosphere section, so no worries if it seems tough to understand. The key takeaway here is that the Bering Sea is a key area for high pressure to form in the stratosphere, which can then lead to severe cold weather events in North America.

Let’s take a look back at Figure 28 and focus our attention on the Bering Sea. The Bering Sea should draw your attention even if it weren’t the focus of this section: the waters in that area have the highest positive SST anomalies in the Northern Hemisphere, and actually in the world per this chart! This is a significant anomaly, and provides a good look at what the coming winter could entail if these strong positive anomalies persist. The presence of strong positive SST anomalies in the Bering Sea indicate a materially-increased chance of sudden stratospheric warmings this winter, which therefore increase the risk of severe outbreaks of cold air into the United States. This is not a given, of course, but the chance of lobes of the polar vortex protruding into the United States this winter is increased by a non-trivial amount with the presence of such strong positive SSTAs in the Bering Sea.

I will touch on this topic again in the next iteration of this winter forecast, given its importance, and these anomalies will need to be watched to see if they do persist into the fall."

"making it more likely that geopotential heights in the stratosphere will be higher, weakening the stratospheric polar vortex and boosting the chances of a cooler than normal winter.  I believe it is more prudent to expect the stratospheric polar vortex to be somewhere between average strength and weaker than normal for the coming winter, given how the QBO will have an increasingly-weak influence as the winter moves on."

 

The Weather Centre: Preliminary 2019-2020 Winter Forecast

THEWEATHERCENTRE.BLOGSPOT.COM

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Home to critically-acclaimed winter outlooks, our Weather Models page, and near-daily detailed, informative, and easy-to-read posts.

Says at the bottom that the official winter forecast would be released on 12th October but not sure where it is or if it is a paid forecast.

[Kirkcaldy Weather]

  "Now, we take the historical re-analysis data, from NCEP, to create a graphic of how the average weather pattern looked like in winters during these periods. Obvious right away are positive anomalies over the north pole. This corresponds to higher pressure. And opposite for negative anomalies. This is a typical negative NAO/AO pattern, which brings colder (and snowier) conditions into Europe and North America."

 "After removing all the cold phases and strong warm phases of ENSO, we get a very interesting and more defined picture. We see a high pressure area focused over Greenland and the Arctic, typical for negative NAO & AO. Lower pressure is displaced a bit further south, along with polar fronts and colder air. This type of pattern usually brings colder and snowy weather to Europe and USA. If you love winter and you want snow, and you happen to live in Europe or USA, this is what you want to see in the forecasts. The problem we have, is the large low pressure area in North Pacific. That is a more typical feature for a proper stronger ElNino, and is completely opposite of what the latest long range model forecasts are calculating." 

  "Looking at the surface temperature anomaly, we see colder air in eastern and central parts of USA and north Europe. What stands out is a positive anomaly in southeast Europe and parts of central Europe. This is due to the southern shift of low pressure systems, centering over west/central Europe. On the east and south-east side of low pressure systems, we usually find south/southwest winds and warmer air, but also more precipitation, like we see in south/southeast Europe in these graphics. But the pressure patterns have more significance in statistical forecasting, compared to just temperatures, and the pressure pattern in the graphics above, is more favorable for Europe than what the temperature  chart suggests. A similar pressure pattern was in January-February 2013, or in winter 2009/2010.""

"Summary:

So, what does history tell us? It shows us that solar minimum years and moderate positive ENSO is a good combination for winter lovers in Europe and USA. But what it fails to mention is, that we are looking at only two parts of the whole equation. There is much more than just the Sun and ENSO that influence our weather. There is an endless list of things that influence our climate, both major and minor. We are only looking at two pieces of the puzzle. Tho statistical forecasts can be useful as a guidance, there is consensus that it is better to look at actual model calculations, because they tend to look at the entire world in real time, rather than from a historic perspective. 

Nonetheless, the statistical forecast is optimistic, and there have been situations when they proved to be superior. This year though, the long range models are forecasting an unusually similar picture, which increases the confidence in their forecast. We will soon take another look at the updated long range model guidance. Are the new calculations looking more similar to their statistical counterparts? Or are they firmly set on a milder pattern? Stay tuned to find out!"

*Winter 2019/2020* Statistical winter outlook – Solar cycle and ENSO! – Severe Weather Europe

WWW.SEVERE-WEATHER.EU

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Two weeks ago, we wrote about the latest long range model forecasts, and what they show for the upcoming winter 2019/2020. While we wait for the latest October model updates, we will take a more statistical...

 

[feb1991blizzard]

@CreweCold   True but we haven't had a really early strat - trop coupling recently, it has coupled Mid Dec or Jan, if we could get it earlier this time, surely it cannot last for 3 months, i am thinking 11/12 or 08/09, mid Jan SSW followed by Feb Easterly but hopefully longer lasting with better personal results, hoping though that we can get things breaking down earlier, i think it is looking inevitable that we will have to endure a very zonal strong PV phase this year - i agree with chiono's assesment.

[Cheshire Freeze]

2 minutes ago, feb1991blizzard said:

@CreweCold   True but we haven't had a really early strat - trop coupling recently, it has coupled Mid Dec or Jan, if we could get it earlier this time, surely it cannot last for 3 months, i am thinking 11/12 or 08/09, mid Jan SSW followed by Feb Easterly but hopefully longer lasting with better personal results, hoping though that we can get things breaking down earlier, i think it is looking inevitable that we will have to endure a very zonal strong PV phase this year - i agree with chiono's assesment.

I just have a feeling that if we get an early connect, we won't get out of it this year. We'll be staring down the barrel of months of zonal- pretty much as the seasonals predict. Our best bet is a 2009 type situation. I like your assessment of a 'pseudo zonal' November- pretty much what happened that year. 

[feb1991blizzard]

Just now, CreweCold said:

I just have a feeling that if we get an early connect, we won't get out of it this year. We'll be staring down the barrel of months of zonal- pretty much as the seasonals predict. Our best bet is a 2009 type situation. I like your assessment of a 'pseudo zonal' November- pretty much what happened that year. 

Yes, don't forget even the best long range model will struggle to pick out a pattern change 3 months away, let alone a strat lead one that changes the trop pattern to a non default pattern, agree if we are to see anything decent in early winter then yes, we desperately need the modelling to pick up and preferably by the next update, wouldn't worry too much about the modelling for Feb just yet though.

[booferking]

11 minutes ago, feb1991blizzard said:

Yes, don't forget even the best long range model will struggle to pick out a pattern change 3 months away, let alone a strat lead one that changes the trop pattern to a non default pattern, agree if we are to see anything decent in early winter then yes, we desperately need the modelling to pick up and preferably by the next update, wouldn't worry too much about the modelling for Feb just yet though.

 

[feb1991blizzard]

1 minute ago, booferking said:

 

Would imagine that will just fizzle out or skirt around the edge of the surf zone, given the time of year, i suppose it could give a minor displacement if it strengthens but not really going to threaten the vortex's normal strength and location i wouldn't have thought.

[booferking]

4 minutes ago, feb1991blizzard said:

Would imagine that will just fizzle out or skirt around the edge of the surf zone, given the time of year, i suppose it could give a minor displacement if it strengthens but not really going to threaten the vortex's normal strength and location i wouldn't have thought.

Will be interesting to see were it heads from here start of a warming is better than no warming showing at all but all early doors.

[feb1991blizzard]

8 minutes ago, booferking said:

Will be interesting to see were it heads from here start of a warming is better than no warming showing at all but all early doors.

Yes - very early yet.

[frederiksen90]

Are we heading into -PDO? Now note the sea at Alaska and the west coast of America. It gets colder and colder as the hot water moves west:

https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.10.17.2019.gif

This is how it looked a month ago:

https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.9.16.2019.gif

[damianslaw]

50 minutes ago, CreweCold said:

I just have a feeling that if we get an early connect, we won't get out of it this year. We'll be staring down the barrel of months of zonal- pretty much as the seasonals predict. Our best bet is a 2009 type situation. I like your assessment of a 'pseudo zonal' November- pretty much what happened that year. 

Hope we don't see a November like 2009 - that brought torrential rain here, and significant flooding, and coming on the back of a very wet period since August, would quite likely do the same. Nov 2009 was interesting though, as it saw strong ridge development to the east and also to our NW, with the trough locked in situ pumping up mild SW winds/s winds, the trough never properly broke through eastwards until the end of the month - a sign all was not normal..

 

[Cheshire Freeze]

2 minutes ago, damianslaw said:

Hope we don't see a November like 2009 - that brought torrential rain here, and significant flooding, and coming on the back of a very wet period since August, would quite likely do the same. Nov 2009 was interesting though, as it saw strong ridge development to the east and also to our NW, with the trough locked in situ pumping up mild SW winds/s winds, the trough never properly broke through eastwards until the end of the month - a sign all was not normal..

 

Well I don't really see a way of avoiding flooding at some point given the general set up. If we're going to go zonal, I'd rather we went zonal with a wintry end product!

[feb1991blizzard]

28 minutes ago, frederiksen90 said:

Are we heading into -PDO? Now note the sea at Alaska and the west coast of America. It gets colder and colder as the hot water moves west:

https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.10.17.2019.gif

This is how it looked a month ago:

https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.9.16.2019.gif

Yes i have noticed that, also are we not due a -PDO?, although i presume there are other indicators for the PDO as well, like with enso you can have an el nino but until the SOI goes negative, then the atmosphere isn't responding.

Edited October 17, 2019 by feb1991blizzard

[Mr Frost]

9 minutes ago, feb1991blizzard said:

Yes i have noticed that, also are we not due a -PDO?, although i presume there are other indicators for the PDO as well, like with enso you can have an el nino but until the SOI goes negative, then the atmosphere isn't responding.

Table from September 2018 to September 2019. (Also link below)

 

-PDO nine out of the last twelve months.

Might be worth keeping it to hand as this gets a mention most days of the week on here. 
 

https://www.ncdc.noaa.gov/teleconnections/pdo/

All the best!

 

[feb1991blizzard]

Just now, Mr Frost said:

Table from September 2018 to September 2019. (Also link below)

 

-PDO nine out of the last twelve months.

Might be worth keeping it to hand as this gets a mention most days of the week on here. 
 

https://www.ncdc.noaa.gov/teleconnections/pdo/

All the best!

 

So what are the elements involved - is it the higher the pressure difference between 20N and the equator - the higher the PDO?

[feb1991blizzard]

Seen it now - thanks.

[feb1991blizzard]

Basically what we don't want is ridging sending the Jet deep into the USA on the Eastern side - in other words places near the deep South getting freezing temps, not if its then spilling into the Atlantic anyway - thats what we want to avoid.

[Premiere Neige]

56 minutes ago, frederiksen90 said:

Are we heading into -PDO? Now note the sea at Alaska and the west coast of America. It gets colder and colder as the hot water moves west:

https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.10.17.2019.gif

This is how it looked a month ago:

https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.9.16.2019.gif

Hopefully that cooling starts to stretch out into the deeper waters further west.

Edited October 17, 2019 by Premier Neige

[SMU]

Something certainly worth noting is the ongoing -NAO

The models keep trying to remove it however it keeps bouncing back-

The models at the start of last week ( both UKMO & GFS ) painted an increased strat > trop coupling feature at the close of October pictured below-

 

However this is the near time reality-

Note the anomalous +VE heights in the troposphere....

But the icing on the cake is a November start warming beginning to develop in the models - 

Remember historical Decembers with peak negative AOs have generally all been driven by a warming in November / December. Examples being 09 / 1981

So watch this space carefully as these would be the ingredients to propose a forecast thats opposite to the Met office / ECM seasonal runs...

S

[cheeky_monkey]

10 minutes ago, feb1991blizzard said:

So what are the elements involved - is it the higher the pressure difference between 20N and the equator - the higher the PDO?

me thinks -PDO is warm in the western Pacific and cold In the east..currently its warm and warm so its neutral

[Kirkcaldy Weather]

On 09/10/2019 at 18:13, Kirkcaldy Weather said:

 

Possibly some better news especially for the marine life 

UW Weather Prof: 'Blob (Part 2) is Dying...'

KOMONEWS.COM

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SEATTLE -- The second coming of The Blob is dying, says University of Washington atmospheric sciences professor Cliff Mass. But that's a...

 

[feb1991blizzard]

1 minute ago, cheeky_monkey said:

me thinks -PDO is warm in the western Pacific and cold In the east..currently its warm and warm so its neutral

Thanks - get it now.

@Steve Murr   Have you got the website for those charts please so i can bookmark it ready for winter please?

[booferking]

[feb1991blizzard]

22 minutes ago, booferking said:

Bottom chart screams semi-permanent Greenland high.