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https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018GL078838 

If the winter NAO is strongly negative or positive the models show this in advance. 

Recent studies of individual seasonal forecast systems have shown that the wintertime North Atlantic Oscillation (NAO) can be skillfully forecast. However, it has also been suggested that these skillful forecasts tend to be underconfident, meaning that there is too high a proportion of unpredictable noise in the forecasts. We assess the skill and overconfidence/underconfidence of the seasonal forecast systems contributing to the EUROpean Seasonal to Interannual Prediction (EUROSIP) multimodel ensemble system. Five of the seven systems studied have significant skill for forecasting the wintertime NAO at 2‐ to 4‐month lead times. Four of these skillful systems are underconfident for forecasting the NAO. A multimodel ensemble (ensemble size 126 members) is both skillful and clearly underconfident. Underconfidence becomes more pronounced as the ensemble size increases. Certain years in the hindcast period are well forecast by all or most models. This implies that common teleconnections and drivers of the NAO are being captured by the EUROSIP seasonal forecasts.

Plain Language Summary

In this paper we provide an intercomparison of seven seasonal forecast systems, with particular focus on the wintertime North Atlantic Oscillation (NAO). The wintertime NAO is the main driver of winter weather variability in the United Kingdom and Europe, and being able to forecast the NAO for the season ahead has potential benefits for many different sectors such as agriculture, energy, health, transport, and water resource management. We show that five of the seven systems studied can skillfully forecast the NAO, and a multimodel ensemble has even higher skill. Four of these skillful systems are found to be underconfident, which means that there is too high a proportion of unpredictable noise in the model. Being underconfident makes it more difficult to fully utilize the skill of a forecast. However, one system is skillful but not underconfident. We also find that there are common years in which the NAO is well forecast by all the skillful systems. This is an important result because it implies that common drivers of NAO predictability are being captured by these systems. These results are an important contribution to our understanding of seasonal forecasts systems and the predictability of the NAO.

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11 hours ago, sebastiaan1973 said:

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018GL078838

If the winter NAO is strongly negative or positive the models show this in advance. 

Recent studies of individual seasonal forecast systems have shown that the wintertime North Atlantic Oscillation (NAO) can be skillfully forecast. However, it has also been suggested that these skillful forecasts tend to be underconfident, meaning that there is too high a proportion of unpredictable noise in the forecasts. We assess the skill and overconfidence/underconfidence of the seasonal forecast systems contributing to the EUROpean Seasonal to Interannual Prediction (EUROSIP) multimodel ensemble system. Five of the seven systems studied have significant skill for forecasting the wintertime NAO at 2‐ to 4‐month lead times. Four of these skillful systems are underconfident for forecasting the NAO. A multimodel ensemble (ensemble size 126 members) is both skillful and clearly underconfident. Underconfidence becomes more pronounced as the ensemble size increases. Certain years in the hindcast period are well forecast by all or most models. This implies that common teleconnections and drivers of the NAO are being captured by the EUROSIP seasonal forecasts.

Plain Language Summary

In this paper we provide an intercomparison of seven seasonal forecast systems, with particular focus on the wintertime North Atlantic Oscillation (NAO). The wintertime NAO is the main driver of winter weather variability in the United Kingdom and Europe, and being able to forecast the NAO for the season ahead has potential benefits for many different sectors such as agriculture, energy, health, transport, and water resource management. We show that five of the seven systems studied can skillfully forecast the NAO, and a multimodel ensemble has even higher skill. Four of these skillful systems are found to be underconfident, which means that there is too high a proportion of unpredictable noise in the model. Being underconfident makes it more difficult to fully utilize the skill of a forecast. However, one system is skillful but not underconfident. We also find that there are common years in which the NAO is well forecast by all the skillful systems. This is an important result because it implies that common drivers of NAO predictability are being captured by these systems. These results are an important contribution to our understanding of seasonal forecasts systems and the predictability of the NAO.

Many thanks Sebastian. Good education for some of us.

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From http://easternmassweather.blogspot.com/2018/

More to read over there.

Potential 2018-2019 Analogs Binned by QBO and Solar Cycle

 

It should be fairly evident, unless you have your head firmly entrenched within the deepest recesses of a jack o'lantern, that this composite portrays a fairly harsh winter for at least the northeast. And potentially the mid atlantic, as well. However note that the word "composite" is emphasized, as there are voices of dissent among our analog set. The winter of 2006-2007 is perhaps the most prominent outlier of this set, so it was discussed at some length what variable(s) may have contributed to that particular outcome. The fact that the modoki characteristic of that warm ENSO event begin to decay very early in its life cycle, about at this time of year, was cited as one prominent reason  why this particular analog is beginning to diverge a bit from the current season.
 

 We also began to discuss the Quasi Biennial Oscillation (QBO) and the solar cycle as two contributing factors to the degree of blocking experienced in a given season. Please refer back to the last update for a deeper explanation of the QBO, but the simple explanation is that a negative, or easterly QBO favors blocking because it renders the polar vortex more diffuse and prone to disruption, and a positive, or westerly QBO is less favorable for this to occur. The mean QBO value in August 2006 was +9.10, and ascending, as compared to the August 2018 value of -20.41. This is one notable disparity between the two seasons, which could imply that 2018 is more likely to feature substantial high latitude blocking. However we also implied last week that this year's QBO value is in a state flux, and this is because it is rising, and transitioning with time to a westerly direction. This renders any prognostication a bit more nebulous. The trend of the QBO and its pace can be every bit as important as its absolute value at any point in time, which is an important consideration regarding analogs. That being said, here are the respective analog years and corresponding August QBO values and trends.
 
August 1953: -1.21 and growing more negative. No match
August 1958: -15.59 and slowly falling. Trending Opposite direction. Decent match
August 1969: +9.78. No match.
August 1976: -4.89 and trending more easterly. No match.
August 1977: -11.24 and fairly rapidly becoming westerly/positive in time for winter. MATCH
August 1979: -22.24 and peaking, but remained negative for winter. Decent match.
August 2004: +8.74 and trending negatively. No Match.
August 2006: +9.10 and very slowly trending easterly. No match.
August 2014: -21.64 and trending negative. Matches absolute value, but wrong trend. Decent match.
 
Clearly, based solely upon the QBO data, 1977 is the strongest analog of the weak el nino comparisons.  However both QBO and the solar cycle need to be considered within the context of assessing the probability of sustained periods of blocking during the cold season.
Solar Minimum Looms
The number of spots on the sun is utilized as a rough proxy for how much solar energy is being emitted at any given point in time. And like everything here on plant earth, this waxes and wanes on a cyclical basis.  This solar consideration is important because low solar output has been linked to sustained blocking, and thus harsher winters. For a better idea of whether or not this is true, lets assess the data.
The following is a list of solar cycles since 1950, which runs back to solar cycle 19, along with dates of  accompanying solar minimum and solar maximums, as well as average length of cycle.
 Thank you, wikipedia:    
Solar cycle 19 Solar Min:1954 April 5.1 Solar Max:1958 March 285.0 3.9 10.5 446
Solar cycle 20 1964 October 14.3 1968 November 156.6 4.1 11.4 227
Solar cycle 21 1976 March 17.8 1979 December 232.9 3.8 10.5 272
Solar cycle 22 1986 September 13.5 1989 November 212.5 3.2 9.9 273
Solar cycle 23 1996 August 11.2 2001 November 180.3 5.3 12.3 309
Solar cycle 24 2008 December 2.2 2014 April 116.4 5.3 In progress 817
Solar cycle 25 First spot[13]           137
Average   11.1
 
The solar minimum is marked by the fewest sunspots over a prolonged stretch before activity begins to increase, which marks the start of a new cycle. The solar maximum marks the apex of activity before descent into the next minimum, and then the cycle begins a new. The average length of these cycles is about 11 years, however they can take as long as 13 years, or progress as swiftly as 9 years time. The last minimum occurred in December of 2008, as evidenced by the chart above, thus it is reasonable to anticipate that the minimum may be imminent.  It is true that the solar minimum was originally anticipated to occur a year or two from now, but just as the anticipated minimum before the 2006-2007 winter was slower to occur than forecast, there are signs that this one may be faster. I know that it is difficult to comprehend that we struggle to forecast the precise timing of the solar cycle years in advance, when we often struggle to forecast whether 3 or 13" of snow will fall at 24 hours lead. But trust us, its true. And just like we do leading up to and during winter storms, forecasts adjust. 
The curent model consensus concurs that the minimum may arrive by mid 2019.
Solar%2BMethods.gif
Courtesy Solar blogger Javier

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Quick question from a total numpty here... read recently that the quiet sun is causing the thermosphere to cool, will this have an impact on the stratosphere and if so, what?

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In this study (http://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.3280) they analyse the North Atlantic regimes with the stratosphere at 100 hPa, 60N from november till march. 

https://www.mupload.nl/img/0wxb82yujz1hl.jpg

https://www.mupload.nl/img/i8cf01k7gz.jpg
Frequency of occurrence of North Atlantic weather regimes immediately following weak stratospheric vortex conditions (left, red bar), neutral stratospheric vortex conditions (central, white bar) and strong stratospheric vortex conditions (blue, right bar). The 95% confidence interval (see text for details) is shown at the end of each bar.

So:
For neutral conditions, BL is the most frequently observed regime, followed by NAO+. Stratospheric vortex conditions significantly shift weather regime frequency as expected. Following weak stratospheric vortex conditions, NAO- occurs almost twice as frequently as during neutral stratospheric vortex conditions with consequent reductions in the occurrence frequency of both AR and NAO+. Following strong stratospheric vortex conditions, the opposite sensitivity is found, large reductions in NAO- frequency and increases in both AR and NAO+. Changes to BL frequency are smaller and not significant. Previous studies have highlighted the links between Greenland Blocking and stratospheric vortex conditions (Woollings et al. 2010a; Davini et al. 2014), reflected here in the sensitivity of the NAO- regime.

Edited by sebastiaan1973

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Thanks Knocker.

http://twitter.com/WorldClimateSvc/status/1047538750715305984

 

In light of the monster Bering/Alaska ridge, an analog based on negative EPO and WPO in September shows a striking warm pattern for western/northern Europe in Nov-Dec. There's also a connection here to a Modoki-like Niño state (warm central Pacific).

A typical positive NAO (see the tweet) and temperatures above normal.

Doma00FXoAECCTp.jpg

Edited by sebastiaan1973

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http://iopscience.iop.org/article/10.1088/1748-9326/10/5/054022/pdf 

 

Numerous studies have suggested an impact of the 11 year solar cycle on the winter North Atlantic Oscillation (NAO), with an increased tendency for positive (negative) NAO signals to occur at maxima (minima) of the solar cycle. Climate models have successfully reproduced this solar cycle modulation of the NAO, although the magnitude of the effect is often considerably weaker than implied by observations. A leading candidate for the mechanism of solar influence is via the impact of ultraviolet radiation variability on heating rates in the tropical upper stratosphere, and consequently on the meridional temperature gradient and zonal winds. Model simulations show a zonal mean wind anomaly that migrates polewards and downwards through wave–mean flow interaction. On reaching the troposphere this produces a response similar to the winter NAO. Recent analyses of observations have shown that solar cycle–NAO link becomes clearer approximately three years after solar maximum and minimum. Previous modelling studies have been unable to reproduce a lagged response of the observed magnitude. In this study, the impact of solar cycle on the NAO is investigated using an atmosphere–ocean coupled climate model. Simulations that include climate forcings are performed over the period 1960–2009 for two solar forcing scenarios: constant solar irradiance, and time-varying solar irradiance. We show that the model produces significant NAO responses peaking several years after extrema of the solar cycle, persisting even when the solar forcing becomes neutral. This confirms suggestions of a further component to the solar influence on the NAO beyond direct atmospheric heating and its dynamical response. Analysis of simulated upper ocean temperature anomalies confirms that the North Atlantic Ocean provides the memory of the solar forcing required to produce the lagged NAO response. These results have implications for improving skill in decadal predictions of the European and North American winter climate.

 

An important graphic:

Composites of upper stratospheric zonal mean temperature (dashed red line) and DJF NAO-index (black line) as a function of lag with respect to solar maximum minus solar minimum. The upper stratospheric temperature is calculated as the annual average of the region bounded by 0.5–5 hPa (approximately 40–55 km), and 30 °S–30 °N. The NAO-index is defined as the DJF surface pressure difference between the Azores and Iceland. The points where the NAO-index is significant at the 95% level are highlighted with squares.

NAO-link-1.jpg

Edited by sebastiaan1973

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15 hours ago, karyo said:

It is rising fast! I guess it will go positive this month.

This wouldn’t appear to be good news for the coldies amongst us. 

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1 hour ago, Paul_1978 said:

This wouldn’t appear to be good news for the coldies amongst us. 

 

1 hour ago, Paul_1978 said:

This wouldn’t appear to be good news for the coldies amongst us. 

Wont be great news if we get to the stage where we are reliant on a mid winter major SSW if the Strat and trop are cuddled up like a cosy little couple.

https://journals.ametsoc.org/doi/10.1175/JAS-3297.1

However, a lot of water to go under the bridge before then though.

 

Hopefully ED will be along soon to give us the a) the low down on the likely stratospheric playout this winter and b) a new thread to discuss it in.

Edited by feb1991blizzard

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6 hours ago, feb1991blizzard said:

 

Wont be great news if we get to the stage where we are reliant on a mid winter major SSW if the Strat and trop are cuddled up like a cosy little couple.

https://journals.ametsoc.org/doi/10.1175/JAS-3297.1

However, a lot of water to go under the bridge before then though.

Well, we had a cracking SSW earlier this year. We shouldn't expect one every winter (although it would be nice).

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17 minutes ago, sebastiaan1973 said:

Latest EC seasonal doesn't show cold in januar. Drier than normal in december and januar. 

http://effis.jrc.ec.europa.eu/applications/seasonal-forecast/

thanks sebastiaan, if we take the encouraging bits from month to month basis, then the below average precipitation between Iceland,Scotland and West of Norway is good. blocking around first half of winter, then as the QBO turns more positive we have zonal February, so a front loaded winter perhaps suggested? 

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20 minutes ago, sebastiaan1973 said:

Latest EC seasonal doesn't show cold in januar. Drier than normal in december and januar. 

http://effis.jrc.ec.europa.eu/applications/seasonal-forecast/

Seems similar to last update i think!pretty blocky to the north of the british isles and wet across southern europe and spain!!maybe a good thing for those wanting a cold winter!!

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More from ECMWF seasonal update, anyone ordered Scandi high?

ecm ensemble mean.png

dec.temps.png

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2 hours ago, sebastiaan1973 said:

For the individual months please check https://weather.us/monthly-charts/euro/europe/anomaly-msl/20181201-0000z.html

 

Latest Glosea5 shows a postive NAO. (once again)

 

glosea5 oktober.png

Looks very similar to the pattern we have been in for a while, seasonal models are still not worth the electricity used to generate the data IMO but then that's part of the "fun"

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I don't think Adam Scaife agrees with you

http://iopscience.iop.org/article/10.1088/1748-9326/aa57ab/meta 

Abstract

We assess the utility of seasonal forecasts for the energy industry by showing how recently-established predictability of the North Atlantic Oscillation (NAO) in winter allows predictability of near-surface wind speed and air temperature and therefore energy supply and demand respectively. Our seasonal prediction system (GloSea5) successfully reproduces the influence of the NAO on European climate, leading to skilful forecasts of wind speed and wind power and hence wind driven energy supply. Temperature is skilfully forecast using the observed temperature-NAO relationship and the NAO forecast. Using the correlation between forecast NAO and observed GB electricity demand, we demonstrate that skilful predictions of winter demand are also achievable on seasonal timescales well in advance of the season. Finally, good reliability of probabilistic forecasts of above/below-average wind speed and temperature is also demonstrated.

 

Edited by sebastiaan1973

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Fantastic Recretos! So being an absaloute newb...I’m guessing the British Isles in the blue/purple shades is a good thing, at this moment time, for long term forecasted cold for the upcoming winter??

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