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Model output discussion - August hot spell - how hot, how long?


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On 18/08/2020 at 06:21, bluearmy said:

Looking way ahead, the last two eps clusters have raised height anoms across the Atlantic and w Europe at the back end of the past few runs which ties in with general EC46 continuity and consequently a pleasant start to September ......

 

16 hours ago, Man With Beard said:

ECM clusters - just for trends of course.

D14/D15 - be aware that the anomalies are matched against September averages from this point,

I realised my stupidity and came on to see!  Nice that no one took the opportunity to publicly berate me!

but it looks to be an improving situation once we get through the less summery period 

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Astonishing rebound in momentum transport that is behind the current spectacular synoptics and associated high impact weather. Both the heat, and also the powder keg potential for thunderstorms.

*** USING THE ECM TO FORECAST TEMPERATURES IN A HEATWAVE - A REVIEW *** I often make predictions based on models several days ahead, and then I find it useful to revisit these predictions after t

The reality is that NWP is wholly congregated on, but susceptible to be blindsided and over preoccupied by, the re-ignition of the low frequency tropical convective standing wave across Africa and the

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1 hour ago, bluearmy said:

 

I realised my stupidity and came on to see!  Nice that no one took the opportunity to publicly berate me!

but it looks to be an improving situation once we get through the less summery period 

Looks to be possibly improving a little at the very end of the month with a weak ridge:

image.thumb.png.44f04c75507f4814b385eea386fe801e.pngimage.thumb.png.470bfa0ec9fc72563cc28e39dcd7bbc2.png
 

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Morning Gang, I found a few early September peaches 🍑 in the GEFS 0z if a return to summery conditions is what you’re hoping for?...overall it’s a mixed bag but I do think a north / northwest / south / southeast split is the LONGER TERM form horse 🐴 currently which would mean predominantly more pleasant surface conditions eventually returning further s / se.🙂☀️

78E51AFE-D79C-4D8B-9FC2-358760928CD5.thumb.png.9a07f8c6b6b1f8f9fff61f9926a7652e.png3CF0C2AB-6A4B-4C68-8E33-9BBB2D6E6518.thumb.png.1d7ecaac65a808bfd0f9076e58d7624f.png7216BD2B-561A-411F-B465-363E8312B12C.thumb.png.72a1baa99b87aad43260b50fa7ede4da.png7D956ADF-4B5D-4061-AAA1-66A9D55FC497.thumb.png.c2fd883e9120dd00a2fe1a8f66b81185.png

Edited by JON SNOW
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10 hours ago, Mike Poole said:

Evening all!

As the medium term is dross, I’m focussing on T240 today.  Here’s the ECM, GEM, GFS and the JMA (T192):

9BE675E1-BA0F-41E5-B80B-F9E385FD8F34.thumb.gif.5dc94b4a3003a3fe52a3204b74cffd6c.gif1F00E34A-E08F-4942-BD4E-73085E2CEF41.thumb.png.d7a1ae4fc4d295e1fdf5087b1bd19133.png1CA0C00D-BD8C-469F-A3D4-529A8A3812A0.thumb.png.eb49aafcc199fd88a4baa0987a503e9b.png8D661CA3-7AAF-4297-92DC-3BD07549EDF7.thumb.gif.94e16fed7a51975a746cc6463a3a394f.gif

Tentative signs on ECM and GEM that a ridge may push across the UK at day 10, meanwhile the other two are not horrendous, anyway.  If predictions by many including me are for a settled September, worth noting the SST anomaly, here:

D39A6AA6-CBF6-4D8E-AD4A-F1A531E49FDB.thumb.png.3f126129d92616f1faf96e77cbbdb87c.png

Very warm all around the UK.  If settled conditions prevail early September, it will be an extension of summer, I think....

I do very-much hope that those warm SSTs will still be there, when the first NNE blast (with -14C T850s) makes its presence felt!:oldgrin:

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Nowt here to suggest any real sign of a pressure rise, its still suggesting a moderate/strong  westerly upper flow with troughing over the UK  for the next two weeks. Personally ill not be pinning any hopes of rogue charts suggesting high pressure returning to become dominant until these charts support it. I realise its not what most of us (including myself) would like to see, but the chances of these charts being far out are really very low IMHO.

I guess that IF theres any swing towards higher pressure becoming more dominant itll come off the Azores ridge building in the mid Atlantic as it approaches us, so future runs will be interesting to see if anything starts to develop in that area... after all, thats practically what happened when the recent high pressure dominated hot spell developed.

 

814day.03.gif

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10 minutes ago, mushymanrob said:

Nowt here to suggest any real sign of a pressure rise, its still suggesting a moderate/strong  westerly upper flow with troughing over the UK  for the next two weeks. Personally ill not be pinning any hopes of rogue charts suggesting high pressure returning to become dominant until these charts support it. I realise its not what most of us (including myself) would like to see, but the chances of these charts being far out are really very low IMHO.

I guess that IF theres any swing towards higher pressure becoming more dominant itll come off the Azores ridge building in the mid Atlantic as it approaches us, so future runs will be interesting to see if anything starts to develop in that area... after all, thats practically what happened when the recent high pressure dominated hot spell developed.

 

814day.03.gif

They don't at the moment, but as @Tamara says, it's unlikely at that lead time they'd pick a day to day signal up anyway.

image.thumb.png.92872fd5c7399e57a772379b77c064b7.png

This chart above doesn't exactly scream heatwave either, but it was very warm by the 5th (28c), and blisteringly hot by the 7th (36.5c). 

It wasn't until a few days later it really showed the amplified pattern that set up:

image.thumb.png.25ea6b27415721e774e1dc83a7d0eaee.png
 

Edited by mb018538
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59 minutes ago, mushymanrob said:

Nowt here to suggest any real sign of a pressure rise, its still suggesting a moderate/strong  westerly upper flow with troughing over the UK  for the next two weeks. Personally ill not be pinning any hopes of rogue charts suggesting high pressure returning to become dominant until these charts support it. I realise its not what most of us (including myself) would like to see, but the chances of these charts being far out are really very low IMHO.

I guess that IF theres any swing towards higher pressure becoming more dominant itll come off the Azores ridge building in the mid Atlantic as it approaches us, so future runs will be interesting to see if anything starts to develop in that area... after all, thats practically what happened when the recent high pressure dominated hot spell developed.

 

814day.03.gif

These are some of this morning's ECM clusters covering the period in the NOAA chart you've posted.

ec-ens_nat_z500scenarios_2020081900_192.  ec-ens_nat_z500scenarios_2020081900_240.  ec-ens_nat_z500scenarios_2020081900_300.  ec-ens_nat_z500scenarios_2020081900_336.

As a collective picture, they definitely back up your chart and your assessment.

If I try to assess them as individual frames, though, my sense is there's a bit more amplification in the pattern over the 8-14 day period than the NOAA chart suggests - it's just that over the course of the 6 days, the amplification gets averaged out due to the fast moving trough/ridge cycles.

Two additional points: First, the general trend I've been following still seems to hold - ridging towards the UK seems to be slightly on the up by the end of the period (the monthly change of anomalies slightly confuses) - however, clusters 1 and 2 on the T336 still prevent us from being too sure if the period of Atlantic is likely break. Second, clusters around D10 provide a little hope that the trend towards a UK ridge might possibly come a little earlier than previously shown.

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Afternoon all. Sorry for not posting in here for ages, I have been pretty busy in the storms thread over the past week and as there doesn't seem to be any action going on today, I thought about posting in here!

So, as others have mentioned, the outlook for the next 5 or so days doesn't look too good. There are signs on a few models that after 10 days it might warm up a bit and we could see something settled. Here is the 00z ECM @240:

634157045_ECM1-240(2).thumb.gif.ea8d93783b19eefc232c1d1c7d167961.gif

Not the best of charts if you live in the east but it's showing signs of weak ridging coming in from the west. It has uppers of 12c approaching from the west as well meaning that it won't be too hot. FI at this stage though.

Speaking of FI, take a look at this GFS chart @306:

gfs-0-306.thumb.png.b4dbf4c971a05ef8eb090acbf6c4eaae.png

The MetO's long range outlook suggests something much more settled and warmer as we head into September, so this could perhaps be one of the scenarios we end up on that month. I, personally, think that we will see a very sunny and warm September. But for now, it's up to watching the models...

Edited by Zak M
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1 hour ago, mb018538 said:

They don't at the moment, but as @Tamara says, it's unlikely at that lead time they'd pick a day to day signal up anyway.

image.thumb.png.92872fd5c7399e57a772379b77c064b7.png

This chart above doesn't exactly scream heatwave either, but it was very warm by the 5th (28c), and blisteringly hot by the 7th (36.5c). 

It wasn't until a few days later it really showed the amplified pattern that set up:

image.thumb.png.25ea6b27415721e774e1dc83a7d0eaee.png
 

Absolutely, which is why i said in the second paragraph to watch for signs of a pressure rise in the mid Atlantic off the Azores high. I believe that if theres a drift towards the next high pressure spell, itll first become evident there. Im not so sure about these charts not picking up on the day to day signal, they certainly did with the pressure rise youve illustrated above. Did things develop quicker then those charts suggested? well possibly, and they wont show "upgrades" under 6 days, these charts are not perfect all the time, but most of the time when they are consistent they are more often then not much closer to the eventual solution.

 

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The MetO's long range outlook suggests something much more settled and warmer as we go into the end of August and heading into the start of September,

 

Bit optimistic to me that Zak, the latest I've seen is this, out to Wed 16 Sept

Towards the end of this period, there are some tentative signs that high pressure could begin to dominate, especially across the south of the UK, with a return to more settled conditions.

 

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44 minutes ago, mushymanrob said:

Absolutely, which is why i said in the second paragraph to watch for signs of a pressure rise in the mid Atlantic off the Azores high. I believe that if theres a drift towards the next high pressure spell, itll first become evident there. Im not so sure about these charts not picking up on the day to day signal, they certainly did with the pressure rise youve illustrated above. Did things develop quicker then those charts suggested? well possibly, and they wont show "upgrades" under 6 days, these charts are not perfect all the time, but most of the time when they are consistent they are more often then not much closer to the eventual solution.

 

Can anyone link me to the NOAA charts between issues on 11-17 inclusive. I see m to have 'lost' my set of chart over that period-please?

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12 minutes ago, johnholmes said:

Can anyone link me to the NOAA charts between issues on 11-17 inclusive. I see m to have 'lost' my set of chart over that period-please?

https://www.cpc.ncep.noaa.gov/products/archives/short_range/srarc.ind.php

You can search for any anomaly chart from the last 20 years now! A great addition.

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1 hour ago, mushymanrob said:

Absolutely, which is why i said in the second paragraph to watch for signs of a pressure rise in the mid Atlantic off the Azores high. I believe that if theres a drift towards the next high pressure spell, itll first become evident there. Im not so sure about these charts not picking up on the day to day signal, they certainly did with the pressure rise youve illustrated above. Did things develop quicker then those charts suggested? well possibly, and they wont show "upgrades" under 6 days, these charts are not perfect all the time, but most of the time when they are consistent they are more often then not much closer to the eventual solution.

 

That was more my point - the longer range ones didn't look special, then a few days later as it began to get resolved better, it really honed in on that amplified height rise. So even if it's not showing much in the 8-14 day outlook, that doesn't mean that in the next 14 days you'll see nothing at all every single time. In this instance i'd say we won't see much before the month is out.

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Just now, mb018538 said:

That was more my point - the longer range ones didn't look special, then a few days later as it began to get resolved better, it really honed in on that amplified height rise. So even if it's not showing much in the 8-14 day outlook, that doesn't mean that in the next 14 days you'll see nothing at all every single time. In this instance i'd say we won't see much before the month is out.

we concur 🙂

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8 minutes ago, mb018538 said:

That was more my point - the longer range ones didn't look special, then a few days later as it began to get resolved better, it really honed in on that amplified height rise. So even if it's not showing much in the 8-14 day outlook, that doesn't mean that in the next 14 days you'll see nothing at all every single time. In this instance i'd say we won't see much before the month is out.

The 8-14 day charts are very often a 'toned down' version of the 6-10. In my experience they don't often show a major change, oddly enough, before the 6-10 does. No idea why.

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It seems that we are now looking ahead towards more typical UK pattern with transient Azores ridging interspersed with Atlantic weather fronts.

No real sign in the next 10 days of a return of settled weather and notable heat of recent times but there still lies the promise of some decent interludes between the rain bands from Azores ridging- as the 006z GFS shows for days 5/6 before the next low moves in.

120.thumb.png.94d634dcc3bc6a7852caadc90c4bbc16.png

It does look like the warmest and driest weather is favoured for the south and east as often the case in this pattern.

It has certainly been a mixed Summer for sure with plenty of interest for weather fans with extreme heat,thunderstorms and now the change to wind and rain off the Atlantic.

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5 minutes ago, mb018538 said:

9ECD51D5-EAD3-43BE-85E0-5F0BE1789B12.thumb.png.b152d720ca70b528cfbe40b4f9b486e9.png
84DE0C2E-A8DA-41B6-965E-2142EB5D0B1F.thumb.png.b39c745166ec0b9bf0f8be8a67237a8d.png

12z GFS has a remnant TS/Hurricane headed our way that wasn’t there on previous runs....it’s that time of year after all. MDR starting to get very active now:

1DB0D759-78C1-42B0-B922-AB9C6D9D34A3.thumb.jpeg.970ef0f435fa249ba62e67efba264991.jpeg

 

MDR? Please advise those of us not used to such terms. Many thanks Dave

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1 minute ago, claret047 said:

MDR? Please advise those of us not used to such terms. Many thanks Dave

Apologies - Main Development Region. It’s the area in the tropical Atlantic where most hurricanes and tropical storms begin their life as the easterly waves leave Africa.

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Again taking a look at the models at T240 to search for that glimmer of hope for summer lovers....here they are:

1C5A7882-A823-4A84-BC2F-85F3C2D1910A.thumb.gif.02e2645ad7c9d4f6ec1ad486650038b1.gif86EEF694-ACBD-4892-80A2-F4CADBAF5A1C.thumb.png.9f7ece9e6898917a4dd2855d9ec9a5bc.pngE3A160EB-6D73-4CF4-B1DF-51E2CAE14288.thumb.png.cc1c77f9c810852aab828db375942b1b.png7D9EC457-CF96-4705-A8C0-7F39C20A35A4.thumb.png.5f3b5258e2dcbe73a936b9f2c5451f6a.png

ECM and GEM have some suggestion that high pressure might move in in days from this, GFS not so, parallel GFS interesting as that second ridge looks to develop over UK later, T318:

4D55588E-8F67-4688-8D42-896C6EA51E7C.thumb.png.6c65b4f8f929c77901c478738b1bbbe4.png

I would not expect the op models to be that bullish about a settled start to September yet, but that is still what I think, tentative signs in the right direction today.  CFS AAM still very bullish:

38E73891-1065-4196-A108-79448B49AF7C.thumb.png.df378d6a529bbbd9a6cdb1f0157c8e23.png

We will see....

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On 18/08/2020 at 14:25, johnholmes said:

Well I must take issue with you re high pressure moving closer by the day.

I know it is each of our interpretations of these charts, as with any, but I cannot see what you suggest. Neither in the 6-10 nor the 8-14. In my view it is best to call the charts, what they are pressure charts at 500 mb, around 18,000 ft up in the atmosphere. Strictly speaking they are not what we usually refer to as 'pressure charts'. I think using that term it is too easy to suggest pressure at 500 mb will be what occurs at the surface; often it won't.

So having said that, the height rises and contours do not shows what you suggest wb in my opinion.

Just to show the charts, first the 6-10:- There is quite a marked, fairly rounded, trough over the UK, and over England and Wales this is quite strong, less so over Scotland. Any height rises are pretty small, over Greenland and Iberia. As an average over the 6-10 day period I would not expect much in the way of settled weather The contour height over mid England/Wales, 564 DM spends a fair amount of time well north of the UK so is not going to be 'warm' and thus neither is the surface temperature, as an average over those days.

https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Turning to the 8-14 chart and it shows even less in the way of any +ve height rises, again with a noticeable trough over the UK. The flow over the Atlantic has a hint, no more than that, of being diffluent. Diffluent flow in the upper atmosphere is a major factor in any surface features running into it to deepen quite a lot. So again, even without this effect, I don't see any real grounds for any change from the 6-10 day pattern. More unsettled than settled as the average and not warm really other than possibly the odd day with a passing surface ridge.

 

I'm not getting at you wb just using your comment to try and explain a little more about how to interpret these charts for new folk.

John

ps just noticed the post from mushy, no major differences with his comment

 

Apologies for the belated response to this. I obviously bow to your infinitely greater knowledge and experience, and I recognise that I probably exaggerated somewhat. I also realise that my language was sloppy, talking of high pressure and low pressure - it was a quick post in a snatched moment and unfortunately I wasn't clear. And "promising" was definitely an overreach...

Equally, to suggest that high pressure was moving closer was highly contentious. I was looking at the Greenland positive anomaly shifting slowly SE and at the Azores positive anomaly drifting slowly E towards Europe, but truthfully there was little to suggest significant and relevant height rises even by the end of the 6-10 day period.

With that said... I would defend my original comment up to a point. I observed at the time and still observe that the focus of the negative anomaly is shifting gradually towards the NE, while the extent of the negative anomaly over the UK seems to be gradually declining. It's not dramatic, but as you explained a few days ago, this is a five day average, so you would expect the changes day to day to be subtle most of the time. It seems to me there is a trend towards more average conditions at least.

I should add that I didn't mean to suggest settled weather was necessarily on the way within the 6-10 period itself, just that there was a trend in the right direction...

Here are the last 5 charts in order:
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The chart from the evening after my original comment (18th Aug) actually did me no favours, but given today's much better chart, I'm reasonably comfortable making my case above...

Edited by wellington boot
style!
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85D20A8C-9791-4C3A-8FFD-660CB5E67E20.thumb.png.fb63e7890e1c3b6b2171047595f82bff.png52A011B6-39E6-4A1C-8779-8C38D7652176.thumb.png.07e7e9ee226d61588d05168ade22d098.png945C27D8-86C8-43CC-B5EF-B54F96F05E80.thumb.png.48c02bbac04cf3c7936876a193a86c4b.png
 

Model runs starting to show the potential for another bout of gales/severe gales in around 6 days time. Needs watching again. Another unseasonably deep low could develop - not showing on the UKMO run however.

 

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