Model Output Discussion - A cold start to Spring?

[ItNeverSnowsInWindsor]

It looks pretty dry from the Op despite some very cold uppers in Oslo. Could the GFS be underplaying convective activity and trough activity in the unstable flow ?

[london-snow]

1 minute ago, minus10 said:

....GFS 18z..

Let’s see how it pans out but i would expect a slight shift towards a blend of ukmo and ecm. If however it sticks to its guns and or worsens (If your a coldie) then the solution can not be discounted. 
 

[Bricriu]

9 minutes ago, prolongedSnowLover said:

It looks pretty dry from the Op despite some very cold uppers in Oslo. Could the GFS be underplaying convective activity and trough activity in the unstable flow ?

You should have stayed in the UK:) 

[nick sussex]

A good ECM op with the block showing more resistance initially . We do see that moving further nw but that’s still into FI and we’re still seeing changes between runs .

Chances for frontal snow but the main interest is still too far out to nail down in terms of detail .

 

[bluearmy]

17 minutes ago, sebastiaan1973 said:

 

"Consider 27th of february as the start date. When we take a look in the literature, we see this picture by Baldwin. The composite of weak vortex events. 

In 10-12 days after the start date [27th of february], we see less downwelling. Perhaps we see this too in the EC NAO forecast. First we have a negative NAO, around 11 of march it will become positive. When we fellow the picture of Baldwin, this will period will be short. After negative NAO, round the end of march again positive NAO, turning negative in april.  

Perhaps this is a guideline for things to come." 

 

First of all. Little akward to quote yourself  

EC46 is showing the pattern described above. 

But Sebastian, the start date wasn’t the 27th of feb …… the start date was the 15th feb.  This is the conundrum we currently face - are we seeing a quick response to the warming started yesterday with its steep drop towards -20m/s or are we seeing the downwelling wave arrive in the trop 3 weeks after the initial ssw began ????

 

[lawrenk]

2 hours ago, ICE COLD said:

WALLOP

I struggle to keep up when the thread starts getting technical like this.

[Rain All Night]

Just for fun, the 24 hour snowfall totals for each of the last four days of the ECM 12z op run. The South doesn't do too badly, given that the cold is coming from the North!

Interestingly, day 9 (the Wednesday) is the only day that is very cold nationwide all day, which I suppose is the March effect.

Edited February 27, 2023 by RainAllNight

[Cheshire Freeze]

8 minutes ago, bluearmy said:

But Sebastian, the start date wasn’t the 27th of feb …… the start date was the 15th feb.  This is the conundrum we currently face - are we seeing a quick response to the warming started yesterday with its steep drop towards -20m/s or are we seeing the downwelling wave arrive in the trop 3 weeks after the initial ssw began ????

 

The EC appears to believe it’s the latter…hence the 46 sees the initial block waning before re-emerging later in March.

[Dancerwithwings]

5 minutes ago, lawrenk said:

I struggle to keep up when the thread starts getting technical like this.

When one is a coldie I certainly don’t struggle to understand what one is stating in whether it’s in a technical format or just a simple layman’s…”Wallop” it’s okay with me

[alexisj9]

1 hour ago, Mike Poole said:

Completely agree.  In my opinion, this is the effect of the SSW that has been hinted at over the last week in the ensembles etc. coming into sharp relief on the best op models.

If anyone comes on here and tries to claim that the above is being modelled due to the MJO farting about near the COD in phase 7, they need to take a look at themselves!

Nope this is definitely SSW. The high going up in the first place was mjo though, now the SSW has happened the pre westerlies are not fighting and more, and as modeled for a while, both working together.

[bluearmy]

1 minute ago, CreweCold said:

The EC appears to believe it’s the latter…hence the 46 sees the initial block waning before re-emerging later in March.

But ssw events have repeated downwelling waves several weeks apart - one would assume that each significant reversal in zonal flow will kick off downwelling waves and these can occur over the next 6 to 8 weeks - one wonders what happens if there is more than one sig event within a short time span - do the waves potentially interfere with each other and perhaps cancel/weaken themselves ??

[Cheshire Freeze]

Just now, bluearmy said:

But ssw events have repeated downwelling waves several weeks apart - one would assume that each significant reversal in zonal flow will kick off downwelling waves and these can occur over the next 6 to 8 weeks - one wonders what happens if there is more than one sig event within a short time span - do the waves potentially interfere with each other and perhaps cancel/weaken themselves ??

That’s beyond my pay grade mate

[ItNeverSnowsInWindsor]

17 minutes ago, Bricriu said:

You should have stayed in the UK:) 

Just being greedy and wanted some fresh cover while we’re skiing there!

[Guest]

Just now, prolongedSnowLover said:

Just being greedy and wanted some fresh cover while we’re skiing there!

You're going skiing? I wish you'd said!

[Ali1977]

ICON at 120 looks like another slight upgrade, with a more potent Northerly setting up and a stronger block around Iceland

 

Also looks like a better set up for sliders down the line - delayed too so colder air being further south. 

Edited February 27, 2023 by Ali1977

[steveinsussex]

7 minutes ago, prolongedSnowLover said:

Just being greedy and wanted some fresh cover while we’re skiing there!

Where are you going? I don’t think you have mentioned it, at all…

[damianslaw]

13 minutes ago, CreweCold said:

The EC appears to believe it’s the latter…hence the 46 sees the initial block waning before re-emerging later in March.

I mentioned 2018, there was a week of very cold weather then a warm up after Storm Emma then the cold came back then milder then colder again into April.

[Daniel*]

Yeah ICON slight upgrade the ridge strengthens again and further up to Greenland and pressure slightly lower to south.

120hr 18z v 123hr 12z

[Rain All Night]

@mushymanrob What are the wise Americans seeing, Mystic Mushy? 

Edited February 27, 2023 by RainAllNight

[sebastiaan1973]

25 minutes ago, bluearmy said:

But Sebastian, the start date wasn’t the 27th of feb …… the start date was the 15th feb.  This is the conundrum we currently face - are we seeing a quick response to the warming started yesterday with its steep drop towards -20m/s or are we seeing the downwelling wave arrive in the trop 3 weeks after the initial ssw began ????

 

The first SSW didn't have a response, because of the cyclone setting at the moment. The second SSW has a anticyclone setting in NW-Europe. Which is a much better tropospheric setting for downwelling. So, we see in the charts for the coming days QTR. 

[Mucka]

5 minutes ago, Daniel* said:

Yeah ICON slight upgrade the ridge strengthens again and further up to Greenland and pressure slightly lower to south.

120hr 18z v 123hr 12z

 

Significantly better I would say, especially if we consider that is only out to 120.

Just another run but much better then going the other way. 

PS You need to advance two frames to get the same time equivalence as the frames are 3hr snapshots and the time between runs is 6 hours.

 

Edited February 27, 2023 by Mucka

[sebastiaan1973]

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

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Abstract. Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in particular in the North Atlantic–European (NAE) region. While the...

 

For EuBL around the onset of the SSW event, a robust (10 % level) positive tropospheric anomaly can be observed at the time of the SSW (Fig. A4c). This anomaly is not significant (Fig. 3c), reflecting that it is not different from generic anomalies during EuBL. However, robust, significant, and strongly positive geopotential height anomalies are present in the troposphere at lags of 15–20 and 30–55 d after the SSW event. This is consistent with the classification of all of the here defined seven EuBL events as having a tropospheric impact in Karpechko et al. (2017). These positive anomalies are consistent with the finding that first AR and then GL are much more likely in the aftermath of an SSW with EuBL around lag 0 (compare to Fig. A2c). Furthermore, comparing to the panel for all SSW events (Fig. 3a) indicates that the EuBL cases dominate the perceived downward response in the canonical response for SSW events.

During cyclonic regimes around the onset of the SSW, there is no substantial tropospheric anomaly in the NAE region at the time of the SSW, but a positive albeit weak anomaly can be observed around days 15–20 after the SSW event (Fig. 3d). This anomaly is not robust at the 25 % level, but it is significantly different from a random sample at the 25 % level (Fig. A4d). Several SSWs with a cyclonic regime around the onset are followed by GL at a longer lag (Fig. A2d), thus likely causing these anomalies. Still, the GL absolute frequencies remain below 30 % (Fig. A2). These findings and the small amplitude of the anomalies suggest that the variability in the tropospheric flow evolution after SSWs is large after a cyclonic regime at lag 0, which is also confirmed by the inspection of individual cases (not shown).

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So, I wasn't quite right. It can be that what see at the charts, can be a result of the first SSW (15th february) according to graphic. Or it is QTR by the second. 

[Don]

Wonder if the high solar activity will help scupper the chances of a cold spell?

[bluearmy]

25 minutes ago, sebastiaan1973 said:

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

---

Abstract. Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in particular in the North Atlantic–European (NAE) region. While the...

 

For EuBL around the onset of the SSW event, a robust (10 % level) positive tropospheric anomaly can be observed at the time of the SSW (Fig. A4c). This anomaly is not significant (Fig. 3c), reflecting that it is not different from generic anomalies during EuBL. However, robust, significant, and strongly positive geopotential height anomalies are present in the troposphere at lags of 15–20 and 30–55 d after the SSW event. This is consistent with the classification of all of the here defined seven EuBL events as having a tropospheric impact in Karpechko et al. (2017). These positive anomalies are consistent with the finding that first AR and then GL are much more likely in the aftermath of an SSW with EuBL around lag 0 (compare to Fig. A2c). Furthermore, comparing to the panel for all SSW events (Fig. 3a) indicates that the EuBL cases dominate the perceived downward response in the canonical response for SSW events.

During cyclonic regimes around the onset of the SSW, there is no substantial tropospheric anomaly in the NAE region at the time of the SSW, but a positive albeit weak anomaly can be observed around days 15–20 after the SSW event (Fig. 3d). This anomaly is not robust at the 25 % level, but it is significantly different from a random sample at the 25 % level (Fig. A4d). Several SSWs with a cyclonic regime around the onset are followed by GL at a longer lag (Fig. A2d), thus likely causing these anomalies. Still, the GL absolute frequencies remain below 30 % (Fig. A2). These findings and the small amplitude of the anomalies suggest that the variability in the tropospheric flow evolution after SSWs is large after a cyclonic regime at lag 0, which is also confirmed by the inspection of individual cases (not shown).

-------------

So, I wasn't quite right. It can be that what see at the charts, can be a result of the first SSW (15th february) according to graphic. Or it is QTR by the second. 

Thanks for finding that 

so we would need much detailed analysis of second half February and into March to know exactly what causes the predicted set up for next week. (First reversal or the current one) 

[ICE COLD]

Gfs starting to smell the other models coffee . 18z 1st image 12z 2nd image 

Edited February 27, 2023 by ICE COLD