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Interitus

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  1. Of course the models can account for cold air - they wouldn't be able to forecast changes to milder conditions elsewhere in the world either - and the cold itself is not a barrier to milder Atlantic air, southerly plumes of air as happening concurrently with this easterly, seem to penetrate the deep cold inversion of the Arctic with increasing regularity. Surface temperatures at the North Pole are expected to reach above freezing this week. The thing in this case is that the cold is not at the moment forecast to be accompanied by blocking by any of the models for this time next week - the storm tracks and subsequent temperatures may be open to question but as it stands no block means incursion of low pressure is inevitable.
  2. Nord reached 0.7°C / 33.3°F on February 10th just last year http://www.ogimet.com/cgi-bin/gsynres?lang=en&ind=04312&ano=2017&mes=2&day=28&hora=12&min=0&ndays=30
  3. From the other place - Lock up your daughters, rampant blizzards forecast!
  4. It was some stratocumulus or altocumulus formation, IR image shows colder than surface so not fog, but not very cold so cloud tops not high image from Eumetsat
  5. This article from the Meteorological Society Weather journal is worth reading at this point - An historical and climatological note on snowfalls associated with cold pools in southern Britain - http://onlinelibrary.wiley.com/doi/10.1002/wea.666/pdf Jan 1987 rates as the record deep cold pool at around 495/496 dam 1000-500mb thickness. The authors say - In fact that whole edition of the journal from Jan 2011 is freely available and is a special issue focused on severe winter weather and worth a look for those inclined - http://onlinelibrary.wiley.com/doi/10.1002/wea.v66.1/issuetoc
  6. Sorry, not had chance to reply. Not sure about the turnaround and "the validity of precursors vs the precision in analysis". My specific analysis from 2nd Jan was for no SSW in January with the forecast data for 10th suggesting it was unlikely before 3rd Feb at earliest, which was correct. It was predicated on simple observation of the stratosphere climatology. Using the 80°N temperature at 30mb it can be seen that there tends to be a clear trend over time prior to an SSW. The graph below shows this with day 101 = date of reversal, and the green line the 2017/8 temperature up to 10/1/18 - The trend can be seen in other temperature data too and at different levels, though 30mb values tend to correlate best of all with 10mb (better than at 10mb itself), and results from a global circulation model suggest that the most significant temperature indicator of SSW is at 36mb (Jucker et al http://onlinelibrary.wiley.com/doi/10.1002/2014JD022170/full) This chart shows that it was at least 24 days before a similar temperature preceded a SSW. Temperatures have risen to values that have seen SSW in a shorter time, but without actually achieving one. If assuming the temperature trends to be roughly gaussian (normally distributed) it was 16 days outside of what would be 2 s.d event SSW - It might be that the temperature is a simplistic proxy for vortex strength which typically requires a certain time to overcome. The 10/1/18 temperature was on the low side for SSW years so maybe a small sample of similar values wouldn't be representative. However, when including non-SSW years also it can be seen that no SSW has been achieved within 21 days of a 30mb 80°N temperature of 191K a couple of degrees above the value of the tenth, and that these low temperatures are not that unusual, having been reached in half of the winters since 1979, shown below - Knowing that the Glo5eas ensembles use climatology combined with a raft of hindcasts means that it not predicting an SSW from early January while the GFS long range was 'going off on one' wasn't particularly surprising. I have posted similar temperature data before, in early December 2015 ( https://www.netweather.tv/forum/topic/84231-stratosphere-temperature-watch-20152016/?do=findComment&comment=3300215 ) which suggested that an SSW might not be likely 'til February (no likes, lol) contrary to excitement and clamour over the forecasts (including from JC a couple of days later) and of course there wasn't an SSW until the very early final warming in March. Now after considering the temperature tendencies as a viable probability density function, compare with the trends of MJO phase preceding SSW - only Jan and Feb included for clarity - Pick a trend...any trend. The use of phases is too granular, so here are the RMM1 + 2 combined as angles of the Wheeler-Hendon phase space - - bit better, perhaps some clustering but nothing clear. The reference to Garfinkel et al with Indian ocean phase 2 (or 3) is interesting because as they note with regards to MJO effects - "The lag between MJO phases 3 and 7 is consistent with the 30-60 day periodicity of the MJO", and the emphasis is upon the later phases affecting the Pacific, despite finding that they tended not to lead to tropospheric NAM anomalies from the strat, unlike phase 3. In subsequent papers, he only considers phases 6/7 (http://onlinelibrary.wiley.com/doi/10.1002/2016JD025829/abstract and http://onlinelibrary.wiley.com/doi/10.1002/2017GL074470/full) A better choice for referencing phase 2/3 might be Liu et al ( http://onlinelibrary.wiley.com/doi/10.1002/2014JD021876/full ) the results of which are largely similar to Garfinkel et al with SSW following shortly after late phases - but that the initiation likely occurs during phase 3. There is however one important difference - they set out to examine if there were any differences between displacements and splits with regards to the MJO - and that progressive and strong MJO lead to split SSW which explains the Garfinkel results. Schwartz and Garfinkel countered that the results following p6/7 were fairly even between splits/displacements so it is not significant. Liu et al produced different composites for MJO responses prior to splits/displacement - one size does not fit all, composite users take note, but most interesting is that there is little MJO effect for displacements, which are most commonly preceded by phase 0 or "circle of death". So where does that leave this event? It's a split, but it was preceded by a long period of displacement with wave 2 only peaking immediately before splitting. Throw in research from the likes of Albers and Birner ( https://journals.ametsoc.org/doi/abs/10.1175/JAS-D-14-0026.1 ) and the wave 2 may not even have propagated from the troposphere but be actually internal to the stratosphere, a symptom of the vortex splitting, not the cause. But also, it is gravity wave drag that may be the important factor for splits, once again displacements little influenced. But it has been very hard to find good analogues for this year's MJO which show similar patterns of propagation through the varied indices to the stratosphere - no analogues also means the value of composites is questionable - so I would like to see more evidence before ascribing more than a tenuous link to the MJO, despite it's recent amplitude.
  7. Clearly not tomorrow (today) morning, the green line is the forecast. FWIW the 228h prediction for the 22nd would be a daily record https://ozonewatch.gsfc.nasa.gov/meteorology/figures/merra2/temperature/tminn_30_2017_merra2.txt
  8. The question/answer is the wrong way round - the warming is happening there because the tropospheric vortex is still strong over Canada.
  9. The blog post unfortunately links to the current live version of the 10mb temperature anomaly animation but from the text it is obvious that there was an early season warming, over Siberia or east Asia. It also makes the common mistake that the warming somehow comes from the region below - it doesn't, it is descending air that warms adiabatically. The description in the chart below is self-explanatory, but it shows during a warming over Switzerland, a parcel of air descending around 4km in height over a 3 day period from over the US, warming around 40 K in the process. http://onlinelibrary.wiley.com/doi/10.1029/2009JD011940/full This blog is a poor resource to be fair. The next one is a bit better though very dated. It's simply showing that simulating the atmosphere requires stationary waves from topography as well as temperature forcing to reproduce the climatological wave pattern as we know exists from observation. But it is the excitement or interference with this wave pattern which is important for SSW. Though the principles remain the same, simulations have moved on a long way since 1974, see Held et al 2002 or more recently Chang 2009, who makes some interesting points not only with regards orographic but also tropical forcing - https://journals.ametsoc.org/doi/abs/10.1175/2008JCLI2403.1 Very constructive. The question was whether an index such as the NAO is a teleconnection. It fits the definition from the American Meteorological Society glossary - http://glossary.ametsoc.org/wiki/Teleconnection and it's included in IPCC documentation - https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-6.html but I'll let Huug van den Dool of the NOAA Climate Prediction Centre field this. The author of over 70 papers (http://www.cpc.ncep.noaa.gov/products/people/wd51hd/vddoolpubs/), chapter 4 of his book Empirical Methods in Short-Term Climate Prediction is entitled Teleconnections - a few pages of which are available to read online - https://books.google.co.uk/books?id=p61e5iIFudkC&pg=PA37&lpg=PA37&dq=huug+van+den+dool+teleconnections&source=bl&ots=vIpxD0tGOR&sig=0dydWzI8LcNYkK_KV9G6Gg5vZzg&hl=en&sa=X&ved=0ahUKEwiR0dTts47ZAhWSJlAKHQU9ASMQ6AEIRzAG#v=onepage&q=huug van den dool teleconnections&f=false He considers various ways how teleconnections may be defined but writes - That's good enough for me. I am aware of this paper, I made an indirect reference to it in this post a couple of years ago -https://www.netweather.tv/forum/topic/84231-stratosphere-temperature-watch-20152016/?do=findComment&comment=3338422. Anyway, there is a key point regarding this paper, in that it is specifically the contribution from mountains which isn't normally included in the calculated values of mountain torque! As the abstract above states it is an improved parameterisation to account for subgrid-scale drag processes i.e. too small to be resolved in global models, primarily gravity waves which begin to become visible with mesoscale models, eg. here over Greenland - http://onlinelibrary.wiley.com/wol1/doi/10.1029/2006JD007823/full Those into the AAM side of things should be familiar with this gravity wave drag parameterisation problem, as it has been a source of bias in forecasting and reanalysis, resulting in 'missing momentum'.
  10. Contrary to the opinions on this forum, the mountain torques are rarely considered directly in respect of SSW in the scientific literature. It's a rather niche subject which should be looked at after a grounding in rudiments which are explored in 99% of research. Good luck with your search for papers!
  11. Regarding the teleconnections argument, this opinion has appeared on a few occasions - beware - it is counter to the orthodoxy in meteorological circles. The links to the charts come from this forum, Tamara shouldn't be confused - she posted them The data isn't really specialist, the AAM is fairly easily derived directly from zonal winds. The torques are treated stochastically with paramaterizations, using 10 metre (surface) wind and roughness to calculate surface drag and elevation data for MT - numerous papers describe the techniques involved. Don't understand the website's statement, if they have the algorithms in place all they need is model data, unless they are getting the info from somewhere else or someone is taking the code away with them.
  12. Quite bizarre charts from GFS 00z, split removes a third of the vortex but leaves rump far enough north that there is no SSW by T+384 (18th Feb 00z) - u1060 +2.0 m/s at that time and no reversal northwards, but vortex almost encircled by large anticyclone giving easterlies between 58-34°N. Here is the zonal wind profile -
  13. Winds are easterly at the moment but this is the beginning of the return of the southern hemisphere strat vortex at the end of the Austral summer. The 10mb 60°S wind becomes westerly in mid-February on average. Nothing untoward in the wind anomaly plot -
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