Model Output Discussion - Colder spell ending, what's to follow?

[Griff]

[Mike Poole]

Pub run certainly showing more amplification at T162 than the 12z:

Looks well directed WAA too, let’s see how this one goes...

[Allseasons-Si]

At 156 v's the 12 162...

the more we steer clear of that shortwave off the ESB the better,this is the storm i mentioned above,on this run we seem to delay the phasing of said shortwave which should = a better outcome.

then we look for downstream amplification from the trough out of the eastern states after,this is the key to getting more amplitude ahead of it into Greenland.

Edited December 13, 2020 by Allseasons-si

[Weathizard]

Even better ridging on the 18z, I noticed even as early as day 5 the wave of high pressure over US/CANADA was much sharper. The evolution is starting to look quite plausible now.

[TSNWK]

2 minutes ago, Griff said:

Possible amplification (ramplification) alert...

Watch it go pear shape now I cursed it... 

It does look more amplified around  southern tip of greenland.. an yes I can think of two times you have jinked it

[Griff]

1 minute ago, TSNWK said:

It does look more amplified around  southern tip of greenland.. an yes I can think of two times you have jinked it

At least twice

[Scott Ingham]

1 hour ago, Catacol said:

We are seeing ongoing signs of amplification despite the failed attempt for high lat blocking here in a week’s time. Pacific jet forecasts show more in the way of momentum being fired into the system. Jet extension this week

and more jet extension in the mix for Xmas week.

Such forecasts are linked to the next rise in AAM which is now underway. Frictional torque between earth and atmosphere is increasingly sharply now

and what we need to look for is a rise in mountain torque that would typically follow afterwards. Mountain torque is currently strongly negative but it won’t stay that way.

Those GFS pacific jet charts are suggesting that it won’t be too many days before this happens, and +EAMT will be a key ingredient in the overall increase.

On the ground for us what does this mean?

1. The optimism around the run in to Xmas should not fade too much because the impacts of the next cycle are on the horizon.

2. Slightly at odds with some of the MJO enthusiasm in here today I would say that this will happen regardless of whether the MJO makes it to the Nino phases of 7-8-1. It would be good to have MJO support for the spike and if we get that then the likelihood is the spike will be greater...but it isn’t the be all and end all.

3. As momentum spikes and engages mountain torque the pacific jet fires up, and ahead of it encourages wave breaking in form of ridges that give us our chance of a higher let block.

Can we get one of these ridges to get traction to the north of the U.K.? Here we need to hope for timing to click. The outer edges of the ECM strat forecast see the core of the upper trop vortex sitting over Greenland on the 22nd. 

From this position we can see that substantive height rises in the days before Xmas are a long shot (the misery of the last 24 hours!) but beyond Xmas? Notice the vortex is still split on this forecast - a better position than was being touted 2 days ago and so the damage being done right now as wave 1 and wave 2 forcing happens for the next few days may actually be ramping up. So it is not beyond the bounds of possibility that the vortex is left quite weakened, and if the core of the vortex can find its way back across to Siberia then I’d say - yes - chances of a high lat block return for the period leading up to New Year.

So - things to look out for

- Gradient of mountain torque increases over the next 7 days. Big +EAMT would be ideal.

- Any concurrent support from MJO progression.

- Signs of the vortex remaining weakened and perhaps shifting away from Greenland towards Siberia.

Plenty to keep the forecasting pot simmering!

 

As for a SSW? I’m in your camp. I remain cautious about activity in the New Year being enough to bring it down, but later in January - yes...

Brilliant mate. We should have an EAMT peak Tuesday next week and another Christmas week. Im with you in the thoughts that we don't necessarily need MJO assistance due to the frailty of the vortex and also now on a closer page in regards a SSW. 15TH of January is my punt

[Blessed Weather]

2 hours ago, Stevie B said:

So does the MJO drive the ensembles or do the ensembles drive the MJO or do they independently read the background signals?
 

A quick overview. The MJO is one of many drivers of global weather patterns and as such is an important teleconnection for which forecasts are made. The GEFS are used to produce a forecast for the MJO and the forecast is shown in the 8-phase real-time multivariate (RMM) wheel to denote where MJO (enhanced rainfall) activity is currently located, from the Indian Ocean through to the Western Pacific. For the UK, phases 3 and 4 can produce a +ve NAO and phases 6, 7 and 8 can produce a -ve NAO. But these NAO occurrences can take between 5 and 15 days to develop (in the Atlantic) following the MJO entering a particular phase.

It's important to note that the MJO is far from being the ONLY driver of UK weather. The percentages below show that the occurrence of the main 4 dominant weather patterns over the North Atlantic during boreal winter (Nov – Mar) that were the result of an MJO event were:

• -ve NAO 20%
• +ve NAO 30%
• Atlantic Ridge 23%
• Scandi High 27%

As a result of the weather patterns and the Kelvin-Rossby waves created by the MJO it can also have an impact on the Strat PV and can cause a SSW. Best phases are 6, 7 and 8 and again there is a time lag, typically up to 12 days between an MJO moving into these phases and a SSW. (But a SSW can occur without the MJO necessarily being the cause).

Finally, as well as producing a specific MJO forecast, the GEFS is better known for producing global weather forecasts in the same way as the GFS Operational model. The 21 ensemble members are used to produce multiple (individual) iterations of weather forecasts, only with slightly varying starting data. The input data and 'background signals' used in these forecasts include many, many variables including ENSO, MJO, SSTs, snow cover, topography, solar, cloud cover, ground moisture, etc.

Hope that helps..... and now back to the GFS 18z....

 

[Weathizard]

Genoa low, runner low cutting over the top of the Iberian high, Atlantic amplification. It’s textbook stuff.

[Tim Bland]

Where is that low heading Remember the control run from the 12z for Xmas day eyes ️

[Scott Ingham]

7 minutes ago, Blessed Weather said:

A quick overview. The MJO is one of many drivers of global weather patterns and as such is an important teleconnection for which forecasts are made. The GEFS are used to produce a forecast for the MJO and the forecast is shown in the 8-phase real-time multivariate (RMM) wheel to denote where MJO (enhanced rainfall) activity is currently located, from the Indian Ocean through to the Western Pacific. For the UK, phases 3 and 4 can produce a +ve NAO and phases 6, 7 and 8 can produce a -ve NAO. But these NAO occurrences can take between 5 and 15 days to develop (in the Atlantic) following the MJO entering a particular phase.

It's important to note that the MJO is far from being the ONLY driver of UK weather. The percentages below show that the occurrence of the main 4 dominant weather patterns over the North Atlantic during boreal winter (Nov – Mar) that were the result of an MJO event were:

• -ve NAO 20%
• +ve NAO 30%
• Atlantic Ridge 23%
• Scandi High 27%

As a result of the weather patterns and the Kelvin-Rossby waves created by the MJO it can also have an impact on the Strat PV and can cause a SSW. Best phases are 6, 7 and 8 and again there is a time lag, typically up to 12 days between an MJO moving into these phases and a SSW. (But a SSW can occur without the MJO necessarily being the cause).

Finally, as well as producing a specific MJO forecast, the GEFS is better known for producing global weather forecasts in the same way as the GFS Operational model. The 21 ensemble members are used to produce multiple (individual) iterations of weather forecasts, only with slightly varying starting data. The input data and 'background signals' used in these forecasts include many, many variables including ENSO, MJO, SSTs, snow cover, topography, solar, cloud cover, ground moisture, etc.

Hope that helps..... and now back to the GFS 18z....

 

Another high quality post!

[Kentspur]

1 minute ago, Tim Bland said:

Where is that low heading Remember the control run from the 12z for Xmas day eyes ️

Are we going to see a more Northeasterly tangent to the flow over xmas/boxing day ❄

[Mike Poole]

GFS 18z T240:

Good ridge, need that low to move across east, which it should do, moving away the high heights in the med.  850s not good though:

[TSNWK]

Don't like it.. far less heights up into Greenland on Christmas Eve. Toppler?

[chionomaniac]

14 minutes ago, Blessed Weather said:

A quick overview. The MJO is one of many drivers of global weather patterns and as such is an important teleconnection for which forecasts are made. The GEFS are used to produce a forecast for the MJO and the forecast is shown in the 8-phase real-time multivariate (RMM) wheel to denote where MJO (enhanced rainfall) activity is currently located, from the Indian Ocean through to the Western Pacific. For the UK, phases 3 and 4 can produce a +ve NAO and phases 6, 7 and 8 can produce a -ve NAO. But these NAO occurrences can take between 5 and 15 days to develop (in the Atlantic) following the MJO entering a particular phase.

It's important to note that the MJO is far from being the ONLY driver of UK weather. The percentages below show that the occurrence of the main 4 dominant weather patterns over the North Atlantic during boreal winter (Nov – Mar) that were the result of an MJO event were:

• -ve NAO 20%
• +ve NAO 30%
• Atlantic Ridge 23%
• Scandi High 27%

As a result of the weather patterns and the Kelvin-Rossby waves created by the MJO it can also have an impact on the Strat PV and can cause a SSW. Best phases are 6, 7 and 8 and again there is a time lag, typically up to 12 days between an MJO moving into these phases and a SSW. (But a SSW can occur without the MJO necessarily being the cause).

Finally, as well as producing a specific MJO forecast, the GEFS is better known for producing global weather forecasts in the same way as the GFS Operational model. The 21 ensemble members are used to produce multiple (individual) iterations of weather forecasts, only with slightly varying starting data. The input data and 'background signals' used in these forecasts include many, many variables including ENSO, MJO, SSTs, snow cover, topography, solar, cloud cover, ground moisture, etc.

Hope that helps..... and now back to the GFS 18z....

 

Also worth noting though that MJO activity is twice as important than extra tropical when comparing a negative NAO to that influencing a positive NAO.

WWW.TANDFONLINE.COM

 

[BlueHedgehog074]

Really are some magnificent posts in here today. Great effort from people. Is what makes Netweather a cool place to be part of. Feels like you learn more in here than those textbooks you would have read back at School

[Allseasons-Si]

7 minutes ago, Tim Bland said:

Where is that low heading Remember the control run from the 12z for Xmas day eyes ️

Straight for the UK!!!

we need this heading further SE and clear the UK.

 

[alexisj9]

1 minute ago, Allseasons-si said:

Straight for the UK!!!

we need this heading further SE and clear the UK.

 

Yep like I said earlier, the pattern going onwards will be decided by that little low, I'm only interested in it at 144 at the min. The models going forward, don't know what to do with it yet. But looking through the runs, you can get an idea of what the differences are later on. Ideally we need it to go south east, but we'll see. Hopefully it doesn't start to phase with the main low.

[Tim Bland]

4 minutes ago, Allseasons-si said:

Straight for the UK!!!

we need this heading further SE and clear the UK.

 

Yes, unfortunately, this time it cuts straight through rather than riding the jet stream and heading south like the control earlier. Hopefully on the next run it’s so different to the 12z so wouldn’t worry too much. It’s still 100 x better than 2 days ago!

[BelgianBlizzard]

Not a great run... no link up with greenland and a toppler with very mild uppers. 

Probably very different in the morning though

[Allseasons-Si]

I feel like i am re-righting the strictly come prancing and dancing on ice obituary again here lol

the 18z ICON was a good run  although it only goes to 120....shame,as that would i think would produce a stella run into Xmas

the gfs...well,it has it's stella's on the 12z then has a Lambrini on the 18z,...yuck

the ECM on the other hand has a Martini and thinks it should shoot down the gfs in 007 stile ha! ha!

but lets be frank..

we live on a goal post that is so tiny the Greeks would have a field day

lets hope the 18z had a wobble

night guys,nice chatting with you all,great place this forum is.

Edit: i think i had a Nick sussex moment there

 

 

 

 

 

Edited December 13, 2020 by Allseasons-si

[Duane S.]

3 hours ago, Scott Ingham said:

Thanks Ed. I appreciate them words! Not bad for someone with Dixlexia haha! I think the condition makes me even more aware of writing for all level of readers 

I’m going to chip in on the Scott appreciation society

It’s actually quite a skill Scott and surprisingly few people have it.

I’ve always had a pretty firm grip on teleconnections but getting things out of my head and laid out clearly and most importantly,  concisely is not easy at all. Good stuff.

[Ice Day]

Christmas Eve morning on the Control...... yes please!

This run is setting up for a terrific FI - Yep, I've jinxed it.

Edit - The mean for the same time is excellent

 

Edited December 13, 2020 by Ice Day

[A Frayed Knot]

1 minute ago, Ice Day said:

Christmas Eve morning on the Control...... yes please!

This run is setting up for a terrific FI - Yep, I've jinxed it.

 

Very nice but...... Will it verify

Let's not Jinx it

[Ice Day]

1 minute ago, A Frayed Knot said:

Very nice but...... Will it verify

 

Absolutely, unequivocally, no!  But still, it's rather nice to look at before bed! Control at 276 is an absolute beaut.