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Interitus

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  1. Interitus
    The 10-day GEFS mean from December 7th 00z for December 17th 00z was 19 m/s, the eventual GFS analysis value was 52.9 m/s, just saying.
  2. Interitus
    Use the 'Activer Live Compare' for comparisons of runs within 24 hours. For longer comparisons, weatheronline expert charts allow selecting a lead time then varying the base time, as does tropicaltidbits
  3. Interitus
    Two sides of the same coin regarding flow patterns. That said, cool anomalies have not been as large as warm anomalies. BTW, Yellowknife is in NWT, Yukon has been mild like Alaska.
  4. Interitus
    The Alaskan anomaly is the most intriguing - it was unusual when pointed out in this thread over a month ago (Nov 15th) but to be still present now is staggering. Sure, Anchorage has had some snow in the intervening period, but then followed a December record maximum of 10.6°C (previous record 8.9°C). Last 30 days temperature anomaly of 7.2°C
  5. Interitus
    Ozone and CO2 concentrations - https://ozonewatch.gsfc.nasa.gov/facts/SH.html While tropospheric CO2 is now >400 ppm, it is slightly lower in the stratosphere and with increasing altitude and latitude because of the lag of the transport mechanisms - https://www.atmos-chem-phys.net/17/3861/2017/acp-17-3861-2017.pdf Antarctic ozone holes - https://ozonewatch.gsfc.nasa.gov/meteorology/index.html The chlorine / bromine levels as mentioned of course increased with the release of now outlawed CFCs. Comparison of Arctic/Antarctic ozone holes - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4035972/ The Arctic vortex is more disturbed by planetary wave activity so tends to be warmer thus the PSC formation is lower, less frequent and widespread (areally and altitudinally), or persistent into spring and the returning sunlight - https://uk-air.defra.gov.uk/research/ozone-uv/moreinfo?view=arctic-ozone-hole
  6. Interitus
    Stratospheric ozone peaks at about 15 ppm, CO2 is >370 ppm. With regards to the stratosphere vortex, the lob-sided ozone distribution is a response, not the cause. There is UV in the Arctic like the Antarctic......in spring time! Later winter and spring is when the depletion occurs and ozone holes are formed.
  7. Interitus
    MIA... Yes ozone is very reactive, though there is very little UV dissociation it is the polar night. However, you really might want to reconsider its concentration compared to CO2! As for the surface temperature/ozone distribution, there appears to be no coherent correlation whatsoever. And to repeat the graph posted before, there is not an anomalously high amount of NH polar ozone
  8. Interitus
    The age of the paper was intentional to show that ozone has long been used as a tracer following the forcing of the planetary waves as stated. It is the planetary waves forcing the vortex, the ozone follows these. The 'lob-sided ozone excess' is because the air within the vortex is to a large extent isolated from the more ozone rich air which mixes into the stratospheric Aleutian anticyclone. As explained, the peak in the graph at the beginning of the month is because we have just had a substantial period of wave 1 displacing the vortex and transporting ozone polewards. The difference last year of course was that at the end of December - start of January there was a SSW and the vortex broke down. This is what allowed the spread of ozone across the pole.
  9. Interitus
    As indicated in the paper, it is the reduction in ozone not its presence which causes a net cooling effect - reducing interaction with UV in the stratosphere and reducing blocking of IR radiation from the earth surface. The majority of the UV interaction is at lower latitudes, of course there is none now in the polar night, and it is from the lower latitudes that much ozone makes its way to the pole. Currently overall NH polar ozone is within normal bounds, a recent peak was seen with increased poleward transport associated with the vortex displacement - source: https://ozonewatch.gsfc.nasa.gov/NH.html Ozone transport has long been used as a tracer for stratospheric flow, indeed it was important in visualising the vortex with planetary wave breaking, the "surf zone" etc eg see this 1985 paper - https://journals.ametsoc.org/doi/pdf/10.1175/1520-0469(1985)042<0230%3ATOOITM>2.0.CO%3B2 Recent warming in the stratosphere is just a normal early winter event - best taken to the strat thread for further discussion!
  10. Interitus
    The ozone is a tracer, it is not forcing it is following the forcing.
  11. Interitus
    5 days later on this run, the 10mb 60N wind has recovered to a healthy 53.7 ms. Wave forcing initially reduces zonal wind by changing the vortex shape, but also enhances the wind locally. Interestingly, at T357 (26/12 21:00) the 1mb wind reaches 177.9 ms just off the Scottish coast, or in units most might be more familiar with, a incredible 398 mph (640 kmh) -
  12. Interitus
    It looks like the FV3 has the edge on purely simulating the strengthening Autumn vortex but then when the planetary waves really kick in from the middle of November. both tend to go a bit wayward. Don't know whether this is a wave propagation thing in the strat or due to the unpredictability of the waves from patterns in the trop.
  13. Interitus
    Day 10 verification graph - analysis from Nov 9th 00z - Dec 7th 00z, and forecasts on to Dec 17th 00z
  14. Interitus
    Here is a graph of the GFS and GEFS mean T384 forecast zonal wind compared to the actual analysis values, from November 15th onwards - The GFS has forecast higher zonal wind speed, average +9.1 ms. The ensemble mean has forecast lower zonal wind speed, average --4.2 ms. (Obviously a smoother plot as mean of 20 members). Interestingly these biases have been fairly consistent (i.e. above vs below) such that the average of the GFS and ensembles is closer than the two individually. Must be remembered that this zonal wind is a pretty limited 1-dimensional quantity, compared to an areal analysis such as geopotential anomaly correlation - so forecast equal wind speeds which may appear accurate could be achieved from very different geopotential charts. Case in point - Here are the geopotential charts corresponding to the above temperature profiles - The T384 forecast chart may have had the more noticeable warming posted above, zonal wind 28.6 ms, yet the second vortex of the 4th December analysis is more displaced and hence the vortex appears weaker from a zonal wind perspective at 18.1 ms. Not too much should be made of zonal wind or temperature charts in isolation.
  15. Interitus
    Would be worthwhile popping this in the strat thread
  16. Interitus
    It doesn't show easterly winds - as described at the top of the main webpage - https://acd-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/seasonal_strat.html "The plots are all 2-panel. The RHS plot shows the 60-day time-mean profile of the quantity, while the LHS shows the deviations from this 60-day mean." So the blue colours in the forecast show winds below the previous two month average.
  17. Interitus
    In essence, don't put money on it!
  18. Interitus
    Those charts (and subsequent Skew-T) are self explanatory, surely?
  19. Interitus
    Briefly, the ensembles have overdone the weakening throughout this period so far, just six days ago the 00z ensemble mean wind for today 06z was 15.2 ms compared with today's analysis of 21.6 ms.
  20. Interitus
    Vrooom
  21. Interitus
    Interesting difference still in zonal winds between GFS and GEOS from today's 00z runs - However, at day 10 they look by eye to be pretty much on the same page - GFS GEOS The GEOS vortex is marginally more displaced with the GFS propped up with a touch of wave 2. The result is the polar night jet is shifted southwards slightly on the GEOS - GFS GEOS And though the GFS is only marginally stronger - maximum windspeed of 88.6 ms vs 85.8 ms, the difference in windspeeds occurs almost smack bang on 60°N -
  22. Interitus
    GFS 12z 10mb 30mb Full steam ahead!
  23. Interitus
    No SSW in any of those Decembers. Admittedly they occurred in early Jan 1970 and 1977 (end of February for 1983/4) but this and another tweet are emphasising cold Decembers i.e. prior to SSW.
  24. Interitus
    Yes, 6-hourly forecast times, just an unformatted rough and ready plot!
  25. Interitus
    GFS/GEFS zonal wind difference continues on 06z, though the ensembles have some support from the 00z GEOS
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