Model Output Discussion - Autumn arrives

[sheikhy]

Very dry weather continues for my area on all 3 major models!!10mm of rain in 10 days on the ecm is nothing to write home about lol!!!at least the leaves shall have a good colour to them in the coming weeks!must say charts are looking kinda blocky as well!!

[Cambrian]

The Greenland ridge that is about to form over the next few days looks like it’s going to be an important driver in our weather during the middle part of autumn, not just in the UK and Ireland, but also across the Northern Hemisphere.

On the 0z GEFS mean, at day 0, a well-built low over the pole, proper low heights showing up. Some linking up with the circulating lows and the fledgling PV will be in business for sure?

 

But as we know all too well by now, not a hope. The eastern Canadian ridge starts moving up Greenland way by day 3 (60h) and along with the west Canadian ridge, executes its first cut-off, and the trough heading down through the middle of North America yields a low heading to the Great Lakes.

 

By day 6, the same Greenland ridge turns its attention east over the North Atlantic to perform the second cut-off, of the low to our southwest. The low pressure that was over the pole has now been squeezed over to form part of a band of lower heights running from Svalbard, through northern Siberia to the far east of Russia,

 

and by day 9, our relentless ridges push north to raise heights more widely over the Arctic, shunting the low further south over Siberia.

 

By day 12 the transformation is complete with a polar high installed at the top of the Northern Hemisphere, linking up with heights through Greenland and down into the mid-Atlantic.

 

The Greenland ridge, with some help from its western Canadian friend, has cut off two longwave troughs and unceremoniously shoved a promising low pressure system off the pole, moderating the weather over Western Europe and North America, and consigning another PV building attempt to the wastes of Siberia. 

[carinthian]

Morning all. Some agreement this morning with the main three models for this time next week. Mild or rather warm flow from a southerly quarter. The colder incursion's  being shown on yesterdays models being put on hold for the time being. A bit too far out for reliable rainfall predictions but would appear the west or south Britain most likely to receive any looking at that chart. Most Eastern parts and the North could stay mostly dry. The last 10 days of the month still up for grabs as the interaction between that developing slow moving low to the SW of Britain and the eventual location/movement of the high not yet determined and is showing large spread of results on computer outcomes post 168t.

C

[Eagle Eye]

The anomalies are about to properly leave Phase 5 over the Maritime continent and we can see the RMM values are expected to increase as they enter phase 6 specifically based off most models so it's still relatively weak at the moment. You can see the anomalies sort of moving Northeastwards as well as increasing their wave output in the latest GFS run.

Here's the MJO forecast (and history) from most major models' recent updates.

Here's the amplitude at the moment, you can see it increasing quite quickly, I suspect that it'll be nearer the top end of the graph based off RMM1 and RMM2 forecasting, specifically RMM1 is near the top end of the forecasts.

Here's a little help on understanding what RMM is, I will talk more about it soon, have found a document about it as well as other associations with it but will take me a while.

"RMM1 and RMM2 are mathematical methods that combine cloud amount and winds at upper and lower levels of the atmosphere to provide a measure of the strength and location of the MJO. When this index is within the centre circle the MJO is considered weak. Outside of this circle the index is stronger and will usually move in an anti-clockwise direction as the MJO moves from west to east."

[minus10]

Well a classic heat pump situation from the 12z gfs..day 6..

Is that a 24  I see there ....

[Don]

11 minutes ago, minus10 said:

Well a classic heat pump situation from the 12z gfs..day 6..

 

Is that a 24  I see there ....

Yes, summer's last hurrah!

24C more than plausible in London and the south east too.

[damianslaw]

Yesterday models showed a spring switcharound later next week with a southerly then northerly, I say reliable timeframe quite short at present. Expect more swings.

1 hour ago, Don said:

I quite like October warmth as unlike sometimes during summer, it feels very pleasant in the weakening sun!

By mid October the sun has same strength as late Feb and any warmth even low 20s can never feel especially warm for this reason. 

Edited October 13, 2022 by damianslaw

[Allseasons-Si]

2 hours ago, Weather Enthusiast91 said:

Not interested in any more warmth. 

It was nice during spring and summer, but that was then and everything has a time and a place. We are in the middle of autumn now, so I want some autumnal storms mixed with some chilly sunny days.

Warmth in mid October just feels very much out of place, much like with cold wintry spells in mid April.

I don't mind more heat pumps at this time of the year with the Autumn colors because it is great for photography,it has been a lovely day here although i have been at work until now

sooner have all this warmth now than in the winter months

anyway,as @carinthian says,...the phantom northerly has been dropped by both the gfs op/control 12z but that mean is tanking southwards as we go into months end...

a quick look at the day ten EPS 500's and MSLP and you can see a trough over Scandi with mid Atlantic ridge so probably on the cool side with upper winds north of west,the CPC/NOAA shows similar too

so a cooling trend if these anomalies are correct after a warmish next week with winds south of east

lets see what the 18z gfs throws out soon.

 

Edited October 13, 2022 by Allseasons-si
typo

[Don]

12 minutes ago, Allseasons-si said:

the phantom northerly has been dropped by both the gfs op/control 12z but that mean is tanking southwards as we go into months end...

I don't mind 'phantom' northerlies being dropped in October, but hope we don't have them and phantom easterlies during winter which have become a common occurrence in many recent winters!

[Cambrian]

A very pleasant mild morning here with bright skies, doesn’t feel like the middle of October at all! Can’t complain one bit - I’ll be heading out for a walk.

The middle of next week could be very pleasant too, if the 0z ECM operational run for day 5 has it right, as a high sets up to the north of Scotland, giving us a break from the cut-off low for a while.

 

The last couple of ECM runs has the floundering cut-off being rescued by a brief Greenland-Iceland trough dropping another cut-off down to reinforce it at day 7, giving it enough impetus to move east over the UK and Ireland at day 8.

 

By day 9, the op has trended a lot flatter over the Atlantic with the low finally getting up enough steam to head through. Interestingly, the mean and its anomaly is much more amplified, with good heights over the mid-Atlantic up into Greenland giving us a supply from the north, where, as shown on the T850 chart, it’s well and truly beginning to cool down.

   

So though there is no sign of anything cold heading our way before day 10, the potential for a steadily more chilly end to the month is perhaps beginning to get lined up in the form of the mean synoptics and some nascent cold pooling to our north, the door only being opened up though when the cut-off is given its send-off. Have a lovely day.

Edited October 14, 2022 by Cambrian

[carinthian]

Morning all. A week ago ECM produced this chart for coming Monday. Not a bad effort, I would say. Certainly, regarding lows formations to the SW of Britain, I think ECM has out performed its other two big rivals with-in the 144h time span. However, beyond that point out to 240h both ECM and GFS have not grasped the outcome with much accuracy, swinging widely from cold to warm. That in itself is not particularly unusual in period 144-240h. So ,the moral really is look no further than out to 168 h max. Beyond that still in the lap of the gods despite all the extra computing  outputs !

C

[damianslaw]

12z eventually shifts things along, the cut off low to the SW becomes absorbed by the main atlantic trough that pushes heights aside next weekend turning things colder and unsettled, it then moves east replaced by colder drier conditions with heights settling to our west. Let's see if ECM goes same way. we've seen quite marked changes just outside reliable in recent days, 6 day mark, so charts beyond come with large margin for error. 

[Uncertainty]

Could be a rogue op, but the latest ecm op has a stronger ridge early next week which keeps the troughs from phasing and has a completely different outcome for next weekend.

12z 192

 

0z 192

 

I often find the models struggle with these cut off lows and sometimes they fling them over / through the U.K. too easily.

Let’s see how big a cluster goes with this outcome. 

 

[damianslaw]

ECM chalk and cheese, previous run showed low pressure overhead 23rd, now it has high pressure, as said reliable timeframe short at present.

[Kirkcaldy Weather]

10 minutes ago, Uncertainy said:

Could be a rogue op, but the latest ecm op has a stronger ridge early next week which keeps the troughs from phasing and has a completely different outcome for next weekend.

12z 192

 

0z 192

 

I often find the models struggle with these cut off lows and sometimes they fling them over / through the U.K. too easily.

Let’s see how big a cluster goes with this outcome. 

 

It is interesting, the recent output has started going for a low probably Eastern side of Greenland which could join with the trough / lower pressure across Scandi (that might also be a lobe of the Tropospheric Vortex) the Icon particularly caught my eye 

[Kentspur]

On 13/10/2022 at 17:56, minus10 said:

Well a classic heat pump situation from the 12z gfs..day 6..

Is that a 24  I see there ....

Yes right over my place as usual .  No its a 21c I'm sure because of the colour contours look at the 24c in France several shades more red though id love a 24c in the 2nd half of October!!

[PiscesStar]

So. Gfs painting an unsettled picture with wind and rain and a particularly 'mobile' low from around the 22nd showing clearly. Milder temps swapping with colder ones at times. After that a northerly showing at the end of the run so trending colder.... 

[carinthian]

Morning all. Still no agreement this morning at 168t. UK model below . The UKMO still anchors the East Atlantic trough well west of the British Isles, whereas GFS and ECM  shows this on the move eastwards at an increasing pace. In the meanwhile, time to turn the thermostats down a notch or two across much of Euroland this coming week. Hopefully save a £ or old Austrian schilling or two. ! Currently, think so much uncertainly in the models , even at 168t.

Have a nice weekend in Blighty.

C

Edited October 15, 2022 by carinthian

[damianslaw]

As mentioned GFS and ECM push the low pressure to our SW through by this time next week and we then see colder conditions with the UK residing on the cold side of the polar front jet. GFS interesting output, northerly flow eventually after cold cyclonic and showery conditions.

[ANYWEATHER]

Looks like we will be picking up a rather blustery southeast wind by Wednesday, feeling rather chilly in that wind I suspect

[ANYWEATHER]

Looks like any warmth will be pegged further south over France. Perhaps the mildest by the end of the week...☺

[Methuselah]

8 minutes ago, ANYWEATHER said:

Looks like we will be picking up a rather blustery southeast wind by Wednesday, feeling rather chilly in that wind I suspect

18C, in October, 'chilly'? Yeah, right!

[Froze were the Days]

Medium term looks dire on latest ECM output if you're after chilly conditions or at least the continent cooling down...conditions up from the south or south east and then somewhat of a pattern change to the south west and more Atlantic originated but height still over Europe and low pressure still out over the sea...nothing changes!

2 minutes ago, Ed Stone said:

18C, in October, 'chilly'? Yeah, right!

I think there was a hint of sarcasm in that post  ...still looks dreadful in the medium term (at least).

[ANYWEATHER]

3 hours ago, Ed Stone said:

18C, in October, 'chilly'? Yeah, right!

The chart I showed there was the wrong day. It should of showed Wednesday rather than Friday. Indeed Friday looks at this stage the mildest for the south rather than Wednesday being rather chilly in that wind. I'm having trouble at the moment uploading graphs / maps etc . So please excuse my mistake☺

[Kirkcaldy Weather]

On 26/09/2022 at 19:56, Kirkcaldy Weather said:

Finally we are getting a bit of movement into phases from the MJO after a long period meandering around in COD, I know @Uncertainy had mentioned this a little (great minds   )

Its quite an exciting spell of model output at the min with this to end the 00z ECM  and GFS pretty closely agreeing 

The MJO is about to enter phases 4 & 5

and here are the composites for those phases in October

 

Blocking high extending from Scandi > Greenland with the low somewhere around the UK, I was thinking around Mid October to see those patterns as usually its around 2 weeks before the MJO phases transition into surface conditions tho sometimes can be a bit quicker or slower.

Really pleased with how this forecast has went especially from 19 days in advance  

The MJO has now progressed to phase 6   

Not a huge shift from our current pattern but we could have the flow coming from a North-Easterly direction and with conditions gradually getting progressively cooler / colder in that area (Scandinavia etc) it wouldn't be outrageous to suggest that air creeping toward the UK. October 27th/28th is when I'm looking for that pattern to take shape