Glacier Point

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  1. Messy - if nothing else on the basis of the messy and slightly incoherent composites for phase 6-7 of the GWO for January and how we relate those to the back end of January into February where these become more coherent.
  2. GFS starting to pick up the amplification coming out of the Western Pacific 23/24th January - where will the anomalous ridge manifest itself over NW Europe ? 12z going for Scandinavia. Not sure I'd agree with it there, and much will depend on modelling of the decline of the vortex over Greenland.
  3. So, verification for posting in as much I can do so given we are in the midst of model mayhem and projecting forward using NWP is not going to be convincing. The only things I can verify at this stage are: GWO passing through phases 5, 6 and then into 7 with a lagged atmospheric response up to 10 days. Well, Check. Atmospheric response for phases 5 and 6 and observed in this critical period: and the observed mid month so far.. Not bad. Timing was specified out to 10 days from the 9th/10th but still what I would regard as the margin for error, particularly as the posting was dated end December when none of this was sniffed at. Also note the slight west based -NAO observed that was well signalled, long in advance of any model solution. So mid month northerly, followed by lull as the pattern becomes more Atlantic driven as the NAO becomes more west based for a time. This is now, so reanalysis in a few days will be interesting, but I reckon I'm good for that. Turning to the final third January into early Feb, this does present some difficulties as monthly change overs are problematic - do we use composites for January or February ? Notwithstanding this, broad guidance on the assumption of a stalled GWO or even heading back to phase 5 is towards the mid Atlantic / southern Greenland anomalous ridge and northerly / northwesterly./ northeasterly vectors. Granted, current long range modelling is not there (but caution advised in relying on this, moreso at this juncture given synoptic variability), but trending there (06Z GEFS mean has a strong but flat mid Atlantic ridge). Here comes the usefulness of being able to understand why that might be and when that might change. I would suggest the current strengthening of the stratospheric vortex is destructively interfering with the tropospheric pattern by strengthening the vortex west of Greenland. This prevents the Atlantic ridge from extending northward into Greenland. When or more importantly how will this change ? With the GWO heading back to phase 5 around 23rd -28th January, we should expect some more amplification to be levered into the upstream flow. That gives us back end of January or more realistically early Feb, although you'll appreciate the margins for error and the final few days of January would not be beyond reasonably possible. That also coincides with the likely displacement of the stratospheric vortex away from Greenland. So bottom line here is that we continue to see signals for mid Atlantic ridge extension towards Greenland and -NAO conditions during late January into early February. That should be put alongside current model consensus which does not suggest this.
  4. Updated upper level velocity potential update (GFS) is interesting.. Continued migration east of the -ve anomaly towards the Maritime Continent during week 2 but note also split emerging between North and South Hemispheres with the Northern Hemisphere element well into the Western Pacific. That suggests tendency in angular momentum will show an increase during week 2. No dramatic fall off in angular momentum. Also, GEFS and EC EPS consistent on dropping an upper level trough through the Western Pacific (i.e. downslope of the Asian Massif) 23-24th Jan, with upslope ridges and troughs - good precursor pattern for generating westerly inertia into the Asian Jet. Net result, GWO will continue to orbit high amplitude phases 6-7 and, with the renewed injection of westerlies coming, shade phase 5 as well.. Stress again, these composites are for February, and Jan composites not so keen on ridges in these locations but still suggestive of Scandinavian troughing (bet messy otherwise). So the close we get to Feb, the more I would expect the ridge to our west and north-west and trough to the east to bear out. Strat allowing..
  5. Op GFS has just shifted in a massive 600m in its 500 hPa geopotential height over Kara Sea at day 7 between 06z and 12z runs. It also now has the North Atlantic a seething pool of meridional flow where once there was a unified deep upper low.... Atlantic hurricanes in January, this is just bonkers.
  6. GFS has too much bias towards the MJO in phases 8 and 1 which invariably transposes too much negative pressure on angular momentum. Re Strat - not sure we'll get a proper warming, more another perturbed vortex albeit a pretty significant one.
  7. CPC analogues rolled forward days 10-12 confirm the idea that we are heading towards an Atlantic ridge / Scandinavian trough solution in the last week Jan into early part of Feb... which might be useful as the models seem to be losing all coherence as we approach the business end of the winter. Relative angular momentum has peaked in the last few days and, as tendency in relative angular momentum (the rate of acceleration or deceleration) cannot be maintained forever, some negative tendency is expected in the next 10 days. Total and relative angular momentum will however remain high as a large surplus of westerly inertia remains in the atmospheric system, demonstrative of a fully coupled atmospheric - ocean circulation. That places the GWO in a quasi stationary phase 6-7 orbit for the next 10 days. Composites are a bit messy but broadly align to Scandinavia trough a deep low in the Western Atlantic. This is complicated as we are approaching a monthly change, and February's composites hold some value. But generally Atlantic attack from the south-west and re-asserted Scandinavian trough as the theme. The GFS and EC monthly and EPS MJO signals suggest the MJO to become coherent in the Indian Ocean and towards the Maritime Continent during weeks 2-3. It should be remembered that there will remain a low frequency signal for convective anomalies in the Central and Eastern Pacific as well, so the MJO projection onto the system will be altered and angular momentum will remain high. MJO composites alone of limited value and it should be stressed again that the MJO signal needs to be transposed onto the GWO. The main point to draw from this signal is that angular momentum will begin to rise again during week 3 (early Feb). This gives a stable GWO phase 7-6-5-6 type look to the pattern for the next 2-4 week period, with phase 6 being a strong attractor within the base state. Composite is very consistent and now familiar as we turn towards the back end of Jan into Feb...Scandinavian trough, anomalous ridge centred just south of Greenland. Those looking for early spring warmth in the first part of Feb may be disappointed. As wind vectors, I would be thinking NW, N and NE, allowing for a bit of westerly flow days 7-10.
  8. Andrej - are you able to plot previous GEFS means on top of your zonal winds graph so we can keep a check on how the individual GEFS runs are progressing this ? Thanks
  9. I would go along with Cohen's view on a temporary bounce in the AO as a precursor to the early stages of warming being programmed now widely across NWP. Think of at as a Tsunami. The seas get withdrawn prior to the wave breaking onshore as the tropopause is depressed over the Arctic and lifted around the edge of the polar region. That bounce may actually be from -6SD to -2SD, enough though to send the GFS into a tailspin. Today's EPS and GEM ensembles dropping strong hints of mid latitude highs being in position from day 10 onwards, and lowering of pressure over the Arctic. How long will they stay there though, that's the key question ?
  10. @Noballslikesnowballs tropical forcing centred in the central part of the Equatorial Pacific. Check the period forecast off that analogue.....
  11. Not sure the GFS is handling this North American trough, or indeed the blocking over the Arctic too well at all. 06z and 18z runs seem to be particularly volatile on this with large inter run variation.
  12. Wholly agree with this assessment. With a +AO regime, this becomes horribly warm as per November and December. With a -AO, suddenly things begin to look a lot different. What was your foe now becomes your friend. Very good agreement between EC EPS, GEM Ensembles and GEFS around day 10 for increased rate of sub-tropical flow into the Atlantic. Further upstream amplifications already likely, which will all work to cold pattern's advantage. Definite signal for persistence of the cold. Whilst a west based -NAO is a risk at times (guidance suggests more long term trend eastwards - or centrally based to be more accurate), this does open the door for moisture to come into the SW approaches. The upstream amplification coming will help to correct any trend for too much west based NAO stuff I think. Meantime, total angular momentum off the scale.
  13. comparable in terms of pattern, not necessarily temps as we seem to have more sub tropical flow this time round which is helping to perpetuate the northerly flow more into a European trough.
  14. So I think I've spotted my torpedo off the starboard side in the North Pacific. Next week we see a strong jet streak crossing the Pacific. This begins to decelerate and amplify as it interacts with the trough in the eastern Pacific, aided by a further amplification in the Asian jet tied into a trough in the western Pacific cerca 13th. The sub-tropical ridge is pumped into New Mexico and California around 20th. That instantly forces an eddy to break off in the polar flow as much of the flow is driven into the southern arm off Florida. Net result, mid Atlantic ridge is pumped north and north-east towards Iceland. -Nao triggered. Period 17th January through to 7th February 1983 is your template. last 3 gfs runs have toyed with this Pacific side evolution and dropping hints for the North Atlantic around 20th onwards.
  15. Precisely T. The obsession with shortwaves is delusional IMO, as is the reliance and buying into ops for anything beyond day 5 in this current set up. The modelling is getting to grips with the speed of the upper trough moving across North America in the medium range. The fact that this delivers more of a mid Atlantic ridge is no surprise here. I like the GFS op which echoes nicely the ensemble guidance we're getting, and which reflects the longer term thinking on the GWO. It delivers a cold pattern, which will remain cold for some time after, it obliterates the Euro ridge. It also exercises the sub-tropical jet over Mexico. It is here that those critical fluxes in momentum will manifest themselves subsequently in terms of the North Atlantic profile. The fact that the GFS is playing around with this idea (and the ridge close to Greenland) in the extended range should be noted. GEM Ensemble and EC EPS means look very good over the Arctic in the extended. Timing wise, I'm actually advancing my thinking on NAO flip to around the 23rd-26th January period.