Model output discussion - The run up to Christmas

[SLEETY]

Offshore wind if your near the coast and slow moving low pressure are ideal ingredients for snow to make it all the way down to sea_level, in marginal situations, once the upper air gets to minus 10 then its snow from any direction, like in March 2018.

Edited December 21, 2020 by SLEETY

[Ben Sainsbury]

4 minutes ago, Updated_Weather said:

Remember the early December 2020 snowfall we had here in Essex, how marginal that was and the uppers wasn't that cold.. But because of the heavy PPN, we got a good covering.. But a few miles away, absolute nothing.

The benefit in this setup is that the ground should cool with time since we're in that sort of freeze-thaw setup. Should aid in the settling of snow and this should help reduce temperatures further since any radiation is reflected.

[BlueHedgehog074]

5 minutes ago, northwestsnow said:

UKMO 144 NH view...

Looks like a giant monkey dropped a great big banana of high heights over the Atlantic/Greenland/Arctic/Siberia areas causing the Troposphere Vortex to split. An ape-mazing chart 

[ITSY]

10 minutes ago, Kasim Awan said:

This upcoming set up is less marginal on average. The "base" snow line will be ~150m lower than 4th Dec if the current output is correct. This means more places will come into the snow potential, and snow will be easier to achieve. Potential is the key operator here.

Less marginal indeed. No point going to snow levels yet - I'm at 20ASL and had 2cms of slushy snow in early December with -2uppers. The lower they are the easier snow is to achieve but at this point it's too early to say what will fall where. The GFS 12z showed 4inches in Kings Lynn at one point! 

[Kasim Awan]

3 minutes ago, ITSY said:

Less marginal indeed. No point going to snow levels yet - I'm at 20ASL and had 2cms of slushy snow in early December with -2uppers. The lower they are the easier snow is to achieve but at this point it's too early to say what will fall where. The GFS 12z showed 4inches in Kings Lynn at one point! 

Enough said. Potential is there and we have established at what level the potential is. Pros will leave it at that until more data is available rather than becoming emotionally attached to upper air temperatures.

[Scott Ingham]

24 minutes ago, Updated_Weather said:

Something interesting from Matt Hugo - regarding MJO

Yes first week in January we should see a move back through 6/7/8 on top of another mountain torque event. Its why I believe the SSW is practically nailed as we have another 2 upcoming wave breaking events. Any model that shows rinse and repeat with each episode that bit colder is on the money. Then we potentially have the SSW as the big finale. Never been as positive about January AND February in any winter

[Decemberof2010]

Anyone concerned about uppers take a look at the charts below. Starting out as heavy rain. This produced 45cm of snow in 3 hours back in January 95 here in Leeds. 
Wrongly forecasted, it hit at rush hour and caused absolute chaos. For snow alone this beats anything since then
 

Edited December 21, 2020 by Decemberof2010

[KTtom]

I think weve done the uppers to death now, not much has changes, as other have said, localised factors may and probably will come into play as we head into the weekend and beyond, leaving you with the last sentence on the national BBC forecast just now, heading into the new year, 'heavy rain, and with the cold remaining in place things could get very interesting indeed'!

Edited December 21, 2020 by KTtom

[Lincs Observation]

Good evening all 

I don’t normally post in here but I have been following the bbc weather for a few days now and they seem to be quite bullish that there will be no snow over Xmas apart from the normal higher regions of Scotland, however what has changed is on the latest forecast by Louise Lear that in the week up-to new year with the low pressure  over the country that it will remain unsettled with rain but the post script in her words is that with the cold the weather could get interesting.

Read what you will into that statement.

 

LO

[Nick F]

Check out the expanding high dropping down from Russian arctic / Siberia to China and Mongolia, pressure rising to 1076 hPa! That's going to kick off some strong East Asian Mountain Torque.

The SPV in serious trouble ...

Edited December 21, 2020 by Nick F

[northwestsnow]

36 minutes ago, ITSY said:

Without meaning to skirt over the obvious potential 120-192, almost all of the GEFS give serious weight to an FI reload of sorts, particularly in the North Atlantic. 

This is the mean at +240 - up she goes again...

Yup...

Keep that euro low and its a long way to mild ...

 

[AdrianHull]

Any chance of an uppers output discussion thread mods? 

This is starting to get tedious!

[Alexis]

5 minutes ago, Decemberof2010 said:

Anyone concerned about uppers take a look at the charts below. Starting out as heavy rain. This produced 45cm of snow in 3 hours back in January 95 here in Leeds. 
Wrongly forecasted, it hit at rush hour and caused absolute chaos. For snow alone this beats anything since then
 

The problem with charts like that is that there were another 15 similar incidents, with lower 850s that were 100% rain events

[chris55]

34 minutes ago, northwestsnow said:

UKMO 144 NH view...

We need a ‘wow’ and a ‘love’ emoji added to the side menu!! So many times this evening  I’ve wanted to love a chart or say wow lol!! 
 

Synopticaly we are heading into extremely rare territory! The fact that the entire northern hemisphere is displaced from the norm in such a big way is remarkable. Potential SSW included going forward.

Regardless of 850s at day 7 perhaps we should be more focused on shovel supplies come Day 21 (snow blowers are good as well.....especially for powder )
 

[Ashme]

7 minutes ago, Nick F said:

Check out the expanding high dropping down from Russian arctic / Siberia to China and Mongolia, pressure rising to 1076 hPa! That's going to kick off some strong East Asian Mountain Torque.

The SPV in serious trouble ...

Sorry to ask but what will this mean for us?

I get the SPV but EAMT

[Scott Ingham]

11 minutes ago, Nick F said:

Check out the expanding high dropping down from Russian arctic across Siberia, pressure rising to 1076 hPa! That's going to kick off some strong East Asian Mountain Torque.

The SPV in serious trouble ...

Yes this is the stronger of the 2 mountain torques forecast. This will have a noticeable effect on the second round of amplification around the 4th or 5th of January so keep an eye now on trends towards the back end of the GFS. This is where ive gone Icelandic high. Wherever it is though it will be a stronger pulse than the christmas and new year week and will drive further waves into the strat to finish the beast (if you can call it that now)

Edited December 21, 2020 by Scott Ingham

[Kentish Snowman in Yorks]

9 minutes ago, AdrianHull said:

Any chance of an uppers output discussion thread mods? 

This is starting to get tedious!

I can't wait for Boxing Day onwards to arrive simply because Mother Nature will decide if we get rain or snow and we won't have to listen to arguments about uppers every six hours! 

On that note we only have 15 minutes to wait until the ECM comes out and for another round of fantastic synoptics but "cr8p" uppers arguments!

Sorry for getting upperty by the way!

Merry Christmas all! 

Edited December 21, 2020 by Kentish Snowman

[Decemberof2010]

3 minutes ago, Alexis said:

The problem with charts like that is that there were another 15 similar incidents, with lower 850s that were 100% rain events

Agreed, so yes your post highlights the huge variance and factors at play also.  

[Scott Ingham]

Just now, Ashme said:

Sorry to ask but what will this mean for us?

I get the SPV but EAMT

East Asian Mountain Torque. Caused by expanding high pressure over the himalayas. Its drives waves poleward towards the arctic and has been shown to affect AAM leading to higher level blocking 

[Radiating Dendrite]

Just now, Ashme said:

Sorry to ask but what will this mean for us?

I get the SPV but EAMT

East Asian Mountain Torque event - puts more pressure on the Vortex.

Just giving it another good kicking whilst it's on the ropes. After last year, it deserves it!

[Weathizard]

14 minutes ago, Decemberof2010 said:

Anyone concerned about uppers take a look at the charts below. Starting out as heavy rain. This produced 45cm of snow in 3 hours back in January 95 here in Leeds. 
Wrongly forecasted, it hit at rush hour and caused absolute chaos. For snow alone this beats anything since then
 

Satellite pictures from after the event... #M4SnowShield

[The Northern Ramper]

14 minutes ago, Mr Frost said:

Wee Christmas Day falling snowfall surprise for one or two of our North West England members? 
 

25/12: 09:00

 

25/12: 12:00
 

North West England Regional weather forecast below:

 

Great model/chart viewing at the moment!  Anything could pop up! 

Bank

[Kasim Awan]

EC makes a good effort at an Xmas eve North Sea trough

[ITSY]

18 minutes ago, Lincs Observation said:

Good evening all 

I don’t normally post in here but I have been following the bbc weather for a few days now and they seem to be quite bullish that there will be no snow over Xmas apart from the normal higher regions of Scotland, however what has changed is on the latest forecast by Louise Lear that in the week up-to new year with the low pressure  over the country that it will remain unsettled with rain but the post script in her words is that with the cold the weather could get interesting.

Read what you will into that statement.

 

LO

Yes I saw that too "heavy rain at times but because it gets quite cold...things could get interesting". 

Anyway that would pretty much tally with everything we've all said on here and what the models are showing - the potential is there after xmas for some quite unusual weather

[Decemberof2010]