Model Output Discussion - heading into April

[Cheshire Freeze]

2 minutes ago, mb018538 said:

To be fair - it wasn’t just those two particular posters. The Met Office, Meteogroup and ECM extended forecasts all forecasted a return to dry and settled weather through June. It’s a bit early to be writing the obituary on the 2nd!

Of course, and I haven't seen anyone writing any obituaries for summer- quite the opposite.

I'm just pointing out it's something to bear in mind. 

[Djdazzle]

3 minutes ago, mb018538 said:

To be fair - it wasn’t just those two particular posters. The Met Office, Meteogroup and ECM extended forecasts all forecasted a return to dry and settled weather through June. It’s a bit early to be writing the obituary on the 2nd!

Even in the best summer setups, you will find some signal which points to cool and unsettled (if you look hard enough).

[Guest]

Poor output again this morning with little to suggest a return to warm & settled in the next 10-14days. ECM & GFS singing from a similar sheet this taking an age to fill the stationary trough, could be a way back to summer but will take an age and the end of the gfs run is an outlier. GEM and ICON at the end of their runs not pretty, GEM is an absolute stinker. Looks like the June CET at the mid month point will be average at best only propped up by the first couple of days!! 

[mb018538]

 

ECM ensembles aren’t too sharp. Even the most optimistic at day 10 has a SLP of around 1018mb. Low 500mb heights too = unsettled

[Guest]

Hopefully the large height rise over western Russian isn’t going to be a semi-permanent feature Of summer, with a ridge/trough/ridge pattern extending westwards the U.K. often ends up anchored in under the trough, I really think this is going to be a tough pattern to shift. 

[Djdazzle]

If it's still showing the same by the weekend, then maybe some concern is justified going forward. In the meantime, let's just stomach the unsettled spell. It's certainly not a 2007 washout, which has to be a positive, although it will be a bit of a shock compared to what we have been used to.

[MATTWOLVES 3]

1 hour ago, CreweCold said:

I think we have to bear in mind we're in a low solar, likely very low Arctic sea ice year.

A lot of people seem to be hanging on the words of people like singularity and Tamara with regards to summer prospects. Of course, these two (extremely knowledgeable) posters are quite right when they mention the broadscale drivers - however, I remember GP taking this approach and tweaking around the edges for things like solar activity and sea ice. A signature of both of these factors is blocking at high latitudes.

It's not surprising to me that we see HP want to migrate W&N at any given opportunity 

Not so sure about that mate, we have been in low solar minimum for a while, with coupled low sea ice, and I'm yet to see much in the way of Northern Blocking during the winter months from it just lately.. Most likely being over ridden by other factors... Not everyone in the business is convinced of this low solar having any major baring on our weather patterns. 

Its a slow process on the mean, but there are signs of recovery out to day 10 as the Low eventually pulls South, Heights perhaps building a tad more to the North and West.. A better spell of weather coming up in that NW segment of the UK perhaps.. Perhaps June a tale of 2 halves.. 

[Downburst]

It's FI, but the 00 ECM has continued the trend of the low moving down south to south west of Spain and Atlantic High pressure ridging over the top by day 8 to 9. So perhaps 7 days of cooler and wetter weather, but GFS is forecasting less than 20 mm in 10 days, to top up the 54 mm I have had since March 1, and this is Ireland. I am not too worried, especially looking at the LRF ECM data (lagged initialization mind you). Will probably be a poor weekend, but I haven't had a chance to sit in this last few weeks, so maybe that will be interesting to watch some TV, almost forgotten it exists. 

Wednesday Next: SLP with 850 Wind Speed 

Friday: SLP with 850 Wind Speed

[Leo97t]

A warmer but very wet GFS 06z for everywhere bar the south east which looks miraculously dry given the lp domination although due to the lack of fronts and slackness probably actually wouldn't be too bad at ground level

[MATTWOLVES 3]

Some may like the 6z set up come day 11..potentially a thundery situation, very warm uppers in the mix at this stage. 

[Djdazzle]

3 minutes ago, MATT said:

Some may like the 6z set up come day 11..potentially a thundery situation, very warm uppers in the mix at this stage. 

Definite possibilities from there, especially if the pattern backs west a little. The only issue is that pressure is very slack over Europe.

[Leo97t]

if the low had collapsed a little more into Spain that setup could have been very hot and dry but alas

[Djdazzle]

1 minute ago, Leo97t said:

if the low had collapsed a little more into Spain that setup could have been very hot and dry but alas

Who knows - this option may be seen on later runs? The whole synoptic setup is on a knife-edge.

[Zak M]

Day 11 looks good - a low drags in warmer air and thunderstorms from the continent

Edited June 2, 2020 by Zak M

[Guest]

I’m all honesty it’s another poor run from gfs, a few warmer, thundery days in the offing however the door gets opened up to the Atlantic. If the trough is going to drop south west, we really need some of heights to built behind it in its place otherwise even a wet fart from from the west would able roll on through unaided towards the U.K. and potentially get stuck again!! 

[Tamara]

3 hours ago, CreweCold said:

I think we have to bear in mind we're in a low solar, likely very low Arctic sea ice year.

A lot of people seem to be hanging on the words of people like singularity and Tamara with regards to summer prospects. Of course, these two (extremely knowledgeable) posters are quite right when they mention the broadscale drivers - however, I remember GP taking this approach and tweaking around the edges for things like solar activity and sea ice. A signature of both of these factors is blocking at high latitudes.

It's not surprising to me that we see HP want to migrate W&N at any given opportunity 

Thanks for your comments. I think all contributions are welcome and there is always something to take away from many collective minds.

As for summer prospects - well I haven't definitively made any predictions at all, beyond an overview of the shape of the early summer and what to look out for that may evolve from there. I am not personally a "forecaster", or pretend to be. Simply produce summaries as and when appropriate that attempt to make helpful suggestions to look out for and hopefully give some balance to perspective.  

Sea ice as everyone knows has been an increasing factor for some considerable time - summers over such a time however have been a mix of mid and higher latitude patterns for a variety of reasons and which vary considerably from one year to another. Similarly with the other seasons in the year. The summers between 2007 and 2012 seemed to install an x+y= assumption that unstable sea ice patterns equated inextricably to an unstable polar field. Winter probably the biggest culprit c/o the snow watch.

However, since this is the season we are currently opening our doors to , as many summers since 2013 have shown it is nowhere as simple or linear as this . Each year, each season should be taken on its merits with a very open mind that stays uncluttered by pre-conceptions.

I do think there is also a preference/bias element in a lot of this x+y= type of approach and it tends to steer people to these types of assumptions as a form of confirmation bias.  It is natural to have preferences of course, we all have, but fitting/pattern matching those preferences to selected drivers is fraught with error and doesn't work in terms of the meteorological science (as in all sciences) where bias cannot exist.

Analysis of global wind-flow inertia which is the basis of the diagnostic approach that people such as me try to gain understanding of, provides a skeletal framework for deciphering jet stream structures from which it is possible to identify forward or retrograde synoptic patterns - as well as using tropical>extra tropical intra-seasonal phenomena which have scientifically evaluated cyclical timelines and wavelengths. This type of analysis is a very useful supplement to the traditional numerical modelling approaches and provided it is used objectively and not letting confirmation bias invade its use, can be a true revelation and highly rewarding for an ordinary observer. 

Back to the here and now:

Still some agitating evident and not allowing time to look around each corner at a time and find answers. Such answers do not always come every 6 to 12 hours at times like this when a pattern many do not welcome is about to begin and require space to sit back, wait and watch

However, from my own perspective there is a lot of interest growing in the way ahead.

The analysis from on-going NWP is consistent with diagnostic and the ebbing and flowing of the Atlantic ridge. For fully detailed reasons given previously, this is unlikely to change significantly up to mid month and requires the day to day monitoring as discussed related to angular momentum budgets which will give clues as to when forward momentum returns from upstream.  Such developments can only be attempted to be provided in timely fashion as they emerge. This is more sensible and intuitive than trying to make guesses and leading to obvious error through misleading information.

But once the immediate change (and some of the worst weather) is out of the way that is where it starts to get interesting in my opinion. This retrogressive phase up to mid month is intriguing and could well end up re-setting the Atlantic trough as the ridging mechanisms back so far west that trough disruption occurs proportionately to our west . Amplification of a retracted Atlantic ridge is not always bad news for summer interest. Early summer low(er) angular momentum regimes often enough feature cut off low features sinking south to allow much warmer humid air to encroach from the continent as the ridging to the NW extends across and then over the top of these features. There remains credibility towards the end of the 10 day period of the solution hinted at on todays ECM deterministic output for this type of scenario. The overnight GFS also produced a similar idea and now the 6z GFS.

NB: It is the general evolution that matters here, not getting bogged down with what each model suggests in surface detail many days away.

This type of solution would be the maximum possible result to achieve within a limited regime  - but as stated, it could well be that the pattern retrogresses so far it re-sets the pattern to the point where momentum starts to return from upstream and a downstream Western European ridge is re-instated later in the month. That is an extended watching brief of course and will require further diagnostic data to emerge to fully back it up

The blended EC mean at day 10 indeed shows good support for the type of "shape" required for the back door route to happen with the lower heights sinking towards our south. The 12z ECM clusters indicated about a third of a majority support for this solution at day 10

 

 The overnight clusters may well therefore probably provide evidence of what the mean suggests - that it has increased traction. 

Edit: Indeed they indicate that support has grown to at least a half.

 

[mb018538]

20 minutes ago, Tamara said:

Thanks for your comments. I think all contributions are welcome and there is always something to take away from many collective minds.

As for summer prospects - well I haven't definitively made any predictions at all, beyond an overview of the shape of the early summer and what to look out for that may evolve from there. I am not personally a "forecaster", or pretend to be. Simply produce summaries as and when appropriate that attempt to make helpful suggestions to look out for and hopefully give some balance to perspective.  

Sea ice as everyone knows has been an increasing factor for some considerable time - summers over such a time however have been a mix of mid and higher latitude patterns for a variety of reasons and which vary considerably from one year to another. Similarly with the other seasons in the year. The summers between 2007 and 2012 seemed to install an x+y= assumption that unstable sea ice patterns equated inextricably to an unstable polar field. Winter probably the biggest culprit c/o the snow watch.

However, since this is the season we are currently opening our doors to , as many summers since 2013 have shown it is nowhere as simple or linear as this . Each year, each season should be taken on its merits with a very open mind that stays uncluttered by pre-conceptions.

I do think there is also a preference/bias element in a lot of this x+y= type of approach and it tends to steer people to these types of assumptions as a form of confirmation bias.  It is natural to have preferences of course, we all have, but fitting/pattern matching those preferences to selected drivers is fraught with error and doesn't work in terms of the meteorological science (as in all sciences) where bias cannot exist.

Analysis of global wind-flow inertia which is the basis of the diagnostic approach that people such as me try to gain understanding of, provides a skeletal framework for deciphering jet stream structures from which it is possible to identify forward or retrograde synoptic patterns - as well as using tropical>extra tropical intra-seasonal phenomena which have scientifically evaluated cyclical timelines and wavelengths. This type of analysis is a very useful supplement to the traditional numerical modelling approaches and provided it is used objectively and not letting confirmation bias invade its use, can be a true revelation and highly rewarding for an ordinary observer. 

Back to the here and now:

Still some agitating evident and not allowing time to look around each corner at a time and find answers. Such answers do not always come every 6 to 12 hours at times like this when a pattern many do not welcome is about to begin and require space to sit back, wait and watch

However, from my own perspective there is a lot of interest growing in the way ahead.

The analysis from on-going NWP is consistent with diagnostic and the ebbing and flowing of the Atlantic ridge. For fully detailed reasons given previously, this is unlikely to change significantly up to mid month and requires the day to day monitoring as discussed related to angular momentum budgets which will give clues as to when forward momentum returns from upstream.  Such developments can only be attempted to be provided in timely fashion as they emerge. This is more sensible and intuitive than trying to make guesses and leading to obvious error through misleading information.

But once the immediate change (and some of the worst weather) is out of the way that is where it starts to get interesting in my opinion. This retrogressive phase up to mid month is intriguing and could well end up re-setting the Atlantic trough as the ridging mechanisms back so far west that trough disruption occurs proportionately to our west . Amplification of a retracted Atlantic ridge is not always bad news for summer interest. Early summer low(er) angular momentum regimes often enough feature cut off low features sinking south to allow much warmer humid air to encroach from the continent as the ridging to the NW extends across and then over the top of these features. There remains credibility towards the end of the 10 day period of the solution hinted at on todays ECM deterministic output for this type of scenario. The overnight GFS also produced a similar idea and now the 6z GFS.

NB: It is the general evolution that matters here, not getting bogged down with what each model suggests in surface detail many days away.

This type of solution would be the maximum possible result to achieve within a limited regime  - but as stated, it could well be that the pattern retrogresses so far it re-sets the pattern to the point where momentum starts to return from upstream and a downstream Western European ridge is re-instated later in the month. That is an extended watching brief of course and will require further diagnostic data to emerge to fully back it up

The blended EC mean at day 10 indeed shows good support for the type of "shape" required for the back door route to happen with the lower heights sinking towards our south. The 12z ECM clusters indicated about a third of a majority support for this solution at day 10

 

 The overnight clusters may well therefore probably provide evidence of what the mean suggests - that it has increased traction. 

Edit: Indeed they indicate that support has grown to at least a half.

 

Cluster one looks like it may please a few on here. Could be quite humid though.

[Guest]

The GFS 06z ensembles were as wet and anything in the past few months, every ensemble member has some noticeable spikes.

 

[mb018538]

1 minute ago, Alderc said:

The GFS 06z ensembles were as wet and anything in the past few months, every ensemble member has some noticeable spikes.

 

That looks a bit misleading to me - most days (if we are going by the mean) are between 0 and 2mm of rain....hardly a washout! Some of the bigger spikes would be more miserable, but there is so much scatter there I’d not pay too much attention at this stage.

[Guest]

Just now, mb018538 said:

That looks a bit misleading to me - most days (if we are going by the mean) are between 0 and 2mm of rain....hardly a washout! Some of the bigger spikes would be more miserable, but there is so much scatter there I’d not pay too much attention at this stage.

But the point is with so many members producing spikes, or even just a mm or two it’s going to stay mostly cool and damp through the entire period.

[Zak M]

06z GEFS (p15) is showing heaven!

   

[Djdazzle]

1 hour ago, Alderc said:

I’m all honesty it’s another poor run from gfs, a few warmer, thundery days in the offing however the door gets opened up to the Atlantic. If the trough is going to drop south west, we really need some of heights to built behind it in its place otherwise even a wet fart from from the west would able roll on through unaided towards the U.K. and potentially get stuck again!! 

I seriously think it will be a few days before we see a consistent signal in the models for an improvement. So don’t be shocked or annoyed if the 12z suite are poor too. Top that glass up Chris!

[JeffC]

4 hours ago, Alderc said:

Hopefully the large height rise over western Russian isn’t going to be a semi-permanent feature Of summer, with a ridge/trough/ridge pattern extending westwards the U.K. often ends up anchored in under the trough, I really think this is going to be a tough pattern to shift. 

solar minimum tends to produce that meandering Jet stream, pushes patterns meridonal over zonal so when any particular set up sets up, it tends to be around for a while rather than the relatively fast moving zonal influences, hence e.g. 2018 tended to be more consistent in one weather pattern

[Guest]

52 minutes ago, Alderc said:

But the point is with so many members producing spikes, or even just a mm or two it’s going to stay mostly cool and damp through the entire period.

The very same ensembles suite goes back above average well before the end of the run. It looks quite unsettled throughout as pressure never gets too high suggesting the presence of troughs bringing showers. With the rainfall spikes scattered all over the place if you take one run at face value you will get your fair share of dry days as well - later in the run that'll translate to temperatures comfortably back in the low to mid 20s with perhaps a few slow moving downpours knocking about 

[Frosty.]

Well I just had a butchers at the GEFS 6z longer term (towards mid June and beyond) and I have to say the odds of a marked warm up are truly in our favour, not full support obviously but on balance, a return to summery conditions is a good bet!..as for the ECM 0z ensemble mean, following a much cooler, breezy / even windy unsettled phase, by next week winds fall lighter with a filling trough in-situ which to me means a mixture of warm sunny spells with heavy thundery showers..could be worse!!

 

Edited June 2, 2020 by JON SNOW