Model output discussion - first hot, thundery plume of the summer

[feb1991blizzard]

3 minutes ago, h2005__uk__ said:

Where can I see the UKV model please? Had a look but can't find it.

This is it.

https://www.metoffice.gov.uk/public/weather/forecast/map/gcp19y6c9#?map=Rainfall&fcTime=1561777200&zoom=5&lon=-4.00&lat=55.01

You'll have to subscribe somewhere to get the full data set though with uppers, humidity etc though, why an earth you can subscribe somewhere else to get a dataset sold by the UKMO and not to the UKMO is beyond me though.

Edited June 28, 2019 by feb1991blizzard

[shaky]

Very good development this morning on regards to the ampliification showing in the atlantic around the 144 to 168 hour mark!!!much flatter and therefore more ridging over the uk!!ecmwf is an improvement as well as the ukmo!!

[bradymk]

Now I might well be wrong here come Saturday however since we were introduced to Weather.us for Model data which has access to euro4, I have noticed that the parameter “corrected temperature 2m” is usually more accurate for my location, particularly for scenarios like this, than the standard Air temperature 2m parameter. 

If you look at Saturday with this parameter, a 37c is shown North London (chart attached). Saturday has become hotter on Euro4 each run so far.

Just to see how accurate this is, in Cardiff it has 29c for today at 5pm whereas the normal standard parameter has 26c. Therefore let’s see later how it does here later and if indeed it is closer to the mark. Interestingly Metoffice have 29/30 in their video forecast for here, but 26c on their computer generated forecast on website.

I don’t know what the difference is or what is taken into account in the corrected temperature, perhaps someone else may know but a link below.

https://weather.us/model-charts/gbr-hd/united-kingdom/temperature-2m-corr/20190629-1500z.html

 

Edited June 28, 2019 by bradythemole

[northwestsnow]

6 minutes ago, shaky said:

Very good development this morning on regards to the ampliification showing in the atlantic around the 144 to 168 hour mark!!!much flatter and therefore more ridging over the uk!!ecmwf is an improvement as well as the ukmo!!

Yes shaky- UKMO/EC det look OK this morning, no heatwave but mainly dry next week away from the far NW?

With the amount of blocking highs across northerly latitudes i think we can count ourselves a little fortunate if we manage to duck any troughs appearing at mid latitudes in response to this abundance of the blocking to the north.

I would take EC det with open arms if i'm honest,tho  i'm still not convinced the pattern for the 1st week in July is 'nailed' yet.

[northwestsnow]

EC mean looks very benign - no sign of any troughing becoming established so a pleasant outlook after the heat today/tomorrow, perhaps a more traditional NW/SE split with the SE having the warmer temps....

Certainly if a lived near the South/South east i would be expecting a settled dry and warm spell to usher in July.

edit looking at UK RAW data  this backs up the above nicely with temps in the low to mid 20s broadly speaking out to the 11th july in the SE.

Edited June 28, 2019 by northwestsnow

[knocker]

A couple of nights ago the 850mb temp (28.7C) at Bordeaux exceeded the previous record temp by a wide margin. Note the DALR from 900mb >500mb indicating air transported from the Sahara

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

7 minutes ago, knocker said:

A couple of nights ago the 850mb temp (28.7C) at Bordeaux exceeded the previous record temp by a wide margin. Note the DALR from 900mb >500mb indicating air transported from the Sahara

Pretty impressive! Any idea what the uk 850mb record is/was?

[knocker]

4 minutes ago, RAIN RAIN RAIN said:

Pretty impressive! Any idea what the uk 850mb record is/was?

Afraid not but I would imagine we must come close to it over the next couple of days, Of course there are only two designated upper air stations left in the UK so no guarantee of any widespread coverage

[Frosty.]

Looking at the models it's a pretty decent outlook, especially further south, a few cooler changeable blips but predominantly fine and pleasantly warm, perhaps warmer mid 20's c at times further s / se.

[Derecho]

42 minutes ago, RAIN RAIN RAIN said:

Pretty impressive! Any idea what the uk 850mb record is/was?

In the SE UK (52N / 0W) the top ten daily means (left) and bottom ten (right) are as follows up to 2014:
            

This spell of weather looks set to smash the record which just goes to show what a lost opportunity this was though we may see something notable tomorrow.

 

[Interitus]

16 hours ago, Man With Beard said:

A calculated guess! I won't clutter up the thread with more charts but here are links to charts from earlier in the week that explain my thinking; first, the GFS from Monday 00Z, looking at cloud/precipitation - it's pretty clear the air that is in the North Sea today went through the Iceland region 2 to 3 days ago (you can see this from the cloud movement and the sheering-off from a line of cloud moving between Iceland and Norway as it bends around the high). Upper and lower air was pretty cool at that time, between 0C and 10C except in local spots in Iceland itself.

Now, the EURO4 from 48 hours ago (link below), looking at the 950hpa air temperatures. On Tuesday, North Sea air at this level was 15-20C, well above normal. If you look through the timeframes, you can see an area of 5C working its way from the Faroes down to the North Sea close to Northumberland. Quite a big drop within 24 hours. Highly unlikely that North Sea itself is going to behind all this cooling, since it is at 12C more or less, and highly unlikely to be the air above, which doesn't drop to 5C at any time. It must be down to where the air was coming from.

Good and reasonable analysis, there was indeed a cold pool of air that moved from the Icelandic region, it's just that the motion of air parcels tends to be so complicated that there should be caution when relating temperatures to a direct source of SSTs.

For example, here is the GFS 3 day backward trajectory plot of air at 640m asl for a matrix of points across the southern North Sea area to 27/06 00z using isobaric motion -

This motion is pretty much as would be expected by eye, the air follows the isobars and remains at the same height. Temperatures were between 5-7 degrees probably in the Faroes region where the trajectories converge before uniformly warming to 11-13 over the southern North sea. Prior to this though there is quite a scatter of temperatures from the source regions, with also some surface warming over ground in Iceland.

However, this assumes that the air parcels remain at the same height ignoring vertical motion which can be examined using the model vertical velocity -

This gives a wider source area, but none of the air parcels originate near the surface, ranging from roughly 1400-4000 metres asl.

Motion largely follows isentropes of potential temperature so finally here is the isentropic analysis -

This gives a range of source altitudes from near surface to 2000 metres though all reach above 1000 metres where the trajectories converge. The caveat with this adiabatic approach however is that ignores significant diabatic effects from eg condensation, precipitation, strong insolation, mixing etc and can have problems with discontinuities across frontal boundaries.

Trajectory plots courtesy NOAA Hysplit - https://www.ready.noaa.gov/HYSPLIT.php

[Man With Beard]

2 hours ago, bradythemole said:

Now I might well be wrong here come Saturday however since we were introduced to Weather.us for Model data which has access to euro4, I have noticed that the parameter “corrected temperature 2m” is usually more accurate for my location, particularly for scenarios like this, than the standard Air temperature 2m parameter. 

If you look at Saturday with this parameter, a 37c is shown North London (chart attached). Saturday has become hotter on Euro4 each run so far.

Just to see how accurate this is, in Cardiff it has 29c for today at 5pm whereas the normal standard parameter has 26c. Therefore let’s see later how it does here later and if indeed it is closer to the mark. Interestingly Metoffice have 29/30 in their video forecast for here, but 26c on their computer generated forecast on website.

I don’t know what the difference is or what is taken into account in the corrected temperature, perhaps someone else may know but a link below.

https://weather.us/model-charts/gbr-hd/united-kingdom/temperature-2m-corr/20190629-1500z.html

 

Absolutely brilliant spot! I also note that we can see past runs too. Here's yesterday's 12Z. Perhaps people could look and see if the 4pm temperature matched up with official readings from yesterday:

https://weather.us/model-charts/gbr-hd/2019062712/england/temperature-2m-corr/20190627-1600z.html

My sense at a quick glance is that it overstated temperatures in some spots (close to me, Gosport had 25C but the model said 26C, Southampton had 23C but the model said 27C - oops!!). Might explain the Met Office errors if they've been following this and it has been too high.

[Man With Beard]

6 minutes ago, Interitus said:

Good and reasonable analysis, there was indeed a cold pool of air that moved from the Icelandic region, it's just that the motion of air parcels tends to be so complicated that there should be caution when relating temperatures to a direct source of SSTs.

For example, here is the GFS 3 day backward trajectory plot of air at 640m asl for a matrix of points across the southern North Sea area to 27/06 00z using isobaric motion -

This motion is pretty much as would be expected by eye, the air follows the isobars and remains at the same height. Temperatures were between 5-7 degrees probably in the Faroes region where the trajectories converge before uniformly warming to 11-13 over the southern North sea. Prior to this though there is quite a scatter of temperatures from the source regions, with also some surface warming over ground in Iceland.

However, this assumes that the air parcels remain at the same height ignoring vertical motion which can be examined using the model vertical velocity -

This gives a wider source area, but none of the air parcels originate near the surface, ranging from roughly 1400-4000 metres asl.

Motion largely follows isentropes of potential temperature so finally here is the isentropic analysis -

This gives a range of source altitudes from near surface to 2000 metres though all reach above 1000 metres where the trajectories converge. The caveat with this adiabatic approach however is that ignores significant diabatic effects from eg condensation, precipitation, strong insolation, mixing etc and can have problems with discontinuities across frontal boundaries.

Trajectory plots courtesy NOAA Hysplit - https://www.ready.noaa.gov/HYSPLIT.php

Brilliant @Interitus - fantastically complex then. Bookmarked the links!! 

The great thing about events like these are that they stretch our understanding of weather forecasting. I bet there's plenty of us who will never see the 850hpa temperatures as the "ultimate guide" again.

[MATTWOLVES 3]

Much more positive 6z for me... Low pressure much further NE, with high pressure having more influence on preceedings. Perhaps the models now making the Eastwards corrections. 

Edited June 28, 2019 by Mattwolves

[knocker]

28 minutes ago, Man With Beard said:

Brilliant @Interitus - fantastically complex then. Bookmarked the links!! 

The great thing about events like these are that they stretch our understanding of weather forecasting. I bet there's plenty of us who will never see the 850hpa temperatures as the "ultimate guide" again.

Which begs the question why they were considered the "ultimate guide" in the first place

[Methuselah]

Goodness me, what a spiffing chart! Come to Daddy?

  

[knocker]

Some Ci and Ac and ragged Stratus creeping in down here

[northwestsnow]

GFS 6z contiuning the dry theme for the first week to 10 days of July..

Benign, best way to describe the outlook after the heat imo.

 

[MATTWOLVES 3]

3 minutes ago, Ed Stone said:

Goodness me, what a spiffing chart! Come to Daddy?

  

Our worse winter nightmare all over again pete....the big bad Nthly being shunted East or completely vanishing as we move nearer the time!

[northwestsnow]

2 minutes ago, Mattwolves said:

Our worse winter nightmare all over again pete....the big bad Nthly being shunted East or completely vanishing as we move nearer the time!

Indeed,  the only issue for those wanting heat is the low pressure will hamper the azores high getting far enough east to drag in hotter air from the south.

We could end up in a scenario were the south west in particular could be best bet for any warmth, nearer to any High pressure to our west/south west.

[MATTWOLVES 3]

3 minutes ago, northwestsnow said:

Indeed,  the only issue for those wanting heat is the low pressure will hamper the azores high getting far enough east to drag in hotter air from the south.

We could end up in a scenario were the south west in particular could be best bet for any warmth, nearer to any High pressure to our west/south west.

Yeh good point NWS, its very much still an evolving situation. One thing of note at this stage is..... We would be very unlucky to return to a scenario of early June! For me this likelihood is receding bit by bit. 

[Frosty.]

I feel the 6z operational is still under cooking the maxima on saturday for the SE.. showing 31c with a small core of potentially 32c when in reality 34 to possibly 35c in the hottest spots is achievable.. Heathrow anyone! 

Edited June 28, 2019 by Jon Snow

[StormChaseUK]

15 minutes ago, Jon Snow said:

I feel the 6z operational is still under cooking the maxima on saturday for the SE.. showing 31c with a small core of potentially 32c when in reality 34 to possibly 35c in the hottest spots is achievable.. Heathrow anyone! 

Cardiff will be a good marker today.  If Cardiff can hit 30C then I see now reason London cant hit 34-35C tomorrow.

[Frosty.]

11 minutes ago, StormChaseUK said:

Cardiff will be a good marker today.  If Cardiff can hit 30C then I see now reason London cant hit 34-35C tomorrow.

NW Highlands could hit 30c 86f this afternoon. Plumetastic for parts of scotland!

[Mandrake]

20 minutes ago, StormChaseUK said:

Cardiff will be a good marker today.  If Cardiff can hit 30C then I see now reason London cant hit 34-35C tomorrow.

I think Cardiff will not see 30C today judging from live data see map (12:45) however I would suggest somewhere like Exeter or Bristol are more likely to reach 30C today