Model Output Discussion - Autumn arrives

[NewEra21]

7 minutes ago, MattStoke said:

To be fair, discussing the BBC forecasts is the same as discussing the ECM output.

Doesn’t matter how many times it’s pointed out that the BBC just mirrors the ECM, people still get hung up on it.

Only difference is, the BBC are 24 hours behind. Always

[Methuselah]

2 minutes ago, NewEra21 said:

Only difference is, the BBC are 24 hours behind. Always

One could say that that's because all the models, by their very nature, are always one step behind reality?

[Earthshine]

17 minutes ago, Ed Stone said:

One could say that that's because all the models, by their very nature, are always one step behind reality?

How so?

[Methuselah]

2 minutes ago, Earthshine said:

How so?

Is there not a gap in time between data-collection and the run they generate? With the current level of uncertainty, even the very latest runs might be 'wrong'?

[Earthshine]

7 minutes ago, Ed Stone said:

Is there not a gap in time between data-collection and the run they generate? With the current level of uncertainty, even the very latest runs might be 'wrong'?

Oh I see.  I think the gap depends on how long ago the assimilation window was.  I made a post previously on how these weather forecasts are produced using 4D-Var.  It's not a case of just plugging observations into a physics model and waiting for the output, it's a dynamic and continuous process of adjusting an existing forecasts to align it with observations as you collect them.

[Tamara]

Posted on Sunday and copied for purposes of update :

..............................................

The cue for the end of the heat heading into midweek down here is the cue for the heat plume at the same time to head northwards through France towards the UK as well as eastwards into central Europe. With a defined thermal boundary setting up between the heat ridge over mainland Europe and a cold front to the NW of the UK coming around the perimeter of a typical early summer Nina-esque Atlantic ridge, it sets up the prospect of quite a distinct boundary of error either side, as it tries to head SE.

There is little likelihood that the Atlantic ridge will decline and help sustain any ridge further east into the medium and longer term with tropical convection now slumbering after an active period. On that basis, angular momentum has no upwards push from a suppressed level

 

This favours sub tropical ridging holding to the west of UK and mainland Europe. So its a matter of time how long the heat ridge can hold into the weekend in NW Europe and more particularly the UK closest to the cold front and the energy coming around the perimeter of the Atlantic ridge.

A cut off low forming along the cold front boundary and sinking south on the eastern flank of the Atlantic ridge is certainly quite possible. The further west such a development might happen implies this scenario slowing down/delaying the cool air advection at least for a day or maybe even two over next weekend itself. Ultimately the numerical modelling looks accurate in sharpening the Atlantic ridge and fully pushing the cooler air south eastwards into the next week, if it does get delayed a little during the weekend - more especially the further south and east one heads..

................................................

 

It has been interesting watching the progress of the developments as discussed above, and so it has proved that the heat plume looks to be harder to dislodge than the numerical models had been suggesting up to the weekend.

The first partial breakdown of the heat is underway here in the Western most part of the Iberian continent. A subtle boundary between the very hot air from Africa is the focus of some overlay by moist Atlantic air to the west and has resulted in something of a destabilisation of the atmosphere in the mid levels with elevated thunderstorms tracking from south to north from the Algarve coast through the Alentejo regions to central Portugal along this airmass boundary in a defined finger of mid level convection. So the first proper rain to dampen the ground here since probably April.  More booms of thunder as I type.

This very shallow ring of lower geopotential heights just off the Portuguese coast plays a subtle part over the coming days as the plume advects further north and north east towards NW and central Europe. It provides a prop for the anomalous Atlantic ridge as a further more expansive thermal low also develop across North West Spain & France along the same western boundary of the plume  - and which blocks the cool air advection around the North Atlantic ridge from pushing more quickly south and keeps at least southern parts of the UK in the very warm upper airmass for longer.

Meantime as the plume lifts north, larger amounts of Atlantic sourced air pushes into the Iberian continent. Relative to the 35C to 38C heat of  the past 10 days, a much cooler spell of weather lies ahead. Though these ensemble values for the coming couple of days will still seem reasonably warm by UK perspectives, the values from Sunday are several degrees below average for this latitude. Comfortable for outdoor work though!

 

As stated in the quoted post, there is no prospect of the mid Atlantic ridge declining, though the toppling ridge overlaying the thundery trough over France keeps warmer upper air much closer to southern and some eastern parts of the UK for considerably longer than modelling suggested a few days back.

Mid term, upper troughing is clearly advertised to dig south with the Atlantic/Azores ridge displaced well to the west of Europe in general. So heading through next week the cooler North Atlantic air eventually makes inroads across larger parts of NW Europe.

This is consistent with continued low angular momentum, renewed trade winds across the greater part of the tropics as MJO related convection activity is camped across the Indian Ocean with little amplitude and eastward progression suggested for the foreseeable future.

This becomes of greater significance as July high summer wavelengths approach. Continued suppressed convection and trade wind activity preventing westerly wind bursts creating eddies in the jet downstream and therefore reconfiguring heights back into Europe is the likely eventuality in such circumstances. However, if there are signs that renewed convection starts to progress eastwards then this leads to the promise of further summery weather returning to many parts of Europe.

Aproveite o tempo agradável durante o resto da semana.

[Methuselah]

2 minutes ago, Earthshine said:

Oh I see.  I think the gap depends on how long ago the assimilation window was.  I made a post previously on how these weather forecasts are produced using 4D-Var.  It's not a case of just plugging observations into a physics model and waiting for the output, it's a dynamic and continuous process of adjusting an existing forecasts to align it with observations as you collect them.

Now, I get you; that would explain how the Met Office adjusts its expectations, even when no new model runs have been issued? I was thinking purely in terms of, say, the latest ECM?

PS: I'm not sure I'm making much sense even to myself!

[Earthshine]

3 minutes ago, Ed Stone said:

Now, I get you; that would explain how the Met Office adjusts its expectations, even when no new model runs have been issued? I was thinking purely in terms of, say, the latest ECM?

PS: I'm not sure I'm making much sense even to myself!

I'm not particularly familiar with the exact forecasting method the Met Office uses, I'm more on the observations R&D side 

[sheikhy]

Ecm 06z back to an asbolute washout for wales and the midlands for all day saturday!!!gona stick my neck out and say gfs is horribly wrong at such a short time frame again!!!

[johnholmes]

9 minutes ago, Ed Stone said:

Now, I get you; that would explain how the Met Office adjusts its expectations, even when no new model runs have been issued? I was thinking purely in terms of, say, the latest ECM?

PS: I'm not sure I'm making much sense even to myself!

The BBC forecasts are provided by Meteo Group. True their main model is ECMWF but not exclusively.

[Frosty.]

My first reaction upon seeing the end of the Gfs 6z operational was… and my second reaction too!!  

[sheikhy]

Ukv 12z joins ecm with rain all day midlands wales saturday!!expecting gfs to come in line in 45 mins!

[Guest]

3 minutes ago, sheikhy said:

Ukv 12z joins ecm with rain all day midlands wales saturday!!expecting gfs to come in line in 45 mins!

UKV 12Z is very stingy on sunshine for Saturday, with more sunshine I'd expect much higher temps and the potential for thundery showers to return. 

[MATTWOLVES 3]

17 minutes ago, sheikhy said:

Ukv 12z joins ecm with rain all day midlands wales saturday!!expecting gfs to come in line in 45 mins!

I can't understand why your getting so frustrated over this possible rain on Saturday mate...its all but one day of many more to come for Summer. And tbh regardless of whatever happens on Saturday,Sunday does look improved...fresher yes...but drier with sunny spells perhaps.

There is still plenty of scope for corrections regarding the early part of the Weekend...so don't get to frustrated over it shakes my man.

Strong Heights parked to our West through next week on the icon...looks like decent conditions away from the far NE/E...West is best...Ireland would be very favourable...the troughing further East and perhaps looking less impactful than previously thought. I think earlier forecasts the other day from some organisations stating very showery next week look a little wide of the mark...my thoughts are pretty reasonable next week.

Edited June 16, 2022 by MATTWOLVES

[Cheshire Freeze]

17 minutes ago, sheikhy said:

Ukv 12z joins ecm with rain all day midlands wales saturday!!expecting gfs to come in line in 45 mins!

Just N of the rain band here. I’d prefer a shift N as the vegetation needs a watering!

[sheikhy]

21 minutes ago, MATTWOLVES said:

I can't understand why your getting so frustrated over this possible rain on Saturday mate...its all but one day of many more to come for Summer. And tbh regardless of whatever happens on Saturday,Sunday does look improved...fresher yes...but drier with sunny spells perhaps.

There is still plenty of scope for corrections regarding the early part of the Weekend...so don't get to frustrated over it shakes my man.

Strong Heights parked to our West through next week on the icon...looks like decent conditions away from the far NE/E...West is best...Ireland would be very favourable...the troughing further East and perhaps looking less impactful than previously thought. I think earlier forecasts the other day from some organisations stating very showery next week look a little wide of the mark...my thoughts are pretty reasonable next week.

Planned to take kids park but probably wont happen now!!working sunday as well!!!

[sheikhy]

Gfs dont wana back down!!pretty much bone dry for most of england and wales all weekend!!

[MattStoke]

29.2’C today at Heathrow. The very top end of the model predictions for today.

Edit: Now 29.3’C at Heathrow and Kew Gardens.

Edited June 16, 2022 by MattStoke

[tight isobar]

25 minutes ago, MattStoke said:

29.2’C today at Heathrow. The very top end of the model predictions for today.

Edit: Now 29.3’C at Heathrow and Kew Gardens.

Yep/ exactly the same for my location.. which is only 4miles from that plot..As you say top end of temperature plots... tomorrow will be painfully interesting

[Ross Andrew Hemphill]

12z gives a much cooler airmass across the UK back end of next week into the following week compared to the 6z

[fromey]

So does anybody want to tell me which model picked up the rain that’s developed right here in somerset!! 

[bluearmy]

9 minutes ago, fromey said:

So does anybody want to tell me which model picked up the rain that’s developed right here in somerset!! 

  Ukmo 12z not a million miles away 

arpege similar 

 

 

Edited June 16, 2022 by bluearmy

[Liam Burge]

I'm not sure why the Met hasn't issued an amber excessive heat warning for tomorrow yet?

[mountain shadow]

A poor UKMO and GFS with Northerly winds and low pressure possible into late June.

Eternal Autumn continues. 

[bluearmy]

What’s just caught my eye is the wind tomorrow afternoon which is gusting 30 mph in the home counties. That’s pretty unusual with T2 around 33C

3 minutes ago, mountain shadow said:

A poor UKMO and GFS with Northerly winds and low pressure possible into late June.

Eternal Autumn continues. 

I’m sure autumn will be eternal once it finally arrives!