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summer blizzard

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Everything posted by summer blizzard

  1. Three SSW clusters in that first third, the mean avoids it but largely due to spread and the strongest SSW is probably the highest plurality.
  2. 13DEC2023: Nino3: 2.1 , Nino3.4: 2.0, Nino4: 1.4
  3. They were very different years even allowing for warming so I don't think we have to allow a substantial discount to 2022.
  4. It's at ~17 Degrees south so very tropical. Basically in Venezuela.
  5. Modelling currently suggests that we flip from Nino back to Nina. -QBO is likely to flip towards +QBO by end of year. -PDO is likely to persist IMO. 2010 and 2022 seem to be the best analogue matches of recent times.
  6. As the second chart shows even if we end up with a SSW (we don't on this but it would just be a darker blue), it will still be January when it's reached the troposphere. Thus we are as you say dependent on tropical convection but since it looks like we will miss the boat on on the late phases. Current convection suggests we might persist somewhat into 2-3 but the Indian Ocean is normally not our friend.
  7. Still here. Tamara knows more than I and summed up the pattern earlier but essentially my take is that tropical convection is in/moving into a position conducive to blocking to our north east and then north west but bar a poor looking northerly attempt it looks like the tropospheric zonal flow is too strong. We've missed the boat on this tropical cycle I think however it does look like there might be less tropospheric zonal flow and a conducive tropical pattern towards mid January.
  8. SSW or not (not in this case), it's interesting to see that the weakness does actually propagate down. Remember that Jan 12 failed to achieve an actual SSW but the hit was enough to give us the first half of Feb 12.
  9. Interestingly it turns out that the two most likely periods to produce a SSW are 1st-10th January and 20th-28th February. GFS0z operational got as low as 8ms today but the GFS ensemble mean to 1st Jan was still 20ms. 37% of Euro ensembles do get a SSW between the 7th-29th January (only 17% during week 1 of Jan now) but as the mean is actually rising, I think that's noise. So my message is essentially that it looks like we don't get a SSW during early January.
  10. Low is still weak so while it may rain for a long time due to track, it probably won't be that heavy.
  11. Assume your referring to 14 years rather than a decade, Jan 21 was colder than Jan 13 (though the later did have the coldest spell). I'm maybe 40% supportive.
  12. There's normally a lag so globally it's impact would be 2025 however for the UK there's no strong annual link. 2011 and 2014 were very mild and during/after La Nina.
  13. 06DEC2023: Nino3: 2.0 , Nino3.4: 1.9, Nino4: 1.4 MEI also increased to +0.6.
  14. Aug-Nov 2019 was very wet, it just dried up a little by December while this year waited until mid October.
  15. Others have described it well however the two simplest reasons are.. 1) High pressure in winter essentially traps cooler surface air when it builds behind a cold front, this makes it difficult for a high to sustainably produce mild weather unless it remains in place several days 2) In winter the continent is relatively cool and thus a persistant SE flow will tend to draw relatively cool air while the SW flows capable of producing warmth are by their nature less likely to persist because the westerlies will tend to try push the high east.
  16. Some people in the model thread need to breathe. December was always more likely to be somewhat hostile to prolonged cold as per my own favoured analogue set. December vs Jan for example.
  17. The question is whether the 16 day GFS operations have greater resolution in the stratosphere than the Euro 32 day forecast.
  18. Worth remembering that this is decaying WWB from November as per that chart. There was always a chance that it would wane, especially relative to the last orbit.
  19. As Nick explains, when the high builds initially it traps the cooler air that passes the UK on the 14th. Because the high is sufficiently strong, even the intrusion of warm upper air does not entirely remove this at the surface over England. By the time the incoming low is mixing out the air, the GFS has the next cold push.
  20. I'd not worry too much. We have a reasonal amplitude tropical cycle forecast between phases 4-7 (GFS keeps going back and forth on phase (8)) and phases 4-6 in December are pretty zonal (we actually do well to keep higher than average pressure in the current output). The blocking around the UK/North East of the UK is mainly a phase 7-8 thing and current output allowing for a week or so's lag puts that near xmas. Basically when the weather is doing what the tropical cycle says it should, that's not a bad thing because the pattern will probably shift. It's when it does its own thing that we need to headscratch.
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