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Glacier Point

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  1. Glacier Point
    and 12z day 10 with 06z for comparison: and the GEFS temperature anomaly for that time This I think is a reasonable projection based on the global wind oscillation going through phase 4/5 type evolution. The key point that heights remain strongly below average across Europe. That supports +ve height anomalies to the north and prevents any widespread ingression of the Atlantic. So low pressure signal in the Atlantic, agree with that. Atlantic powering through across NW Europe on a positively tilted jet - disagree with that, but with the caveat of a less cold spell 20th - 25th Jan is very likely based on the waxing and waning of the downelling stratospheric warming impacts.
  2. Glacier Point
    .. and also Nick the deep troughing over Europe which is going nowhere fast. This the 06z GEFS H5 anomaly for day 10: The development of the residual vortex over Hudson Bay should not be looked at in terms of how we might look at a traditional pv which has a strong zonal wind profile behind it. As we know, the vortex has been shattered, and zonal winds reversed or very light. That allows the stratospheric vortex to wind itself but not able to draw the downstream response, which explains why the flow across the Atlantic is running out of puff and disrupting. Temperatures look to be 3-4C below average according to latest GEFS out to day 12 at least. Interestingly, to reignite the 'which is the better teleconnective index for UK cold' issue, the AO continues negative whilst the NAO positive. Which index is performing better (as a predictive tool) in terms of the UK ?
  3. Glacier Point
    Yes it does show a more sustained influence in February, although just where the blocking would be in this scenario would be open to some doubt. Generally, the more 'mature' the blocking signal, the further west the block is, which could well be over Canada during mid Feb. Long way off though.
  4. Glacier Point
    Thanks Ed, that's useful to get that second view. Wonder how well the NWP will pick this second wave up ? The fast initial downwell really only was captured a few days out. Theoretically as it's a more obvious and gradual progression across the tropopause we should see better modelling although I'm far from convinced with models and strat developments. Although it's a modelled parameter, the degree to which it influences the circulation doesn't seem to be too good (my anecdot) and perhaps borne out by the complete meltdown in usually reliable timeframe modelling.
  5. Glacier Point
    Useful to compare Baldwin's composites for weak vortex events and where we are now: That's a good match on the initial 'outrider' +ve GPH anomaly and the first main downwell centred on 15th January. Based on this, second phase to impact around 25th-28th January.
  6. Glacier Point
    Models exhibiting shocking inter-run and intra run continuity, and that's just the ensemble means ! The only constants that stand out here when assessing the next 10-14 days: - troughing signal for Europe; - below average signal for Europe; - general signal for +ve height anomalies to our north and NE. Beyond that, don't bother attempting to place any value in model solutions, of any type. A good time to be able to put non-NWP assessment alongside the myriad of options here. With angular momentum increasing off the back of tropical convective waves in the Pacific, we should see the above general synoptic as the benchmark.
  7. Glacier Point
    The real developing story for me being the impending collapse of the polar vortex. We should be looking around day 9/10 for a complete cleaving in half across the Arctic with tropospheric reponse a few days later. A few GFS ensembles showing this. Still looking very likely that the second phase of cold will come out of the NE. Strog ensemble mean and teleconnective support for a deep trough to take up residence over Europe in the meantime, and also signal for low pressure in the Atlantic. ECM op not for me.
  8. Glacier Point
    Day 10 GEFS anomaly Deep upper lows in the Atlantic and Europe, beginning to come together. Plenty of potential for undercutting and sooner or later, we have to see the atmosphere respond to the north with height rises as a way of balancing the system. Still very much favouring the golden triangle between Greenland, Svalbard and Scandinavia for height rises, possibly the pendulum swinging back to Scandinavia for the time being. Remember though the typical stratospheric warming timelines.. Initial downwell response about 15th Jan, brief respite from the cold around 20th -24th (just how much of a respite remains to be seen) before a reload and much more significant impact around 28th Jan (which should come from the NE).
  9. Glacier Point
    The key developments around t96 so we still could go for another 24 hs before final resolution. Key things fo me, the 06z GFS has begin to adjust a positive tilt to the jet towards a negative tilt angled south of the UK. Also, main lobe of pv is becoming detatched from west of Greenland and the field vacated is seeing some signs of a divergent flow.
  10. Glacier Point
    briefly... Next week's forecast looks horrid and complex. I would go below average and becoming increasingly cyclonic. That brings an attendant snowfall hazard. Ironically, day 10+ might be less problematic to get a broad view on. Tendency in relative angular momentum is very likely to spike in the next few days. That will shoot the Global Wind Oscillation towards high amplitude phase 4. That teleconnects with the core of the +ve height anomalies in a triangle between eastern Greenland, Svalbard and northern Scandinavia. GEFS has trended this way in the last 24 hrs, as has ECM. Also trending is the development of some energy off the residual pv over Canada into the North Atlantic, which most likely to reinforce the blocking signal further north and NE. Low pressure signal over Europe still very strong. Interestngly this perhaps resolves CPC's teleconnective issues w/r/t Greenland and Pacific blocking structures. So period 14-21 Jan looking cold and unsettled with wintry mix. Thereafter, signal for renewed push of Arctic air from the NE.
  11. Glacier Point
    GEFS H5 anomaly at day 6 (GEM?) GEFS H5 anomaly day 10: Spreads day 12:
  12. Glacier Point
    Might be worth separating the data into winters with observed MEI > +/- 1 value; and previous summer GLAAM value where this exceeded -1 or +1 as this might give an insight into lagged Brewer Dobson / entrenched tropospheric pattern.
  13. Glacier Point
    70% ECM 30% GFS
  14. Glacier Point
    If I could allay a few fears here.. The 10 hPa and 100hPa operational 06z still looks consistent with overall strat developments, and general signal for ridge in the NE Atlantic locale. t300 GEFS mean height anomaly very well defined, ridge signal eastern side Greenland and deep trough over Europe including UK. The operational GFS and some ensemble members maybe picking up a reasonable idea for shortwave development between Iceland and Greenland, which makes next week's forecast that bit more problematic. Clearly the quicker the cold uppers become embedded the better for snow prospects next week. Interestingly NOGAPS which had championed this idea has now binned it 06z. Just demonstrates the massive spreads that currently exist in the North Atlantic in the medium range and large scale inter-run disagreement in NWP. That doesn't alter the general trend here. Cold to begin this weekend, continued signal for a slight moderation in this before cold becomes more aggresive once more, timed for second and most significant downwell from the SSW. Note how the GEFS and also ECM ensembles begin to re-intensify cold beyond day 10. Bottom line - don't mistake a tendency to moderate cold next week (and undoubted model variability to expode that out of all proportions) with a failed cold spell.
  15. Glacier Point
    .. Another GFS run which maintains a strong upper ridge over the NE Atlantic and suggests a trend to shift the residual vortex from Canada rapidly towards Siberia in the day 10-15 timeframe. Whenever this occurs, the pivoting in the atmosphere that takes place is extremely supportive of major outbreaks of Arctic air. It may look as the polar stratosphere is cooling but I suspect this ties in with the peak tropospheric impact around the 25th-28th January and then into early Feb. Taken at face value, we also have another Pacific ridge developing in the stratosphere which leads us..... to another warming episode in mid to late Feb ?
  16. Glacier Point
    and the key thing there, the large amplitude in the high AAM phase spaces will induce a significant westerly wind response, first through increased frictional torques (happening now) and then through eddy flux and mountain torques. Tendency in relative angular momentum could reach record levels converging the tropospheric - stratospheric coupling. I suspect that the warming event will actually stall the MJO over Africa and the Atlantic.
  17. Glacier Point
    Indeed, this cannot be stated enough. The strongest tropospheric impacts will likely be felt 20-30 days following the initial warming. Current MJO forecasts are really gunning for a big amplication in the western Pacific which is going to off-load a lot of westerly inertia into the tropics and which will spike the pattern of mid / high latitude blocking structures around the end of the month which will add extra spice to an already persuasive stratospheric signal.
  18. Glacier Point
    .. agree with these sentiments. The period mid Jan has been tipped up as the transition to a colder pattern as first warming impacts transfer downwards. Thereafter, some relaxation in the cold (but still cold) and then we look again period 20th and then more likely around 28th for full impacts of stratospheric warming, with likely tropical convective signal and crucially Global Wind Oscillation becoming highly favourable for weakened sub-tropical ridge. Notice on GEFS the number of members heading into the very cold bracket at the extended range.
  19. Glacier Point
    anyone else picking up on GFS long range trend, very sharp movement of the residual vortex from Canada towards Sberia ? The whe stratosphere seeming to move at once. Once again, parallels with many a sharp outbreak of very cold episodes, the most graphic I can think of showing this type of evolution was 1987. The timing of this very interesting, about the same time our downwelling from first warming (and 10 day from second warming) is due to hit the lower levels.
  20. Glacier Point
    A cracking 06z GEFS ensemble mean which sits well continuity wise with the 00z GFS and ECM runs. Not overly cold at face value but get the synoptics into position first.... The split tropospheric vortex looks like following the strat lead at this range. The fundamentals being residual vortices over North America and Siberia with a ridge over the Arctic. The balance of energy post split in these two vortices being the key modelling issue at present. Todays runs have placed a bit more emphasis on the North American vortex whereas yesterdays were favouring the Siberian / Scandinavian one. What doesn't seem to be an issue here is long term. Strat lead pulls the North American vortex further and further west and south. We should continue to see the tropospheric vortex pull away from Greenland allowing for height rises (06z op an outlier here!). The upper and middle stratospheric modelling is unbelievable at this stage and is as clear a signal as you could get for a Greenland ridge.
  21. Glacier Point
    Recretos - those NCAR reanalysis numbers are always tricky to read - 1987 !
  22. Glacier Point
    Ok, seen enough consistency in GFS forecasts to suggest that there the main residual chunk of the vortex will be trending towards Scandinavia, with a ridge over the Arctic and weaker pv chunk displaced into the Canadian interior / mid west States. GFS 18z 03/01/13 a good representation of this at t300. Composites for this pattern: Rolled forward for January: Rolled forward for February: (might be under-doing the AO although highlights nicely the potential for Atlantic incursions in February) A potentially very special period of wintry weather upcoming, particulalry with the MJO choreographing itself so nicely.
  23. Glacier Point
    http://www.meteociel...&mode=0&carte=1 .. probably one of the most negative AO charts you'll see. Polar vortex completely, utterly destroyed. The gyre of the whole upper atmosphere is clockwise for a considerable 5-10 day period which pancakes the tropopause and the entire hemispheric circulation breaks down. Cold air is displaced into the tropical stratosphere and ypu'll likely see a U-wind response in the tropics with severely weakened trades and intense convective activity in the central Pacific region and Africa with feedback responses which will extend well into the spring (not necessarily a cold signal for Europe for the entire period though). Remember, this is potentially the starter. A bigger wave response likely around the 25th - 28th Jan. Upper stratospheric profile continuing to bear a strong resemblance to 1987 for our side of the hemisphere.
  24. Glacier Point
    Every model run developing the strength of the +ve H5 anomaly to the north as it latches onto the downwelling -ve zonal wind anomaly. GEFS 15th January now showing a very coherent -AO signal: and compared to Baldwin's composite, this is just for starters. Imagine in another 10 days time what the potential is here when the stratospheric signal matures. With the continued modelling of the main PV lobe into Scandinavia and secondary lobe lifting out of Hudson with solid ridge straddling the Pole, composites for this suggest a blocking signal centred over Iceland. The best analogues for the upper stratosphere right now are 1979. 1982 and 1987.
  25. Glacier Point
    Strat profiling is very interesting... tendency to drop the main residual pv into Scandinavia !! Cold block and cyclonic for month's end ? We could well be looking at some brutal cold entering through Finland and wstern Russia / eastern Europe. So it begins, first rapid downwell underway. Main body of the impacts at day 20 (latter part of January).
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