Model Output Discussion - Into Winter

[Notty]

8 minutes ago, Day_9 said:

 

there is, in beautiful technicolour, the forecasting accurate and “less accurate”  timeframe of modern day meteorology 

Pretty good agreement until the LP turns up

[damianslaw]

GFS18z shows exactly what I was saying, potential for atlantic longwave trough disruption courtesy of the dense cold pool of air to the NE going nowhere, forcing the jet on a southerly path steering low pressure on a NW- SE trajectory.

Certainly plausible.

Edited November 27, 2023 by damianslaw

[BLAST FROM THE PAST]

5 hours ago, BLAST FROM THE PAST said:

GFS 12z op improved up to t192 , then it goes full blown Atlantic.  To far ahead to trust that.  GFS control very viable t192 onwards and is beautiful.  Lots to play for and lots to resolve still ……looking at t192 and the way the hemisphere is with deep cold close  by I would expect the follow on to be more like the Control.  

 

BFTP

And 18z delivers as does ECM.  This is FAR from over

BFTP

[alexisj9]

4 hours ago, Tim Bland said:

Finally found a snow chart to post ! 

Looks similar to last year actually lol, I'm in the weak SW rain flow again.

[Severe Siberian icy blast]

54 minutes ago, Kasim Awan said:

We potentially have our first streamer interest - the Thames may come alive on Thursday as far as I can see 90% of hi res are in support of some Suffolk/Kent/Thames streamer action leading to the possibility of a good few cm inland due to nocturnal eradication of surface warmth. Also note a slight kink Wednesday Night /Thursday AM which looks to push into the North East, could produce a dusting inland as it moves in. These are speculations at present.

And thats our 5%

[andy989]

6 minutes ago, BLAST FROM THE PAST said:

Possible but too soon in the longterm cycle….but very possible going forward 

 

BFTP

[snowbob]

47 minutes ago, saintkip said:

Every year it’s the same on here, a few good runs and posters are saying locked in no way the Atlantic can get through and a few hours later it’s all gone wrong.

I have no interest in cold if it’s not going to snow, pointless like last December, over a week of freezing temperatures and not one snowflake. I want that low to move north on Thursday.

With respect and I mean with respect

saying your  not interested in cold without snow is like saying you don’t like football unless there is just penalties for the whole 90 minutes.

there is so much more to model watching than just the highlights.

models are just doing the same thing they do each winter they show us gold but produce 4th most times but this winter maybe they are on to something.

there are some really great knowledgeable posters on here that I’n my opinion are great at reading the models (I for one have been trying for years and are no where near the talent on here) 

if anything this winter is an amazing learning curve so far

[Met4Cast]

The spike in AAM tendency is just the beginning. As the MJO transitions into phases 3/4/5 we should see an increase in frictional & mountain torque further spiking AAM tendency driving the overall GLAAM upwards once again.

I'd expect to see a fairly large spike in +EAMT, interestingly many studies show a strong +EAMT event often proceeds SSW's due to Rossby wave propagation which is why I've been banging on this drum for so long and monitoring this so closely. 

This is a perfect example of the tropics (MJO) & subtropics (GWO) working harmoniously together pointing in one direction.. a very disturbed jet stream & increased likelihood of high latitude blocking & cold weather outbreaks into the mid latitudes. *IF* we see a return to Atlantic driven mild weather I can't see it lasting particularly long. This spike in AAM tendency will likely increase westerlies across the Atlantic for a time, but that doesn't mean those increased westerlies cannot be south shifted.

Wedges to the north & a south shifted jet, what would that suggest I wonder.. very exciting time to be a cold/snow lover.

Naturally 2+2 does not always = 4 in terms of weather so no guarantees but broadly speaking it doesn't look like we're going to see endless mild wet Atlantic driven weather.

Edited November 27, 2023 by Met4Cast

[Scott Ingham]

12 minutes ago, Met4Cast said:

The spike in AAM tendency is just the beginning. As the MJO transitions into phases 3/4/5 we should see an increase in frictional & mountain torque further spiking AAM tendency driving the overall GLAAM upwards once again.

I'd expect to see a fairly large spike in +EAMT, interestingly many studies show a strong +EAMT event often proceeds SSW's due to Rossby wave propagation which is why I've been banging on this drum for so long and monitoring this so closely. 

This is a perfect example of the tropics (MJO) & subtropics (GWO) working harmoniously together pointing in one direction.. a very disturbed jet stream & increased likelihood of high latitude blocking & cold weather outbreaks into the mid latitudes. *IF* we see a return to Atlantic driven mild weather I can't see it lasting particularly long. This spike in AAM tendency will likely increase westerlies across the Atlantic for a time, but that doesn't mean those increased westerlies cannot be south shifted.

Wedges to the north & a south shifted jet, what would that suggest I wonder.. very exciting time to be a cold/snow lover.

Naturally 2+2 does not always = 4 in terms of weather so no guarantees but broadly speaking it doesn't look like we're going to see endless mild wet Atlantic driven weather.

Excellent summary this mate. I have to give you enormous credit for how quickly your knowledge has grown in the past 2 years!

[Met4Cast]

1 minute ago, Scott Ingham said:

Excellent summary this mate. I have to give you enormous credit for how quickly your knowledge has grown in the past 2 years!

Thanks! 

I have to give all the credit to @Tamarathough, she has been wonderful in providing links and resources to learning material & putting up with all my questions!

[alexisj9]

4 hours ago, Stabilo19 said:

12Z MOGREPS and GEFS

 

So at least a week of cold, seasonal weather before the scatter begins around 3rd/4th Dec. Much better to see than mild SW'erlies.

That looks like a high ridging over us, then cold again to me, remember we are looking at 850s, so possibly showing an easterly with the drop of temps perhaps. Difficult to know without the chart, re morgreps

[alexisj9]

4 hours ago, sheikhy said:

Hmmm screams slider scenario to me!!!!

Possible actually. It's not getting high enough 850s for a high. Wasn't thinking straight 5 minutes ago lol.

[alexisj9]

4 hours ago, Thunders said:

Yeah, it seems like snow is very hard to forecast until days if not hours before the event actually starts.

Has always been so.

[Cheshire Freeze]

1 hour ago, Daniel* said:

Interesting how we all interpret things differently I see a lot of promise on GFS 18z it remains cold and heights reemerging to north with a slidey look to it.

That cold to the E is inching closer and closer each run too. I mentioned that after the 0z this morning.

[Notty]

6 minutes ago, alexisj9 said:

Has always been so.

I’m sure Chris Fawkes said yesterday that 0.1 degrees C can be the difference between rain and snow 

[alexisj9]

3 hours ago, nick sussex said:

Greetings from Cyprus .

After a long days travel I’m now settling into an exciting evening of model watching ! 

The models really made a drama of the low to the sw which now turns into a shallow feature . 

The dropping south of shortwave energy phasing with low pressure to the sw clearly is an issue for them and something to remember when we next get this set up .

I know some are disappointed that we didn’t get at least the chance to see what would have happened re snow chances if that low had deepened and moved ne .

Anyway the outlook looks cold and there are still some chances for snow .

So still an interesting week to 10 days coming up.

 

 

It was/is a tropical feature, I'm glad it's not coming, there's a reason GFS was bad for snow chances, would be a lot of warmth wrapped up in that low.

[alexisj9]

3 hours ago, Ali1977 said:

Fax chart for Thurs /Fri - is this suggesting the low is little closer to the U.K. than the ECM is showing? 

Looks like a boom, for the SE if correct.

[MATTWOLVES 3]

Fantastic 18Z run and just goes to show how blocking once in place can be as difficult to get rid of as the inlaws on Xmas day.

Little heads up from Judah on that Canadian warming.....well its stretched! Stretch something long enough and it weakens and sometimes breaks.

I'm liking all of this and something that sticks in my mind was that a forecaster who worked for noaa for many years said last year that the UK was on the verge of a mother of all Winters! Could have been someone named Rodger not sure now! But the way things are setting up this year my optimism is steadily rising.

[TallPaul]

2 hours ago, legritter said:

Hi gang , Thanks to all the posters who contribute to the BEST Forum in the northern Hemisphere. Very interesting Synoptics and the usual Garden paths , I'm usually about a couple of times a day and its great to read your posts .Sausage baps aĺl round and Stella s on ice Cheers gang .

Always great to see you on here Like myself, youre 100% dedicated to this forum, year in year out. 

We don't need to be Einstein's, we have others who input the most comprehensive and formative posts day in day out... Thank you all

Keep going with the Stella's and sausage baps - I can guarantee you've got all of this amazing forum tucking in to your year on year generosity...

[alexisj9]

2 hours ago, Tim Bland said:

High risk but potential for high reward for snow lovers …

That low has a warm core, where did it come from?

Not even developed fully, a wave in front of the sliding low. 

Edited November 28, 2023 by alexisj9

[Mcconnor8]

10 minutes ago, alexisj9 said:

That low has a warm core, where did it come from?

From the Azores for the small low to the South East of the UK and obviously the big one is atlantic.

Edited November 28, 2023 by Mcconnor8

[alexisj9]

24 minutes ago, Mcconnor8 said:

From the Azores for the small low to the South East of the UK and obviously the big one is atlantic.

So that's why it's so tricky, yet another warm low in the mix like Thursday, makes sense 

[Kasim Awan]

6 hours ago, TillyS said:

This isn’t really right Kasim. It was the coldest start to meteorological winter since 2010, not my words but the official Met Office analysis of the month. I remember snow flurries in London.

"The first two weeks of December were the coldest start to meteorological winter since 2010, with high pressure and a cool northerly airflow resulting in a prolonged spell of low temperatures with snow and icy conditions at times, albeit with interludes of clear skies.  

A weather station at Braemar, Aberdeenshire, recorded the lowest daily maximum temperature of the year, with -9.3°C the highest it reached on 12 December. In the early hours of the following morning, the same station recorded the lowest minimum temperature of the year with –17.3°C. 

Mike Kendon is a climate information scientist working for the National Climate Information Centre in the Met Office. He said: “December’s weather will principally be remembered for the notably cold start to the month, with prolonged low temperatures, hard frosts and snow and ice at times, even to areas further south in the UK.  

“This cool weather was principally brought on by an Arctic Maritime airmass, with daytime temperatures struggling to rise above freezing for many in what was one of the most significant spells of low winter temperatures since the exceptional December of 2010.” 

 https://blog.metoffice.gov.uk/2022/12/30/cold-december-concludes-warmest-year-on-record-for-uk/ 

 

Two reasons for posting historic weather in a model output discussion. First, for good or ill, it shows we’ve been here before. It’s not exceptional but it is going to be cold.

Second, it doesn’t mean we’re heading for either a repeat of last year or a 1962-3. It’s too early to say.

What the models are not now showing, at the moment, is sustained northerly blocking. The 12z ECM is an interesting scenario:

 

@ScottSnow that's a high sliding from west to south-west of the uk in the T216 to T240 charts, which is not really what we want to be seeing for sustained cold. It would be brilliant for the Alps mind you. NB @ICETAB maybe ‘toppler’ isn’t the correct word, but transitional high moving southwards would be an accurate assessment of the latter stages of tonight’s ECM on those two charts? Not that it’s necessarily right about that, mind you. It’s one possible route. As someone else just mentioned, there’s a wide scatter in the ensembles so all to play for https://www.netweather.tv/charts-and-data/ensembles

 

I was referring to the heavy trough which only impacted around 5% of areas.

[Jordan S]

9 hours ago, Severe Siberian icy blast said:

What makes you say mild air wins so confidently around mid month ? 

Hey, good question especially being as a lot of cold blocked potential over and to the north of the uk on many runs have shown recently during mid month as well .. I’m not confident of anything significantly mild but confident of a brief unsettled spell around mid month milder temps for the majority or all, because and just a few examples being general model guidance in the last few days, also mentioning mid month accounting to a delay of the eventual unsettled weather, as you can see some weather models have shown unsettled milder conditions more widely in the second week of December and of course in reality the high pressure blocking patterns tend to shift slower than models indicate most of the time which is partly the reason why I’ve said a pattern like that looks most likely a few days later with a middle ground scenario of low pressure systems moving over more southern and western parts on a southerly track during that second week of December looks most likely also, with frontal snow risks along with blocking areas of high pressure continuing to some extent to our northeast and northwest throughout second week of December.

Also one or two background drivers favour a return to milder westerly conditions for a time, but this looks brief which is why I’ve mentioned that in my post, also from experience of watching synoptics from past events give a decent idea as to what the forward weather pattern may be.

 

That isn’t full proof of course but is a good indicator to work with in certain scenarios such as this one, Another example for my brief milder view around mid month being ensemble forecasts have generally either hinted at more mobility approaching the west or full blown very unsettled conditions such as the Gfs over more than just one or two  model output updates over the last 2 or 3 days as well as using a super ensemble taking information from the majority of the weather models and deciphering what the weather conditions could be based on that from my view, of course I could be wrong and we stay cold and blocked throughout mid month, but I see that as unlikely but next week yes for all, into second week for some possibly all yes and after mid month also possibly cold and potentially snowy at times too but not for the mid month period I don’t think. 

 

Hopefully this makes sense, it looks different this year compared with a lot of other years with higher than normal chance of cold and snow even for southern regions and for anyone who dislikes the default westerly pattern then you’ll probably be very pleased with how December looks to pan out. 

[northwestsnow]

ICON 144

Looks good