Model output discussion - hot spell beckons but then what?

[feb1991blizzard]

4 minutes ago, Gael_Force said:

A couple of tweets @knocker has posted over in model tweet thread.

Also another previous seasonal signature Nino Modoki currently but if you read in entirety, with such novel extremes, it would be a mugs game trying to second guess any season now. 

Another variable here in play, last season i said the downwelling w-qbo in solar min might do for us but then someone built analogues or discussed the fact that during a transitioning qbo that the signs were good as SSW's were more prominent than during a whole winter with the aforementioned combination, wonder what the analogues are with a downwelling e-qbo during the winter season and what the best time for that transition would be. I agree it is futile to speculate with any certainty thus have not even looked at the likely transition timeframe although surely the earlier the better.

[Frosty.]

Looking at the Ecm 0z, Friday stands out as being potentially very warm or even hot for the SE in particular depending on sunshine, but whether it's sunny or wet it looks humid with continental +15 850's for a time.

Edited August 4, 2019 by Jon Snow

[Methuselah]

24 minutes ago, Jon Snow said:

Looking at the Ecm 0z, Friday stands out as being potentially very warm or even hot for the SE in particular depending on sunshine, but whether it's sunny or wet it looks humid with continental +15 850's for a time.

Well, I'm nae liking the GFS, for Friday, that's for sure! Yet another unwelcome deluge for the NW, should it verify?

  

[Frosty.]

Looking at the GEFS 0z there's no sign of high pressure gaining a foothold, there is some transient ridging bringing fine interludes but overall it's an unsettled outlook with sunshine / heavy and thundery showers and spells of persistent rain, warmish during the week ahead further s / se but cooler further n / nw and even the southeast trends cooler beyond the week ahead.

Edited August 4, 2019 by Jon Snow

[Don]

Just now, Jon Snow said:

Looking at the GEFS 0z there's no sign of high pressure gaining a foothold, there is some transient ridging bringing fine interludes but overall it's an unsettled outlook with heavy and thundery showers and persistent rain, warmish next week further s / se but cooler further n / nw and even the southeast trends cooler beyond the week ahead.

I still think we are in for another heatwave this month with temperatures well into the thirties.  This ties in with some long range forecasts, too.

[Frosty.]

48 minutes ago, Don said:

I still think we are in for another heatwave this month with temperatures well into the thirties.  This ties in with some long range forecasts, too.

I'm not seeing any sign of that in the output, quite the opposite for the next few weeks, especially week 2 of the outlook period (w/c 12th August..probably even w /c 19th)..the longer term GEFS mean is awful actually..to me anyway.

Edited August 4, 2019 by Jon Snow

[Don]

22 minutes ago, Jon Snow said:

I'm not seeing any sign of that in the output, quite the opposite for the next few weeks, especially week 2 of the outlook period (w/c 12th August..probably even w /c 19th)..the longer term GEFS mean is awful actually..to me anyway.

True, but these things have a habit of appearing from nowhere.  Obviously, I could be very wrong and to be honest I wouldn't mind being wrong as I'm not fan of extreme heat!

[Methuselah]

Despite the likelihood of too much rain falling on already saturated ground (if that wasn't bad enough!) the GEFS 06Z ensembles suggest that, temperature-wise, things will never be too 'autumnal'...?

    

   

                            Lancashire rainfall: 

[MATTWOLVES 3]

1 hour ago, Jon Snow said:

I'm not seeing any sign of that in the output, quite the opposite for the next few weeks, especially week 2 of the outlook period (w/c 12th August..probably even w /c 19th)..the longer term GEFS mean is awful actually..to me anyway.

I have to disagree with you there mate... Don rightly points out about some of the longer term signals pointing to better conditions in the final 3rd of the month. And to me the ECM seems to be have a good go at raising pressure from the SW by day 10...it may remain unsettled a bit longer in the NW, but I feel an improving picture further S/SW.. I think it's safe to say we can't really make a call on the long term outlook based on just the GEFS! 

[Tamara]

On 30/07/2019 at 12:29, Tamara said:

Personally, for what it is worth, I'm not attaching confidence in a Scandinavia/UK trough as any long term sustained solution encompassing 'the rest of summer' - and continue to think that the numerical modelling risks over dwelling on this signal. For me anyway, its a case of sitting on hands, and letting the scenario play out.

Quoted a further time simply for purposes of continuity and in the face of some advertised less than desirable computer modelled weather through to mid month

This sticking trough solution is now, not unexpectedly, coming very much under the radar in the 10 day period - but (for what it is worth) am still very much of the view that it needs to be seen as just another phase of weather, rather than anything sustained very long term.

The greater problem in the coming days, than the synoptics themselves, continues to be the risk of taking each individual ensemble data at face value wrt this trough solution and extrapolating it too far forward. More of that shortly.

For the near mid to end of week term, the models did not seen the slowing trough solution until the resolution came within the 7/8 day period either. Until fairly recently the ensemble means saw a seamless phasing of the departing mid week trough and the advancing one at the end of the week and a flatter pattern with no warm air advection evident. 

It is only a transitory downstream reinforcement of warm air advection, and unlikely to much assist those further NW - and does not prevent a continuation of unsettled conditions, and flatter solution beyond this in the medium term,. But it is a reminder of how surface patterns can take on different shapes to the suggested interpretations of pressure anomaly charts at distance.

Irrespective of the likely somewhat cooler and remaining unsettled sequence in the following week, it means that temperatures for the next 6 days at least, despite showers and rain about, look set to remain in the average to warm category (warmest further SE).

From later next weekend and into the following week comes that suggested cooler incursion as the upstream pattern amplifies in the Western Atlantic with a holding UK/Scandinavian trough downstream. The tropical diagnostic support for this points to blame c/o -ve zonal trade wind increase in the Eastern Pacific as a result of suppressed convection and interruption to the low frequency signal in the central Pacific (that has supported ability of downstream ridges to develop between Atlantic troughs  for quite some time this summer)..

The increased trade wind burst close to and east of the dateline very evident on Hovmollers (shaded deep blue) and reflected by the strong suppression in the same location(shaded orange) on the VP200 convection anomaly chart

The convection anomaly forecast is now just starting to focus on the eastward propagation of this suppression phase and return of dateline active phasing of convection convergence, soon after mid month. Despite a neutral Nino 3 zone, there remains considerable warmth to the west in Nino 4 - and this suggests that central Pacific convergence still remains a valid default signal. In tandem with the return of the low frequency signal, the MJO 'mini ENSO cycle. convection pattern also perhaps re-cycling back to the Pacific for the last third of  August and early September period. This would add even further support for a warm end to official summer and leading into September.

NWP cannot, this soon, be relied on to 'see past' the suppression phase and associated programmed amplification upstream which holds the downstream trough in place. So simply not worth agitating about the inevitable under par operational and ensemble suites in the coming week and little sense at all in drawing conclusions longer term about them.

However, with time as suppression focusses further east in the tropics across the Equatorial Atlantic and Africa, and active convergence of convection returns across the Pacific - then this cuts off the supply of -ve trade zonal wind close to the dateline . The consequent increase in upstream momentum from the Pacific>US as this wind-flow switch occurs should flatten out the upstream pattern and blow a hole in the ridge in the Western Atlantic and across W/Greenland, and as a result greater sub tropical ridging forced downstream instead - so in this way lifting out the downstream trough from SW>NE for the last third of August and retreating it away across NE Europe.

On this basis, continued (and increased) supportive reasoning, in my opinion, for an improved scenario with warmer and drier conditions to see out the last official days of the summer

 

[Frosty.]

3 minutes ago, Mattwolves said:

I have to disagree with you there mate... Don rightly points out about some of the longer term signals pointing to better conditions in the final 3rd of the month. And to me the ECM seems to be have a good go at raising pressure from the SW by day 10...it may remain unsettled a bit longer in the NW, but I feel an improving picture further S/SW.. I think it's safe to say we can't really make a call on the long term outlook based on just the GEFS! 

Hi Matt, I wasn't referring to the longer term signals (background)..I was only discussing the extended GEFS mean...I'm certainly not dismissing the possibility of another hot spell..indeed I hope there will be.

[MATTWOLVES 3]

6 minutes ago, Jon Snow said:

Hi Matt, I wasn't referring to the longer term signals (background)..I was only discussing the extended GEFS mean...I'm certainly not dismissing the possibility of another hot spell..indeed I hope there will be.

Sorry mate... I think Tams sums up the situation perfectly there. Some of the signals pointing to one last summer hoorahh, pretty much along the thinking of Exeter as well. Obviously this is all along way off, so caution is required! I would be very surprised though if we entered another spell similar to early June. Infact if we do, I will say I will no longer make a weather prediction again.... Sighhh, I hear some of you thinking.... Seriously though, the next 7 days look mixed to say the least!! After that we enter anything goes territory. 

[Singularity]

17 hours ago, Gael_Force said:

Strong ocean temperature signatures at present. Very warm PDO , almost perfect Atlantic tripole and La Nina signal in east Pacific. What's your thoughts for later in the year @Singularity

I can’t  give away much but broadly, I expect a -NAO to feature more than usual. Not without some significant breaks, it should be noted.

 

Great update from Tamara today. I’ve been struggling to place as much confidence behind the C Pac warmth, but what she writes makes total sense; the dynamics are true. So I’m feeling more hopeful again about the final third of Aug. 

Shame the interim looks so wet for N parts of the UK where flooding’s already an issue in many areas. The troughs continue to track south of usual, but mostly (late this coming week a notable exception) not as far south as seen in 2012 or 2007, when S parts also saw a lot of flooding issues.

[knocker]

Developing upper low mid Atlantic midweek leading to a very wet Friday with strong wind/gales

Edited August 4, 2019 by knocker

[Methuselah]

Out to August 18, and the trusty GFS 12Z appears to suggest that the 'rut' in which we've been for quite a while now, might be here to stay (or at least keep returning?)...It must be kind of a super-resistant-to-change pattern???

  

Whatever...more rain!

And, just as @Tamara suggested might happen (at least that's how I interpreted things) the NWPMs might be backtracking viz their expected change to more 'autumnal' conditions...we will have to see?

  

Edited August 4, 2019 by Ed Stone

[knocker]

Quite an interesting later half of the ten day period with the gfs. It merges the Arctic and Iceland lows to form a new low over northern Greenand whilst a high cell develops in the Arctic courtesy of the Aleutian ridge Thus the lobe over N. Canada is now displaced to NE Canada with the westerly upper flow running across to the the trough in the east where there is now dual flows across the UK. This portends unsettled with temps a tad below average

[Frosty.]

The Gfs 12z operational shows a generally unsettled run with only very brief respite at best from showers and bands of persistent rain, most alarming is the amounts of rain that could fall in already flood hit / threatened areas but also how cool it looks from next weekend, much sooner than that across northern uk and scotland would be in for seriously below average temps. No way am I giving up on another very warm or hot spell but no sign on this run.

Edited August 4, 2019 by Jon Snow

[MATTWOLVES 3]

33 minutes ago, Jon Snow said:

The Gfs 12z operational shows a generally unsettled run with only very brief respite at best from showers and bands of persistent rain, most alarming is the amounts of rain that could fall in already flood hit / threatened areas but also how cool it looks from next weekend, much sooner than that across northern uk and scotland would be in for seriously below average temps. No way am I giving up on another very warm or hot spell but no sign on this run.

I'm not so sure about this much cooler spell by the weekend, there is talk of things becoming warm and humid by then from the south. I'm just looking at the conditions for the Midlands through next week, and I'm seeing largely dry and warm on Monday.... Showers and sunny spells after that, perhaps more general rain on Friday clearing to sunny spells and showers by next weekend! I'm certainly not seeing a seriously unsettled spell away from the N/NW. Weekend has been great here... Very warm and humid and bone dry... Pretty sure someone said the other day about Sunday being a washout around the Midlands!!! Hmmm the jury is out. 

[Methuselah]

12Z ensembles paint an interesting picture IMO, in that chaos seems to increase in two separate places: up to around August 13, the members are tightly bunched with the op and control running pretty much in tandem with one another; but, post August 15, even the op and control go their separate ways...? Anything could happen?

   

   

So, to put it all that in a nutshell: I think it'll be unsettled!

[Frosty.]

Looking at the GEFS 12z mid month indicates the best opportunity for some ridging, probably from the azores but no way guaranteed, there are plenty of very disturbed members, especially beyond mid month and also unseasonably cool.

[knocker]

The ecm takes the low a tad further west so the detail still to be resolved

[MATTWOLVES 3]

Even with low pressure on the scene we still have some very warm uppers by the end of the week and weekend.... Tentative signs of high pressure trying to ridge in from the SW at the end of the run... I'm hopeful folks...

[knocker]

The ecm total rainfall is indicative of the forecast upcoming pattern

[knocker]

The upper low anchored over Iceland and the vortex lobe over northern Russia look like they may become it bit of a pain through the ext period

as they merge and form a slack area of low pressure to the north of the UK with an extended trough south.Thus although there is still some ridging in the Labrador Straits there remains a strong westerly upper flow across the Atlantic some cooler air gets involved in the mix so portending unsettled with temps below average if this is on the money. But to reiterate in this pattern the detail of the day to day weather can be very regional as the Pm and Tm airmassess phase.

This evening's NOAA in the came ball park

 

Edited August 4, 2019 by knocker

[Weather-history]

Thats a terrible chart for late summer, ECM 12z mean at 240hrs