Model discussion highlights

[Kirkcaldy Weather]

Time to do a recap of my previous outlook and looking to where we are likely headed now & upcoming weeks

"First we are at the beginning of a super high amplitude MJO progression in phases 7 + 8 "

This was one of the highest amplitude phases 7 & 8 ever seen 

Also the effects I mentioned for the accompanying WWB (westerly wind burst) bringing the historical triple did La Ninà to its end materialised "This MJO progression at high amplitude in phases 7 + 8 will be producing a substantial WWB which will bring the rare triple dip La Ninà to an end"

"Certainly opportunities over the next 7-10 days roughly, for snow events in various areas of the UK and frequent frosts some of which becoming increasingly severe particularly with any laying snow." 

We did see many regions of the UK and Ireland have brilliant snow events (yes my jealousy and amazement remains for you Sheffield members ) and low temperatures which you'd probably class as at the severe end for March. I know there were many comparisons on twitter to the snowfalls in 2010, overall March was a quite remarkable month of weather actually I was probably one of the most Unlucky in terms of snow as I didn't see any laying and only 1 brief bit mixing in a shower BUT my highlight of March no question is the STUNNING CB and Anvil from a meaty snow shower which was approaching Edinburgh   

Also have to mention the pressure reading I got of 967.08 hpa on the 13th .. impressively low.

I also discussed there were likely to be further conditions which were conducive for Atmospheric river events once again drenching California, its been mindblowing just how many have occurred throughout winter  

End result the biggest accumulative snowpack in history (also plenty of rain records in the lower elevations) 

'For Mid > latter stages of March we will see a fresh development of blocking ..be watching for high pressure setting up to the east and/or near to the UK with repeat retrogression into Greenland'

We've had another pretty fast progression through phases 1-5 and are verging on the arrival into phase 6

We see the current setup resembles March phase 1 quite closely 

 

 

The signs for continuing high pressure sitting to the east ties to phase 2 in March 

 

Phase 3 composites are similar but I just wonder if we might at least for a bit of time have the high centred to draw in the flow from the East 

 

CFS Certainly giving signs 

Though brief the travel through phase 4 should eventually have low pressure around the UK 

Arriving at the current stage of phase 5 which will see high pressure develop to the south of the UK, possibly extending towards us at times 

 

 

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4838330

[Eagle Eye]

On 20/03/2023 at 15:13, Eagle Eye said:

 

The destructive influence of the WWB can be seen at just day 3 really well now and it'd setting up a more semi-zonal kind of setup with a jet retraction rather than an equstorward jet as the AAM falls from the recent -VE EANY though the retraction is unlikely yo be large. The SE US ridge isn't entirely stable in terms of advection given that it's the start of US storm season it can easily be pulled up via WAA from troughs and that may favour a weak RWT like pattern especially as momentum rises rather than falls over the North Atlantic and so I could see the rising of the UK-Scandi high possibly sometime around April. AAM is unlikely to rise enough for it now and the North Pacific Jet stays slightly retracted buy I think eventually we'll see a poleward shift/extension and as we go into Spring that may favour AWB that leads to a UK-Scandi type high. Given the nuetral/Nino ENSO state expected and how the AAM has been acting over Winter, there may be a slight favour towards a warmer summer however thers only if the high is forced correctly. As it could quite easily be forced into the mid-Atlantic if the SE US ridge remains in place as that's the typical response given that setup as a Rossby packet 'pushes through'. Alternatively, if the forcing from the background signal is for AWB similar to early March then unlikely early March; the high might be pushed more towards a UK-Scandi high and that's typically a warm summer flow as far as I know. It's what some of the seasonal models are showing with an Ekman pumping esque WAA scenario which is really not good for the heat haters.

I miscounted for surface slack flow with destructive divergence at the mid-troposphere level accounting for slack line cold development in opposition to the pivot of the high. The extreme low-levels (e.g surface skin layer or the area roughly up to the 925 hpa area) will lose a lot of heat by radiation and at this time of year this hangs about just about. Given a few months and that quickly changes with very warm 850's and warm air artificially trapped near the surface so this same setup would be a lot more potent in Summer.

The thing is that the constructive wave influence of the AAM and destructive local influences (e.g. zonal wavebreaking supporters such as destructive WWB's of which one is expected relatively soon over the more influential than it's given credit for area, the north Pacific) given the transitioning of the ENSO and the near neutral AAM are likely to mean that forcing will remain generally pattern like and I think the UK-Scandi high could set the tone for the Summer and that's a hot summer setup. Alternatively, the fall of the east US ridge might allow it to be a bit wetter and maybe less hot but I still think it could be quite a warm summer given the strength plumes now hold (also appear to be getting drier so harder for the classic thunderstorms unless a subtle trough or something similar advects moisture but I think that's just me) and also the east US ridge has been setup there for a while now.  

The NPJ Phase Diagram appears to be going back to where it was about a month ago, hence my thoughts behind a repeating pattern appear to be backed up.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4838498

[mushymanrob]

12 hours ago, mb018538 said:

Expect this to change pretty soon….what was looking like a settling down period after mid month now looks ghastly. Very unsettled, wet and windy. Not particularly warm either after Sunday. Yuck yuck yuck.

Not sure on how you reached that conclusion, but these charts havnt changed, are supported by the EPS GEFS and GEPS. These charts (centred on the 18th) are warm, bright, unsettled but most of the rain will be in the far North. These charts suggest a lot of very pleasant mainly bright, dry, warm Spring weather...

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4839816

[damianslaw]

As is often the case as we move through the middle of Spring, we have synoptics on offer that often don't occur at any other time of year, but are very common in April and May, in this case a cold cyclonic pattern followed by a easterly anticyclonic spell that could have some staying power against what is traditionally the quietest time of the year atlantic and jet stream wise.

I like this time of year for the interesting synoptics it often produces, watching the atlantic not have it's way.

Wednesday is looking particularly cold and wet in the north, snow for modest levels. By the weekend a warm up is forecast, early next week could quite easily deliver that first 20 degrees of the season, and the GFS is suggesting a long sustained dry warm spell. I use the word warm as 'high teen maxes' are certainly above the April average, if this was summer such temps are not classed as warm, but under a sunshine as strong as in late August it will feel almost summerlike I think.

In the immediate is the wind and rain that will rule the roost.

Turning into a very topsy turvy spring with a bit of everything.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4840621

[Mike Poole]

As winter drew its last breaths, I suggested that it would be about mid April before we saw a transition to proper spring warmth, and with this week’s dross to get through to take us to that point, it doesn’t look wide of the mark.

ECM clusters this morning very consistent on high heights to our NE next week, T192-T240:

Variations on a theme there, but cluster 3 with more of an Azores Scandi link.  The extended loses the pattern but replaces it with uncertainty:

GloSea6 out today, and so thoughts turn to summer, following charts are for Jun-Aug, first 2m temperature outer quintiles:

Very strong signal there for significantly above average temperatures right through summer.  Tercile plots for other parameters:

No clear signal on precipitation, or surface pressure, but a significant signal for higher than average heights, and higher SSTs.  SST anomaly as of now:

The ECM seasonal update is perhaps even more bullish for summer heat, and this plot showing probability of heights in the upper tercile to be 70-100% in the SE is interesting:

This knuckle marked in green binding us to weather to our SE, suggests a continental influence extending across a significant part of the UK for much of the summer season.  Putting it together, I think a northerly tracking jet stream allowing heat to build into the UK from the continent, and with GloSea6 showing slightly lower surface pressure to our south, may be suggesting possibility of plume setups.  The pattern looks to be promoted slightly by the current SSTs, which in turn may be reinforced by the modelled pattern, so I think a persistent warm pattern is likely.  All very interesting in terms of outlook for the warm season, and the next 6 weeks will be interest as we look at the model op runs and ensembles to see signs of such a pattern taking hold properly into May.  

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4840827

[Eagle Eye]

As a general rule of thumb despite the ENSO having only a weak effect on the Summer, I think Nino tends to be more of a tipping point than Nina summers and so the strength of it is extremely important. We run the risk of overrunning a Nino summer in terms of strength because there's a real tipping point between hot and quite dry and wet that's more pronounced during the Nino phase than the Nina phase perhaps more to do with the strength of the AAM response being responsible for overriding other Rossby Wave responses in Summer and therefore also being responsible for Rossby-Kelvin wave interactions (e.g the ITCZ may be important for late Summer and Autumn time reponses given that Nino tends to enhance the shearing in the east African and northern Atlantic corridor) so it's important to monitor both the westerly wind responses in the ENSO state and the atmospheric response to that. Given that tropical forcing for the interactions of waves is less meaningful in the Summer but still has somme relative importance, the subtilties have to be more pronounced in terms of ocean-atmospheric response. A strong Nino tending to have a stronger atmospheric response in terms of jet phases. It's no wonder it's not been great so far this Spring given the climbing out of Nina and I think most people would prefer it now than in Summer where it would likely introduce NE'ly falling low's if there was a high in place pre-WWB given jet response. An extending and equatorward jet is not really what you want in Spring because it can have two responses. Either you get low after low or a UK-Scandi high builds but it's similar to Winter and therefore easterly lows undercut to the south and budge the high quite quickly and we just end up with a cloudy and cold easterly. We've had both however what these WWB's have done have climbed us out of Nina right towards high end nuetral and close to Nino and a few models are showing us getting close to a super Nino for Summer which increases the chances of a washout Summer but the closer we get to neutral the better for warmth because it promotes the UK-Scandi high that the Seasonal models have been showing and that's very warm. However,  it's more setting up for the Winter I'd say is where we want a low end Nino to really get the old classic cold Winters.

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4842902

[summer blizzard]

Just now, Kentspur said:

When I last checked the models a few days ago I was thinking oh crap I'm off to the Canaries Tusday until next Saturday and it looked potentially warmer and sunny here than there which showed showers. Thank god its changed there now to ! Shocked by how much its changed here for this coming week why is it that in winter when we're cold chasing cold synoptics tend to get watered down to mild not the opposite like this!

Polar Vortex strength. 

The norm between August-April is for upper westerlies to attempt to downwell and push a mobile pattern. Betweek May-July this is not the case (though i admit i've no idea why we don't see continued summer retrogressing patterns as the norm). Thus the deeper we go into spring, the weaker the stratospheric vortex and the stronger the troposheric pattern (dictated by things like tropical convection).  

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4842964

[Kirkcaldy Weather]

On 02/04/2023 at 17:38, Kirkcaldy Weather said:

Time to do a recap of my previous outlook and looking to where we are likely headed now & upcoming weeks

"First we are at the beginning of a super high amplitude MJO progression in phases 7 + 8 "

This was one of the highest amplitude phases 7 & 8 ever seen 

Also the effects I mentioned for the accompanying WWB (westerly wind burst) bringing the historical triple did La Ninà to its end materialised "This MJO progression at high amplitude in phases 7 + 8 will be producing a substantial WWB which will bring the rare triple dip La Ninà to an end"

"Certainly opportunities over the next 7-10 days roughly, for snow events in various areas of the UK and frequent frosts some of which becoming increasingly severe particularly with any laying snow." 

We did see many regions of the UK and Ireland have brilliant snow events (yes my jealousy and amazement remains for you Sheffield members ) and low temperatures which you'd probably class as at the severe end for March. I know there were many comparisons on twitter to the snowfalls in 2010, overall March was a quite remarkable month of weather actually I was probably one of the most Unlucky in terms of snow as I didn't see any laying and only 1 brief bit mixing in a shower BUT my highlight of March no question is the STUNNING CB and Anvil from a meaty snow shower which was approaching Edinburgh   

Also have to mention the pressure reading I got of 967.08 hpa on the 13th .. impressively low.

I also discussed there were likely to be further conditions which were conducive for Atmospheric river events once again drenching California, its been mindblowing just how many have occurred throughout winter  

End result the biggest accumulative snowpack in history (also plenty of rain records in the lower elevations) 

'For Mid > latter stages of March we will see a fresh development of blocking ..be watching for high pressure setting up to the east and/or near to the UK with repeat retrogression into Greenland'

We've had another pretty fast progression through phases 1-5 and are verging on the arrival into phase 6

We see the current setup resembles March phase 1 quite closely 

 

 

The signs for continuing high pressure sitting to the east ties to phase 2 in March 

 

Phase 3 composites are similar but I just wonder if we might at least for a bit of time have the high centred to draw in the flow from the East 

 

CFS Certainly giving signs 

Though brief the travel through phase 4 should eventually have low pressure around the UK 

Arriving at the current stage of phase 5 which will see high pressure develop to the south of the UK, possibly extending towards us at times 

 

 

 

"Phase 3 composites are similar but I just wonder if we might at least for a bit of time have the high centred to draw in the flow from the East" 

️  

"Though brief the travel through phase 4 should eventually have low pressure around the UK" 

We've had the low around the UK with storm Noa but the upcoming pattern is a blend of the high bringing an easterly flow combined with a developing upper level Low.

We have the upper level low starting to develop through the low countries on Wednesday (in @Cold Winter Nights backyard ) 

Given the steering flow this will get to us by Thursday and remains stagnant barrelling around even into the weekend 

With the cold pooling at 500hpa and the pool of 528 dam close to the centre I'd expect hail and a wintry mix though CAPE values aren't really worth a mention unlike with Storm Noa so precip unlikely to be as convective in nature. 

 

Even as we are getting closer to May the temps at night even for most of us will be close to frosts developing 

With MJO progressing through phase 6 and now in phase 7 this will see high pressure developments ranging from our east across the UK and potentially in the Atlantic 

 

 

 

Again CFS already feeling this out in the extended range (I think it will be starting to materialise a bit ahead of those dates but we'll see ) 

Does appear to be a trend in the West Pacific being the main zone of interest for the MJO even heading to the extended range   

 

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4843331

[MattH]

The cold (poor) spring this year is, overall, not something of a surprise, especially given the late winter SSW and particularly so given the evidence of how the influences from the late winter SSW have continued to influence the tropospheric pattern for weeks down the line. I certainly think the up-coming blocking pattern and retrogression towards Greenland has some links still, even though it is a time of year, as we all know, that this kind of amplification of the pattern can occur. How many times over the years, whether there has been a late winter SSW or not, do the 'winter fans' often bemoan the synoptics that arrive in March and April, that they all wanted about 8 weeks prior... Personally, this is why spring, IMO, is the worst season of the year, if we could jump from Feb to May each year, given the UK's climate, then that would be superb. I, for one, am always glad to turn the calender over and see the 1st of May each year and leave behind the likes of what we have seen this year that can arrive through March and April, sometimes two of the "longest" months of the year...

Looking further ahead though and this high latitude blocking signal will, eventually wane as seasonal wavelength changes continue to influence the overall outlook. Northern blocking patterns at this time of year can become locked in under the right broader setups, as they did in 2012 and 2017, but that is usually linked to a fundamental fall in AAM (La Nina regime) and an eQBO combination. Clearly, we are not going into late spring and early summer in a falling AAM setup, in fact it is the opposite as the below EPS data shows...

Another active MJO passage seems likely during May with an associated signiifcant WWB. Equally, what stands out on the latest EPS VP200 plot is the development of the low frequency El Nino standing wave signature as well, near and just to the west of the dateline, this a sure-fire piece of evidence that El Nino is on the way. Clearly, note the continued rise and trend in the AAM signal as well throughout May and, again, no doubt linked to the expected next up-coming MJO and WWB signature.

So, while this spring has been a long-ol slog and we are not yet out of the woods, given what is on the way next week, there may well come a time when with a reduction in northern blocking patterns, that a more typical late spring/early summer pattern will emerge and, IMO, that will be focused around NE extensions of the Azores high, rooted within a broader El Nino background state, especially atmospherically, but also increasingly oceanically as well.

The MJO may well still have some big influences on the first half of the summer, especially with ENSO neutral conditions dominating, with a 'waxing and waning' +ve AAM and -ve AAM patterns possible as the MJO passes through the Pacific, with associated WWB, while then clearing to see something of a return to the trades (falling AAM etc), which could see the rossby wave train alter to bring both ridges and troughs to the British Isles at times. However, if you're looking for a half decent summer, then, overall, you want to be going into the summer period within a broader rising (El Nino) AAM regime, not the other way around and that could be one key piece of the puzzle for summer this year...

Regards, Matt.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4843542

[Tamara]

Boa tarde e todos

Since the middle of last month the GSDM site has not been working, so without wind-flow & torque budget data to hand this makes diagnostic analysis less straightforward - but there is clear evidence of quite a seismic shift in the core ocean>atmosphere dynamic and low frequency standing wave shift of tropical convection rossby wave trains into the Pacific. 

A late Spring and Summer dominated by westerly wind bursts across the tropics lies ahead. The impact this has on frictional torque inertia and associated upstream wind shear heading downstream from the Equatorial Pacific into the Equatorial Atlantic (supressed trade winds)  suggests intermittent ebbing and flowing of this feedback (enhanced by periodic MJO cycling) and a consequent series of weakenings of the strength of the Azores high pressure likely. This implies phases of cut-off low pressure across the Atlantic and downstream response anticyclones across much of mainland Europe (including also UK) and Scandinavia. This looks increasingly like the default pattern for the coming months - with relatively short interruptions as torque mechanisms reverse temporarily according to cyclical lulls in the MJO "mini cycle"

The legacy of the late winter SSW is the obstacle to a warm air advection pattern,associated with this trough>ridge sequencing setting up sustainably across NW Europe, but already the Hadley cell is exerting strength on the downstream ridging pattern across Portugal & Spain 8 into the Western Mediterranean with true summer-like conditions and values in excess of 32C already (including locally in my part of Portugal) - way above average for the middle period of April. This type of pattern taking hold ahead of summer has quite worrying implications for potential heat intensity in the coming months as the rossby wave sequences keep amplifying the trough>ridge pattern with repeated plumes building from higher and higher temperature bases across southern Europe and with time also advecting north through France towards UK & NW Europe as the default Atlantic trough in the Atlantic forges instability from the west - with thundery breakdowns before re-setting.

Hopefully at some stage the GSDM site will be operating up to date once again and some more cohesive analysis might be possible.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4844071

[Kirkcaldy Weather]

Looking more closely at the incoming upper level Low, I mentioned it was unlikely to be as convective in nature as we got with storm Noa and this remains the case but there will be a couple of opportunities for convective developments

Firstly we'll have frontal precip which breaks down into showers especially focusing on Wales and Southern England for Friday 

For a short period there might be instability from the low countries attempting to feed into Southeastern areas 

Following on we see a frontal wave develop on the northern flank aided by that instability moving into the North Sea, there is also a bit of shear and vorticity within that so wouldn't be totally shocked for some spinup attempts along it 🌪🌪

 

I'm also focusing on overnight Friday into Saturday across southwest France as I believe there will be supercell opportunities there, good SRH, shear and vorticity with discrete cells  

 

I was discussing the recent West Pacific MJO phases, I've mentioned before how often whichever region the MJO is progressing through often can increase cyclone development ..

Pretty cool the storm was in the right area to see the solar eclipse move over it

 

 

 

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4844360

[Mike Poole]

11 minutes ago, Howie said:

This is getting a bit tiring now. Most SSWs don't seem to have this effect in winter but can ruin an entire spring, I just hope it doesn't continue into summer

I think the SSW effects on our weather blew themselves out two or three weeks ago.  It is true it made for a disappointing first half of spring, but that is behind us now.  What we may be seeing now though, is the rather more benign but still potentially significant impact of the final warming which has just happened in the stratosphere, as you can see from the 10 hPa 60N zonal winds plot:

5 minutes ago, CreweCold said:

Remember we can get -NAO/-AO periods in summer without forcing from an earlier SSW. We’ve just become used to +NAO and increased Azores HP interference over the past few summers.

Yes, and this is the thing after the final warming, there is no polar vortex - and therefore no forcing to prevent blocking patterns like there is in winter when the vortex is rampaging.  This is why blocking patterns occur more frequently in spring, whether they continue to do so into summer rather depends on what summer patterns develop - these can be notable, like 2018, but sometimes much less clear cut.  The modelling, on the 10-15 day timeframe at least, is not giving much away about the upcoming summer pattern just yet, and we wait to see what happens, but I’d be inclined to sit out this period with the final warming just happened, before drawing any negative conclusions on how May will pan out.  An improvement in a week or so, and then we watch for the next signal.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4846526

[Cambrian]

The ambivalence continues for a while at least into the last month of spring. Some strong early heat forming over Spain during the last few days, 35 degrees in parts there today. It sets up that mini-plume of heights heading our way by the middle of next week, Wednesday being day 5, here on the 0z ECM op.

  

But don’t be seduced by this hot little tease, there’ll be little heat for us this time. It’s being undercut by a Northern European flow, cold air sinking  our way, through the high from the Baltic, leaving us high and dry with a bit of a stiff one in Bognor, 6-16 degrees summing up the best we can hope for. This shouldn’t be knocked though, a very reasonable few days in store as we go through next week, and feeling pleasant in the sun away from any onshore breezes. Still bubbling away in Spain, but the heat watered down through France and getting cut off altogether at the Channel. 

Thereafter, the 0z ECM mean anomaly charts at day 5 and day 10 show a similar progression to the overall pattern that we frequently saw happening through much of March, European heights receding northwestwards, retrogressing over the high north of the Atlantic to Eastern Canada, leaving Atlantic and Scandinavian troughs attempting to link up over the UK and Ireland around the bottom of residual northern heights around Iceland.

 

Yesterday’s ECM weekly mean pressure anomaly chart gives a firm low pressure anomaly for the second week of May (8th-15th), echoed by the negative heights anomaly, and the extended range weather regimes forecast shows a persistent NAO+ signal through the following week too. 

  

This is ameliorated by a reasonable blocking signal too though and the weekly anomaly charts by week 3 (15th-22nd) are a bit of a bust, so really no firm sign of anything too protractedly unsettled…

 

and with the GFS mean anomaly at day 15 showing some interest in heights pointing our way from the Azores, but the GEM mean still keeping the Atlantic in the game…

 

the all-round undecidedness continues well into May. 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4847335

[Tamara]

Ed Berry, previously an NOAA affiliate who designed the GSDM wind-flow diagnostic product, passed away a few months and he held the primary authority for the use of the product and which David Gold inherited rights to its use. There may be something in this that is stalling processes of fixing & updating the site - but a degree of speculative reasoning in that admittedly.

For those in the UK and NW Europe generally, there shouldn't be too much concern at this time about summer. In fact with the tropics & extra tropics continuing to amass truly substantial surpluses of +AAM westerly inertia, this is set to drive highly anomalous anticyclonic wave trains across mid latitudes as the effects of an unstable tropospheric boundary to the polar field at higher latitudes continues to lose residual influence. With summer wavelengths approaching there could well be a seismic shift towards northwards advection of heat as the Hadley cell expansion from Africa into southern European is producing staggering record breaking heat down here. Records broken here in Portugal during April that go back 78 years.

A flick of a switch could mean quite a dramatic change in weather moving northwards across greater and greater parts of Europe - as this heat can only keep building through May and into June. So much so, that summer down here is a subject of quite some apprehension in contrast to the wait for heat to arrive in the UK.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4848987

[Eagle Eye]

Definitely feeling the effects of the WWB's now with strong Nino atmospheric responses and that can be seen in our current weather. We remain likely to be in a high orbit GWO with strong tropical forcing for wave modes that favour WWB's in the ENSO area and perhaps not great modes here. However, the local dominance of the Hadley cell which I suspect can be modified and conditioned by latent heat exchanges,means that the inertial strength of the RWT can be ourbalanxed under a strong mass response from the Hadley cell. The stronger, the heat buildup over North Africa-Spain as a rough guess and the better chance of breaking through the Nino response there is. We've already seen this in the small plume we're having currently. It may become a year of small but hot plumes that could potentially be thundery in nature given the reference frame for the slowing down of the wave speed (or more bluntly, more chance of a trough out to the west or southwest than a Nina year theoretically). Heat buildup over the UK is likely to not be as significant as if a stationary high was over it unless the Hadley cell replaces to the north which earlier seasonal models were suggesting with a UK-Scandi high. A more mobile (ish) pattern is perhaps favoured but I don't think it's absolute and depends on the atmospheres redistribution of smaller space Kelvin waves for future MJO reference.

It's important to note that during the Summer, in the Nino response MJO phases, there is a time where the reaction based off composites of strong forcing is close or even near spot on to a good pattern. That appears to be sometime in July where thst response is best seen and thst seems to be a general concensus among Nino MJO phases of the expansion of Hest from our south more generally. Though it's not looking great based off most composites, they are just composites and many of them have a well positioned high close enough to us for a little leniency.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4849053

[MattH]

The constant with the outlook deeper into May is still linked to the expected and noteworthy eastward progression of the MJO and associated -ve VP200 anoms and the associated WWB. As usual, all this brings about a long-predicted rise in AAM, as, atmospherically, we get another Nino push, which will no doubt aid (oceanically) the trend towards El Nino as well. The last few runs of the EC46 for the AAM anoms have, literally, been off the scale and it has been an upward trend in AAM for the last 2 weeks as this signal has grown and developed...

Unfortunately, for those with interest in the GSDM, we continue to be walking 'blind' by the fact that the primary GSDM website remains well out of date and despite several attempts to gain information from the owner of the site, it doesn't look good at all for this to come back, which is a very bad thing indeed. One can only hope that someone over in the US picks this up separately moving forward and it returns, but, for now, it's gone.

Moving on from that and, overall, despite the cyclonic outlook to the first half of May one would still expect, with reasonable confidence for there to be a Rossby wave pattern and evolution that supports a more troughed Atlantic and ridged pattern over W Europe, including NW Europe towards and beyond mid-May. This is still a long-term prediction of mine for May, and, tentatively, there is some evidence of this now in NWP which I would hope will gain some traction in the coming days.

Personally, this has been a dreadful spring and is a perfect example of why (again personally) spring is my least favourite season in the British Isles, but that is for another thread. One can only hope that with the assistance of the upstream Pacific developments a more pronounced warmer, anticyclonic spell will (finally!) arrive this month, but that isn't likely until mid-May at the earliest I would suggest.

The summer itself, as some have already said may not follow what spring has brought, it doesn't necessarily work that. However, the positive for those hoping for warm, anticyclonic summer days is that we are progressing into early summer clearly within a more Nino regime, some of the worst summers usually come with a -ve AAM pattern at this time of year, plus other factors, that isn't the case this year, but the eQBO summer can, sometimes, aid northern blocking.

With ENSO neutral conditions set to rumble one for a while yet I still think, overall, most of the summer will be relatively volatile, potentially flipping from very warm, anticyclonic NW European ridge patterns (as MJO passages come to pass and we get +GLAAM), to then an approaching trough pattern from off the Atlantic, as AAM then falls. It is, however, as usual, very difficult to call and with the usual uncertainties these days that AGW brings, then confidence is obviously low. Personally, though I don't expect a repeat of 2018, nor do I expect a horror show like 2012, but a more changeable, volatile period.

As ever, time will tell. Cheers.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4848968

[Kirkcaldy Weather]

On 17/04/2023 at 14:51, Kirkcaldy Weather said:

"Phase 3 composites are similar but I just wonder if we might at least for a bit of time have the high centred to draw in the flow from the East" 

️  

"Though brief the travel through phase 4 should eventually have low pressure around the UK" 

We've had the low around the UK with storm Noa but the upcoming pattern is a blend of the high bringing an easterly flow combined with a developing upper level Low.

We have the upper level low starting to develop through the low countries on Wednesday (in @Cold Winter Nights backyard ) 

Given the steering flow this will get to us by Thursday and remains stagnant barrelling around even into the weekend 

With the cold pooling at 500hpa and the pool of 528 dam close to the centre I'd expect hail and a wintry mix though CAPE values aren't really worth a mention unlike with Storm Noa so precip unlikely to be as convective in nature. 

 

Even as we are getting closer to May the temps at night even for most of us will be close to frosts developing 

With MJO progressing through phase 6 and now in phase 7 this will see high pressure developments ranging from our east across the UK and potentially in the Atlantic 

 

 

 

Again CFS already feeling this out in the extended range (I think it will be starting to materialise a bit ahead of those dates but we'll see ) 

Does appear to be a trend in the West Pacific being the main zone of interest for the MJO even heading to the extended range   

 

 

'With MJO progressing through phase 6 and now in phase 7 this will see high pressure developments ranging from our east across the UK and potentially in the Atlantic'

Decent enough match with the current setup 

Also we've had a super impressive -NAO and whilst the SST's elsewhere in parts of the Atlantic have warmed, around the UK the SST's have actually cooled a bit

I'm just suspecting if we get a true Tripole setup by late autumn into Winter, I believe the last true one was 2010 (could be wrong on that not sure if 2012 had that setup)

Phase 8>4 through April & May give us these overall patterns 

 

 

So far that looks a bit of a middle-ground pattern, some lower pressure and the consistency for the high to our south (Spain) possibly extending into the UK 

However phase 3 does have a big agreement for low pressure over the UK possibly deeper lows too so an unsettled period within the next 2-3 weeks would be likely IMO

  

 

Phase 4 which is where we are at the mo will likely see the low pulling away in a northerly direction 

 

I posted my thoughts for where I see us getting to by summer proper in the Scotland thread the other day,

with other similarities to 2015 I see that being a good benchmark so I'm thinking warm conditions and storms 🌩🌩 plume style setups. Some of the monthly models have been hinting at wetter conditions near & across the UK which increases my thinking of the above.

^^^"Does appear to be a trend in the West Pacific being the main zone of interest for the MJO even heading to the extended range"

CFS and GEFS look the most aggressive with this next phase into the Pacific from the MJO 

 

Others agreeing with my views that the next substantial WWB is on the way which will take us into official classification of El Ninò IMO

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4849673

[MattH]

40 minutes ago, Mike Poole said:

Models at T216 this morning:

There’s been a signal for high pressure to nose in around this time for a few days in various op runs and the ECM clusters, but it has always been a minority signal.  That may be changing to something we can have a little more confidence in this morning.  

High pressure pushing in from the right direction, towards the right place - without a competing low encroaching from the NW.  Let’s see if this evolution has a stronger showing on the clusters…

The north-eastward extension of the Azores high with more of a troughed pattern over the N Atlantic has clearly been flagged as an expected/possible evolution deeper into May, for some time, despite little evidence for this within the NWP. As usual, especially in certain circumstances, this is where the usefulness of the GSDM comes into play, especially seeing it is often a far more stable variable to look at. We know the MJO is on the move, with a significant WWB on the way, one can surmise (despite still no GSDM website) that both +FT and +MT events are taking place and AAM will rise.

That process, at the moment, is likely now underway, given where the analysis of the AAM was up to the 6th of May and clearly where it is set to go. The MJO is rapidly moving through the phases and those trying to use it as a guide will struggle. There has been some in-depth analysis on the composite anoms in recent posts, but, again the problem is that the MJO is quickly progressing through the phases of 3-4-5-6 and trying to match each one to a likely evolution, under this situation, will likely lead to confused and uncertain end results.

Definitely need to keep a watchful eye on NWP moving forward to hopefully see this broader signal gain consistency with an Atlantic trough and downstream ridge pattern.

Cheers, Matt.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4850274

[MattH]

NB: As a side note, the PNA is set to go positive as well....

Again, all no surprise given the WWB and the atmospheric push towards a Nino regime (High GWO orbit) and we can see that pattern well just looking at the 00Z GEFS anom plot. The key thing for the N Atlantic and W Europe is where the primary trough, after the W USA ridge, ends up. The GEFS mean has it somewhat further west than we would like, but clearly this can all be refined eastwards somewhat, it is the broader pattern that is now, finally, gaining momentum (no pun intended!) for an improving, anticyclonic scenario as we progress deeper into May, linked to upstream, Pacific developments etc.

Cheers.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4850292

[Tamara]

4 hours ago, MattH said:

Definitely need to keep a watchful eye on NWP moving forward to hopefully see this broader signal gain consistency with an Atlantic trough and downstream ridge pattern.

Yes agreed.

Forthcoming strong WWB's will re-set the developing and rapidly strengthening Nino influence in the Pacific and this has very interesting implications heading towards and into June and the start of summer.

Heights in the Atlantic and an ebbing and flowing Azores High are not likely to be the default this summer as they have been in recent summers. Low pressure encroachment to the west and downstream ridges (with thundery potential breakdown to re-set rinse and repeat) look more probable with only temporary interruptions to this pattern when ridging in the Atlantic is evident.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4850394

[MattH]

Steady as she goes, following on from comments and discussions yesterday, we can clearly see the predicted Atlantic trough and downstream pattern, it's the small-scale details and trough disruptions that continue to cause the problems for NWP, but I would leave that aside for now and continue to focus and look for this broader synoptic pattern. We can also see how the 00Z GEFS has shifted from the previous run again as well as NWP continues to evolve and try and resolve the outlook deeper into May.

This is when hovmollers can come in handy as well as you can see how the forecast evolves compared to what has been. One of the key things is the retrogression of the pattern, with time and how the broader troughs and ridges back westwards, as modelled, looking ahead leaving our corner of the world with the Atlantic trough and downstream ridge pattern.

EPS is less keen than the GEFS with the amplification, but this is just one snapshot and one example of what is a broader expected evolution, as per the upcoming +GLAAM event, etc.

Cheers, Matt.

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4850629

[Cambrian]

Hope you’re all well. 

Saturday looking good for the UK and Ireland on the 0z ECM op as the ridge builds through from the Azores to Scandinavia. Dry with decent temperatures, in the high teens for many, though chilly on the east coast. Very pleasant inland, the highest temperatures over Ireland. A bit better than last Saturday anyway!

 

A change by Sunday afternoon as a band of rain works its way in to Scotland and Ireland, with the better temperatures pushed east before the rain,

 

but all leading to a showery day for most next Monday, courtesy of the low pressure over Europe. 

 

A cold northeasterly flow is maintained early next week, so that by a week today, the temperatures are pegged right back again. That’s decidedly cold for the middle of May over much of England and Wales, and very cold up over the hills with plenty of rain about. Drying up further north and west though.

  

A similar northern blocking pattern through to the following weekend, the barometric pressure is quite reasonable but the upper level trough towards Iberia is stubborn, 

 

the setup supported strongly by the ensemble means. 

 

That little low on the op dropping down into the mid Atlantic at days 8-10 is interesting. As it is, the low heights are getting eased southwest through France and Iberia. If they continue to get drawn further west into the Atlantic, it could help nudge the high to our north a bit further east and pull in more of a southeasterly and maybe something a little warmer.

 

Fair to say though no proper heat on the cards for a fair while to come, but with that high pressure so close, it could turn very pleasant for a while further north and a reasonable chance the ridge will eventually topple and give many of us a few days of good weather heading into the last third of the month. 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4852181

[MattH]

Despite the usual doom and gloom posts in the model thread, even though NWP hasn't been showing anything like as such for a good few days, the northeastward extension of the Azores high is clearly gaining traction, something which has been long predicted as a possibility. The early indications for the May MJO passage and +GLAAM spike were there back in mid-April. I have a forecast documentation here that I produced on the 18th of April, for work, alluding to that possibility...

NWP has been flipping and flopping around for much of this week but has now finally settled down with regard to next week and the build of pressure. Interestingly, one of the best models to capture this in recent days has been the GEM, the worst the ECMWF, make of that as you will.  For those with an eye for the GSDM we continue to 'fly blind' by the lack of actual observed GSDM data, but generally speaking you can still predict some outcomes and evolutions based on other data and what is actually going on.

Using the likes of the ECM and GFS data AAM is now approximately at +2sd , the key thing looking forward is the persistent forecast (from EC46 at least) for GLAAM to remain in positive territory, likely leading to a continued repeating pattern whereby ridging NE towards NW Europe will occur but with potential trough disruption events at times. As the coming days and weeks progress clearly temperatures will naturally rise anyway, despite the cooler start to next week.

If we link this into the EC Monthly and the VP200 forecast looking ahead, we can see a pattern that is far more Nino, than Nina-like, with often -ve VP200 anoms over the Pacific, while the low frequency standing wave setups over the I/O. The combination of a likely El Nino and a possible +ve IOD this summer is, however, an interesting one and there is currently a lot of focus on how these two will interact with each other, how the SST's will evolve over the Pacific and just how significant the El Nino will become. I still believe/expected/predict that the upcoming summer will see rather typical British-like modulations of heat, humidity and thunderstorms, with cooler, cyclonic Atlantic incursions. How long each setup lasts obviously depends on short-term synoptics and how slow-moving the broader Rossby wave regimes are. We all know both can become locked in for quite long periods of time in the summer. One could argue this covers all angles, which in a way I guess it does, but a summer like 2018, seems unlikely, while a complete disaster like 2012, is unlikely either, as mentioned previously we aren't progressing into this summer with a -GLAAM trend and with an eQBO combination, often leading to some of the worst summers with a resolute NW European trough.

Stripping it right back and it has been a pleasing watch to see NWP slowly evolve towards a long-term prediction. A heatwave, certainly not, but a welcomed spell of late spring weather is most certainly on the horizon, despite what some would have you think here...

Cheers, Matt

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4853178

[Cambrian]

A tranquil Atlantic through the mid latitudes ensues for the next few weeks, that takes us comfortably into early June according to yesterday’s extended range weekly mean anomalies from the ECM for weeks 1-3. There’s a persistent positive heights anomaly stretching west across the Atlantic, carrying on all the way round the hemisphere at those mid latitudes, with lower than average heights over the pole and the Mediterranean.

  

The main caveat is the slow encroachment of the lower than average pressure anomaly from the south by week 3, as the week 1 UK / Ireland positive pressure anomaly firstly pulls east into Scandinavia by week 2 and then shimmies back west again by week 3 to keep the higher than average pressure to our north firm. 

  

The week 2 and 3 charts are a continuation of the recent trend in the outlook charts of good heights for the UK and Ireland but close to normal surface barometric pressure - suggests plenty of upper level warmth, but that occasional incursions of disturbances from the south look possible, potentially thundery as they tuck in a warm southeasterly flow on their approach. All this is a long way off though, and for now, any substantive weakening of the block keeps getting pushed back. 

The last three extended range weather regimes forecasts show this nicely. The forecast from a week ago lost its majority blocking signal around the 25th / 26th May, but hardly a hint of a NAO+ signal, rather to slightly higher Atlantic ridging and NAO- signals. The Thursday update was a belter for blocking, extending the signal to the end of the month. On yesterday’s chart, the strong blocking signal has now been extended to the 3rd June and the NAO+ signal is squeezed out altogether around the turn of the month. A tranquil ocean indeed. 

  

Moreover, with a foundation of strong blocking during the rest of May and continuing into the start of June, bringing plenty of strong sunshine and light winds, this is broadly looking like a good promising start to the summer. 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4855141

[Tamara]

22 hours ago, mushymanrob said:

Ok, its verification time... what the MJO should be giving us now, as per the phase 5 composite, compared with the EPS prediction for today both made on the 5th ...

Heres todays EPS chart..... id suggest the result of this is pretty clear ..... MJO? MJ NO more like!

 

You have provided a very good example of something I have repeatedly made on the few occasions I visit this thread. The MJO is just one part (an important part) of the whole atmospheric circulation wind-flow budget. The relationship and interaction of forcing in the tropics has to include the extra tropical circulation as determined by the Global Wind Oscillation (GWO) which is a plot depiction of aggregate wind-flow in both tropics and extra tropics.

Providing an accurate diagnostic analysis using these particular weather tools continues to be hampered by the diagnostic maproom of the Global Synoptic Dynamical Model (GSDM) being out of operation since the middle of March. Despite indications that this would be fixed, nothing as yet has materialised in respect of resolving the problem.

In the absence of this highly useful and insightful information & data, comparison of VP200 tropical convection anomalies, convergence zones within these anomalies, trade wind strength and fluxing of wind-flows between tropics and extra tropics can't be be compared as usefully against the ongoing strength of atmospheric angular momentum (AAM)

Westerly Wind Bursts (WWB) continue  across a wide swathe west of the dateline

 

However, in respect of the tropics it is complex presently with this extensive area of attempted eastward push of westerly inertia across both the  Maritimes and the Western Pacific and with some (relative) weakness of inertia from the dateline and into the eastern Pacific. Such "west based" forcing is influencing the extra tropics in a way that is a-typical of many El Nino transitions, especially with -ve PDO forcing persisting.

Angular momentum is above average in accordance with the direction of travel of increased propagation between the tropics and extra tropics, though is is not possible to see both frictional and mountain torque budgets which would confirm the precise locations and strengths of wind-flow propagation into the extra tropics.

C/o the -ve PDO and extensive forcing across a wide swathe west of the dateline then the total angular momentum anomaly does not have a breakdown analysis of the aggregate forcing and therefore not tell the whole story as much of this extra tropical propagation from the tropics is blindsided by this -ve PDO and residual 3 year La Nina lag. Hence the present stronger pressure anomaly of the Azores High (which in previous posts was predicted to play less of a role this coming summer).

I think this continues to be the case. The forcing west of the dateline is very strong with a lot of warm water upwelling trying to push eastwards across the dateline. Summer wavelengths heading into June, a waning of the a-typical ENSO forcing in the coming weeks, and the tropical standing wave becoming greater focussed across the Pacific itself (and less around 120E to 150E) are likely to evolve the advertised pattern towards less Azores ridging across the Atlantic and  troughs cut-off west and south west of mainland Europe bumping up against downstream high pressure zones across much of northern Europe.

This could be a summer of thundery/thermal low being advected northwards and north eastwards and repeated plume type heat - rather than stationary prolonged dry heat conditions.

The coming week down here across Portugal and Spain sees the first hints of that change which should become more influential with time as they embed across continental Europe as downstream high pressure ridges establish themselves fairly close to the N and NE of the UK

 

Original post: https://community.netweather.tv/topic/98519-model-output-discussion-15th-march-onwards/?do=findComment&comment=4855546