Model Output Discussion - Into November 2019

[carinthian]

3 minutes ago, Steve Murr said:

06 Looking good mid term 114 

Higher pressure to the NE could filter thar deeper cold ever closer...

Hi Steve, just have had that discussion with the team over here. At this time of the year tracking the 300mb flow becomes more important. The latest chart below from GFS shows how much more this is now diving south in the vcinity of The British Isles and is similar to what the earlier GEM  operation med term run was showing. Looks like Low pressure disruption on the increase with every run over the coming weekend. Maybe , precipitation forecasting getting more complex as the trough looks to dig into the continent early next week with associated pressure rises further North. Looking long term , hopefully from a cold prospective this transfers NE. Sort of thinking over here, hence a up grade warning for significant snowfall in the Alps in the 120 hour range.

C

[northwestsnow]

6Z going down a completely different route to EC..

[mb018538]

Absolutely monster Siberian High:

[Man With Beard]

Oh the trials involved with getting cold to the UK!

EC clusters this morning tick almost every box for cold at T204 (D8/D9) - except in that very far right corner of the chart, we can see a pinch of heights:

If the heights become too strong, the easterly flow gets cut off too quickly to send deep cold towards the UK. Cluster 1 looks like it may keep heights weak enough across Central Europe to ensure the flow comes from Eastern Europe rather than the Eastern Mediterranean (and this is the largest cluster), but the other two clusters have stronger heights to the east and eventually less cold air filters in from the south (That said, air crossing the continent by mid-November is likely to cool down quickly if the flow is slack, so below average conditions would probably continue, just not snowy conditions)

The picture at D12/D13 is not as cold as the clusters were yesterday, but all the same, the largest cluster with 51% of the runs maintains a good Scandi height anomaly with little chance of the block being sunk over the top - still possibly drawing in slightly less cold air from the SE but experiences tells us that the longer such a pattern stays in situ, the greater the chances that eventually something will give to allow a fresh injection of cold from the NE. Also, battleground possibilities on cluster 1 as the Atlantic fights to get back in. Clusters 2 and 3 already see the Altantic re-establishing.

 

[northwestsnow]

Well, GFS certainly keen on some kind of warming - becoming a trend?

[MattStoke]

1 minute ago, northwestsnow said:

Well, GFS certainly keen on some kind of warming - becoming a trend?

Moved forward from previous runs.

[feb1991blizzard]

I like the trop pattern right at the end of the run as well, getting towards the time of year now where if this type of output continues for much longer, it will start manifesting itself in terms of flatliners between -8c and -10c on the GEFS 850hpa graph charts.

[northwestsnow]

Ens 6Z look cool/cold and unsettled - 

Perhaps some frosts /fog thrown in for good measure...

 

[swfc]

18 minutes ago, northwestsnow said:

Ens 6Z look cool/cold and unsettled - 

Perhaps some frosts /fog thrown in for good measure...

 

My worst form of weather man tbh and slightly depressing!!tbh tho nhp isn't bad and there's no SW winds howling in 

Edited November 5, 2019 by swfc

[Frosty.]

The GEFS 6z mean indicates a cold unsettled outlook, certainly cold enough at times for snow on northern hills and perhaps to lower levels at times..plus overnight frosts, icy patches and fog...can't see much potential for sw'ly zephyrs!

[Ali1977]

A slight dip in excitement on here due to fewer NH PV massacres in the models and Ens, hoping this trend starts to reverse on the 12z but we’ll see. The mean FIs still show weaker than average PV but with an array of options, looking at the mean is pretty fruitless as a guide I guess. I remain positive of a cool/cold few weeks but really it’s late Nov where the Interest starts !!
 

[Catacol]

15 hours ago, feb1991blizzard said:

EC46 W3 mixed, Scandi high but Greenland low but slightly -ve anomaly over the North of continental Europe, could be a battle of airmasses.

The thing i would take most from that is that the Scandi high is the strongest signalled feature so ready with the old corporal jones upward thrust to stop the downwelling of +ve Westerlies.

If that sustained signal is correct then genuinely we may be looking at more significant vortex disruption earlier in the season than might have been expected a month ago. There is an awakening of the MJO at present entering favourable orbit for wave activity to support high lat blocking, and also a signal for a period of aleutian low dominance. Lag times for patterns like this dictate I think that we are still likely to see a December where the atlantic remains in charge though with very much a polar maritime dominance in circulation...but given the likely next cycle of the MJO in early January and the strength of this wave 2 first assault I am becoming more firm in the belief that back loaded cold of some description will arrive following what might be a second perturbation of the vortex shortly after Christmas. Sea surface anomalies continue to support a more southerly tracking jet and are significantly different to the profile this time last year when they strongly suggested a +NAO signature. Still 10 more days before I firm up on a call for the season, but these clues are all helping make the jigsaw....

Edited November 5, 2019 by Catacol

[Kirkcaldy Weather]

So a week on and here is an update.

Going back to an earlier post I had mentioned higher pressure across Russia, latest GFS -  also  picks up on the NW - SE track of the lower pressure from Newfoundland / Greenland towards the UK that I mentioned  and the accompanying cooler / colder air with a potential snowfall risk (especially over higher ground) for the North this weekend  

MJO moved briefly into phase 4 during the last days of October https://1316da03-e6e5-4264-d4a8-7d2a1b50b5ed.filesusr.com/ugd/31d9e0_b438a5126b4cf5a32f67041512156dad.pdf again this suggests higher pressure to the N / NE and lower pressure to the south so the possibility of an easterly (which some ensembles have hinted at recently) and as I have mentioned with cold conditions across Scandi should we get an easterly I wouldn't rule out the chance of some wintry conditions.

Currently the MJO is in phase 5 and conflicting signals arise - https://1316da03-e6e5-4264-d4a8-7d2a1b50b5ed.filesusr.com/ugd/31d9e0_dc8ab3d428301ce27fdc8058c7edba5f.pdf which suggests higher pressure right up through the arctic,   which suggests higher pressure towards UK and some lower pressure to the north, which suggests higher pressure to the south and lower pressure to the north east. So 3 different options and my current feeling is leaning more toward the more blocked option for 2 reasons, first the MJO is forecast to move through phase 6,7,8  https://1316da03-e6e5-4264-d4a8-7d2a1b50b5ed.filesusr.com/ugd/31d9e0_7b1111024e3cdd623d605106fba33f51.pdf https://1316da03-e6e5-4264-d4a8-7d2a1b50b5ed.filesusr.com/ugd/31d9e0_9bbcf411b167ba537e629659eacd304a.pdf https://1316da03-e6e5-4264-d4a8-7d2a1b50b5ed.filesusr.com/ugd/31d9e0_3c062d439cb841d2eea3ea174256642b.pdf    which appear to suggest phase 6 - higher pressure to the north / blocked , phase 7 - a bit more unsettled with lower pressure in the vicinity of the UK, phase 8 - lower pressure drops to the south with signal for higher pressure to the east and my second reason is developments in the strat with the chance of a stratospheric warming developing during the second half of November and the recent MJO phases would appear to suggest this too. 

On 01/11/2019 at 22:29, Kirkcaldy Weather said:

"We are also concerned here with three specific questions regarding the MJO–SSW teleconnection. The first is the time scale of the teleconnection. Garfinkel et al. (2012a) showed a warming of the polar vortex 10 days after MJO phase 7 and another one about a month after MJO phases 2 and 3, leaving the teleconnection time somewhat uncertain. Because the MJO is quasi periodic, an observed connection seen after a given MJO phase may be either a slow response to earlier phases or a faster response to later phases. To reduce the ambiguity in the teleconnection time scale, it is useful to understand the physical processes involved. We analyze the teleconnection time scale for this path, starting with a horizontal propagation from the tropics and followed by additional time for vertical propagation within the Arctic stratosphere, although we also note some caveats that may affect the specific time scales deduced. The second issue of interest here is the teleconnection path. Garfinkel et al. (2014) showed evidence that, through constructive interference with climatological stationary waves, the perturbation associated with MJO phase 7 (3) leads to an in-phase strengthening (out-of-phase weakening) of the eddy meridional heat flux, but they did not discuss the path of propagation. We show that there is an MJO-forced wave train propagating poleward and upward through the upper troposphere and lower stratosphere to the Arctic stratosphere, which is consistent with the abovementioned teleconnection time. The third specific issue examined here involves the way the MJO waves affect SSW events. We demonstrate two different mechanisms in which the MJO-forced transient waves affect SSW events, both distinct from the constructive interference discussed by Garfinkel et al. (2014): via a direct propagation of these transient waves and a corresponding EP flux into the polar cap and, distinctly, via a nonlinear interaction with the climatology that changes the stationary wave forcing.The teleconnection time scale is another factor considered here. Garfinkel et al. (2012a, 2014) find that MJO phase 7 occurs 1–12 days before SSW events, and MJO phase 4 occurs 13–24 days before SSW events. While this seems to suggest a 3-week teleconnection time scale, they also find correlation between the MJO and the polar cap at lags exceeding 40 days. Our idealized model, with its perfectly periodic prescribed MJO forcing, allows us to identify the propagating signal in a Hovmöller plot of pseudomomentum flux with some confidence. While this analysis cannot determine the teleconnection time scale with certainty, it suggests a horizontal propagation time scale between 10 and 20 days, and we point out uncertainties in this estimate. This horizontal propagation is followed by additional time for vertical propagation within the stratosphere." 

JOURNALS.AMETSOC.ORG

"KT17 showed that Rossby wave trains excited by MJO phases 3–5 propagate northward, then upward, to the Arctic stratosphere within one month, and as a result, that stronger MJO forcing can nearly double the SSW frequency. They noticed a northward wave train departing from the tropics in MJO phases 3–5, which corresponds to enhanced convection near Indonesia. In observations, Garfinkel et al. (2014) found that the MJO effect on the average polar cap temperature also occurs preferentially after MJO phases 3 and 7; and Schwartz and Garfinkel (2017) noted that more than half of SSWs occur after MJO phase 6/7 (other studies have found that MJO-related convection in other phases can also impact the extratropics; Goss and Feldstein 2017). These results imply that the MJO-forced waves may propagate only at certain longitudes, which can either be a result of the different forcing structure associated with different MJO phases, or because of the interaction with the background zonal asymmetry. In this work, we demonstrate the second effect by forcing a model with an idealized wavenumber-1 MJO-like forcing." 

JOURNALS.AMETSOC.ORG

"It is clear that phases 7 and 8 are preferred during the 12 days preceding SSWs (Figure 1c). During days 13 to 24 before SSWs, MJO phases 4, 6, and 7 are preferred, while during days 25 to 36 before SSWs, MJO phases 2 and 3 are preferred (Figures 1a and 1b). The lag between MJO phases 3 and 7 is consistent with the 30–60 day periodicity of the MJO. This effect is statistically significant for many phases. The results are not sensitive, in a qualitative sense, to discriminating between displacement or split SSWs (described in Charlton and Polvani [2007]), or to distinguishing between El Niño or La Niña SSW. The key point is that the potential for predictability extends back as far as one month: if a MJO phase 2 or phase 3 is occurring, the probability that a SSW will occur in one month is apparently increased. A strong connection has been shown to exist between the Madden‐Julian Oscillation (MJO) and the Northern Hemisphere wintertime stratospheric polar vortex. SSWs in the reanalysis record tend to follow certain MJO phases, likely because the MJO influences the region in the North Pacific most strongly associated with tropospheric planetary wave driving. Similarly, the strength of the polar vortex is significantly modulated by particular MJO phases at specified lags, and the magnitude of the influence of the MJO on the polar vortex (∼4 K) is comparable to that associated with the Quasi‐Biennial Oscillation and El Niño."  

Error - Cookies Turned Off

AGUPUBS.ONLINELIBRARY.WILEY.COM

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https://www.seas.harvard.edu/climate/eli/reprints/Kang-Tziperman-2018b.pdf

MJO‐Related Tropical Convection Anomalies Lead to More Accurate Stratospheric Vortex Variability in Subseasonal Forecast Models

WWW.NCBI.NLM.NIH.GOV

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The effect of the Madden‐Julian Oscillation (MJO) on the Northern Hemisphere wintertime stratospheric polar vortex in the period preceding stratospheric sudden warmings is evaluated in operational...

if some of those didn't link correctly just type "sudden stratospheric warming mjo" in google and go through the articles and you will find the bits I have quoted 

Well worth keeping an eye on the strat thread over the next few weeks to see how things play out. 

[jules216]

36 minutes ago, Catacol said:

If that sustained signal is correct then genuinely we may be looking at more significant vortex disruption earlier in the season than might have been expected a month ago. There is an awakening of the MJO at present entering favourable orbit for wave activity to support high lat blocking, and also a signal for a period of aleutian low dominance. Lag times for patterns like this dictate I think that we are still likely to see a December where the atlantic remains in charge though with very much a polar maritime dominance in circulation...but given the likely next cycle of the MJO in early January and the strength of this wave 2 first assault I am becoming more firm in the belief that back loaded cold of some description will arrive following what might be a second perturbation of the vortex shortly after Christmas. Sea surface anomalies continue to support a more southerly tracking jet and are significantly different to the profile this time last year when they strongly suggested a +NAO signature. Still 10 more days before I firm up on a call for the season, but these clues are all helping make the jigsaw....

so a more La Nina December you think? PM shots and enhanced subtropical ridging but not enough for proper - NAO? If the enhanced subtropical ridge will be Sceuro one not Azores one Europe will be looking at mild December then. I am also going for back loaded winter,many analogs pointing out that direction.Its a risky one again thinking of last February failed blocking signal

[knocker]

The Pembroke Dangler has been in full swing today with frequent showers

[tight isobar]

20 minutes ago, jules216 said:

so a more La Nina December you think? PM shots and enhanced subtropical ridging but not enough for proper - NAO? If the enhanced subtropical ridge will be Sceuro one not Azores one Europe will be looking at mild December then. I am also going for back loaded winter,many analogs pointing out that direction.Its a risky one again thinking of last February failed blocking signal

The Pac ridge..has been for the last few years...an excitement for early signals..

And had 'ultimate'  been the downplaying signal when angular momentum-}and breach overriding of wave activities..

However this term there are many more spaners..in the clockwise momentum.

 

And signal breach that coincide with relapse and positivity at the placement formats...whereas previous...these have been counter synced.

=even a bypass warming layer event -visible @10 hpa..is a reference to execute of the TPV..

Were In a different ball park here....

And LRF cast/models...are imo behind the phase...and that may soon rear.. in exaction!!!

 

So in the meantime...decipher of raw data...imo is advisable!!!

Remember...#@fill..then @drain..

 

#Large lobe vortex...

The feeding machine...I said this last season..and was proved incorrectly....I'm confident much moreso...this 1 !!!!

Edited November 5, 2019 by tight isobar

[swfc]

9 minutes ago, knocker said:

The Pembroke Dangler has been in full swing today with frequent showers

Love a dangler tbh

[nick sussex]

The models have made a real drama over what happens to the low which tracks se into the UK.

This is quite important in whether colder air can move in from the ne later .

Coldies definitely want to see the back of the UKMO 00 hrs output . 

[jules216]

1 minute ago, nick sussex said:

The models have made a real drama over what happens to the low which tracks se into the UK.

This is quite important in whether colder air can move in from the ne later .

Coldies definitely want to see the back of the UKMO 00 hrs output . 

I would take the ICON 12Z solution Nick, the more eastwards the front edge of that low end the better, also cracking hemispheric profile.

[booferking]

2 minutes ago, nick sussex said:

The models have made a real drama over what happens to the low which tracks se into the UK.

This is quite important in whether colder air can move in from the ne later .

Coldies definitely want to see the back of the UKMO 00 hrs output . 

ICON moved towards the earlier UKMO 00 run..

[Allseasons-Si]

D7 UKMO tracks the low into Iberia just like the Icon

i see it's been posted already^

 

 

[nick sussex]

22 minutes ago, jules216 said:

I would take the ICON 12Z solution Nick, the more eastwards the front edge of that low end the better, also cracking hemispheric profile.

That’s a lot better than the earlier UKMO . It’s key here to have the pattern sufficient se .

Low pressure over Iberia isn’t good as that will just send milder air nw ahead of it .

The stand off continues . The GFS and UKMO at day 5 miles apart .

Edited November 5, 2019 by nick sussex

[Jonathan Rhodri Roberts]

34 minutes ago, knocker said:

The Pembroke Dangler has been in full swing today with frequent showers

Must be quite far out in the Irish Sea from Pembrokeshire then today as there's been blue skies & sunshine here on the SW coast making a welcome change

[nick sussex]

Stakes just got higher .

Another possible slider on the GFS , colder air in place .

The UKMO is complete pants compared to that , horrible deeper low and the cold air stuck well to the north .

[Allseasons-Si]

Just now, nick sussex said:

Stakes just got higher .

Another possible slider on the GFS , colder air in place .

The UKMO is complete pants compared to that , horrible deeper low and the cold air stuck well to the north .

Yes,just about to comment on it,they are totally different

i have to go,my other half is unwell in hospital due to a stomach hernia