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Stratosphere and Polar Vortex Watch


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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

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1 hour ago, snowy weather said:

What does that mean in terms of the weather? 

That the overall early formation of the PV will be weaker than usual - suggesting weaker westerlies ....

Edited by Steve Murr
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2 hours ago, sebastiaan1973 said:

Latest Glosea5 (august) shows a positive NAO. https://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/gpc-outlooks/ens-mean

2cat_20180801_z500_months46_global_deter_public.png

An all too familiar winter pattern.  At least it's early days!

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33 minutes ago, Don said:

An all too familiar winter pattern.  At least it's early days!

To be fair if the old Met Office belief that the May Atlantic SST profile is linked to the NAO state during winter then we are definitely screwed. In recent weeks it has been developing a better profile though. 

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2 minutes ago, summer blizzard said:

To be fair if the old Met Office belief that the May Atlantic SST profile is linked to the NAO state during winter then we are definitely screwed. In recent weeks it has been developing a better profile though. 

Defiantly some positive signs for a cold winter though such as a cold north Atlantic, strong negative QBo, weak El nino, solar minimum, gulf stream position. But a couple of signals the other way. Let's wait and see. I'm sure the met office will make a comedy prediction either way

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1 minute ago, Leo97t said:

Defiantly some positive signs for a cold winter though such as a cold north Atlantic, strong negative QBo, weak El nino, solar minimum, gulf stream position. But a couple of signals the other way. Let's wait and see. I'm sure the met office will make a comedy prediction either way

At the levels that matter to our winter stratospherically (10-50hpa) the QBO will be westerly by the time we are out of winter bar some abnormal event. That is my primary concern. I agree that the solar cycle, -PDO and a weak Nino at best are in our favour.

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21 minutes ago, summer blizzard said:

At the levels that matter to our winter stratospherically (10-50hpa) the QBO will be westerly by the time we are out of winter bar some abnormal event. That is my primary concern. I agree that the solar cycle, -PDO and a weak Nino at best are in our favour.

When was the last extended easterly QBo period of more than 2 years

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Predictions for winter from now look very problematic to me, whether they are by people or models, particularly models.   We're coming off a hot season that has been exceptional in so many places in the NH not just the UK.  

With the westerly QBO not gaining full strength until later into winter(?) I still think the  likelihood of a front loaded cold start to winter is the form bet, milder later.  Place your chips!

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2 hours ago, summer blizzard said:

To be fair if the old Met Office belief that the May Atlantic SST profile is linked to the NAO state during winter then we are definitely screwed. In recent weeks it has been developing a better profile though. 

I believe it was a similar situation in 2009 when the May Atlantic SST profile pointed towards a strongly positive NAO for winter 2009/10.  However, the rest is history.

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1 hour ago, Don said:

I believe it was a similar situation in 2009 when the May Atlantic SST profile pointed towards a strongly positive NAO for winter 2009/10.  However, the rest is history.

Pattern in May 09 looks fairly neutral looking at the archives. 

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14 hours ago, summer blizzard said:

Pattern in May 09 looks fairly neutral looking at the archives. 

Oh, ok.  Still, what will be will be.

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On 11/08/2018 at 18:37, CreweCold said:

The SLP plot is even worse

August 2018 Months 4-6  Global Pressure

If it's any consolation, I recall that the long range plots for JFM last year were even worse. The Atlantic SST profile doesn't look promising though, that's for sure.

Some more positive news:

...and a follow up...

 

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16 hours ago, knocker said:

 

Yes, GEFS forecasting the Zonal Mean Zonal Winds at 10hPa 60N switch to a gentle westerly on 24th August 2018. The Polar Vortex returns after its summer holiday - welcome back....... although we look forward to you having a very disturbed winter! :)

1800638862_GEFSZMZWforecast16Aug2018.thumb.jpg.8329ffe2130aa5de0d715f1254495bd7.jpg

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Looking at Glosea5 for November-January is useless. The only year it did show northern blocking in its August update for that tri-monthly period was 2013-14....... and we all know how that turned out. To me, this Winter provides a lot of conflict and complications.

Webp.net-gifmaker (10).gif

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https://www.clim-past.net/14/1179/2018/

Abstract. The effect of external forcings on atmospheric circulation is debated. Due to the short observational period, the analysis of the role of external forcings is hampered, making it difficult to assess the sensitivity of atmospheric circulation to external forcings, as well as persistence of the effects. In observations, the average response to tropical volcanic eruptions is a positive North Atlantic Oscillation (NAO) during the following winter. However, past major tropical eruptions exceeding the magnitude of eruptions during the instrumental era could have had more lasting effects. Decadal NAO variability has been suggested to follow the 11-year solar cycle, and linkages have been made between grand solar minima and negative NAO. However, the solar link to NAO found by modeling studies is not unequivocally supported by reconstructions, and is not consistently present in observations for the 20th century. Here we present a reconstruction of atmospheric winter circulation for the North Atlantic region covering the period 1241–1970CE. Based on seasonally resolved Greenland ice core records and a 1200-year-long simulation with an isotope-enabled climate model, we reconstruct sea level pressure and temperature by matching the spatiotemporal variability in the modeled isotopic composition to that of the ice cores. This method allows us to capture the primary (NAO) and secondary mode (Eastern Atlantic Pattern) of atmospheric circulation in the North Atlantic region, while, contrary to previous reconstructions, preserving the amplitude of observed year-to-year atmospheric variability. Our results show five winters of positive NAO on average following major tropical volcanic eruptions, which is more persistent than previously suggested. In response to decadal minima of solar activity we find a high-pressure anomaly over northern Europe, while a reinforced opposite response in pressure emerges with a 5-year time lag. On centennial timescales we observe a similar response of circulation as for the 5-year time-lagged response, with a high-pressure anomaly across North America and south of Greenland. This response to solar forcing is correlated to the second mode of atmospheric circulation, the Eastern Atlantic Pattern. The response could be due to an increase in blocking frequency, possibly linked to a weakening of the subpolar gyre. The long-term anomalies of temperature during solar minima shows cooling across Greenland, Iceland and western Europe, resembling the cooling pattern during the Little Ice Age (1450–1850CE). While our results show significant correlation between solar forcing and the secondary circulation pattern on decadal (r = 0.29, p < 0.01) and centennial timescales (r = 0.6, p  0.01), we find no consistent relationship between solar forcing and NAO. We conclude that solar and volcanic forcing impacts different modes of our reconstructed atmospheric circulation, which can aid in separating the regional effects of forcings and understanding the underlying mechanisms.

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Thanks for sharing that one Sebastiaan :)

I think studies using the NAO have run into trouble related to the fact that it is, after all, an extremely simple dipolar measure of the atmosphere that can't portray more west or east-based variations, for example, or the difference between a mid-Atlantic ridge into Greenland and a cut-off blocking high.

The East Atlantic pattern appears to fare better in this regard.

There's also climate change to consider, as it's likely tweaking the nature of the atmospheric responses to particular forcing just enough to cause some otherwise significant results to become not so.

 

This coming autumn-winter, for example, unprecedented sea ice patterns may produce some of the largest deviations from past experience that we've seen so far. How the heavily distorted surface temperature patterns interact with the developing polar vortex is going to be fascinating to observe; will the vortex become rooted to the displaced surface cold locations, or will it be controlled by other forces to the point that we see an unusual amount of stratosphere-troposphere disconnect with resultant stratospheric warming event potential?

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13 hours ago, Singularity said:

Thanks for sharing that one Sebastiaan :)

I think studies using the NAO have run into trouble related to the fact that it is, after all, an extremely simple dipolar measure of the atmosphere that can't portray more west or east-based variations, for example, or the difference between a mid-Atlantic ridge into Greenland and a cut-off blocking high.

The East Atlantic pattern appears to fare better in this regard.

There's also climate change to consider, as it's likely tweaking the nature of the atmospheric responses to particular forcing just enough to cause some otherwise significant results to become not so.

 

This coming autumn-winter, for example, unprecedented sea ice patterns may produce some of the largest deviations from past experience that we've seen so far. How the heavily distorted surface temperature patterns interact with the developing polar vortex is going to be fascinating to observe; will the vortex become rooted to the displaced surface cold locations, or will it be controlled by other forces to the point that we see an unusual amount of stratosphere-troposphere disconnect with resultant stratospheric warming event potential?

There's been some very interesting research lately into the impact of a warming climate on the future frequency of SSW's. Here are two such papers.

"No robust evidence of future changes in major stratospheric sudden warmings: a multi-model assessment from CCMI"

This August 2018 paper looks at the results from the 12 models involved in the 'Chemistry-Climate Model Initiative' and concludes:

  • No statistically significant changes in the frequency of occurrence of SSWs are to be expected in the coming decades and until the end of the 21st century. This result is robust, as it is obtained with three different identification criteria.
  • Other features of SSWs – such as their duration, deceleration of the polar night jet, and the tropospheric precursor wave fluxes – do not change in the future either in the model simulations, in agreement with other studies, such as McLandress and Shepherd (2009) and Bell et al. (2010).
  • The absence of a future change in SSWs is a robust result across all models examined here, regardless of their biases or different representation of the QBO, coupling to the ocean, solar variability, etc.

https://www.atmos-chem-phys.net/18/11277/2018/acp-18-11277-2018.pdf

On the other hand, this July 2017 paper finds there will be an impact:

"More Frequent Sudden Stratospheric Warming Events due to Enhanced MJO Forcing Expected in a Warmer Climate."

  • Given that the MJO is predicted to be stronger in a warmer climate, these results suggest that SSW events may become more frequent, with possible implications on tropospheric high-latitude weather.

https://www.seas.harvard.edu/climate/eli/reprints/Kang-Tziperman-2017.pdf

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