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Interitus

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  1. Interitus
    Good estimates, -10.6 min at 1mb, 0.6 at 2mb. Compared to 21.9 ms and 27.3 on the 06z mind you.
  2. Interitus
    The wave 1 modifies the vortex enough to bring values closer to the range where a SSW has occurred. Taking the GEOS forecast from 15/1 for 24/1, the earliest an SSW has happened from the 10mb zonal wind is 6 days (30th Jan), 10% by 14 days (7th Feb), 20% 17 days (10th Feb) From 30mb wind earliest 7 days (31st Jan), 10% 10 days (3rd Feb), 20% 21 days.(14th Feb) From 30mb polar cap temperature earliest 6 days (30th Jan), 10% 7 days (31st Jan), 20% 17 days (10th Feb) From 50mb polar cap temperature earliest 6 days (30th Jan), 10% 13 days (6th Feb), 20% 19 days (12th Feb) Note the percentages are not quite absolute chance as not all SSW were immediately preceded by the forecast values forecast for 24/1, it is the percentage of all SSW that were.
  3. Interitus
    Roughly half-way through winter, taking the daily CET data from December and estimated values to January 15th, how mild has it been? This winter is 13th mildest (out of 245) with 2015/6 unsurprisingly top after the incredible December, but there are some short memories, last year was a tad milder to this point and of recent years 2006/7 is also ahead. Close behind are 2013/4 and 2011/2 in the top 20 - An alternative view is the absence of cold to this point, seen from the lowest daily CET. By this measure 2019/20 is joint 12th with a coldest day of 1.5°C, albeit right at the start of December. However 2013/4 is top with the coldest day a barely below average 3.5°C -
  4. Interitus
    Have to see the effect of the Euro/UK/North Atlantic high giving spike in wave 1. Vortex displacement again (as is the norm) but probably no quick change from the strat.
  5. Interitus
    Without knowledge of the exact dates used, the MJO - 500mb anomaly composites are an even blunter tool.
  6. Interitus
    Well, since last February anyway.
  7. Interitus
    Yes it can, if you have time for example read this link posted by @knocker
  8. Interitus
    No, you really wouldn't! 30th March 8000 B.C.
  9. Interitus
    No simple answer really. With regards to the years mentioned however, 2008/9 featured a roaring vortex at record strength from 4-8th Jan before the SSW. 2009/10 did have an SSW but on February 9th after the main cold spell. 2010/11 had no SSW and a generally stronger than normal strat vortex. Somewhat puzzling that while conditions are considered in remote influences such the Tropics and Pacific, Atlantic SSTs on the other hand rarely get a mention (indeed didn't feature in the Netweather winter forecast) when they have long been known to directly affect synoptic patterns for the UK and western Europe.
  10. Interitus
    Tomorrow about 67 ms, about the same as 1981 but less than 1989 for that day of the year.
  11. Interitus
    Can see where he's going with the MJO plot but the 500s?? They look nothing alike and in any case similarity should be of interest after a similar MJO i.e. at the end of the MJO forecast period, surely?
  12. Interitus
    OK, a quick look at something interesting from the analogues. The 30 day 10mb wave 1 heights from the GEOS analysis and forecast to 17/1/20 shows two very similar years, 2006 and 2013 - Day 31 corresponds to 17/1/20, 11/1/13 and 25/1/06. all dates are preceded by a similar peak in wave 1. This year it is currently easing off with an increase in zonal wind in the near term, but in 2013 and 2006 this reduced wave 1 was for a very different reason as can be seen in the wind chart - Both years had SSW on exactly the same dates from the corresponding wave 1 data, which would be 12/1 this year. What could cause the difference, MJO perhaps? The RMM plots show that 2006 and 2013 were almost identical - But get this, the amplitudes were generally low, only reaching 2 in both cases just 1 day before SSW (day 26) And the phases 7-8-1 don't feature at all in the previous fortnight - Clearly the similarities would suggest that there is some relation between the MJO and SSW in these instances but it would appear that the SSW or cause of it was affecting the MJO rather than the other way round.
  13. Interitus
    Read the rest of that twitter thread.
  14. Interitus
    Obviously a large degree of uncertainty is involved, but what may be of particular interest in this paper is the inclusion of SSW dates in reanalysis going back to 1850! https://www.mdpi.com/2073-4433/10/9/519/htm
  15. Interitus
    With respect to him, how well have Michael Ventrice's composites performed based upon these in tweets posted on here? All the resources should be used, but the point is as said none of them are set in stone beyond the deterministic limit. It's relying on tentative long range trop predictions then supposing that the strat is merely passive in response (it's not, its state matters) so...maybe, maybe not.
  16. Interitus
    We know how good they are.
  17. Interitus
    Maybe....maybe not - As shown many times, northern blocking is as likely to lead to a SSW as be caused by one.
  18. Interitus
  19. Interitus
    The 0.6C figure was for the most recent weekly data prior to the Dec 24th Climate Model Summary update, the 0.3C value was the latest weekly value on Dec 29th. Interestingly, given the association of a postive IOD with Indonesian drought, severe flooding has hit the capital Jakarta - 377.4 mm was reported in 24 hours on New Year's day at Halim Perdanakusuma airport in the southeast of the city, the highest one day total on record.
  20. Interitus
    To illustrate this, the 31/12 GFS 00z had a large wave break cleave a large chunk off the vortex at the 1mb level - source: instantweathermaps.com 1mb 60°N mean zonal wind 15.2 ms in the above 348 hr charts falling to 7.7 ms at 377 hr. But by the 31/12 18z run and subsequently there has been virtually no wave propagation and dartboard charts like today's 06z - 1mb zonal wind up to 82 ms, If these were to verify it would likely guarantee no SSW in January such is the timescale for one to develop.
  21. Interitus
    For tropopause defined by lapse rate the 500mb level is in the stratosphere and the GFS analysis 2PVU pressure gave a dynamic tropopause pressure of about 629mb. Interestingly though the actual GFS tropopause pressure value was 490mb, not sure how that's calculated, and at these low altitudes relative humidity is much higher than typical stratospheric air which can be seen with the dew point depression above 250mb.
  22. Interitus
    Obviously the ECM HRES doesn't go out to 10/1/2020 at this point so there is no way to compare. The GFS chart above has since updated and toned down that vortex disturbance, but at that range beyond the accurate deterministic limit, a SSW is likely to appear quite suddenly if one occurs (along with numerous false alarms).
  23. Interitus
    Just for context, most parts of Alaska display a continental temperature range such that difference between the average monthly minimum and daily mean minimum is typically quite a bit more than we are used to in the UK - (for December) varying from 11.5 degrees C for Anchorage in the south with more Pacific influence, to 13.5C for Bethel and Fairbanks and 16.2C for Bettles further north in the cold interior. So these anomalies typically appear annually on average and are a long way from December records (Anchorage -34, Bethel -42, Fairbanks -52, Bettles -51).
  24. Interitus
    Was going well, then he invoked the CFS.....here various members are simultaneously forecasting for February a SSW and record u1060 for the time of year.....well it's going to be somewhere between these, all bases covered! source: weatheriscool.com
  25. Interitus
    This chart shows GFS day 8 vs GEFS day 5 since 7th November. Over the whole period they have a similar RMSE, but while the GFS got the recent peak fairly accurately eight days in advance, the ensembles didn't even 3 days later. Indeed the GEFS only showed a mean >50ms for the first time at 3 days prior to the peak whilst when the GFS cottoned on it showed >50ms at day 10 -
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