KyleHenry

Step by step, we are watching the huge tropospheric process developing and it takes time. All began last week in the Pacific which now leads to the creation of Scandinavian HP and Aleutian LP. This process is running later than the GFS predicted. Beginning of December/ tail end of November is the current prediction. This is is how a wave one enters the stratosphere and disrupts the TPV and eventually displaces the SPV. Pacific is ready to repeat this process but this time it will be during winter proper hence why many are the end of December and beginning of January for the true effects. Asia first then USA will go and Europe last. If all goes to plan.

Excellent observations from Nick F. In hindsight we all see that the El Niño in conjunction with the WQBO has me believing that any periods of UK snowfall this winter, was quite an achievement. A momumental achievement against those two major forces. Long range models picked up the signal for blocking, although they predicted them to be higher up latitude wise. They were in effect correct just not on the exact positions of the HP cells. ( Very rare to see such long periods of HP dominating UK pattern/not to be confused with a Bartlett pattern) In my opinion that does not constitute as a forecast failure but simply that they could not accurately predict the effect of the downwelling WQBO and the continued tropical forcing/ thermal energy release from El Niño. So we face a transition period, that will only break when the tipping point is reached. What we want now is for this pattern to hold through the summer months. When the + NOA pattern does break and it will, HLB will become more fesiable. If asked. “Will we ever see a repeat of 2010?” My answer would be yes. It requires specific parameters I.e solar minimum, EQBO and above neutral ENSO state.

In short form, this cold spell will have significant longevity. It’s the cause of upcoming -AO, cold air cannot return back into Arctic region and so remain in the mid latatudes I.e UK

Yesterdays data already has shown the ability for high pressure to oscillate between Scandinavia and Greenland regions. I’m intrigued.

I don’t expect to see a QTR until wave 2 develops. SSW/wave 1 is not enough, had I not observed wave 2 then I wouldn’t have been confident of a UK cold spell. 7-10 minimum to see true evolution of Stratospheric influences.

Significant but SSW can reach up to 25-30C.

No not at all. Trop lead with EAMT event that sends energy up(20-22nd Dec) Downwelling following reversal from approx 23-24th Dec to oust the upper PV. Then Trop lead again 24th-26th into pole.

GFS is now showing effects currently. SSW displaces PV which allows Pacific WAA up into pole for negative AO.

March 2018, the ECM failed to factor the effects of SSW and was late to portray the correct displacement effects down to the tropospheric level. Whereas the GFS had the right overall idea but failed with the correct Synoptics at the Trop level. When the ECM corrected its input (4 days later than GFS) it displayed the correct outcome. At 240z but models are following the same March 2018 resolution in reading SSW effects. SSW equals PV displacement equals Pacific WAA equals -AO. That we know is certain. Strength of SSW (unknown at present). Is it enough to overcome dampening effect of upper WQBO remain unknown.

Why is the ECMWF not following the GFS? For that you must observe what the ECM is showing for a specific atmospheric geographical region ie is high pressure propagating or does it have opportunity to propagate in the atmosphere above Greenland. ECM’s data (A day behind on FU Berlin site) says no at present. It reaches 144z in line with GFS but from there it cannot accurately follow suit and retains the HP cell to move from Iceland out west of the Uk region. So follow the higher levels above 500hPa to attain where and what direction High pressure can move towards. WQBO already at the 30 hPa level which does make an obstacle to get HLB but not impossible. I’ve been hesitant until I could see this window evolve. My confidence has increased to 65% lilkehood of sustainable cold spell.

All factors count, with that in mind it is necessary to look at this event from all levels and not just at the 850 and 500 hPa levels. SSW split the Stratospheric PV. That propagated down and was assisted by wave 2 to dominate the entire atmosphere from surface to upper Stratosphere. That opened the Arctic to HP. Wave 2 prevents the PV from reforming. As the timings draw closer to surface reactions you only have to look at the Upper Tropospheric charts to observe how the Scandi HP can develop and hold position. Observe the 150 hPa. HP dominates the Tropospheric PV and holds the Atlantic via the block. It is these observable charts that encourage deep confidence with what the 500/850 hPa charts show, to actually come to fruition by next weekend. To take that further, you can follow the 150 hPa level charts to see when retrogression will or will not follow towards Greenland and to predict when the cold spell will end. Add a 2 day lag from 150 hPa level to 500 hPa for best results. Remove the guess work and the confidence in long range prediction is increased.

If it transpires with this actual outcome below and with a WAA of this magnitude. You will see the formation of an Omega block on a magnitude not seen since 2010. You’ve got to realise that the more energy that goes up then the stronger the block when it closes off. This would be a very very special event.

Anthony has picked out a composition that results in best -NAO for the Eastern US. March 2013 would have featured had it resulted in a colder outcome for our cousins in the states. Watch the migration of the Euro HP- Travels west over UK, into the Atlantic and up towards Greenland. Gave them a late winter in 2001 with large amounts of snowfall. 2018’s -NAO is to travel NE from the Atlantic towards Scandi and then NW towards Greenland. Synoptics are very different. Outside influencing factors are also different. I believe the US will get their West based -NAO in week 1 into week 2 of March, as the tropospheric PV moves Westward and breaks out into lobes.

The ECM sees the reversal. It’s just not within the range of the 10 day model outputs of this past weekend. My post was in reference to those that were writing off the SSW effects by not seeing the tropospheric response showing an Easterly with every output. When the time table was always pointing towards 21st-25th Feb, if all proceeded as expected. Minor displacements in the Stratosphere give us a -AO, I expect the same and much more from this event. I felt that if the ECMWF’s Stratosphere and Troposphere modelling were in sync, that it would show the formation of a significant-AO. That didnt happen and therein lays my sole criticism of the ECM. As for the GFS, it sees the signal, it just doesn’t know where and what date to proceed with the correct solution. Ive put a timetable of my expectations and upcoming events and expect to die on my sword for trying to be an SSW oracle. All good.

Absolutely 100% agree with you as to the ECM’s current model output. It is not even registering the bare minimum of a -AO from this event as the effects of the SSW are out of its range at present. Minor displacement event at the beginning of Jan 2018 Required 12-14 days to register a -AO on the ECM . We don’t even have a reversal registering at the 10 hPa level at 60 N as per Berlin. Which will show by tomorrow or Tuesday at the latest. So it stands to reason that in reality it does not know that it’s coming. As seen on the 10 Day model forecasts of this weekend. Propagation towards the surface on the 14th/15th. WAAs to occur around the 17th-20th Pacific and Atlantic routes. Shortly after we should see an enforcement of -AO from the WAAs. 21st-25th for -NAO. Scandi HP to show first until wave 2 dismantles the US vortex and hunts down the meandering Asian lobe. Once that is complete we would be expecting to see retrogression of HP towards Greenland by the beginning of March. As the HP on Tropospheric level gains more in roads into US Trop PV. Apologies for using your post Sebastian to vent on the failure of some to merely stand firm and watch the developments occur.

UKMO has a strong -AO at 144z. The GFS is now onto the correct solution. Scandi HP developing. Retrogression to Greenland is on the horizon. (20th approx)

“How I learned to stop worrying and love the SSW” Dr Strangelove. I have always attempted to keep my explanations of the atmospheric processes in the most basic of terms. Simplistic, yes but wanting them to be very understandable too. SSW creates a split at the 10hPa level commencing over the next 24 hours. As seen below. Inside the gap of the split vortices there becomes an opening for High pressure to locate to that position. We have seen several times this winter, the development of a -AO. Displacement of the PV off its natural peg hole- Greenland. The wave energy burns out and we see a return of the PV back to its natural position. What we have now is not only displacement but also destruction of the PV and no return to its default position. The SSW downwells enough that it allows upwelling from the surface (wave 2) access to an altitude and position that would be unattainable without the SSW. That easterly winds exist in all levels from Mesopause to the surface. Firstly at the pole= -AO and the lower latitudes. Above see how the HP moves into the gap of where the upper Trop PV existed. We have a cross polar link up. Allow 2 day lag to make the same positions at 500 mb level. Then by the 17th Feb the -AO acts as an elbow into the face of the US daughter vortex and pins in down. While at the same time the vortex is attacked again leaving more certainty that the PV will not reform or reposition at its default for approx 4 weeks. That is if it can recover from such a brutal assault. The ECM has a better handle on the upcoming surface reactions. Strat/Trop PV is gone and so the -AO opens the way for a -NAO to develop. As seen below I feel the GFS is struggling to interpret to upcoming developments and is messy in comparison. Hope this explains the quiet confidence of the SSW effects and the incoming surface responses based on logic, physics and the process.

Omega

Scandi tonic, GIN chaser.

Very marginal 1/2 km, it will change again tomorrow for sure.

The ECMWF has wave 1 tantalisingly close to full reversal. As it is so close many will have to watch stats up to and after the event. Wave 2 is going to require the same observations

What are your thoughts on Tropospheric responses? Decoupling between Trop and Strat PV by 10-14 days. Then reliance on WAAs to disrupt the Trop wave pattern into several extending lobes towards the lower latitudes. As to where I’d only be guessing, very difficult to calculate.

Who is willing to predict the NH Tropospheric scatter from this reversal. If the GFS is reading to split correctly and both lobes are hit with down welling it is effectively a continuous atmospheric shotgun blast.

Pleasantly surprised with the energy contained inside the two initial pulses from wave 1 at the 1hPa level. GFS is predicting PV relocation towards Eastern Canada a non to common event if it does transpires. Patience is a virtue of stratospherics but all worth it when we arrive at this point.