Model Output Discussion - Autumn arrives

[Kirkcaldy Weather]

11 hours ago, mushymanrob said:

Nope.
That chart suggest a very very average spell, a moderate Westerly upper flow with some height rises to the West and weak low pressure to our East. But basically thats a westerly, average, chart.

That's a little contradictive for the chart you referred to because if we get higher pressure west of us (say mid Atlantic to Greenland) and low pressure to the east that's not going to result in a westerly but actually most probable it would be a flow from the north possibly north east ....could be something like this 

11 hours ago, mushymanrob said:

But the MJO doesnt orbit very strongly in phase 6, so id question its impact on our pattern, and in any case - ive not found the MJO composites to be very accurate... neither the NOAA anomalies nor the EPS support that pattern.. we shall see ...

 

Well the ones I used with that recent forecast of mine I was referring to (and have used for my forecast methods for a few years) have been pretty good and accurate overall.

[Tim Bland]

Would be interesting to see a pattern like this heading toward winter….

[mushymanrob]

9 hours ago, Kirkcaldy Weather said:

That's a little contradictive for the chart you referred to because if we get higher pressure west of us (say mid Atlantic to Greenland) and low pressure to the east that's not going to result in a westerly but actually most probable it would be a flow from the north possibly north east ....could be something like this 

Well the ones I used with that recent forecast of mine I was referring to (and have used for my forecast methods for a few years) have been pretty good and accurate overall.

Not so .... that Anomaly chart only showed a slight height to our West, weak trough to our East, but the green flow lines were flat indicating a moderate mean Westerly. The only North/Northeasterly that chart could produce was a very short lived one.

But thats all academic now, as the NOAA has developed a mean trough to our West, producing a moderate unsettled mild Southwesterly. Plus the MJO is heading towards the COD, so i cannot see that composite chart becoming reality as the MJO signal simply isnt strong enough. IMHO.

 

[carinthian]

Morning all. Oh, the cut off upper low continues to diversify the models in the medium term.  At 168t the positioning of the upper trough continues to vagrantly spin out several different outputs. Gfs trending much colder for this time next week, whereas ECM keeps the very mild flow going. Looks like UKMO , sort of in between. Well for most of the week should not be too bad. Good for keeping those thermostat's down for a while longer.

C

Edited October 17, 2022 by carinthian

[northwestsnow]

Yuk ..

Not at all keen on the 00z runs.

Looks wet and windy in the main and we can clearly see mainland  Europe bathed in a strong HP belt.

[ChannelThunder]

Fantastic autumnal charts in the short-mid range, plenty of interesting weather on offer from a series of lows coming up from the south west. While there will be dry days for people to make use of, it's also looking like we'll continue to make a dent in the rainfall deficit from the drought 

[Froze were the Days]

1 hour ago, northwestsnow said:

Yuk ..

Not at all keen on the 00z runs.

Looks wet and windy in the main and we can clearly see mainland  Europe bathed in a strong HP belt.

Yes!...a lot of cold weather stored way up in the pole but that's where it seems to stay or very occasionally spills into the middle of the north Atlantic...the continued warmth in Europe is not good for the coming months, this pattern really needs to do one.

[damianslaw]

GFS most progressive of the models this morning, reverting to type.. ECM least, UKMO in the middle. Often the case..

GFS shunts the trough east by the end of the week, ECM keeps the low to the SW going nowhere... 

End results, colder from GFS, staying mild with ECM.

Long term GFS shows kind of evolution tied to la Nina Nov composites, high pressure out west and a chilly northerly/ north westerly flow.

Models have been caught out by tye positioning of the jet in recent days, only until very recently has a warm southerly source with low to the SW been forecast. 2022 continues to not follow the script.

 

 

[Ross90]

The ecm is doing a gfs with that low at day 9-10. If that actually happened somewhere will be getting 80mph winds at the end of next week...

[Eagle Eye]

On 13/10/2022 at 11:25, Eagle Eye said:

"RMM1 and RMM2 are mathematical methods that combine cloud amount and winds at upper and lower levels of the atmosphere to provide a measure of the strength and location of the MJO. When this index is within the centre circle the MJO is considered weak. Outside of this circle the index is stronger and will usually move in an anti-clockwise direction as the MJO moves from west to east."

Here's lots of information about RMM1 and RMM2, how they're calculated and the interpretations of the latest MJO forecasting.

The RMM's are calculated using a combination of different functions to do with outgoing longwave radiation (OLR) values onto a spacial patterns based off the MJO characteristics (the way that it's graphed). The MJO convective patterns can be captured using the OLR values because it's a proxy (substitute) for convection. As well as that, zonal winds in the upper and lower part of the Troposphere, an increase in zonal wind activity and amplification means that the oscillating pattern has likely reached that area. OLR values are realtime but zonal winds do run a few days behind so RMM values may be slightly off. There is then a removal of the ENSO in this calculation because the values associated with the La Nina/El Nino patterns resemble that of the MJO and so the removal of SST values is introduced into the RMM values. The mean of the last 120 days is also subtracted to make sure that the ENSO does not make any change to the MJO positioning.

The variation in RMM1 values frequency, you can see the typical 30-80 day patterns in where they are associated (sometimes quoted as 30-90 days).

As well as RMM2.

An analysis from 1974 to 2003 of the MJO positioning, you can see the typical movement in terms of being in the weaker values with phases 5-8 looking to be the most common when the MJO is out of the weaker values.

The lag between RMM1 and RMM2

Seemingly, the only difference between RMM1 and RMM2 are the height of the Troposphere. One is at the entry and the other at the ceiling of the troposphere from what I understand. If that is true then RMM1 is likely as it enters the Troposphere and RMM2 at the ceiling of the Troposphere because that makes the most sense.

So how do we calculate amplification.

It's not as difficult as you would think:

When you think of it like that it makes sense, it makes the RMM a 3D model by squaring the values but the square root of them together calculates the difference between their (OLR and zonal wind) values at different heights to work out how much forcing there is specifically in the troposphere as created by the MJO.

The amplification of the MJO and it's forcing for Tropospheric waves is reaching similar values to what you would expect going into late Autumn/early Winter so we're in a similar period to last year but we've entered slightly earlier, perhaps giving time for blocking to occur so we may have a better Winter if the amplification lasts and we get lucky with the positioning of blocking, either Greenland or Scandinavian blocking. If there's enough vertical propagation then a SSW may occur as I have said previously but whether we'll get the Pacific toughing is a big question and minor SSW's are possible that have little effect on surface conditions so there are 'drawbacks' as such. We could of course get stuck under blocking high's so that's another 'drawback', this sort of pattern is a 25% success rate I would say. So don't act too surprised if nothing happens majorly this Winter, we're sort of clutching at 4 straws and only 1 of them is going to be what we want.

The MJO is currently somewhere between phase 6 and 7 with forecasts going towards phases 7 and 8.

So what happens in those phases?

Not really much difference in terms of NAO so don't expect major changes towards cold but apart from that there's not much that can be expected except maybe some blocking if I had to hazard a guess.

The RMet's has a section on this based off change of NAO regime.

So, what will we be looking for over the Winter, here's the figures:

"In the observational data, the lag 0 NAO+ response to MJO phase 3 is zero (i.e. climatological probability of observing NAO+). After approximately one week, the probability of occurrence of NAO+ rises by more 30%, implying predictability of entering an NAO+ regime. However, in the model, the chances of experiencing an NAO+ event are approximately constant from lag 0 onwards, at 20% higher than the climatological mean."
"There is a strong NAO− response to MJO phase 6 in the observational data. In this case, the response peaks approximately two weeks after phase 6 and exhibits a 47% increase in NAO− occurrence, suggesting phase 6 as a precursor to an NAO− event."

There's quite a lot to read there but it does hopefully set you up on what to look for in the MJO this Winter as a -NAO event is what we would want for a colder pattern.

Next time(?) I'll likely be talking about certain Arctic oscillations to look out for but some of them are more low frequency events that are more to look out for in your peripheral vision because they're even less frequent than SSW's.

Edited October 17, 2022 by Eagle Eye

[Kirkcaldy Weather]

5 hours ago, mushymanrob said:

Not so .... that Anomaly chart only showed a slight height to our West, weak trough to our East, but the green flow lines were flat indicating a moderate mean Westerly. The only North/Northeasterly that chart could produce was a very short lived one.

But thats all academic now, as the NOAA has developed a mean trough to our West, producing a moderate unsettled mild Southwesterly. Plus the MJO is heading towards the COD, so i cannot see that composite chart becoming reality as the MJO signal simply isnt strong enough. IMHO.

 

The tropospheric patterns with any associated direction of flows (northerly westerly etc) are beneath the green lines though, those green lines on that chart are in a > direction right around the hemispheric view which won't be the lower level flow.

The exact time staying in phase 6 is far from determined and your claim for the heading to COD isn't set in stone either (might actually go to phase 7)   

[mushymanrob]

1 hour ago, Kirkcaldy Weather said:

The tropospheric patterns with any associated direction of flows (northerly westerly etc) are beneath the green lines though, those green lines on that chart are in a > direction right around the hemispheric view which won't be the lower level flow.

The exact time staying in phase 6 is far from determined and your claim for the heading to COD isn't set in stone either (might actually go to phase 7)   

The green lines are at 500 hpa level and are the mean for the timeframe the chart covers. The wind direction between 500 hpa and ground doesnt vary much at all, as the attached charts illustrate.
The fact is that the NOAA charts simply do not support the phase 6 composite pattern, and neither does the EPS. But these are only predictions, and are subject to change - like i said previously, we just have to wait and see.

[knocker]

For what it's worth my two pennyworth on this discussion

The green lines represent the height of the 500mb level in dm and indicate where the troughs and ridges are located from which much can be deduced., not least the flow of the upper wind. But in a fairly strong westerly flow as indicated they will not pick up.  say,  frontal wave developments in the flow which then track quickly east. And thus for a time the surface wind can be completely different in a particular region, albeit these developments should be consistent to the overall pattern. The dotted red and blue lines are the anomalies against climatology and not physical entities on the chart but their intensity should be noted

Edited October 17, 2022 by knocker

[damianslaw]

Current pattern is a classic west based negative NAO, low pressure to the SW, high pressure further north and north west but crucially to the SE as well. End product very mild southerly source, a lesson Negative nao doesnt necessarily equate to cold in the colder half of the year, in the summer often means very warm. We saw this set up in early Sept.

It is an interesting pattern though, not your normal October fayre. 

[Cheshire Freeze]

11 hours ago, Tim Bland said:

Would be interesting to see a pattern like this heading toward winter….

Very GLOSEA December like. Heights W Greenland and a cold UK trough.

[damianslaw]

Just watched GFS 12z timeframe, any attempt to pull in polar air thwarted throughout... its been the theme of 2022, low pressure to the SW and heights to the east.. its persistance is remarkable combined with a sluggish jetstream.

[Cambrian]

The ECM mean anomalies give a good illustration of how the modelling of the trough has moved it progressively westward from 10 days ago at day 10, through to today at day 0, here the charts at 2 day intervals from the 0z runs. Ten days ago the trough modelled over the UK for today, the modelling first nudges it west and then steadily firms up on progressively lower heights well out to our west. A big difference for us as the outlook changes from cyclonic becoming northerly to being stuck with a southwesterly.

     

Two other points worth mentioning. Firstly, by contrast, how good the positioning and heights of the Greenland ridge was - pretty much spot on from 8 days out. And secondly, despite the effect of the local adjustments being profound in terms of the difference between the expected and realised feel of our weather here, just how well the hemispheric pattern is modelled from 10 days out. 

A pivotal period in this autumn’s models? Could well be, with the outlook now for low pressure likely anchored to our west over the Atlantic for most of the rest of October, unless and until of course, the models adjust again…which they no doubt will!

Edited October 17, 2022 by Cambrian

[damianslaw]

32 minutes ago, Cambrian said:

The ECM mean anomalies give a good illustration of how the modelling of the trough has moved it progressively westward from 10 days ago at day 10, through to today at day 0, here the charts at 2 day intervals from the 0z runs. Ten days ago the trough modelled over the UK for today, the modelling first nudges it west and then steadily firms up on progressively lower heights well out to our west. A big difference for us as the outlook changes from cyclonic becoming northerly to being stuck with a southwesterly.

     

Two other points worth mentioning. Firstly, by contrast, how good the positioning and heights of the Greenland ridge was - pretty much spot on from 8 days out. And secondly, despite the effect of the local adjustments being profound in terms of the difference between the expected and realised feel of our weather here, just how well the hemispheric pattern is modelled from 10 days out. 

A pivotal period in this autumn’s models? Could well be, with the outlook now for low pressure likely anchored to our west over the Atlantic for most of the rest of October, unless and until of course, the models adjust again…which they no doubt will!

Good post, what looked like a cold cyclonic latter part to October has flipped to mild cyclonic. Shows how local subtleties have profound consequences for this neck of the woods, the atlantic trough is very weak, its really a cut off low feature - caught between heights either side, and with no oomph to the jetstream has nowhere to go - an odd outcome, in normal circumstances we would have a more mobile flow. Can see how we may easily exchange the current unsettled outlook for something more settled eventually - if the pattern shifts east.

Edited October 17, 2022 by damianslaw

[Don]

2 hours ago, damianslaw said:

Can see how we may easily exchange the current unsettled outlook for something more settled eventually - if the pattern shifts east.

The pattern needs to shift if we are to see something more interesting later in November and December.  For the time being, mild it is! 

[Penrith Snow]

Wow, look at that Euro high slug on the ECM 240, it stretches from Morocco to Finland, that must be 4000 miles!

[damianslaw]

Models behaving as they did in the summer, the atlantic shall not break through the N Sea it seems.. alas we do finally see a break through in about 10 days time, that 10 day timeframe again

In the meantime its a case of watching low pressure spin round like a washing machine to our SW seemingly unable to stop, until the jet gives it a kick.

[carinthian]

Morning all. The main models continue to show the cut off low to keep the European heat pump going for much of the rest of this week. Yesterday in parts of  Northern Austria and Southern Germany reached 27c. Even the top of our local mountain scored 19C at 2000m.  So looks like the sunny theme continues and possible even higher temps today and tomorrow over Central Euroland. Of course the British Isles nearer to the Low circulation may see some rain in places , but not widespread with temps continuing very much on the mild side. Fine or damp, good for keeping those increased heating costs in check before the cold eventually arrives ?

C

Edited October 18, 2022 by carinthian

[BlueHedgehog074]

8 hours ago, damianslaw said:

Models behaving as they did in the summer, the atlantic shall not break through the N Sea it seems.. alas we do finally see a break through in about 10 days time, that 10 day timeframe again

In the meantime its a case of watching low pressure spin round like a washing machine to our SW seemingly unable to stop, until the jet gives it a kick.

Looking at the models, it does look all quite stalemate at the moment. I guess as Anyweather says, the South-Westerly to Southerly flow on this setup does provide some further chances of warm weather, especially between the rain bands and showers. While not particularly settled, and would be some blowy weather about, Summer trying (certainly temperature wise and during brighter spells), to have a further little spat with Autumn. (Although I can’t help but wish everything was shifted just a little more further West). 

At some point I’ll be looking forward to some colder weather with some frost and snow. Even if it’s just a couple of 1 week cold spells.

Perhaps all you need to do, though, is simply turn off the washing machine

[northwestsnow]

* Groans ..

wet mild and windy for the forseeable ..

[minus10]

Certainly not a cold set of ens from gfs0z...

Mean and op above long term average for practically all of the run...at least some rain showing ..