Model Output Discussion - Autumn arrives

[Djdazzle]

31 minutes ago, Wimbledon88 said:

Met Office going for a fairly standard very warm week here in the capital. Far from exceptional. As expected. 

The usual under-playing of temperatures. They are always below what actually transpites.

[MKN]

13 minutes ago, Djdazzle said:

The usual under-playing of temperatures. They are always below what actually transpites.

The original poster saying Standard lol.  they are forecasting nearly 2 weeks in London werby the capital doesn't fall below 26/27c I think that is a noticeable heatwave for the UK.

[Mike Poole]

30 minutes ago, kold weather said:

Just looking through the ensembles and man what a tough forecast to make, they really are all over the place past mid week. Some keep a real Atlantic driven flow and the heat blows away ENE into central Europe, resulting in perhaps slightly below average temps for the time of year.

Others as we know bring the upper low northwards which introduces very hot airflow, though to what extent the surface temps warm up depends on just how cloud laden such a flow could be, especially if the LP is more developed.

One trend that might auger towards the first option is the fact the models have been slowly trending weaker with the high pressure aloft, if that trend continues into the latter part of this pattern wouldn't be hard to imagine the heat never makes it. With that being said very much uncertain right now.

If I had to stick my neck out, I'd guess the north ends up with a more atlantic driven flow and much cooler, whilst the heat will creep far enough north to reach at least the far south for a 1-2 day period resulting in 35c somewhere next weekend before they too join a more atlantic driven pattern.

I agree it is a difficult one but I think I lean slightly the other way, the initial high pressure is right now taking hold over the UK and to the west, and my feeling is that some of the model runs allow this to relinquish its influence too quickly leading to the runs which show the Atlantic exerting some control.  

I would expect the initial high pressure to be a little more resilient into next week, and then regarding the plume the following week (or not) - well that is still anybody’s guess but I don’t see it disappearing from the model runs over the next few suites, more remaining a slightly odds against bet for anything really notable.

[MattStoke]

48 minutes ago, Ed Stone said:

It just goes to show how much our climate has warmed these past 50 years -- 1975 was considered exceptional at the time when 90F was recorded two days in a row, instead of once in three years! 1976 was of course an exception among exceptions!

It's also worth noting that next week hasn't happened yet!

Indeed. People saying a week of high twenties to low 30s isn’t exceptional, but a few decades ago it was. It used to be that some summers 30’C was never recorded. Now it occurs several times each summer (Every summer since 1993).

[ANYWEATHER]

1 hour ago, Ed Stone said:

It just goes to show how much our climate has warmed these past 50 years -- 1975 was considered exceptional at the time when 90F was recorded two days in a row, instead of once in three years! 1976 was of course an exception among exceptions!

It's also worth noting that next week hasn't happened yet!

You could likewise show how hot it was back earlier in the 20th century, 1911 was noted for its furnace heat longevity lasting into the first half of September, where back then in September the temperatures were still in the 90sf,  that was exceptional then unheard of now .....

[Frosty.]

Perhaps I’m whistling Dixie..    but by the end of the ICON 12z the heat is building to the south and is poised for round 2 for an even stronger surge of heat, at least across the s / se?…of course, the icon ends at T+180 and I think the potential interest is beyond that…anyway, just my opinion!

 

 

[Coopsy]

1 hour ago, Ed Stone said:

It just goes to show how much our climate has warmed these past 50 years -- 1975 was considered exceptional at the time when 90F was recorded two days in a row, instead of once in three years! 1976 was of course an exception among exceptions!

It's also worth noting that next week hasn't happened yet!

I’d have to challenge that. 

Its been common place to reach at least 30oC over the last century at least. In fact between 1932 and 1957 it reached 30oC every year. With almost every year breaking the 32oC, 90oF mark as well.

Over the last 120 years it’s reached 30oC 87% of the time.

 

Edited July 8, 2022 by Coopsy

[Methuselah]

1 minute ago, Coopsy said:

I’d have to challenge that. 

Its been common place to reach 30oC over the last century at least. In fact between 1932 and 1957 it reached 30oC every year. 

Over the last 120 years it’s reached 30oC 87% of the time. 
 

But 90F is 32C, not 30!

[Coopsy]

3 minutes ago, Ed Stone said:

But 90F is 32C, not 30!

I thought you’d mention that. That wasn’t my point though. I’ve edited it for extra content. 

[Methuselah]

24 minutes ago, ANYWEATHER said:

You could likewise show how hot it was back earlier in the 20th century, 1911 was noted for its furnace heat longevity lasting into the first half of September, where back then in September the temperatures were still in the 90sf,  that was exceptional then unheard of now .....

But it never exceeded 100F, did it? And, it was only one year out of 100 years, if it did? TBF, I recall an old record of 100.5C from that year, but I'm not sure whether it still stands. Or was it late in the 19th Century I lost my book of old records about 50 years ago!

PS: We are wandering off-topic.

Edited July 8, 2022 by Ed Stone

[kold weather]

Hot on the 12z GFS for Tuesday and Wednesday. Whilst the model has been very progressive ab out what happens later in the week it has been pretty consistent in raising the temperatures bit by bit over the mid week period, now forecasts a 34c on both days, and you'd imagine a 35c might be possible based on that.

[Guest]

GFS 12z for Wednesday, again keeping many places hot for another day. Note the 35C across a wide area in the SE.

That is notable, and far from standard.

[sheikhy]

Just now, kold weather said:

Hot on the 12z GFS for Tuesday and Wednesday. Whilst the model has been very progressive ab out what happens later in the week it has been pretty consistent in raising the temperatures bit by bit over the mid week period, now forecasts a 34c on both days, and you'd imagine a 35c might be possible based on that.

Hows ukmo for same time?!!

[Guest]

ARPEGE also showing 35C on Tuesday. That might prove a couple of degrees too high - didn't it do similar for the previous bit of heat we had? Still, even if that translates to 32/33C peak on Tuesday we are seemingly seeing the first blast of heat undergo slight upgrades as it enters hi-res range. 

Edited July 8, 2022 by Steel City Skies

[Guest]

5 minutes ago, sheikhy said:

Hows ukmo for same time?!!

Heat not as intense on Wednesday, restricted to the far south by Thursday.

[Scorcher]

33 minutes ago, ANYWEATHER said:

where back then in September the temperatures were still in the 90sf,  that was exceptional then unheard of now .....

'Unheard of' since 2016 you mean? 

[Guest]

No plume then on this run? With that low so close we don't see that really intense heat push successfully to the UK. Over-progressive GFS or a new trend to lift the low more quickly into France then BENELUX? Imagine the storms there!

That being said, that weekend still has widely settled and hot conditions SE of the common NW/SE split line with 27-30C widely.

Edited July 8, 2022 by Steel City Skies

[kold weather]

So the GFS remains very progressive indeed post Wednesday with the upper low near Iberia getting rapidly absorbed into the broader flow and sweeping NE before it ever allows us to engage with any sort of heat and leaves us in a warm flow, with the south remaining above average, but the north always at more risk of fronts. 

The GEM meanwhile keeps the Iberian low westwards and doesn't appear to be absorbed intothe flow nearly as rapidly which keeps the ultra heat still possible.

UKMO looks like a fusion of the two, the LP does get into the flow but appears to be slower in doing so than the progressive GFS.

[kold weather]

1 minute ago, Steel City Skies said:

No plume then on this run? With that low so close we don't see that really intense heat push successfully to the UK. Over-progressive GFS or a new trend to lift the low more quickly into France then BENELUX? Imagine the storms there!

That being said, that weekend still has widely settled and hot conditions with 27-30C widely.

The GFS is the only run thus far to be anywhere near as rapid it is.

Even if the trend were right, its highly likely going to be 24-48hrs too fast in that pattern as is per normal when the GFS tries to flatten out things.

This far out though any option still on the table for sure, and at least in the reliable time frame the heat on Tuesday does seem to be getting a little stronger.

[Captain Shortwave]

The UKMO will probably be good enough for 30c+ from Birmingham southwards on Wednesday. 

GFS even hotter with 30c likely from the Bristol Channel to around York with 34c or even 35c across the south east.

I will take that at the moment.

[kold weather]

So upon looking at the models the key time appears to be at 120hrs. On the 12z GFS the cutoff low gets absorbed into the broader flow caused by a small upper trough feature that moves to the south of Iceland W-E which allows the upper low to lift out.

These cutoff lows are an absolute mare to forecast because if the models get even a small amount wrong (say if the upper high is a little stronger, or the upper trough a little weaker) it can in terms of real world weather by the difference between 23c in London and 40c in London down the line.

Expect the GFS ensembles to be a bit of a mess post Wednesday as they struggle to resolve this feature. My guess is though the GFS OP will be one of the more progressive in the suite in terms of how rapidly it brings it NE. 

PS - a more progressive movement MAY allow for a hotter Tues-Wed period instead as per the 12z GFS op. Your effectively trading a smaller risk of extreme heat for a higher risk of very hot, but not quite as extreme temps.

Edited July 8, 2022 by kold weather

[Fourty Point Three Degrees]

and we're quickly back to life and back to reality 

 

[ChannelThunder]

UKMO at day 7.

A plume vs Atlantic kind of stand-off. Come on plume, you can make it...  

[Guest]

9 minutes ago, 38.7°C said:

and we're quickly back to life and back to reality 

 

Not when it's nearly two weeks away we aren't. It'll be different by the 18z given the range.

[kold weather]

6 minutes ago, Steel City Skies said:

Not when it's nearly two weeks away we aren't. It'll be different by the 18z given the range.

Besides shortly after another ridge is thrown in and we go back into a warm and dry pattern again as we have at the moment...

Ensembles are, as expected, abit of a mess with alot of varying solutions in there it has to be said. Alot are still bringing up some pretty impressive heat, though some are now looking very progressive indeed with that cutoff low (as I said previously, just would mean a warmer Tues-Wed and cooler relative afterwards)

Also increasing chance the far south stays in the hot air past Wednesday.

 

Edited July 8, 2022 by kold weather