Model Output Discussion 00z 19/07/13

[nitro_deluxe]

If that comes off, 36C even above would be possible. Outer Hebrides just escaping the inferno...

Just to be fair, I do think that the western side of the Western Isles would probably have average temperatures in the following chart:

 

Recm1682.gif

[Uncle_Barty]

That is as much to do with human use of the models as it is to do with weaknesses in the models themselves. Some weather situations are more unpredictable than others ("flow dependence"). Some of the ensemble models gave a decent enough hint that a cut off 500hPa low would persist to the west, hence making an Atlantic breakdown more difficult. Although you say "I just knew that this......would take longer than forecast" and it verified, so well done. But this could also be achieved by interpreting the models (notably, the ensembles for a situation as uncertain as this) and using science and conceptual models (e.g. Omega blocks can be hard to break down).

You get the same result as "knowing", but the problem is there will one day be situation where you "know" something and get it totally wrong. Surely it's better to go with the science.  

 

A classic case of this was in January, when despite the model output being very bullish on a snow event from the west (not an undercut from the SW) even right down to the coast, I was 90% certain (based on experience) that we would only get rain or sleet on the coastal 10 miles or so. I was not the only one - I remember Old Met Man posting a similar opinion. Even the night before, dewpoints were still too high to support snow.

We simply don't get snow in these setups!!

I was asked the day before what I thought was the likelihood of snow and I said "10%". It was only that high because the models were so bullish predicting it.

 

What happened was that as the front moved in from the west, it engaged colder drier air off the continent and we did get snow in all areas bar the coastal few hundred yards as dewpoints fell low enough.

I have never seen that before in nearly 40 years of weather watching.

 

Often, instinct based on experience does work, but in exceptional circumstances you can get caught out.

This coming week may well provide more instances of this.....

[Mini tiger]

The 12Z ECM actually has 24-26 uppers reaching up into the UK. With 26-28 touching the Channel.

 

 

 

So surface temps in slack winds under sunny skies could potentially reach 106oF ?

[Cheshire Freeze]

WOW!! That would be pushing the high 30c mark with out doubt in the south and dare I say it but 40c would be in danger as well

 

Nowhere near 40C on the chart in question- getting carried away there. You have to account for the likelihood of a lot of cloud and downpours in that set up....an absolute thunder fest and temps widely 30-35C. For 40C to be breached you'd probably need 2-3 days to establish rather than a wham bam thank you mam type of thundery plume as shown.

Edited July 26, 2013 by CreweCold

[Weather-history]

WHOAH!! If this comes true, what a record breaking summer indeed.Hard to believe in the middle of June it was 14/15c in places and gushing down with rain.

I think histrionics and exaggeration are coming into play here, what is record breaking about this summer? Nothing: no temperature, rainfall nor sunshine records have been broken so far.We need to get grip with the facts and analyses here. Edited July 26, 2013 by Weather-history

[Milhouse]

The ECM mean in FI suggesting high pressure will be building from the south as next weeks low responsible for the potential plume slips away northwards. Average temperature likely.

[Cheshire Freeze]

I think histrionics and exaggeration are coming into play here, what is record breaking about this summer? Nothing, no temperature, rainfall nor sunshine records have been broken so far.We need to get grip with the facts and analyses here.

 

LOL exactly my point.

[nitro_deluxe]

Nowhere near 40C on the chart in question- getting carried away there. You have to account for the likelihood of a lot of cloud and downpours in that set up....an absolute thunder fest and temps widely 30-35C

Indeed. May as well shelve it lol...Let's see how it looks, next stop mid next week? Plenty of water to get under the bridge until then..for some quite literally.

[Summer Sun]

Latest model summary from Gibby

 

In Summary tonight it looks like after a few days of unsettled and cooler conditions early next week when sunshine, showers and even longer spells of rain are possible the common theme is for there to be a warmer phase lasting two or three days later next week. ECM has the most pronounced version of this event with a vigorous thundery outbreak likely for the South and East should it verify while the other models suggest a more moderate version of this event. Longer term the weather looks like turning cooler and changeable under Westerly winds, at least for a time though there are still some suggestions that High pressure could make a comeback later on into August

 

Full analysis as ever is here - http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Frosty.]

The Good news is tonight's Ecm 12z ensemble mean is not a million miles from that sensational operational run, overall, the synoptics are similar with a trough digging down to the southwest of the uk and high pressure building to the southeast across the near continent with hot sultry air being drawn up from france although the mega heat is slightly further east, the south & east have a few continental like hot and sultry days and nights with thunderstorms and hazy sunshine, a few slight westward adjustments to the pattern and it will be like jumping out of the frying pan and into the fire.

Edited July 26, 2013 by Frosty039

[Captain Shortwave]

Nowhere near 40C on the chart in question- getting carried away there. You have to account for the likelihood of a lot of cloud and downpours in that set up....an absolute thunder fest and temps widely 30-35C. For 40C to be breached you'd probably need 2-3 days to establish rather than a wham bam thank you mam type of thundery plume as shown.

Not sure whether this is relevant but surely we would have needed the heat to be fully entrenched to get the maximum values from charts like that. For example before 38.5C was recorded in August 2003, we had several consecutive days of 32C+  before we broke the record.

Saying that a post earlier said the ECM was showing little cloud in central/southern areas so I would say the south east could hit 34-36C. No record breaker but certainly a chance of conditions getting very hot. Even where I am would be pushing 30C with a SSW wind.

Of course the other excitement is the potential explosive activity which could dwarf tomorrows antics.

ECM mean gets the 16C isotherm onto southern coasts. What can I say. FIngers crossed because I'm sure many people on here like to walk on the wild side 

Edited July 26, 2013 by Captain shortwave

[cheese]

I think histrionics and exaggeration are coming into play here, what is record breaking about this summer?Nothing: no temperature, rainfall nor sunshine records have been broken so far.We need to get grip with the facts and analyses here.

Cannot speak for the nation as a whole but July 2013 will be one of our warmest months on record in this part of the world, and if tomorrows rainfall fails to deliver, one of the drier ones too. Sunshine is thoroughly unremarkable however and could easily end up below-average.

 

No records, but July 2013 will be remembered by me as one of the 'classics', similar to August 1995, but without the very high +30C temperatures. Just consistently very warm, with only two days having a max below 20C compared to 5 in August 1995 (including a max below 15C!).

Edited July 26, 2013 by cheese

[Duane S.]

The ECM is showing something rather extreme but plausible. Euro high coupled with prominent low pressure to the sw and then a formation of a small secondary feature off southern Brittany to help advect the silly temperatures right up through the British Isles.

 

I'm not sure it will challenge any actual temperature records but in terms of thunderstorms it would be extreme to put it mildly! If that came to fruition then the Daily Express headline of tomorrow will be more than justified.

Edited July 26, 2013 by s4lancia

[Cecil Hogmanay Melchett]

Im more interested in the ecm operationals idea of high pressure moving in at day 10,we saw this a coupe of days ago and the model backed away,hopefully this time the idea will be continued in subsequent runs.In teh meantime possibilty of a plume next wee with thundery potential.

After a scorching July the summer lovers have no complaints.

PS it was 22deg here today and has been warm and mainly dry all week,on the back of the 2 week heatwave earlier in july i think i'll take summer 2013 with open arms after the last few summers.

The ecm mean supporting the jet lifting north at day 9 and 10.

Edited July 26, 2013 by happy days

[Cheshire Freeze]

Not sure whether this is relevant but surely we would have needed the heat to be fully entrenched to get the maximum values from charts like that. For example before 38.5C was recorded in August 2003, we had several consecutive days of 32C+  before we broke the record.

Saying that a post earlier said the ECM was showing little cloud in central/southern areas so I would say the south east could hit 34-36C. No record breaker but certainly a chance of conditions getting very hot. Even where I am would be pushing 30C with a SSW wind.

Of course the other excitement is the potential explosive activity which could dwarf tomorrows antics.

ECM mean gets the 16C isotherm onto southern coasts. What can I say. FIngers crossed because I'm sure many people on here like to walk on the wild side 

 

We'd certainly be looking at some very wild weather conditions were it to verify at face value ala ECM 12z

[forecaster]

The EC ensemble mean shows Friday in a different light, which shows the level of uncertainty in this situation. 

 

Correspondingly, the EC ensemble mean 850hPa temperature is at least 8C (possibly up to 10C) colder over England when compared with the deterministic. At this stage it is safer to trust the ensemble mean, until they start to look the same.

 

[Methuselah]

The ECM is showing something rather extreme but plausible. Euro high coupled with prominent low pressure to the sw and then a formation of a small secondary feature off southern Brittany to help advect the silly temperatures right up through the British Isles.

 

I'm not sure it will challenge any actual temperature records but in terms of thunderstorms it would be extreme to put it mildly! If that came to fruition then the Daily Express headline of tomorrow will be more than justified.

It's just the previous 364 that have been complete and utter garbage... 

[Duane S.]

A classic case of this was in January, when despite the model output being very bullish on a snow event from the west (not an undercut from the SW) even right down to the coast, I was 90% certain (based on experience) that we would only get rain or sleet on the coastal 10 miles or so. I was not the only one - I remember Old Met Man posting a similar opinion. Even the night before, dewpoints were still too high to support snow.

We simply don't get snow in these setups!!

I was asked the day before what I thought was the likelihood of snow and I said "10%". It was only that high because the models were so bullish predicting it.

 

What happened was that as the front moved in from the west, it engaged colder drier air off the continent and we did get snow in all areas bar the coastal few hundred yards as dewpoints fell low enough.

I have never seen that before in nearly 40 years of weather watching.

 

Often, instinct based on experience does work, but in exceptional circumstances you can get caught out.

This coming week may well provide more instances of this.....

 

 

A good case in point. I remember it well and also could not for the life of me see an Atlantic driven W to E front produce snow down at such a low level, even with the fore-knowledge that it would be engaging with a low dewpoint continental airmass, all reasonable logic went out the window that day!

[Captain Shortwave]

The EC ensemble mean shows Friday in a different light, which shows the level of uncertainty in this situation. 

 

Correspondingly, the EC ensemble mean 850hPa temperature is at least 8C (possibly up to 10C) colder over England when compared with the deterministic. At this stage it is safer to trust the ensemble mean, until they start to look the same.

 

Very understandable given the fine line we walk here. Where over the past days models have shown 20C upper plumes only to be followed by a northerly at the same timeframe on the next run. One good thing is that the models are heading in the right direction, for example the ECM mean is a good 2-3 degrees warmer than the 00z suite.

[Weather-history]

The EC ensemble mean shows Friday in a different light, which shows the level of uncertainty in this situation. 

 

Correspondingly, the EC ensemble mean 850hPa temperature is at least 8C (possibly up to 10C) colder over England when compared with the deterministic. At this stage it is safer to trust the ensemble mean, until they start to look the same.

 

Matt Hugo on twitter concurs

"@Alexbweather - Got be said the 12z ECMWF Det model is a major warm outlier at 168hrs. Ensemble mean has 850mb temps of 12C in the South."

[Cecil Hogmanay Melchett]

Matt Hugo on twitter concurs"@Alexbweather - Got be said the 12z ECMWF Det model is a major warm outlier at 168hrs. Ensemble mean has 850mb temps of 12C in the South."

ECM mean also pushing the jet north long term hopefully subtle hints that things willl settle down nicely as we head through August.

[Strider]

It's just the previous 364 that have been complete and utter garbage... 

 

Why, was it very accurate this time last year too?!

 

But yeah, some extraordinary night time temperatures too, I certainly think there would be a good chance of that record going if ECM came off

[Tamara]

Next week is looking like a complex picture with the models having difficulty as to what happens with that weak troughing near the UK, the UKMO is a bit of a tease and I wouldn't put much faith on the detail past T96hrs.

 

Much depends on how much of a dig south occurs with the jet to the west of Iberia, as this bounces north further to the east it brings in tow some hotter uppers, its still impossible to say whether the Holy Grail of heat the 20c uppers line will make it into the UK.

 

Will be interesting to see what the ECM does soon, can that heat cross the Channel?

Yes, the chances imo of another plume scenario down the line seemed to have increased throughout the models nick  I mentioned yesterday or the day before, I think, the chance that a further heat low could develop in the pattern of troughs to the west digging far enough south to amplify heat this way and create a high level of instability and disruptive weather. On a personal level I don't welcome it all, tomorrow is problematic enough as it is, without an even more intense repeat in a weeks time, and this weekend there are not even unduly high temperatures involved...

 

The pattern this summer has shifted seismically really. From a significantly below average Spring and such a slow warm-up start to the summer with the seas around the UK anomalously cold,..who would have predicted this change around?

 

Edit: And that was taking into account the extreme heat on the ECM which looked over exaggerated

Edited July 26, 2013 by Tamara Road

[Man With Beard]

LOL exactly my point.

But has there ever been a 'verified' chart showing 24C uppers over the UK? Surely it would mean something outrageous? Need to double check but I'm fairly sure the hottest day in 2006 (36C) had uppers of 18C and was not preceeded by that many hot days before - 3 I think? Looking at ECM T120 / T144, that's 2 days that might get close to 30C before the T168 chart. Personally I think the plume will likely miss us to the east but 'if' that ECM chart verified exactly with reasonable cloud breaks, 35C is the very least I'd expect to get.

[NorthernRab]

Conversely I wouldn't take much for the real cool in the N Atlantic to push through.  Bottom line is things remain very finely balanced, so post after post heavily weighted to just one side of the coin will be misleading to many I'm sure. Will be interesting to see where ECM goes later, but still far more questions than definative answers at this stage.

 

I was simply stating that there's an awful lot of potential for built up heat on the continent