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Snowy Liverpool

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  1. Good agreement on the AO to shoot up in around 7-10 days. Statosphere forecasts also suggest the polar stratosphere to cool down to average for this time of year. I always thought there was a considerable lag phase between the two events, but the AO at tropospheric level seems to be following the stratospheric conditions at a lag phase of just a few days and it's beginning to show in the models e.g. some going for a breakdown of cold as early as 6-7 days away. Is it really going to be this quick?
  2. Poleward flux forecast looking great today, almost there.
  3. The PNA is starting to get a few members on the positive side now, and in the positive phase we see lower pressure over the North Pacific and Aleutian Islands. This tends to be a precursor for increased stratopheric wave-1 activity. I have no idea how reliable wave amplitude forecasts are, but ECM is going to a big rise in wave-1 in 7-10 days:
  4. Does anyone know of temperature observation graphs for lower down in the stratosphere and maybe upper troposphere. CPC shows the temperature down to 70mb , but it would be good to have 100, 200, 500 etc.
  5. That 2nd warming over Greenland/Canada keeps disappearing and reappearing, with the latest run showing a very weak warming. I never thought there would be so much uncertainty in a stratosphere forecast for something that's just 7-8 days away. At least the pressure charts at 10hpa still show that the weak warming will push that fragment of vortex away from East Canada/Greenland.
  6. I'm pretty sure some minor warmings occurred in December 2009 and November 2010, like something similar to the start of December this winter.
  7. GFS showing a 3rd warming over Canada in deep FI, at this rate the North Pole will be staying relatively warm for 3-4 weeks. Also showing the colder air going to the North Pacific, if the vortex can end up there and we get a deep low in that area we could set off another round of wave 1 activity. Just a concern about tropospheric impact of the SSW, the GFS continues to show low pressures running the show in that gap between scandinavia in Greenland, despite the split in the vortex down welling very smoothly from 10mb to 100mb. Kind of frustrating seeing very little on offer in terms of cold i
  8. It's looking that way, but looking at that graph it seems the same thing happened early in December before the minor warming changed it towards the Pole. At least the strength of it away from the Pole is set to decrease rapidly.
  9. It's very likely to happen as the stratosphere is nowhere near as variable as the troposphere, so is much easier to forecast. 7 days out (the time when the SSW is expected to happen) is still a very reliable time-frame for the stratosphere. At the moment zonal winds expected to just about still be positive at midday on the 4th of Jan, so I would say the SSW will happen on the 2nd half of the 4th of Jan or the 5th of Jan. The date has been pushed back very slightly, it's almost negligible.
  10. You can't get excited about cold weather on this site, apparently excitement is the same thing as guaranteeing a record breaking cold spell for the UK. The simple fact of the matter is that almost all cold spells come from SSWs and it's rare to get a cold spell without an SSW. People have every reason to get their hopes up for an SSW, would you not get excited in a poker game if you got a card that turns your chances of winning from 10% to 70%? To associate every SSW with cold for the UK is naive and of course patience is needed to wait and see where the northern blocking develops in the tropo
  11. Anyway, just wanted to post that Cohen will be releasing a paper in January about tropospheric precursors to large AO events, sounds like it could be a very helpful read and it hopefully builds on the knowledge of existing known precursors. https://ams.confex.c...aper219017.html
  12. Major SSW is looking likely, which will cause a displacement of the vortex. The vortex will then split several days after this as well though. Interesting strat temperature from the 12z today, going for a second warming, this time over Canada. The PV must be getting fed up of this now.
  13. I'm not sure if this is a split or a displacement going on here, or is it possible to have both? With wave 1 hitting first, followed by a wave 2, the stratospheric pattern seems to reflect this with a displacement first and then a split.
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