Jump to content
Sign in to follow this  
Paul

Model output discussion - winter proper underway

Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

Message added by Paul

Recommended Posts

4 hours ago, TEITS said:

Having read some of the posts from last night and this morning, if you don't mind me saying some are in denial. No evidence as mentioned last night of the jet continuing to run NW-SE. Little evidence of any significant height rises to our NE. The return of a milder pattern was obvious to me as I mentioned a few days ago.

What we are likely to see is a rather typical UK winter weather pattern of a flat jetstream with low pressure systems tracking NE to the N of the UK. Milder SW,lys with the weather more settled further S and rather more unsettled and windy for Scotland.

If we do see pressure rising then it is more likely to occur over the UK bringing settled conditions and cold nights. The last thing I see is any cold, snowy E,ly whilst heights remain low to our NW/N.

Sadly I would be amazed if any of the above changed before xmas. My punt is a dry, settled Xmas but at least we should wake up to frost which is better than wind/rain.

So much I agree with about this.  The "signs" that are there are signs that are nearly always there.  They are the same signs that are seen when it looks like the zonal norm is set to return to ruin a cold snowy period and we are told we can safely ignore them.

I do admire the work and effort that Tamara puts in for example, but you only have to look at early December last year for hints being given of something developing to our north east.  we know how that turned out. 

Personally I always value TEITs input and am delighted to see him back.  I think Knocker is one of the best and I like Steve Murr though I read his post like I think he intends them to be read, as explanations of what needs to be seen to be the cold and snow over us, rather than determining what will actually happen.

Just three mentioned but many more admired who's comments are driven by what the models are showing as opposed to an expectation of what "background signals" will cause them to show eventually.

I got quite a bit of kudos from mates for picking this last weekend out as a potential snowy one two weeks ago from viewing from GFS output.  Over the course of those two weeks some of the runs swung wildly but it kept coming back to what it was once showing in the far reaches of FI.

My concern for Christmas is that it will be more on the ball now than it will be on a few runs it makes up to the day itself. And, unlike TEITS, my conclusion is that we are in for a very mild wet and windy Christmas period!

airpressure.png

Share this post


Link to post
Share on other sites
4 hours ago, Weegaz said:

I can't seem to be able to upload the charts but surprised Wednesday evening through Thursday's snow event isn't being discussed.  Its showing again on the 6z GFS charts which are rolling out now.

Bitter cold here today......reached -9.5 at 9pm last night, warmed this morning to a balmy -1.5.  

It would be, at least, a consolation prize after the last few days. The Arpege 0.1 shows very little snow chance, however, WRF snow for high ground (usually the moors off to my west) and ICON, weirdly putting it tomorrow night instead. Chances look very slim then, unless we have the reverse of the recent debacle. EURO4 is usually closest so the midnight run should give a clue.

Edited by ukpaul

Share this post


Link to post
Share on other sites

Just looking at the GEFS 6z mean regarding next week shows a more settled spell as the Azores high builds in, at least across the southern half of the uk, perhaps more changeable across the far nw / n..doesn't look unsettled at all next week in the run up to christmas, doesn't look particularly mild either!:)

21_246_500mb.png

21_270_500mb.png

21_294_500mb.png

21_294_2mtmpmax.png

21_318_500mb.png

Share this post


Link to post
Share on other sites
4 hours ago, Weegaz said:

I can't seem to be able to upload the charts but surprised Wednesday evening through Thursday's snow event isn't being discussed.  Its showing again on the 6z GFS charts which are rolling out now.

Bitter cold here today......reached -9.5 at 9pm last night, warmed this morning to a balmy -1.5.  

Not a criticism of your post at all, but just to say, I will never trust another GFS snow chart again after this weekend. Yesterday, it missed out about 50% of the areas receiving snow at T0! Then, this morning, again at T0, it had the entire south coast under a covering of snow!!

From now on I will stick to ARGEPE inside D5, and ARGEPE/AROME/HIRLAM/EURO4 inside D2Thank goodness we current have the ECM charts at weather.us - the "significant weather" chart has been pretty good at picking up snow trends (not the "snow total" chart which seems a total sum of any possible flake falling from the sky)

Share this post


Link to post
Share on other sites
1 minute ago, Man With Beard said:

Not a criticism of your post at all, but just to say, I will never trust another GFS snow chart again after this weekend. Yesterday, it missed out about 50% of the areas receiving snow at T0! Then, this morning, again at T0, it had the entire south coast under a covering of snow!!

From now on I will stick to ARGEPE inside D5, and ARGEPE/AROME/HIRLAM/EURO4 inside D2Thank goodness we current have the ECM charts at weather.us - the "significant weather" chart has been pretty good at picking up snow trends (not the "snow total" chart which seems a total sum of any possible flake falling from the sky)

Most of those were poor at those ranges, only in the last 24 hours did they shift the heavy snow from here elsewhere, for example. So, trust none of them!

There really is no way of certainty until the last possible moment given not only the likely track but also the numerous parameters needed to predict what will be snow, sleet or rain.

T24 and no earlier.

Share this post


Link to post
Share on other sites
Just now, ukpaul said:

Most of those were poor at those ranges, only in the last 24 hours did they shift the heavy snow from here elsewhere, for example. So, trust none of them!

There really is no way of certainty until the last possible moment given not only the likely track but also the numerous parameters needed to predict what will be snow, sleet or rain.

T24 and no earlier.

That is also a fair comment!! (But at least they got there in the end!)

ECM probably the best over a longer period of time?

Share this post


Link to post
Share on other sites
15 minutes ago, Man With Beard said:

That is also a fair comment!! (But at least they got there in the end!)

ECM probably the best over a longer period of time?

One thing for sure i agree with you is the snow totals are a joke London has 4 inches and the city has come to a standstill at the minute:rofl:, to be honest there all brutally crap at predicting snow.

snow.png

Edited by booferking

Share this post


Link to post
Share on other sites

It's almost time for a massive, huge, ginormous GFS 12Z...Eyes down. Let's get ready to rumble! Or crumble!:cold-emoji:

Edited by Ed Stone

Share this post


Link to post
Share on other sites

Hello, first post for a few days as I have been away

Looks like we have a pattern change coming this weekend and I’ll describe what I think may happen based on the model output.

However first, lets have some context… why is the pattern changing? Well a big part of the change can be attributed to the Pacific North American pattern (PNA). What is this?, well here are some basic diagrams to show its effects. The top two panels show the synoptic pattern and the bottom two show the temperature anomalies.

The synoptic pattern over the USA when the PNA is strongly positive is one where we have high pressure over the western USA (like recently). That is the main thing and usually there is lower pressure over NE Canada or the NE USA.

                     Positive PNA - SLP                             Negative PNA - SLP
image.thumb.png.f9ed9e238c6d8c0b8ef11270a7501f1b.png    image.thumb.png.285d2a624b6640b2aac86d974f58625d.png

            Positive PNA - temperature                       Negative PNA - temperature
 image.thumb.png.4f3a292024ab00dd175e99286506d51b.png image.thumb.png.8e838e5a246b5610dff543bc488da08c.png 

So its probably little surprise that this pattern has contributed to increased wildfire activity in this region. The downstream effects (North Atlantic) are that the Azores high is more likely to ridge North which is what we have been seeing.

Due to the cold air from Canada being deposited over the SE USA, low pressure systems over around the coastal areas where cold continental air meets the warmer temperatures of the North Atlantic. Low pressure systems typically move NE off the Eastern seaboard and some of these get trapped in the far NE Canada or USA. Thus encouraging ridging of the Azores high.

However we are seeing a transition to a more negative PNA which is shown on the right hand panel. Often the high Pressure over California is not as strong allowing the jet to dive further west in the USA instead. The SE USA is often under warm air from the Gulf of Mexico. Areas of low pressure zip across Canada and carry cold Canadian air into the North Atlantic.

We therefore see a region of rapid deepening of low pressure due to the cold Canadian air meeting the warmer Atlantic. Low pressure moves past Greenland and warm air from the SW Atlantic hits us instead.

Now there are some variations over the PNA but a somewhat similar kind of pattern change explains why there is a stronger chance of mild westerlies coming into play over the UK.

Though how this Atlantic energy is split will determine how mild the UK gets. So here is the basic scenario on Sunday. Now we have mild air racing across the North Atlantic but a slightly displaced Azores high close by. From here three scenarios could develop within the following couple of days.

                    Sunday
image.thumb.png.e26938863a60df5f9d00581c5df78e3d.png

                     Scenario 1: 15%                                   Scenario 2: 35%                                         Scenario 3: 50%
image.thumb.png.fd3c207acdd73f05649c56bbb77e5afd.pngimage.thumb.png.94ac7ab5b6f096a63b45570bb1d0096c.pngimage.thumb.png.421c8744478367c5acfe413bc280e387.png


The first is a Scandinavian high which has a fair chance of happening but it probably wouldn’t occur that quickly due to the amount of energy in the North Atlantic jet. Also there is the issue of that low over Scandi blocking its Eastward progress.

The second is an anticyclonic outlook. Here the Azores high ridges across but a lot of energy goes over the top. Many parts of the UK would still be cold because of the short days. Slack winds and weak solar heating means temperatures can’t recover during the day. In these situations T850 ensembles can be misleading because it can be cold at the surface despite warmer temperatures higher up (known as a temperature inversion). Warm air will likely affect NW areas though and a slight modification could see either the whole of the UK cold or mild.

The final scenario is one where the Atlantic wins out over the following few days. This could lead to either mild SW winds if there is a pressure build to our east as well or a more alternating mild/cool pattern with westerlies.

Finally a Scandi high could develop later from the other two Scenarios. The middle panel wouldn’t be that bad if some blocking could develop from the high pressure. Overall these are just a bunch of scenarios that I think will develop from the model output. Lets see what the 12z’s bring.

Edited by Quicksilver1989

Share this post


Link to post
Share on other sites

I'm glad parts of the southeast got some snow today, especially higher parts of surrey. Tonight looks bitterly cold with severe frost, especially over the snow fields with minus double digits celsius for some!..needless to say tomorrow looks cold after such a bitter night and then we have a midweek less cold blip before colder air returns from the north with wintry showers to exposed n / e areas and overnight frosts and ice.:santa-emoji::cold-emoji:

Edited by Frosty.

Share this post


Link to post
Share on other sites
11 minutes ago, Quicksilver1989 said:

Hello, first post for a few days as I have been away

Looks like we have a pattern change coming this weekend and I’ll describe what I think may happen based on the model output.

However first, lets have some context… why is the pattern changing? Well a big part of the change can be attributed to the Pacific North American pattern (PNA). What is this?, well here are some basic diagrams to show its effects. The top two panels show the synoptic pattern and the bottom two show the temperature anomalies.

The synoptic pattern over the USA when the PNA is strongly positive is one where we have high pressure over the western USA (like recently). That is the main thing and usually there is lower pressure over NE Canada or the NE USA.

                     Positive PNA - SLP                             Negative PNA - SLP
image.thumb.png.f9ed9e238c6d8c0b8ef11270a7501f1b.png    image.thumb.png.285d2a624b6640b2aac86d974f58625d.png

            Positive PNA - temperature                       Negative PNA - temperature
 image.thumb.png.4f3a292024ab00dd175e99286506d51b.png image.thumb.png.8e838e5a246b5610dff543bc488da08c.png 

So its probably little surprise that this pattern has contributed to increased wildfire activity in this region. The downstream effects (North Atlantic) are that the Azores high is more likely to ridge North which is what we have been seeing.

Due to the cold air from Canada being deposited over the SE USA, low pressure systems over around the coastal areas where cold continental air meets the warmer temperatures of the North Atlantic. Low pressure systems typically move NE off the Eastern seaboard and some of these get trapped in the far NE Canada or USA. Thus encouraging ridging of the Azores high.

However we are seeing a transition to a more negative PNA which is shown on the right hand panel. Often the high Pressure over California is not as strong allowing the jet to dive further west in the USA instead. The SE USA is often under warm air from the Gulf of Mexico. Areas of low pressure zip across Canada and carry cold Canadian air into the North Atlantic.

We therefore see a region of rapid deepening of low pressure due to the cold Canadian air meeting the warmer Atlantic. Low pressure moves past Greenland and warm air from the SW Atlantic hits us instead.

Now there are some variations over the PNA but a somewhat similar kind of pattern change explains why there is a stronger chance of mild westerlies coming into play over the UK.

Though how this Atlantic energy is split will determine how mild the UK gets. So here is the basic scenario on Sunday. Now we have mild air racing across the North Atlantic but a slightly displaced Azores high close by. From here three scenarios could develop within the following couple of days.

                    Sunday
image.thumb.png.e26938863a60df5f9d00581c5df78e3d.png

                     Scenario 1: 15%                                   Scenario 2: 45%                                         Scenario 3: 55%
image.thumb.png.fd3c207acdd73f05649c56bbb77e5afd.pngimage.thumb.png.94ac7ab5b6f096a63b45570bb1d0096c.pngimage.thumb.png.421c8744478367c5acfe413bc280e387.png


The first is a Scandinavian high which has a fair chance of happening but it probably wouldn’t occur that quickly due to the amount of energy in the North Atlantic jet. Also there is the issue of that low over Scandi blocking its Eastward progress.

The second is an anticyclonic outlook. Here the Azores high ridges across but a lot of energy goes over the top. Many parts of the UK would still be cold because of the short days. Slack winds and weak solar heating means temperatures can’t recover during the day. In these situations T850 ensembles can be misleading because it can be cold at the surface despite warmer temperatures higher up (known as a temperature inversion). Warm air will likely affect NW areas though and a slight modification could see either the whole of the UK cold or mild.

The final scenario is one where the Atlantic wins out over the following few days. This could lead to either mild SW winds if there is a pressure build to our east as well or a more alternating mild/cool pattern with westerlies.

Finally a Scandi high could develop later from the other two Scenarios. The middle panel wouldn’t be that bad if some blocking could develop from the high pressure. Overall these are just a bunch of scenarios that I think will develop from the model output. Lets see what the 12z’s bring.

The scenarios add up to 115%😉

Share this post


Link to post
Share on other sites
9 minutes ago, Singularity said:

ALL_emean_phase_full.gif

Quite the turnaround from the models with the dip into the 'circle of death' almost eradicated and much better amplitude into 6/7 from GEFS and 7/8 from ECMF.

Both are good for boosting HLB starting a week or two later in time from onset... so around 10-18 days from now. Question is whether we can achieve the 'almost' situation of recent GFS runs in the 7-10 day range, or end up with more work needing to be done to rescue things as per recent ECM runs.

With the near-term reduction in MJO forcing removed, there may even be additional amplification on offer in the 6-10 day range so that's something to watch out for.

Maybe.

That is possible good news Singularity, if the MJO was to occur as projected, is there anything currently showing which might override this signal? ENSO remains favourable i believe as does the lower energy from the sun.

Share this post


Link to post
Share on other sites
2 minutes ago, mountain shadow said:

That is possible good news Singularity, if the MJO was to occur as projected, is there anything currently showing which might override this signal? ENSO remains favourable i believe as does the lower energy from the sun.

I think the amplitude is relevant

as far away as poss from the COD to generate a downstream response 

 

Share this post


Link to post
Share on other sites
1 minute ago, mountain shadow said:

That is possible good news Singularity, if the MJO was to occur as projected, is there anything currently showing which might override this signal? ENSO remains favourable i believe as does the lower energy from the sun.

Indeed it is, and I'm not seeing any particularly troublesome stratospheric behaviour at the moment, well not consistently in model projections anyway. Still signs of a strong warming event, in fact, although more uncertain since the modelled tropical forcing started dancing about.

The ENSO state is tied into the MJO and GLAAM behaviour, with the eastward bias of cold anomalies allowing the MJO to move further east than would be seen during a canonical La Nina and so send GLAAM on the rise. This has led to interesting developments in similar historical years as discussed by GP (for example) at times these past few days and weeks.

The Met Office now putting back renewed HLB chances to early January does make me wonder if something's lurking in the shadows, though...

Share this post


Link to post
Share on other sites
52 minutes ago, ukpaul said:

Most of those were poor at those ranges, only in the last 24 hours did they shift the heavy snow from here elsewhere, for example. So, trust none of them!

There really is no way of certainty until the last possible moment given not only the likely track but also the numerous parameters needed to predict what will be snow, sleet or rain.

T24 and no earlier.

I agree . Met office amber warning and ALL models had us in nw Wales in inches of snow. But we only had a few flakes blowing in the wind all day. 

Share this post


Link to post
Share on other sites
46 minutes ago, Ed Stone said:

It's almost time for a massive, huge, ginormous GFS 12Z...Eyes down. Let's get ready to rumble! Or crumble!:cold-emoji:

The 12z looks a lot more amplified by 102h compared to the 6z, now let's hope it's enough 

Share this post


Link to post
Share on other sites

Better chance of a block building later on this time?

This will get shunted east, but the more the Atlantic gets halted the better chance a high will build over Scandi.

                      12z                                                              06z 

 GFSOPEU12_105_1.png  GFSOPEU06_111_1.png

Edited by Quicksilver1989

Share this post


Link to post
Share on other sites
7 minutes ago, Ed Stone said:

Midweek and on looking good for the Scottish ski resorts:

h850t850eu.png

What's the chances of another slider from that low south of Greenland ed?? 

Share this post


Link to post
Share on other sites
Just now, ArHu3 said:

The 12z looks a lot more amplified by 102h compared to the 6z, now let's hope it's enough 

I know, the Atlantic really struggling to push through with heights over the pole and Greenland evident. Could be wintry again from midweek into the weekend again for some.

Share this post


Link to post
Share on other sites

Interestingly there's quite a bit more amplification in the Atlantic at day 4-5 with pressure lower in Europe.

Probably nothing but hopefully the trend can continue, it's something.

IMG_8621.PNG

IMG_8622.PNG

Share this post


Link to post
Share on other sites

If we can get this next low to slide energy under then its game on for heights to build.

gfs-0-126.png

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

×
×
  • Create New...