Model Output Discussion - Into Winter

[Notty]

6z OP in the FAR REACHES OF FI (not reality) is moving towards a Genoa LP and a slider into cold air.

Pleeeeaaaase

[sebastiaan1973]

I suppose we have to wait until the MJO i getting out of phase 5, till we see a real change in the forecast (couple of days) if the MJO has enough amplitude.

[Ali1977]

Control about to follow the op too I think HP starting to pivot and head north 

[DIS1970]

1 hour ago, Met4Cast said:

I think some would benefit from stepping away from the models for a couple of days, the ranges were looking at here make following individual deterministic runs a waste of time. 

 

The ENS are beginning to trend colder at the extreme end of the run, that’s all we’d really expect to be seeing for now. 

See if any can leave the models alone for 5 days, 7 would be a huge challenge.

[Vikos]

Last chart, massive Artic Outbreak

[jmp223]

Would prefer that Azores ridge to be less amplified but on the whole I'd take it.

 

Given the fact GEFS tends to overestimate vortex strength and that 6% of it's ensemble members are still predicting a change to an easterly around New Year's week, I'd certainly say we still have a chance of an SSW event.

 

 

 

Edited December 8, 2023 by jmp223
Typo

[Met4Cast]

It’s going downnnnn 

 

[CoventryWeather]

Think the only downside of the GFS run is that the block never really sticks - collapses and brings back the Atlantic. 

However we all know models have struggled with the blocking at short time scales over the past few weeks, so I think there's no need to worry about this for now. Also a bias for the GFS to bring back the Atlantic too soon in the outer frames. 

But can we just give a moment to say what model consistency we have at 240hrs across the majority of models? Rarely do we see such good agreement at longer timeframes here in the UK. Just a case of where the high ends up after the UK high and can it be secured enough for some pretty cold uppers? 

[northwestsnow]

If there is going to be a Block it's going to be Iceland/ Greenland ,certainly initially.

The theme seems solid enough ,Atlantic regime  followed by a Blocking High in our locale.

We then move onto the tricky bit ,will the High retrogress and how will shortwaves/energy  effect how much the High retrogresses.

Would be amazing to get a Greeny High Christmas week, alternately we could see zero retrogression and the High sinking into Europe ..

Lots to analyse inc background drivers .

 

 

[That ECM]

Should we be looking for it to go nw or ne? That’s quite a change on the mean.

edit. On reflection it’s probably more to do with the Russian high than the one that is likely over us.

Edited December 8, 2023 by That ECM

[northwestsnow]

2 minutes ago, That ECM said:

Should we be looking for it to go nw or ne? That’s quite a change on the mean.

NW 

[johncam]

14 minutes ago, CoventryWeather said:

Think the only downside of the GFS run is that the block never really sticks - collapses and brings back the Atlantic. 

However we all know models have struggled with the blocking at short time scales over the past few weeks, so I think there's no need to worry about this for now. Also a bias for the GFS to bring back the Atlantic too soon in the outer frames. 

But can we just give a moment to say what model consistency we have at 240hrs across the majority of models? Rarely do we see such good agreement at longer timeframes here in the UK. Just a case of where the high ends up after the UK high and can it be secured enough for some pretty cold uppers? 

That's the problem,  it collapses,  and the ECM  control is any better , but all academic as its 14 days away , hopefully get something more seasonal between Xmas and New Year 

[That ECM]

We keep moving forward.

[Downburst]

3 hours ago, Spah1 said:

Can someone send me a link to learn about how to read these type of charts pls. 

MJO

 

Tropics, starting in Indian Ocean and eastward movement of rain across the pacific (storms, with a lot of convection) occurs usually. This moved from the west to the east over time. It can be strong or weak and this can be measured. It can move fast or slower and again this can be measured.

What we measure?

The tops of the clouds at 200mb and the bottom layer at 850 pressure. This helps understand the strength of disruption. One can analyse previous pressure patterns (to pick one constant for this guide) and consider given the base state, for instance ENSO state what happened previously when the MJO was in this phase? One can then expect with certain probabilities that the atmosphere will react favourably to the way it has in the past. This is sometimes usefully shown in Composite pressure maps for the planet.

 

Recent forecasts have shown that as December progresses we can expect a possible Phase 7 to 8 transition at some amplitude (strength) and the composite pressure maps would suggest possible high level blocking in north Atlantic/arctic. Hence the interest. At the same time a low amplitude or not getting into these phases in time will not have any effect etc. There are so many variable.

 

As air rises a low pressure occurs and air enters underneath, a the top it cools and splits east and west. To the east it sinks and causes Higher pressure and less or no rain.

 

The whole process moves from the East all around the tropics over a month to 6 weeks and kicks off again.

 

 

Phases

Section the areas off and give them a number around the tropics. If in the area one gets that number.

 

These common Diagrams below, instead of  MAP OF THE TROPICs, we can see the world split into 4 quarters, each quarter 2 phases of 8 total. It’s confusing at first, but it shows the current phase (Red), the previous phase and the forecast phase. But it also shows the amplitude of the phase, the higher above the centre circle the higher the phase, below the centre circle and it’s a very suppressed MJO signal. And of course, multiple ensemble runs to try to find consensus in the forecast. One can see even yesterday's plots show a lot of divergence in the 5 days forecast already, never mind Day 15 etc.

[northwestsnow]

GEFS mean is really good heading into Xmas.

 

[northwestsnow]

Control run day 10 

few days later 

merrrrry xmas  

[northwestsnow]

Control Xmas eve 

yes please santa 

[Bricriu]

Very disappointing the high collapses , that could be due to the MJO letting us down.  Well I'll take that run if  it means we have the chance of a White Christmas before all that happens.

[Met4Cast]

5 minutes ago, Bricriu said:

Very disappointing the high collapses , that could be due to the MJO letting us down.  Well I'll take that run if  it means we have the chance of a White Christmas before all that happens.

It’s a single deterministic run at day 15..

[MattStoke]

3 minutes ago, Met4Cast said:

It’s a single deterministic run at day 15..

Aye. Nowt ta worry about. The trend be our friend!

[northwestsnow]

Just now, Met4Cast said:

It’s a single deterministic run at day 15..

Looking at the GEFS towards Xmas it suggests the model suite is picking up a signal to pull heights W/NW, the mjo plots I'm hoping,will be picking up a bit more amplitude in the wave ,really would be a big positive if we see this occur and lend more weight to this retrogreessive signal )..

[Downburst]

I figured out why the Australian MJO forecast is higher in Phase 5 through 8 all the time. They are of course plotting these in the southern hemisphere and are upside down, so the line falls away from the COD naturally. Simple working this out in the end after trying to look into it this week. 

 

[Bricriu]

11 minutes ago, Met4Cast said:

It’s a single deterministic run at day 15..

Yes,I suppose the post was a tad negative.  Even if it proves to be correct  , it doesn't really matter as it could be the appetiser before the main course in January. Also even the best winters  in terms of cold and snow had milder periods.

[booferking]

Just now, Bricriu said:

Yes,I suppose the post was a tad negative.  Even if it proves to be correct  , it doesn't really matter as it could be the appetiser before the main course in January. Also even the best winters  in terms of cold and snow had milder periods.

This is our mild period the onslaught of cold starts just before Christmas and runs right through January

[Met4Cast]

9 minutes ago, northwestsnow said:

Looking at the GEFS towards Xmas it suggests the model suite is picking up a signal to pull heights W/NW, the mjo plots I'm hoping,will be picking up a bit more amplitude in the wave ,really would be a big positive if we see this occur and lend more weight to this retrogreessive signal )..

Indeed, pretty big signal within the GEFS for that which is remarkable given we're talking 15 days out & during a time when climatology would naturally favour flatter/Atlantic driven patterns. The BOM MJO is now updated to the 6th;

Encouraging to see no real backing down from the more amplified phase 7. I fully suspect we'll see the GFS/EPS amplify the signal as we transverse through phase 5, just like it did previously with the phase 5 prediction. All eyes on the upcoming +EAMT event, should drive the AAM more robustly into +ve territory. 

In terms of NWP output, early trends are very, very encouraging.