Model Output Discussion - Mid Summer Onwards

[Cheshire Freeze]

2 hours ago, Addicks Fan 1981 said:

Most of this ECM hovmoller looks OK, but the last days of August fill me with dread in the sense that the easterly trades will be making a comeback.  Meaning a potential trough towards the end of August.    

Time-longitudes diagram - Extended range forecast

CHARTS.ECMWF.INT

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This is a time/longitude diagram (Hovmoller diagram) of 500 hPa or 1000 hPa mean height anomaly (contours) and spread (shading). The mean anomalies are derived from the ECMWF extended...

 

That’s ok.
 

Hopefully we’ll see some autumn as autumn commences. Warm Septembers aren’t good in terms of correlation to cold winters. So a trough returning to end August will set us up well as we enter September.

[Addicks Fan 1981]

4 minutes ago, JayAlmeida said:

Looks like Fridays yer lot if your after heat and don't live in the SE. GFS 18z seems to now be following the other 12z runs by pushing any warmth away fast to be replaced by showery interludes by the 21st.

Scandi ridge never really gets going on this run. What a massive dissapointment 

I don't find GFS 18Z all that trustworthy to be honest with you, we will have to wait and see if its a cool outlier or not.   

To my eye GFS 12Z actually looked pretty decent especially in the south.   The models seem very temperamental at the moment and it's a job knowing what will actually transpire.   

@summer blizzarddid a very good post earlier over a standing wave and whether that'll take effect soon.    

[JayAlmeida]

4 minutes ago, Don said:

Similar to the last couple of days?

Definetly a new trend developing today it seems. Will it lock in tommorow or will the models conjure up something new?

[near northampton]

41 minutes ago, Addicks Fan 1981 said:

Thing is those hovmoller charts change on a daily basis so it could have a different outcome say like tomorrow.   

Of course they change on a daily basis! Are you expecting them not to? I reckon the outcome will be different tomorrow!  

[Don]

Just now, JayAlmeida said:

Definetly a new trend developing today it seems. Will it lock in tommorow or will the models conjure up something new?

Could be the models are struggling and may eventually settle for a middle ground scenario?

[JayAlmeida]

2 minutes ago, CreweCold said:

That’s ok.
 

Hopefully we’ll see some autumn as autumn commences. Warm Septembers aren’t good in terms of correlation to cold winters. So a trough returning to end August will set us up well as we enter September.

Do cold winters tend to follow cool/wet summers in a weak nino type setup?

[Addicks Fan 1981]

1 minute ago, CreweCold said:

That’s ok.
 

Hopefully we’ll see some autumn as autumn commences. Warm Septembers aren’t good in terms of correlation to cold winters. So a trough returning to end August will set us up well as we enter September.

I'm feeling more uneasy over September if I'm honest @CreweColdbut these hovmoller plots are always subject to change and it all hinges on the GWO.   

Await to hear the next update from @MattHas it will be very interesting.    

[Don]

1 minute ago, Addicks Fan 1981 said:

I'm feeling more uneasy over September if I'm honest @CreweColdbut these hovmoller plots are always subject to change and it all hinges on the GWO.   

Why, do you feel September might have an unsettled theme?

[Addicks Fan 1981]

1 minute ago, Don said:

Why, do you feel September might have an unsettled theme?

It does seem like it's not that clear cut to me now as it was, initially I thought September was going to be OK, now I'm not so sure.

[near northampton]

7 minutes ago, Don said:

Why, do you feel September might have an unsettled theme?

Yep good question, love to have some insight from this very thankful prolific poster as to why September "might" have an unsettled theme?

4 minutes ago, Addicks Fan 1981 said:

It does seem like it's not that clear cut to me now as it was, initially I thought September was going to be OK, now I'm not so sure.

Why

Edited August 11, 2023 by near northampton

[Addicks Fan 1981]

3 minutes ago, near northampton said:

Yep good question, love to some insight from this very thankful prolific poster as to why September "might" have an unsettled theme?

Why

From what other posters with greater knowledge than myself seem to indicate that the GWO and AAM seem connected with the hovmoller plots or something like that anyway.   

[Cheshire Freeze]

23 minutes ago, JayAlmeida said:

Do cold winters tend to follow cool/wet summers in a weak nino type setup?

I've no idea to be honest with you. I just know that there does seem to be a fairly significant correlation between a warm September and a mild winter.

[Don]

29 minutes ago, JayAlmeida said:

Do cold winters tend to follow cool/wet summers in a weak nino type setup?

Not necessarily but a very warm September with a CET of 15C or more does not bode at all well for a cold winter.  I've no idea why this is the case though.

[clark3r]

Gfs run this morning goes for a longer period of warmth but only a couple of hot days

ECM looks hotter to my eye with low further south allowing to pull in the very warm air, next weekend looks hot on ECM providing we get sunshine 

Edited August 12, 2023 by clark3r

[mushymanrob]

11 hours ago, Addicks Fan 1981 said:

Very good NOAA 8-14 chart below albeit with below average confidence levels with ECMWF 00Z ensemble mean and GEFS 6Z ensemble mean being the closest at 40 % each and GEM 00Z ensemble mean at 20 %.    

that charts isnt as good as it might first appear .... the contour lines are too close together, not wildly so, but they show westerly mobility meaning theres no chance of a large, strong, lasting high over us...
 

8 hours ago, Addicks Fan 1981 said:

Thing is those hovmoller charts change on a daily basis so it could have a different outcome say like tomorrow.   

every model changes on a daily basis, the hovmoller goes out to a month ahead meaning they will change more.. its consistency we need before they can be taken too seriously more than 14 days ahead.

[ANYWEATHER]

This is the time of year when the big Boyz Gfs and Ecm often differ vastly with their outputs during and up to the ten day range ,with a good example below , probably due to the complications of tropical features in the Atlantic Basin  being developed or not!

[WinterOf47]

8 hours ago, Don said:

Not necessarily but a very warm September with a CET of 15C or more does not bode at all well for a cold winter.  I've no idea why this is the case though.

Could it be related to the establishment of the jet stream further north for later into the year? To be honest, if this correlation is really strong…i.e. warm September mild winter, I am ready to throw September under the bus and write of this summer (except June) and hold out for something exceptional in terms of cold over the winter. Also I am away most of September

[SollyOlly]

13 minutes ago, ANYWEATHER said:

This is the time of year when the big Boyz Gfs and Ecm often differ vastly with their outputs during and up to the ten day range ,with a good example below , probably due to the complications of tropical features in the Atlantic Basin  being developed or not!

Wow, to my amateurs eye these look like they'd produce wildly different outcomes...!

[johnholmes]

Saturday with 500 and EC update

and the NOAA chart for 11 th shows some changes close by UK that may indicate changes in the 6-10 day time frame

The trough has altered shape along with 150DM +ve heights in the ridge to the NE of the UK. Together these may allow some inflow of warmer air from the south even SSE in the 6-10 day frame. The 8-14 shows little signal for this but it is not unusual for changes to appear first with the 6-10. Anyway worth keeping an eye on for a couple of days.

Looking at the ECMWF for the same 6-10 days 18-22 August it shows a brief 15 C 850 incursion into the SE but then loses it again?

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

[Uncertainty]

Yesterday the modelling reacted to a signal for the jet steam off the eastern seaboard to amplify significantly. This can be seen on yesterday’s gfs 6z

This invigorated the downstream trough to the our sw,  pushing it towards the Uk

 

The latest runs make less of that amplification around Greenland.

Resulting in less emphasis on heights over Greenland and weakening the troughing to our sw.

This allows heat and heights to build to the E.

The ecm has similarly brought the trough back west.

12z yesterday 

0z today 

All of this makes a high difference to our surface weather. Sultry south easterlies vs moist south westerlies. Thunderstorms vs rain.

As is often the case, the modelling explores the two most extreme options ( in this instance, high dominates totally —> low dominates totally) and finds a middle ground.

The uncertainty increases early Saturday to our west

After this, many options on the clusters.

6 is rather unhelpful, but the addition of a few green borders (-nao) indicates the Greenland blocking will be a factor in the forecast for after the weekend. The SE does look to be the favourite for holding on to drier weather. The latest op highlights this.

Beyond day 10, very interesting. The 3 main ensemble suites disagree about the potential for  a stranger to visit our shores, the fabled U.K. high!

GEFS sees it strongly

GEPS sees it sort of

 

 

EPS sees it not

So nothing easy. Even Monday’s rain from the south is uncertain. But some high impact weather (heat, thunder, rainfall) is possible in the next two weeks. 

Edited August 12, 2023 by Uncertainty

[Tamara]

11 hours ago, CreweCold said:

That’s ok.
 

Hopefully we’ll see some autumn as autumn commences. Warm Septembers aren’t good in terms of correlation to cold winters. So a trough returning to end August will set us up well as we enter September.

This is another variety of the many x+y=theories on this forum which has no founding other than a sense of something anecdotal and hoped for to happen again.

Finally some fragile coherence has come to the expected synoptic pattern vs diagnostic wind-flow pattern with downstream ridging and Atlantic trough as far as the European sector is concerned - but there is so much extreme oceanic micro forcing around the globe (very much including the Atlantic) that is now testing medium range diagnostic analysis to the limit, let alone seasonal predictions.

Seasonal wavelength changes and the increasing gradient differentials between the cooling at the pole and the lagged heat in the tropic with such anomalously extreme pockets of ocean heat look set to cause further chaos heading into autumn based on this additional superimposed forcing. Truly, all bets continue to be off and sitting back and trying to grapple with the global tipping point that is clearly underway is required.

This summer has been a stark red flag for what is to come. Sensationalism this genuinely isn't.

 

Edited August 12, 2023 by Tamara

[Addicks Fan 1981]

47 minutes ago, Tamara said:

This is another variety of the many x+y=theories on this forum which has no founding other than a sense of something anecdotal and hoped for to happen again.

Finally some fragile coherence has come to the expected synoptic pattern vs diagnostic wind-flow pattern with downstream ridging and Atlantic trough as far as the European sector is concerned - but there is so much extreme oceanic micro forcing around the globe (very much including the Atlantic) that is now testing medium range diagnostic analysis to the limit, let alone seasonal predictions.

Seasonal wavelength changes and the increasing gradient differentials between the cooling at the pole and the lagged heat in the tropic with such anomalously extreme pockets of ocean heat look set to cause further chaos heading into autumn based on this additional superimposed forcing. Truly, all bets continue to be off and sitting back and trying to grapple with the global tipping point that is clearly underway is required.

This summer has been a stark red flag for what is to come. Sensationalism this genuinely isn't.

 

Thank you very much @Tamaraon all of this, i now have a much deeper understanding of it all.   

[Earthshine]

Beautiful

[Alderc 2.0]

10 minutes ago, Earthshine said:

Beautiful

Surface conditions look poor.

 

[Methuselah]

12 minutes ago, Earthshine said:

Beautiful

We might even get some decent storms out of that?