Model discussion highlights

[Tamara]

58 minutes ago, Mike Poole said:

As June progresses, we will need to watch the low anomaly to the SW, the extent to which it encourages southeasterly winds and warmth to the UK, and the potential for thunderstorms if it encroaches into the UK.

Yes. The sub tropical jet stream continues to be the interest as summer wavelengths take stage c/o a Nino-esque split flow driving an increasingly amplified trough in the Atlantic and corresponding tendency to inflate downstream ridges and warm air advection. Worth watching for renewed heat build moving north from southern Europe interplaying with the Atlantic trough. Which translates to larger and larger plumes and thundery potential across much of Europe/UK.

Its been some time since this type of summer pattern has been seen. The broad scale trend should greatly please many rather than getting bogged down in the detail of each and every intra day output

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4861967

[Kirkcaldy Weather]

On 23/05/2023 at 14:04, Kirkcaldy Weather said:

 

About 3 weeks on from that and we are at that point of MJO activity across the Pacific 

 

Matching to the composites with phase 5>7 for May+June 

We can see the evolution of the Atlantic high which is currently the main driver of the UK weather this begins to transition to an Atlantic trough with possibilities for the high to reposition further east which with favourable alignment might setup the first plume opportunity within 3-4 weeks 

I especially like this composite for accuracy of the recent setup, Note the trough over Italy which I'll discuss in a sec 

 

 

CFS in agreement pretty much and beginning signs for the Atlantic trough and high further east

Incredible that the low that started across the UK evolved into a stagnant trough parked over Italy delivering record rain amounts and sadly Fatal flooding

 

We also did have heavy snow in Iceland with blizzard warnings on 15th May

'I'd say we could have high pressure records and/or high temperature records broken across the Pacific Northwest and Alaska / Canada'

Amazingly the smoke from the wildfires (especially in Alberta) are being moved across the Atlantic and over the UK

 

 

On 23/05/2023 at 14:04, Kirkcaldy Weather said:

We can see the evolution of the Atlantic high which is currently the main driver of the UK weather this begins to transition to an Atlantic trough with possibilities for the high to reposition further east which with favourable alignment might setup the first plume opportunity within 3-4 weeks 

  

Intuition tells me we are probably just a slight bit early for a proper plume pattern though clearly we're trending in that direction still a bit of a slower evolution, though i suspect the next MJO cycle could be the catalyst required to get to that setup proper.

Speaking of the MJO again with recent activity in the Pacific we are seeing an active Jet Streak and troughing toward California (remember my posts from winter this was an almost non stop pattern then)

Might get some impressive severe wx action as this trough ejects further east in the near term 

More examples of how the atmosphere has been in a repetitive state with similar anomalous pressure setups throughout May which are almost a carbon copy of our current pattern 

May

June 

What do we mean by using the word 'anomalous' basically it can apply to either high pressure or low pressure (in the cases above its mostly the retrogressive Highs across Canada and UK / Atlantic I'll give another link showing this below) if you look at the charts from November + December 2010 of the Greenland Blocking that's a really good case too.

A few more points to watch 

• Official classification from BOM of El Ninò. I expect once the current WWB has done its thing we will get the announcement (taking a guess maybe last week of June > week 1 of July)
• Possible tropical nature within the low to the SW of the UK with Atlantic MDR SST values still increasing

Atlantic 2-Day Graphical Tropical Weather Outlook

WWW.NHC.NOAA.GOV

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4862565

[Cambrian]

Some very high levels of instability beginning to show on the 850 hPa Theta-E charts for Friday afternoon through to Sunday morning, day 4 to 6. These are from the 12z GFS operational run, the very rich red hues showing an area of high level of available energy and high potential instability working it’s way up over the UK and Ireland. 

 

The theoretical value of 46 degrees Celsius is the temperature the air would have been if all of the moisture had been condensed out of it and it was at sea level, putting us on a par with many parts of Southern Europe for that burst. 

The front edge of the wave of higher instability (Theta-E around 42 degrees) precedes the modelled precipitation by a few hours, here on the charts for 114h,

  

the main belt of showers and heaviest precipitation embedded in the middle of the zone, with the highest Theta-E values, as it all trundles north firstly over southern parts of the UK and Ireland during Friday night into Saturday, and then over northern parts later on Saturday into Sunday morning. Potential for some particularly severe storms later on Saturday afternoon over northern and eastern parts of England and Ulster with the peak instability coinciding with maximal afternoon heating. 

The timing and intensity is no doubt all going to be refined in the interim but going on the 12z GFS op, it does look like there’s plenty of scope for fun and games this weekend. 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4862549

[MattH]

It will be interesting to see how the patterns will evolve through the rest of June, because as forecasters are finding out now, what was looking to be a dry, sunny and very warm weekend is now increasingly convective, muddying the waters somewhat, from a retail perspective in particular (who want the dry, sunny, hot combo). Clearly, this is or will be the first very warm and humid spell of the season from Friday onwards as the theta-w plume heads northwards. Some places are likely to see some significant TS as things stand and certainly something to keep an eye on...

In terms of recent discussions on the MJO, it is definitely interesting to see an increasingly 'strong' -ve VP200 signature again through the Maritimes and W Pacific over the next 10-14 days. The MJO has returned to the W Hem, and will likely restrengthen through the I/O, short-term and then on into the Maritimes thereafter. As usual, RMM plots kill off the MJO far quicker than is likely to be the case, and a more coherent progression into the Pacific is likely through the final third, or so, of June, this has been well-advertised mind for some time, then continuing into early July.

The latest EC46 is noteworthy, especially the AAM prediction which goes off the scale within the next 10 to 20 days or so, obviously linked to the -VP200 anom and the associated WWB.

There was always a window of opportunity for a more troughed pattern to develop towards mid-June, this is certainly a long-term prediction and we can see that now in more short-term NWP, with MSLP draining away, highlighting a more convective outlook and finally breaking us out of the resolute, anticyclonic pattern that has dominated for the last few weeks, or will have done by the time we get to the end of this week.

As mentioned at the beginning it'll be interesting to see how the pattern then reshuffles further down the line, as the likely increasingly significant -VP200/WWB event will not only push us more towards El Nino but likely tip the balance in favour of a more Atlantic trough and downstream ridge pattern. Don't forget that jet extension is often associated with suppressed trade winds and a WWB, that can influence and alter the downstream pattern, again, particularly at this time of year, to me that would likely bring us into a pattern of European heights, with Atlantic troughs and all the 'fun and games' that may bring as we approach and move beyond the solstice.

Cheers, Matt.

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4862667

[Cambrian]

With these ECM extended range regime probabilities charts, which I’ve been studying and using for many months now, and found to be really valuable, there are continually differences between a predicted regime designation for a particular day compared with what actually happens.  This can affect just one or two days, or up to spells even longer than a week, with frequent signal flips as the particular date(s) draw closer and so phantom signals are in effect part and parcel of how they work. 

This is particularly the case when the designations are so marginal, which happens quite often, like we’ve seen recently with the competition between the Atlantic ridge and blocking signals. This I guess has to be built into their interpretation, by cross-referencing them with the weekly mean pressure and heights anomalies. The regime charts are a useful tool, but more so in conjunction with the simultaneously issued weekly anomaly charts and the daily anomaly charts in general. 

The Atlantic ridge (ATR) / blocking designation is perhaps the most marginal differentiation because we’re looking at the meridional placing of a slow moving or slowly developing ridge and slight differences in the positioning of a block. A couple of hundred miles extension of an Atlantic centred ridge into Central Europe will flip the signal from ATR to blocking, it’s very sensitive to timing and marginal differences in heights and pressure, but the western half of Europe can  often be in what is broadly a northerly flow with both designations. 

Contrast this with the stark difference between NAO+ and NAO- signals that handle the prediction of the zonal flow, distinguishing between a westerly or easterly flow is a much easier call for the algorithm that is looking at the differences across the Atlantic/ Europe zone - it’s much more typically either mobile off the Atlantic or it isn’t. The tricky scenario for NAO+/NAO- balance is the low centred in the middle of Europe, with a split signal, westerly to the south, easterly to the north. 

It is possible too to take a series of these charts and look for evolving trends to pick up on a change in the modelling for a particular date or spell. If we look at the last three updates, 29th, 1st, 5th, focusing on the period between the 7th and 15th we can see that the ECM had begun to see the writing on the wall for the Atlantic ridge last Thursday, with a waning and pushing back of the ATR signal, cementing this on Monday just gone by flipping to a blocking signal.

 
 
 

Reading these alongside the ECM mean anomaly charts from those days for the beginning of the flipped period, i.e. today, at day 9, day 6 and day 2, show just how marginal it has been. The small differences between the day 9 and the day 6 chart correspond to the change from ATR to no attribution (grey), and the small differences between day 6 and day 2 correspond to the change from no attribution to a very strong blocking signal. The ATR signal was lost when the core heights slipped a little further east towards Scotland, but it’s the extension of the peripheral heights across mainland Europe that clinched the deal for the affirmation of the blocking signal. 

All three charts ostensibly show an Atlantic high edging into northwest Europe and the position of the +10 anomaly has hardly moved at the European end, the main difference being around Denmark. Notice as well that the extension of the high at its western end has also been underestimated, indeed that’s where the +10 anomaly has substantially extended, now totally linking up with the north Canada heights, but importantly for us not through Greenland. So we end up with extensive mid-latitude ridging, elongated west-east from the Pacific to southern Scandinavia, all the way through the Atlantic. It’s this westward extension of the Atlantic ridge and the low heights over the Arctic that the ECM was really underestimating 9 days ago. 

All fascinating stuff, happy days!

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4863287

[Cambrian]

Oh my days, another case of to R-word or not to R-word! A cross-model consensus from the ensemble means of the big three at days 4-7 on the 0z runs for the brief Scandinavian high to move west - but not by much, only to directly north of the UK and Ireland, in a bit of a dance with the low heights to the south, inserting a wedge between the two lows. 0z ECM, GFS, GEM

  

Rather than us scratching our heads looking around for something new, it might be worth us considering that the pattern for summer 2023 could well turn out to be a continuation of that of the late winter and the whole of spring - docile Atlantic, northern blocking, phases of high pressure retrogression to the Atlantic (northerly / northeasterly flow) alternating with phases of eastward transfer to Scandinavia (warmer easterly / southeasterly flow that will get progressively warmer as the summer progresses);

sometimes the high pressure transferring through the UK and Ireland (dry periods), sometimes transferring further to the north allowing lower heights to encroach for a while from the southwest (warmer, less settled, scope for thundery spells, wash-rinse-repeat of pulses of heat and moisture for around a week or so, bringing much needed rain), but the transfer never happening to the south of us, so maintaining the broad stop on any Atlantic mobility, thanks to a perpetually stronger southern arm of the jet stream, that stays a long way south. 

Day 12 GFS / GEM mean anomalies 

 

Paradoxically, the real relevance to the developing summer in Western Europe of this type of ambiguous and phasic retrogression is precisely in the way that it doesn’t seem to want to push through to completion by following through to Greenland and opening us up to the north in earnest. 

Next IFS version of ECM 46 weekly pressure anomalies - week 1 vs week 5, base time 7 June, yesterday.

 

Rather, it’s part of a slow east-west-east-west oscillation with built-in day-to-day wobbling, which is pleasing for people who want a properly seasonal summer. Lots of dry weather, bursts of hot and humid air, then thundery as the heights withdraw more fully north for a while, then a cool reset to dry as the heights re-establish further south, then off we go again. 

In some ways, the repeat setup and the globally static nature of it all maybe seeming unusual, but definitely completely fascinating that the same broad pattern seems to be lasting so long, this is the fourth month of it (southerly running jet, static Atlantic, heights to the north), and it does seem for now that the new pattern for the first half of the summer at least could well be…..(drum roll)…..more of the same. 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4863700

[Tamara]

With very good confidence that the atmospheric circulation is set to remain broadly similar through the bulk of the summer,c/o of repeated westerly wind bursts across the tropics, with a convergence standing wave in the Pacific, and as a consequence +ve AAM wind-flow anomalies propagating through the turning force exhibited by +ve torque eddy mechanisms into the extra tropics  - then we can look to natural summer wavelengths to see how the global patterns may evolve this wind-flow propagation and associated amplified wave breaking.

Under such a regime as described, as June moves closer and closer towards July, and equally closer and closer to the peak period of summer wavelength, anticyclonic wave-breaking should progressively ebb and flow further east and the split flow in the Atlantic giving ever greater influence to cut off thundery lows to pump heat from southern Europe.

The cycle presently underway with Oscar bringing very warm, humid air northwards, is the first of a likely repeated sequence, each one escalating warm air advection processes and with a subtly changed emphasis, with time, of a rather more longitudinal trough/ridge pattern than the persistent to date dominant N/S delineation. This based on a trend for the very defined & strong southward displaced sub tropical jet to evolve a more diffuse split STJ energy, under slackest peak summer wavelengths, which will also give tendency for less blocking NW of UK/ Europe. With the height anomalies tending with time more sustainably into mainland Europe & Scandinavia then (in respect of UK & NW Europe) the inference is that cool(er) air advection around the eastern perimeter of the ridging gets mixed out more and more as westward adjustments incrementally reduce.

On the basis as described that takes a suggested extended perspective, better to not read too much into hints of any longer term re-set to the entrenched pattern of recent weeks or extrapolating outwards any persistent recurrence factor of the same through any greater part of the summer..

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4863766

[Cambrian]

One of the central objectives of the modelling thread, that I have come to greatly enjoy being a member of, is to consider the latest indications from the numerical models, taken as a whole, compare those with events and trends that we have observed previously, and to read whatever we can into this, openly reflecting whenever we feel happy to discuss these views and ideas with others. 

It’s the modelling thread after all. Most people on here realise the fallibilities and shortcomings of the numerical models, and often we post and discuss outputs that we are well aware are unlikely to verify, but are worth discussing because these fantastically powerful machines and algorithms have generated them. Many on here, including me, don’t post outputs necessarily because we think that they’re definitely going to verify, or even because we’d like them to - the outputs are being posted because they are interesting in themselves and provide valuable indications of what might happen. 

Underlying signals do without doubt drive the numerical models - that’s obvious, but equally, the numerical models pick up on those underlying signals and provide a meaningful readout from which people can form ideas about the potential impacts on the weather for them and others. If the EC46 goes out to 46 days, taking us into late July, comfortably capturing the first half of the summer, then it’s perfectly reasonable to discuss what we think it’s showing in terms of likely weather for our part of the world and how that compares with the patterns of recent times. It’s a fascinating hobby. We should definitely give it a go, despite the fact, and perhaps because of the fact, that it could all change by next week!

Having said that, many of us really enjoyed seeing this chart from 18 May, from the EC46 with the “full house” for the blocking signal. Today is about half-way through that chart - I don’t think it was too far off the mark at all !

Atmospheric Angular Momentum and the Madden-Julian Oscillation and the like are undoubtedly hugely valuable tools, but extrapolating directly from there to the weather we’re likely to see over the next few weeks would I imagine be a rather fraught exercise if we didn’t have the numerical models to translate those signals into something much more easily relatable to what we’ll see on the ground. They do very different things to the numerical models and moreover, all the tools at our disposal should be considered to provide the best overall picture at any one time.

I pride myself on contributing to the multifaceted discussions on here all year round but I do have to take a break for a while. It’s been a great spring and start to summer. I hope you all have a good and healthy time and get to enjoy some summer weather to your liking!

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4863822

[Kirkcaldy Weather]

On 31/05/2023 at 21:13, Kirkcaldy Weather said:

As the MJO is heading through phase 8 currently and El Ninò continuously unfolding, we really shouldn't be far away from official classification here IMO

 

On 05/06/2023 at 19:48, Kirkcaldy Weather said:

 

  

Intuition tells me we are probably just a slight bit early for a proper plume pattern though clearly we're trending in that direction still a bit of a slower evolution, though i suspect the next MJO cycle could be the catalyst required to get to that setup proper.

Speaking of the MJO again with recent activity in the Pacific we are seeing an active Jet Streak and troughing toward California (remember my posts from winter this was an almost non stop pattern then)

Might get some impressive severe wx action as this trough ejects further east in the near term 

More examples of how the atmosphere has been in a repetitive state with similar anomalous pressure setups throughout May which are almost a carbon copy of our current pattern 

May

June 

What do we mean by using the word 'anomalous' basically it can apply to either high pressure or low pressure (in the cases above its mostly the retrogressive Highs across Canada and UK / Atlantic I'll give another link showing this below) if you look at the charts from November + December 2010 of the Greenland Blocking that's a really good case too.

A few more points to watch 

• Official classification from BOM of El Ninò. I expect once the current WWB has done its thing we will get the announcement (taking a guess maybe last week of June > week 1 of July)
• Possible tropical nature within the low to the SW of the UK with Atlantic MDR SST values still increasing

Atlantic 2-Day Graphical Tropical Weather Outlook

WWW.NHC.NOAA.GOV

 

'A few more points to watch 

Official classification from BOM of El Ninò. I expect once the current WWB has done its thing we will get the announcement (taking a guess maybe last week of June > week 1 of July)'

Official classification from NOAA today 

'with an 84% chance of exceeding moderate strength'

BOM upgraded to Ninò alert a few days ago so probably not far away from their announcement also.

Saturday should see the first 30C recorded with 3 distinct zones having a shot

• London and areas in the nearby vicinity
• Midlands 
• Merseyside

This is likely to feel super oppressive with Dewpoints toward 20C (thats not easily achieved in the UK frequently) around Midlands / Wales

Current zones at risk of strongest thunderstorm development Midlands, Wales possibly Merseyside over towards Isle of Man. 

 

We can see quite high PWAT values associated with this modified plume event 

 

Flood risks could be present in the areas mentioned above and I still think it should be elevated as opposed to surface based (possibly MCS mode) I looked at the hodographs which don't appear especially curved in nature (that's one of the indicators for potential tornadic activity) though indications that deep layer shear will be in play so I wouldn't completely rule it out especially if a storm can tap into this and go surface based.

I'm not sure if there are current wildfires in these areas (certainly a number are active across Scotland) but lightning will pose a big threat with incredibly dry ground. 

850 temperatures of this event will be between 12-14C across majority of the UK 

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4863874

[Mike Poole]

Very little to choose between the ECM clusters T120-T168, all look excellent a week from now:

Only one cluster in the next timeframe, so I’ll just show the mean, non too shabby at T240:

I just wanted to remark on the SSTs.  The seas to the west and south of the UK are much warmer than usual now, as shown by the anomaly:

It is of interest to compare this with 2 months ago:

That’s similar to how we came out of winter, a tad above average in most places.  Where’s all this heat come from?  Particularly in Iberia, they’ve had the southern arm of the jet bringing dross there recently.  I think it must be that really unseasonal warmth down there in early-mid spring that has made the difference.  I think the SST anomaly will now be important for summer, potential for more potent storms, but also it is part of a positive feedback loop, which could set in train big heat for the continent from now on.  And for the UK, I always think the continental influence on our weather is made that bit greater in summer by warmer seas in this area to our south and west.

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4864055

[Kirkcaldy Weather]

4 hours ago, Mike Poole said:

I just wanted to remark on the SSTs.  The seas to the west and south of the UK are much warmer than usual now

Some excellent and technical discussions widely throughout Twitter

I really like this super insightful map from Deelan Jariwala comparing the hottest SSTs for the current time period and interestingly the seas around the UK were actually a bit warmer in other years (you need to zoom in on the pic but 1990 & 2008 are indicated)

I spoke of this in a few recent posts in a different thread but the main super intense SST heat has been in the MDR zone which is a bit further south 

And another interesting point end of April / Start of May that region was quite close to 2010 

Another reference of similarities with 2010 and the hotter zone to the south as mentioned 

*This also ties to the posts above about possible tropical activity having a chance to manage getting to UK

One big discussion and likely an integral factor for how the hurricane season works out is the shear activity intensity or lack of across the MDR and Atlantic (I'm no expert in this area but really fascinating stuff quite technical also) 

Fantastic thread this one just picking the part that fits to my post

Not trying to de-rail this Thread but it really does help to dive beyond the standard model outputs as these more in depth factors at play are really fun to learn and explain the whys and how's of whatever patterns are unfolding in various regions worldwide, and hopefully the style I do my posts in are proving insightful & helpful for other members

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4864134

[Met4Cast]

Locked in.

No real change for me now, this dry & warm pattern could be with us for the foreseeable with repeated bursts of very warm/hot weather followed by thundery conditions, expect this weekends pattern to rinse & repeat. The expected summer pattern has developed broadly with expectations and now it's arriving it's likely here to stay. 

No real signal for change is emerging within the tropics/sub tropics and if anything, the current signal is likely to strengthen. Extreme high temperatures perhaps less likely due to the nature of the pattern but persistently warm/above average conditions look very likely. 

The summer many dream about, perhaps?

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4864749

[mb018538]

I dare say it'll be difficult to plan any forecast for this summer with confidence going off North Atlantic SST anomalies....off the scale and a long way warmer than anything in the last 40 years.

 (pic Official Weather UK Twitter)

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4867665

[Downburst]

19 minutes ago, Howie said:

I'm hoping the high takes over again

I think it will, perhaps to the north again, but in time I think that signal will relax as we go into July and August. Basing this off the seasonal signals, so no certainty, but there's still a signal for July/August/Sept to have higher than average pressure to the north, with temps well above normal and suggestion of lower in the Azores across to the USA.

 

Mind you having a peak at autumn and I think we better make the most of this summer and find time to clean drains now. Not sure if it's just the new El Nino this autumn or the crazy sea surface temps adding to it around the north atlantic, but there is a strong signal for low dominated autumn with a possible scandi high. Will be a winter full of debates and contemplations on teleconnections that's for sure.

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4869797

[Mike Poole]

Seasonal models prediction for July?  Pretty much continuing the pattern:

The multi-models mean looks telling here.  It is that pattern, low anomaly to the SW, high to NE, but crucially extending into UK.

I mentioned during spring that the summer pattern was slow to show its hand, it has now and it’s a banker for heat, sun, interspersed with thunderstorms

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4869810

[Kirkcaldy Weather]

On 05/06/2023 at 19:48, Kirkcaldy Weather said:

Might get some impressive severe wx action as this trough ejects further east in the near term 

Indeed with a rare pattern unfolding across Dixie Alley normally we'd expect that zone being active in April, furthest east this shape of severe weather during summer months

You'll remember I expected similarities to 2015 to continue in regards to El Ninò and plume patterns for the UK 

Also I was discussing the MDR temperatures and conversation surrounding Atlantic shear, clearly the Atlantic continuing to behave quite abnormally in that area with the concentration of developing systems looking likely to develop from tropical waves emerging from Africa which again are apparently appearing earlier than usual probably linking with the highest ever MDR temperatures.

What about the MJO, Since my previous MJO Post on May 31st 

Didn't half get a sprint on progress from phase 8 on 3rd June >> Phase 4 today isn't too common getting through 4 phases within a 2 week window.

Also might have a slower exit from phase 4 

What setup do I expect after the fast transition we've had?

Nice level of similarities in a trend of low pressure around / in the UK associated to phases 2+3. I'm interested particularly with phase 4 especially given the signal with this persisting longer than previous phases, here's the CFS weekly & GEM ensemble mean which if you put next to the last composite above is a fantastic comparison and ties to the setups I've been speaking about for a good amount of time aka atlantic troughing + high sets up further east ... looming plume-age

Still very intriguing behaviour in both the stratosphere & troposphere

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4870069

[kold weather]

So a couple of points:

1: Temperatures will go above what you'd typically expect from a pattern, remember the atlantic is utterly roasting and our portion we are watching is generally at record warmth, and so I'd expect even fairly bland looking set-ups to deliver above average temperatures fairly comfortably.

2: Best steer clear of long range forecasts right now, the system in the tropical atlantic is extraordinarily early and I'd normally not consider such a system but the Main development region is literally warmer than most August's  right now, so a cape verde system has to be taken at least somewhat seriously.

3: Typically in El Nino developing you'd slowly expect the subtropical jet stream to exert more and more influence in the pattern. I have on twitter and I think here referenced 1957 before as a possible match given how rapidly the ENSO developed that year. Great June but the rest not so much...

With all that being said I think the general theme from the models of flattening things out is maybe the right one. It probably remains warmer than normal for most. It doesn't have the look 'disaster' written all over it , just a classic looking summer pattern, which is ok. Probably a textbook NW-SE split for the first time in a long time in summer with low pressure flirting closer to the NW probably bringing some needed frontal rain up there.

The wildcard is 92L, any major development and recurve into the jet will throw a stronger ridge towards the UK with a more southerly component to the wind as per the GFS 06z. Remains the be seen.

edit - @mushymanrob it has every chance of beating 1976, I've just calculated that the northern most station that is used averages 16.8c in the next 10 days using the latest GFS. We only need 17.0 and so that is well within striking distance given a real lack of cooler air coming into the CET zone on the models today. Your underestimating just how overhot the Atlantic is compared to normal right now...it won't take much to get much above normal temperatures...

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4871481

[Kirkcaldy Weather]

On 28/05/2023 at 15:00, Kirkcaldy Weather said:

also a wide zone in the central swathe of US noteably below average 

Wanted to start with the verification on this, 

very impressive performing again from the CFS

18 hours ago, Man With Beard said:

LolThis is where just looking at the anomalies leads into error - the NOAA tonight:

You might instinctively look at the red lines, consider it to represent high pressure and think we'll be under a block.

But the lines to look at are the green ones - the ones representing the actual 500mb flow. This show everything is coming from the west, and the narrowness of the lines to the west of the UK suggests the flow won't be that slack. So it's absolutely not a blocked pattern. Slightly raised heights to the SE means slightly more settled towards that part of the country, but wall to wall sunshine unlikely to last more than a day or two during this period.

Hey MWB hopefully you don't see this as me having a go that really isn't in my nature at all just like to be as helpful as I can also might be useful for any newer members attempting to work those charts out

Those green lines will always be in the same orientation pretty much (think global circulations though it's often not that straightforward when deciphering Weather setups)

Most important with those is to focus beneath the green lines as the reds purples and blues are the important indicators of actual lows + troughs / ridges + high pressures, I took the chart you provided and done some editing which should make it easy to understand 

Further confirmation of the above and some further info on the patterns 

Excellent vid this and a point I've spoke about on numerous occasions and I'll discuss again in a min

If we concentrate on the developing setup over the U.S and Canada we have another block unfolding (remember this has been consistent throughout May and already into June hence record amounts of wildfires across Canada) 

'Omega Block' Weather Pattern To Dominate US | Weather.com

WEATHER.COM

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Blocking weather patterns have dominated the U.S. since the start of May, including a new omega block this week. - Articles from The Weather Channel | weather.com

We have a high stretching from Mexico up through Texas (this is already giving record heat and that will continue) the same high connects to the developing block over northern US and approaching Canada. These NOAA charts can go hand in hand with the chart MWB posted

Quite a concerning situation with a large swathe of the Great Lakes and other Northern states are at record dry levels beating anything seen in upwards of 130 years 

Eerily similar to what we've had through May once again the block could be at record intensity for this time of year 

I'm getting increasingly concerned with the potential for severe weather in the UK Tomorrow & Monday

Tieing into my discussions in my previous post regarding MJO phases 2+3

As an area of low pressure develops within the UK this will pose a number of severe weather potential.

Any CG lightning has much heightened severity as with these levels of fire danger that will mean wildfires can be sparked off very easily 

My highest concern is with incredibly high PWAT levels a big flash flood threat will be present especially as the low properly deepens around Northeastern England into East Scotland (IMBY) 

Beyond this we have another event showing the interconnected nature I often talk about as similar to a post I done recently another surge of wildfire smoke from Canada moves across us which could be worth noting for those that deal with breathing related conditions.. might be good to have a mask at hand or limit outdoor activities a bit 

Any haziness to the sky will be explained with that.

More insightful discussions around twitter again connects to my own theories I've been posting with regards to stratospheric goings on and a general abnormality to how retrogressive the atmosphere has continued being since at least May. We've still got a huge quantity of water vapour following Hunga Tongas eruption, obviously Ninò arriving after those mega hot SST's were sat effectively dormant for 3 years, I still think the strat events from winter have had a part in the wacky global patterns too, I'll go further on that shortly.

So yes further evidence of the global climate overall being as far away from any degree of normality

Record cyclone Biparjoy somehow improved in structure AFTER landfall which anyone who is familiar with cyclones + hurricanes knows that really shouldn't happen at that stage 

Oh yeah it's snowing in Siberia 

Yeah it really is week 3 of JUNE 

This is the longest post I've ever done I think really appreciated if you are still reading ha

The tropical wave I discussed in my last post has now advanced to 92L with high odds to become tropical storm Bret within a few days and first signals it *might have another tropical wave following closely behind 

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4871735

[Downburst]

1 hour ago, MattStoke said:

A rather more Atlantic driven regime looking likely from next week but with very warm SSTs keeping the flow warm and high pressure never far from the south.

I find it hard to believe that very warm Atlantic SSTs would fire up the jet stream. The jet stream isn’t fuelled by warm seas but by temperature difference between the North and South Atlantic. A warmer North Atlantic reduces that temperature difference.

There are four Jetstream's, "our" Jetstream in the northern hemisphere, aka the Polar Jetstream, of course has nothing to do with the Jetstream in the south Atlantic. It is as a result of the difference, more pronounced in winter, between the Sub Tropics and the pole in the northern part of the planet, then there is the two subtropical Jetstream's and then Antarctic JetStream.

 

From Wiki

 

Thanks to the every excellent Netweather there is a Jetstream map you can play. AS you can see the Jet next week gets fired up, but this is as a result of the Polar front moving in North America UpStream

Today the Polar Front is north of Hudson Bay. Over the coming days it dives south and gains differential energy and gets a move on.

By Saturday it's kind of like Winter position, plenty of oomph and troughing in the north Atlantic. May not last too long though.

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4874511

[Tamara]

4 hours ago, Djdazzle said:

It does show just how useless the signals can be. Wasn’t July meant to be HP dominated?

July hasn't happened yet. Numerical models that produce seasonal outlooks will provide a smoothed out representation of a dominant default pattern and will not account for periods within that season where the atmospheric circulation has a re-set/re-balance.   Such a re-balance is emphatically advertised at present.

The Spring saw an extraordinary amount of westerly inertia added to the atmospheric circulation with vigorous propagation of +AAM wind-flow eddies from the tropics into the extra tropics. This highly Nino-esque forcing resulted in a strong sub tropical jet from the Pacific downstream into the Atlantic, transferring considerable strength through the Hadley cell.

Such one way impetus is unsustainable ad infinitum. Like a vacuum operates, when such immense power is relaxed, a correction to fill that atmospheric circulation vacuum must occur & is correspondingly proportionately strong the other way to balance the global wind-flow budget. Such corrections are part of every "mini ENSO cycle" and, as stated, proportionate to the strength of inertia within such a cycle. Such strength varies according to the levels of inertia exchanged between the tropics and extra tropics.

In synoptic terms,the "relaxation" is manifested by a large upstream deceleration of inertia into the extra tropics as sudden introduction of -ve easterly inertia regressively pulls the pattern westwards. Hence the inflated Atlantic ridge and trough to fill the void and where pressure falls steeply downstream.

But it has to be remembered that the default pattern has not simply just gone away and it is intuitive to anticipate the next push back, with time, as upstream inertia returns with quite a jolt..

There are good indications of amplified MJO related activity heading through July, and especially based on periodicity (recurrence timelines) of amplified tropical convection cycles. These accord to a circa 60 to 90 day periodicity and respond especially to the relationship of a strong Hadley cell interacting with the tropical cycle.

So a repeat of the type of sequence seen through the Spring is to be watched for - and with summer wavelengths likely expanding the rossby wave-breaking response further than during Spring to produce a wider warm air advection response from a re-set Atlantic trough and downstream ridge.

Extrapolating numerical model indications further out in time, without consideration of the cyclical nature of the atmospheric circulation, leads to unnecessary and premature conclusions. Better to see numerical modelling as snapshots of time only and which will adjust as they evaluate forthcoming signals.

The signals are never useless - it these that lead the numerical modelling, not the other way around.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4875561

[summer blizzard]

The chart below shows where the hope for heat lovers is. You can see that our current spell is the result of a retrograde mean high gradually moving west since mid June from Russia (passing through the UK en route). 

Our next forecast spell of settled weather in mid July is again the result of a mean retrograding high moving through Russia to the UK, starting around the turn of the month. We should be able to monitor this over the coming days to see if the model persists in showing this retrogade motion. 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4876126

[MattH]

The change ahead does seem to be at the more extreme end of the spectrum for what was expected through late June and July. However, does this mean we are heading down one of "those" summers where the last 4-6 weeks was summer? - I don't think it is, not this year. We are not in a La Nina/eQBO summer combo like some of the worst summers can be, but that is just one piece of thr jigsaw of course.

One added caveat here mind is AGW, the unknown and potential influences that are difficult to gauge. Look at the highly unusual global SST patterns currently, for a starters. 

However, if we look at the AAM profile it comes as absolutely no surprise why the last 4-6 weeks have been as they have been - anticyclonic - due to a huge AAM surge and dominant E'ly AAM anoms through the mid-lats throughout May and into June too. 

However, note of late those westerly anomalies have been propagating to higher latitudes while the E'ly anomalies have weakened. Despite a broader +GLAAM atmospheric profile you will still get 'rises and falls' within that general dominant pattern and that is seemingly what we are seeing now, highlighted as well by the GWO evolution. 

Another MJO/-VP200 evolution does seem likely to evolve yet again into July as exampled by the latest EC46 and with it another upstream pattern change. So while it's a poor outlook for now, especislly after what we have been used to in recent weeks, a further re-shuffle of the pattern, out of the short term cyclonic pattern in the short term, is likely to follow, IMO, deeper into July with a return to summer synoptics and a reduction in the influence of a more W'ly, Atlantic pattern. 

Cheers, Matt 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4876472

[Kirkcaldy Weather]

On 31/05/2023 at 21:13, Kirkcaldy Weather said:

there shouldn't be any significant changes to the above patterns until Mid and especially 2nd Half of June

Wanted to begin with that from May 31st. We are now at the start of the changes partly again driven by MJO cycles which have been noteably fast, linking to my post here 

Incredible the progression from phase 4 on June 14th >> back into phase 1 by roughly 1 week later ie 21st/22nd June 

There's the phase 4 Ninò  

 

With tonight I think the highest concerns are wind related damage this could be either embedded tornadic threats or straight line

West Scotland & Ireland highest chances for this

There will be 2 areas for storm developments on Sunday though latest model thinking keeps the really severe developments to the North Sea, I'm expectant for a linear area of thunderstorms moving through Scotland and a separate similar area around Northeast England >> The Humber which could see severity increase there dependent on timing of the upper level features engaging with kinematics 

I'll discuss the changes shortly but further things to talk about with the pattern I've been covering across USA + Canada

I had to save this pic from twitter as it perfectly encapsulates what I have been saying 

 

That really is an extreme visual what it's showing is the differential from average and the setups I've discussed with high from Mexico through Texas > Northern States & Canada seeing a few areas of upto 20C Above average ,we really shouldn't be seeing these sorts of anomalies which are increasing in frequency and I want to focus on the other zone to the west with the anomalous trough and a WIDE area of 20C BELOW average given we are talking about SUMMER that is even more of a concern than the above average zone as during summer that would be a higher expectation to occur than colder conditions (though obviously each end of the scale carry their own severity) 

Lots of confirmation of the above 

Not forgetting the cold setup across Eastern areas also 

More insight into the abnormal snow I showed from Alberta 

Other extreme oddities as simultaneous tropic systems Bret + Cindy are on the go in the MDR 

INSANE

So what am I expecting from this MJO path through phases 5 through 1?

If we take the GEM Ensemble a low developing over Iceland through June 28th will drop over the UK and simultaneously we see high pressure developing further North probably becoming centered in Greenland as our upper level trough becomes a cut off low in the UK

 

Below average upper and lower air temperatures within the UK are likely in association with this which the cfs weeklies are already picking up on

 

fitting these into the associated composites for phase 5 through 1 during June 

 

Starting with the progress across phases 5 6 + 7 Excellently fits to expectations  

The Ninò composites connect pretty nicely too

More unsettled than recent times with temps average > a bit below average through at least week 1 of July. Those who are quickly trying to say 'summers over' I suggest consider that many pattern shifts WILL happen from now til 31st August That leads me perfectly to phases 8 & 1 in June 

I get a vibe that could be via high pressure developing through Europe sat to our Southeast potentially further retrogression up across UK and / or Scandinavia such as ...

 

Wouldn't be discounting more plumeage 

Really cool vid with great discussion on the setups in California where they still await the first 100F this year. I know Vegas is on a 250+ day streak of no 100F pretty crazy for them

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4876984

[Cheshire Freeze]

4 hours ago, danm said:

Yes wouldn’t call it “good” but it’s better than what was being shown a couple of days ago for next weekend. 
 

This was what was being shown for next Sunday a couple days ago:

 

Today’s 12z for next Sunday:

 

As I said a couple of months ago, that happens to pretty much every trough shown to affect the UK these days. The Azores/Euro HP is shown to be more influential the closer to T0 we get.

I honestly believe it’s evidence of Hadley Cell expansion and its knock on effects. Due to the change being so sudden, the NWP doesn’t have enough historical precedent to make the relevant adjustments until the starting data overrides the timescale (much closer to T0).

I know for a fact this is a repeating scenario because the amount of slack-centred convective LPs that have been shunted N over the past few years is eye opening. I take an interest in that synoptic because of the convective potential from April-Sept.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4877050

[johnholmes]

My view from 500 mb this morning

Now the Monday chart 27 June, even worse perhaps in terms of contour values and very similar overall chart to the last few. See below; The upper low centre below 546 DM and the 552 DM line almost over the Borders. This contour never gets further south than about 55 N and starts in the far west over northern Russia and Alaska. In winter I suspect a lot would be drooling over this chart. Consistent pattern as well, with the first suggestion of a cooler spell about 7 days ago. The idea of a deepish upper low now showing has been developing over the past 3-4 days. The 8-14 charts keeps similar contour heights with a less marked trough (no longer closed). This takes us to 10 June. That is IF the pattern shown for several days turns out to be the right idea, which seems very likely to me. Remember this is at 500 mb.

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

The Met Office Fax charts appear to be following this pattern as does their upper air charts to 144 hours, the furthest out on their Fax outputs.

UK Met Office Fax Charts - UKMOMSLP Analysis and Prognosis

WWW.WEATHERCHARTS.ORG

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UK Met Office . . Europe and North Atlantic MSLP analysis and prognosis charts

 

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4878703