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


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Thursday 20 August 500 mb anomaly update

Ec-gfs after showing a broad westerly for most of last few days both show SLIGHT indications of some ridging in the contours, this mail on ec, from the azores region, ec also reduces the flow strength more than gfs over the uk.

Noaa is much less enthusiastic about ridging at least away from the polar region, it has a much flatter flow atlantic into Europe than several days ago and it is easing down the strength from day to day.

Overall there is perhaps just the slightest sign, chiefly ec, of azores ridging starting to look a probable, say 35-45% as of this morning for the 6-10 day outlook in the upper pattern.

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

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

 

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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

Posted Images

The ICON 00Z also tries to restore Summery weather back over the UK towards the end of its run. Higher Pressure moving towards the UK from the South-West mid next week:

60A1D0FD-7912-4D88-A804-55B6D48BE317.thumb.png.522eb326e8850bf755ed2811b03adb8d.png88BDAA3D-6D6C-44F0-B59D-E06AE24EBC42.thumb.png.c8af1bb6731171b044c596037c30d974.png
 

There would probably be a spell of drizzle or light rain towards the far North-West with that Atlantic disturbance over Western Scotland, otherwise mostly dry and settled. 

@johnholmes Thank you, (and anyone else that uses them) for your useful analysis of the anomaly charts. Kinda hope the ECMWF continues to gain more momentum and that ridging becomes more and more influential over the next few days. Helped also by the NOAA anomaly charts to start picking up on ridging around our area. 

Edited by DiagonalRedLine
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20 hours 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.

Actually, on my newsfeed this morning i was commenting on the build up to the bank holiday a year ago.. i commented that the GFS and ECM were predicting heat, whilst imho the anomalies werent quite on board.. now that might be because they were playing "catch up" or more likely, my interpretation of them wasnt quite right! 😄

Hey ho, still learning and only experience will improve that!

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Regarding using the NOAA charts for signs of a change...

Obviously its something i do when im producing my own blogs, and using the 8-14 day chart for signs of where the next pressure rise could develop from does have a degree off success.

Over the last 6 months in particular its an area ive been exploring. Spotting the next potential ridging event by looking for early hints such as are being displayed on the current chart and as @wellington boot has illustrated above, is quite successful when the charts as he illustrated are consistent in their evolution. However, so far imho only 33% of these chances actually develop into a reasonable settled/or high pressure dominated pattern. the other 67% end up being short lived transitory ridges. Several attempts over the summer saw potential ridges collapse, due mainly i believe to a strong upper westerly driving through the weak ridge. Whether these ridges were weak due to low AAM i have no idea.

IMHO the current 8-14 day chart doesnt show any strong pressure anomaly, but does suggest shallow (?) troughing over the UK and a moderate westerly upper flow. As such this could develop or not, there is scope for further development or that upper flow may well be too strong to allow much of a pressure rise other then a transient ridge. Runs over the next few days should resolve this, of course.

 

814day.03 thurs.gif

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Longer term I’m certainly seeing some improvement, at least across southern parts of the u k...well, here is the evidence!!😜

30AD24A3-B106-4F95-8756-50296061CC5B.thumb.gif.5952f7acbbc2f310ffaf419252ce068f.gif01375938-BBBF-40F3-BDC6-B10FA19838FD.thumb.gif.ea43cda9d15d3ed9c86f4879e7e5624b.gif149714D2-09EA-4509-BC5E-3ACE00B38E18.thumb.png.165d055fe35d2d3795538549789daae9.png

 

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Continuing to follow developments on the ECM clusters for the turn of the month. It remains both hopeful and painful!! 27 out of 51 ensembles thrust a ridge over the UK by 1st September (which remains for the rest of the run), whilst 24 out of 51 flatten it into Europe

ec-ens_nat_z500scenarios_2020082000_300.

Not great betting odds!! I note, though, that the control run follows the more settled path, and the op run probably would have done too.

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2 hours ago, johnholmes said:

I hope we can keep these excellent inputs using differing models/methods into winter. It is really refreshing and good to see other ideas on what may happen without the yah boo we see so often in winter.

 

thanks folks, keep posting please.

itll be a waste of time on this thread John.. maybe if "knockers" thread (lol) was re-opened it would be worth it, where is he anyway? i miss his posts.. hope hes not poorly or anything..

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42 minutes ago, Kirkcaldy Weather said:

Possibly another storm next week, certainly worth keeping an eye on B46870F6-EBDA-4C0B-A23B-FE051591CAD3.thumb.png.1fa41a727bcf5ebe1cd7ae73d6ed5f67.pngFED92750-BAE3-496D-8B65-9B8EDB1CC5A8.thumb.png.2612978c18e59d05c601f51b4791f7c0.png

yep, is that a left exit from the Jet? image.thumb.png.882ff79c58e02dfe8d879088c5798073.png

 

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GFS produces another dartboard low, this time over the UK. It does seem overly fond of this type of chart around D6, but interesting none the less.

gfs-0-132.png?12

UKMO has a much more sedate low.

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One thing is consistent this evening almost all the models have a flat jet spearing across the Atlantic, GFS, ICON, GEM and co looks all ramped up pointing the jet straight at the UK for a good week or so. All the models also have another low moving swiftly west to east across the UK, needs watching as could cross the country in a deepening or mature phase. Summer going out with a whimper big time. 

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7 hours ago, JON SNOW said:

Longer term I’m certainly seeing some improvement, at least across southern parts of the u k...well, here is the evidence!!😜

30AD24A3-B106-4F95-8756-50296061CC5B.thumb.gif.5952f7acbbc2f310ffaf419252ce068f.gif01375938-BBBF-40F3-BDC6-B10FA19838FD.thumb.gif.ea43cda9d15d3ed9c86f4879e7e5624b.gif149714D2-09EA-4509-BC5E-3ACE00B38E18.thumb.png.165d055fe35d2d3795538549789daae9.png

 

my birthday crap though on GFS op, to me looks like a N'ly breeze, yuk

gfs-0-288.png?12

 

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Models quite different at T168 tonight, here ECM, GEM, JMA and GFS:

CB2C7B42-6E14-4B08-95EF-66FE9A070D00.thumb.gif.28ab8b190e5bbba85fe8892feb6ffc0c.gifB95032DA-E8EA-4C80-B5C6-309CC3131166.thumb.png.7aaa86f76aa991b63a8b3f98da2cf394.png64CDE3A6-6A91-4BB2-928A-672FB3491D3C.thumb.gif.bdae2df39df4473fb1563577fa17e41a.gif387E8779-F006-48BD-A9C4-769118AA97D4.thumb.png.3745677b830aa59c4bc35fc8b2188607.png

Apart from ECM there is some promise of improvement and settled conditions taking hold, GEM goes on to this at T240:

9AACB52F-70B0-40B8-A3FD-7277566895A5.thumb.png.8968c8d3c6e13bf9c1e3edd5b9e15dee.png

I guess it is a bit of a wait and see stage until the models get a grip on the way forward.  I certainly think there is at least a reasonable chance of a return to more settled and warm weather around the turn of the month...I think we will see the jet stream head north of the UK in September, if increased AAM permits, aided perhaps by the very warm waters around the UK after the last hot spell, compare SST  anomaly chart with the jet stream trajectory (yellows) on the GEM T240 above to see what I mean:

927044F6-0ECD-4FB9-B931-F06503E30B9F.thumb.png.3513c83afeaae60c0d3db995c1943af1.png

Edited by Mike Poole
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1 hour ago, mountain shadow said:

Horrendous ECM. Zonal from start to finish.

Certainly would be a fitting end to a dire Summer.

It’s amazing the difference between 2 areas , for me and I’m sure others it’s been a superb summer as I’m sure it’s also been dire for others  , Here May and June was superb, July not great but August back with a bang . Even today In between fronts on the coast at selsey it been clear with temps in the low to mid 20s . Anyway let’s hope the weather deliverers a late happy surprise for those that have gone  Without so far this summer . 

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29 minutes ago, Mark wheeler said:

It’s amazing the difference between 2 areas , for me and I’m sure others it’s been a superb summer as I’m sure it’s also been dire for others  , Here May and June was superb, July not great but August back with a bang . Even today In between fronts on the coast at selsey it been clear with temps in the low to mid 20s . Anyway let’s hope the weather deliverers a late happy surprise for those that have gone  Without so far this summer . 

The NW/SE has been even more focused on the SE than usual this summer. Even here June was poor bar 4 days, July while dryish, was windy and cloudy, August obvs decent for week. Not to mention the complete disaster on the storm front. Summer is maybe scrapping a 5 out of 10, and that probably skewed upwards by the memories of recent heat. 

Back to the models though, lets be honest ECM is pretty awful, numerous depressions and fronts crossing the UK leaving a very poor end to summer being the form horse, ties in well with the rest of the models IMO. 

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image.thumb.png.f56e4a051fec100910ea89ef49ae3758.png

Any tentative signs of an improvement by the very end of the month look to be canned for now. Any ridging looks transient as the Atlantic comes steaming back through. We may have to wait a while longer - summer 2019/2020 going out as it came in - with a whimper.

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Last one from me - both TD13 and TD14 are expected to intensify into hurricanes in the next few days and strike the Gulf states in the USA around the same time Tuesday.
Model uncertainty will massively increase with these systems injecting heat and energy into the mid-latitudes through next week.

image.thumb.png.51b29e0c34be1acfa0255b3e8ae6a4a2.pngimage.thumb.png.56efd2eabc99ce600b7d430bc28b89e3.pngimage.thumb.png.bda1d62b2dc902091dff0ef753e7b67b.png

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The dartboard low projected by the GFS yesterday has been adopted by all models now, so another wind watch looks likely for next Wednesday.

Further on, certainly the last couple of ops have not been on the settled side for the end of the month, but I think it's too early to rule out a very warm start to September. Last night's ECM clusters had 27 out of 51 members with a warm SW draw and a good height anomaly nearby to the SE (clusters 1 and 2) - it's only a 2/3 day affair but would be a noticeable improvement if it happened. 

ec-ens_nat_z500scenarios_2020082012_312.

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Quite a lot of weather entertainment for the coming week, perhaps a better day next Thursday according to the EC46.. Trends a little more unsettled after that though.. Still positive signs from last night's EC weeklies regarding September... High pressure looks to be in control, especially away from the far NW, this pattern could hold right through to mid month and possibly beyond.. All along way off, but the trend is our friend going on its current guidance. Enjoy your weekends, that's if you don't get blowed away.. 👍

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Keeping up with the ECM ensembles for the end of the month. In spite of the op run this morning, a very slight uptick in the number of ensembles pursuing the Azores High ridge idea:

ec-ens_nat_z500scenarios_2020082100_240.

Further into September, it's still a bit messy at first but I note by 5th September most ensembles are working towards a Euro ridge that builds far enough NW to encompass the UK, with signs on the anomalies that a mid-Atlantic high might join up with it over time. 

ec-ens_nat_z500scenarios_2020082100_360.

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17 hours ago, Mark wheeler said:

It’s amazing the difference between 2 areas , for me and I’m sure others it’s been a superb summer as I’m sure it’s also been dire for others  , Here May and June was superb, July not great but August back with a bang . Even today In between fronts on the coast at selsey it been clear with temps in the low to mid 20s . Anyway let’s hope the weather deliverers a late happy surprise for those that have gone  Without so far this summer . 

Agreed. Been a decent summer here. It's simply madness, however, to compare the summer in Surrey with that of Northern Ireland.

The climates of the two areas are so vastly different that it's an apples and pears scenario writ large. 

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