model discussion Model output discussion 11th July onwards

[mb018538]

Quiet and settled by day 7 on the UKMO run

[northwestsnow]

Huge changes on the 12zs...

Much much more HP involvement on offer.

[LetItSnow!]

4 minutes ago, Weather Enthusiast91 said:

As long as it doesn't bring 20+ Celsius temps, and we have some cold foggy nights then I am all for it!  

I love the cool crisp autumnal mornings/nights. 

You really need some oomph to get really warm weather in October. Under a slab of high pressure like the UKMO shows then I think days would be pleasantly mild/warm but nights would be chilly. Depends on cloud. Having said that, Octobers of 2014, 2015 and 2016 all delivered 22+C weather around Halloween, so I guess anything is possible!

[Frosty.]

The GEM 12z joins the more settled and warmer club, perhaps with the exception of the far nw/n?…quite a major swing towards settled on the 12z runs so far today beyond this unsettled / cooler spell! ️ ? 

 

[Methuselah]

Not that (for what it's worth) the GFS 12Z ends entirely without promise?

    

[mb018538]

18 minutes ago, LetItSnow! said:

You really need some oomph to get really warm weather in October. Under a slab of high pressure like the UKMO shows then I think days would be pleasantly mild/warm but nights would be chilly. Depends on cloud. Having said that, Octobers of 2014, 2015 and 2016 all delivered 22+C weather around Halloween, so I guess anything is possible!

Need a southerly wind and warm upper air. What’s currently modelled doesn’t meet those requirements, so while temperatures of 17-19c are pretty good for early October, it’s no heatwave. Could get some fog too with light winds.

[Methuselah]

1 minute ago, mb018538 said:

Need a southerly wind and warm upper air. What’s currently modelled doesn’t meet those requirements, so while temperatures of 17-19c are pretty good for early October, it’s no heatwave. Could get some fog too with light winds.

That scenario sounds just about right, MB!

[Mike Poole]

That low in the Atlantic that the ex-tropical storm gets wrapped up in almost gets cut off on the ECM at T120:

Extraordinary for a low in such a position at this time of year!  

Edited October 1, 2021 by Mike Poole

[Mike Poole]

This looks one seriously weird NH profile, ECM at T192:

Zero off the Atlantic towards the UK.  Zero.  

Strat vortex doesn’t seem to be taking off either, zonal wind plot from Stratobserve:

I understand that lack of a zonal pattern doesn’t mean settled, and can mean prolonged unsettled of course (like this week).  But all the models in this afternoon’s suite suggest to me the start of a prolonged settled spell for the UK from mid next week.  I still think ramifications are for a cold start to winter down the line, increased confidence, but further discussion of that better left to another day…we will see…

Edit: ECM T240!

I rest my case.  

Edited October 1, 2021 by Mike Poole

[sheikhy]

Massive massive changes tonight on the 12zs!!strong surge of high pressure from 120 hours onward!!!!hell its looks like the ecm is teasing a potential beast from the east at 240 hours !!!

[Frosty.]

Astonishing transformation between the 0z / 12z runs…this chart from the ECMWF 12z operational for example, chalk and cheese compared to the 0z…all of a sudden it’s got blocked and there is no northwest-southeast split here! …as I’ve said before though, when you get ex tropical storms in the mix it can play havoc with the models..that’s apparently happened today!  

 

[mb018538]

Crazy turn around for sure. ECM didn’t want to engage Sam with the jetstream a few days ago and kept things unsettled. Now it’s added the extra energy it’s shaken things up to such an extent that we’re going to go from an almost certain extended period of wind and rain to going back to the quiet stuff. Probably need a bit of a dry out after the next few days anyway!!

[northwestsnow]

EC joins the High pressure party...

Cold air flooding into NW Russia on the Eastern flank of the scandy high ...

 

[Uncertainty]

Wow. Weather forecasting is hard. Comparison of models from yesterday’s 168 vs today’s 144:

GFS Yesterday 

 

GFS today

 

GEM yesterday 

 

GEM today

ECM yesterday 

This one went on to prog 40+ hours of continuous rain in the NW

ECM today

The upper trough clears in time for the Atlantic trough (including the remnants of Hurricane Sam) to pump up the AH which bridges to the W Russian high. 
 

UKMO same story.

So why the about face?

Yesterday the models backed off from the MJO maintaining amplitude into Phase 5, today they’ve swung back a tad

Also, perhaps more pertinently, the aforementioned tropical troublemaker Sam is now clearly going to enter the Atlantic flow, sending Monday’s low through the U.K. and into Europe and leaving room for the ridge and associated warm air advection to build through the UK. 

 

Is this the end of the saga? I’d like to see a full set of runs support it tomorrow before calling it. But it’s a huge huge difference in surface weather for most of us and shows how tricky this period is too forecast when smaller vigorous tropical features interfere with the long wave pattern. Fair play to the Beeb long ranger which has emphasised the risk of this interaction giving a ridge as opposed to the cyclonic westerly we presumably would have had if said tropical feature didn’t exist.

Hence why this is a dark probabilistic art as well as a Science. Great model watching nonetheless…

[Mike Poole]

18 minutes ago, jon snow said:

Astonishing transformation between the 0z / 12z runs…this chart from the ECMWF 12z operational for example, chalk and cheese compared to the 0z…all of a sudden it’s got blocked and there is no northwest-southeast split here! …as I’ve said before though, when you get ex tropical storms in the mix it can play havoc with the models..that’s apparently happened today!  

 

Well yes, Karl, but it always has been blocked - for months - as I have commented many times recently, ex-tropical storms if they don’t hit the UK directly can and do promote a ridge ahead.  It happened in September and looks likely based on today’s run to be even more nailed on for a settled and possibly warm spell if the ECM is anything to go by.  This outcome was always on the cards with this unsettled spell and the tropical storm.  

Edited October 1, 2021 by Mike Poole

[Mike Poole]

This is quite a telling ECM mean chart at T144:

Settled (very) for the UK in 6 days.  And in that triangle lies what for the future…?  Very little from the Atlantic for our weather is my view…

Edited October 1, 2021 by Mike Poole

[damianslaw]

As others have said, quite abrupt changes in the models this evening, all courtesy of how they interact ex tropical storm Sam with the jetstream. All are showing the feature promoting a strong ridge ahead - and the jestream pulled away from the UK on a SW-NE trajectory far to our NW. 

Looking at the jestream profile, it looks quite messy longer term, suggestion it will loop in on itself, and strike through scandi, not surprised to see some of the longer range output suggesting heights eventually building NW, quite unusual, indeed very unusual for this to happen in October. It could be the models have it all wrong, and ex storm Sam fools them all.. but if the models verify as shown this eve, we will exchange the very disturbed conditions of now, much drier conditions, and feeling pleasant, but possibly chilly nights, before something more substantively colder possibly if we see the retrogression - relative to the time of year. Very interesting.

[johnholmes]

2 hours ago, Mike Poole said:

This is quite a telling ECM mean chart at T144:

Settled (very) for the UK in 6 days.  And in that triangle lies what for the future…?  Very little from the Atlantic for our weather is my view…

So this output from ECMWF this morning is not going to happen? I wonder!

http://www2.wetter3.de/Fax/00_ECMWF_ENS_p0_500hPa+144_240.gif

[Frosty.]

The GEFS 0z mean becomes much more settled / anticyclonic during the second half of next week away from the far NW, the Gfs 0z operational likewise, however, during the following week the Gfs gradually becomes more unsettled again, however, perhaps we would be looking at more of a northwest-southeast split with the fine weather continuing further SE?…as for temperatures, beyond this unsettled and cool spell, temperatures recover, becoming pleasantly warm by day with sunny spells and light winds but then a growing risk of overnight / early morning mist & fog and nights also feeling chilly, especially in rural areas. ️ ?  

 

[damianslaw]

42 minutes ago, jon snow said:

The GEFS 0z mean becomes much more settled / anticyclonic during the second half of next week away from the far NW, the Gfs 0z operational likewise, however, during the following week the Gfs gradually becomes more unsettled again, however, perhaps we would be looking at more of a northwest-southeast split with the fine weather continuing further SE?…as for temperatures, beyond this unsettled and cool spell, temperatures recover, becoming pleasantly warm by day with sunny spells and light winds but then a growing risk of overnight / early morning mist & fog and nights also feeling chilly, especially in rural areas. ️ ?  

 

Quite normal for Octobe- bit of anticyclonic fine weather especially further SE, and the traditional NW-SE split with most unsettled weather further NW. Word of caution 2021 has not followed the 'normal' default mind.. and I am expect wild contrasting output in model runs for period into mid October.

[Mike Poole]

10 hours ago, johnholmes said:

So this output from ECMWF this morning is not going to happen? I wonder!

http://www2.wetter3.de/Fax/00_ECMWF_ENS_p0_500hPa+144_240.gif

Fair comment, I guess.  I confess that I do tend to focus my attention primarily on the 12z suite unless there is something in the offing which warrants increased attention, as watching the models 4 times a day (in the case of GFS), you can sometimes tend to see more noise than signal.  

[mushymanrob]

4 minutes ago, Mike Poole said:

, as watching the models 4 times a day (in the case of GFS), you can sometimes tend to see more noise than signal.  

Which is why i view the anomalies, to filter out the distracting "noise"..

[johnholmes]

Hi Mike

I'm trying to find the output today for the ECMWF set of charts I showed, so far no luck.

[Frosty.]

The ECMWF 0z ensemble mean indicates the second half of next week onwards becomes more settled / blocked with the Atlantic floundering again, quite a benign / pleasant mid / longer term outlook for the majority,  perhaps the only exception being the far NW? ️ ?  

 

[Methuselah]

A very good GFS 06Z run today; what one might call a 'stonker'! But will the warm spell be long enough to guarantee a substantially above-average October CET?

    

    

    

Edited October 2, 2021 by Ed Stone