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


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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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And from the 500 mb anomaly charts

Sunday 30th

All 3 now show some sort of +ve height rises w of uk over atlantic

Ec-gfs with ec showing a more substantial rise giving a flow n of w into uk, and both show troughing into Europe

Noaa also shows the +ve heights but less than ec and this gives about a w’ly into the uk with slight troughing only over the uk into Europe

All 3 suggest a coolish and rather changeable/unsettled 6-10 days coming up with the 8-14 carrying this on, possibly a touch more in the way of height rises. The usual caveat at this time of year=tropical storms/ex hurricanes will not show on these mean charts and if they do occur will cause havoc with all models and all time scales.

Nothing to me suggests any outlook for warmth or indeed more than the odd settled day or two under any transient surface high.

Another 2-3 days may give a better indication of any movement in the positions of troughs and ridges which could affect the surface weather from that suggested above.

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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10 hours ago, Mike Poole said:

ECM mean 12z here, T168 and T240:

43FE15CD-225E-460D-A52B-40098670EC9A.thumb.gif.620bf7e4784c6f4167aea9b69b6e5dca.gif92477041-BE5D-4F41-97D5-3205A5E0A854.thumb.gif.27a9f1d95077166c63ecf1848440a595.gif

This would strongly suggest that the ridge in the Atlantic would build over the UK over the next 10 days, with 1020 over most of UK at day 10.  Clusters will tell us more I would think...

And this morning, Mike, the GFS goes from this at +240h:

F5D88BC6-9D46-4B5B-A31A-30DF3D9D88AC.thumb.png.1bab6c12c8e06263997900b2c8d60f68.png

to this at +306h:
87B88AAB-C1A6-424D-B7C9-BD3D186618F2.thumb.png.9c01acca80ca8422cdb691569fde4190.png

Far too early to place any bets on this pattern but if it continues to show over the next few days the early September settled spell could prove to be short-lived.

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14 hours ago, Zak M said:

12z GEM shows severe thunderstorms breaking out across S England on days 8 and 9

gemeuw-2-204.png

What, severe thunderstorms in both the Cone & the Triangle?:shok: :oldlaugh:

But I did find one crumb of comfort...the tentative suggestion of height-rises away to the northeast...I know, it's at T+384, but...?

h500slp.png    h850t850eu.png

And the GEFS 00Z ensembles look substantially more appealing than the GFS op:

t850Bedfordshire.png    prmslBedfordshire.png

t2mBedfordshire.png    prcpBedfordshire.png

Who knows!:oldlaugh:

Edited by General Cluster
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Not quite an air frost anywhere last night, butnot far off. Models showing a changeable start to September, signs of something a bit more settled by next weekend with low pressure further north and azores high ridging northwards. Longer term may see a few days of settled conditions with heights building through UK and transferring eastwards, but at this time of year with expected tropical storm activity would not be surprised to see them shunted away quickly with the downstream trough anchoring it's way in. 

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Actually I'm getting more confident we will see another settled spell after next weekend, at least a short one. The ensemble means at D8/D9 are not conclusive but they certainly lean on the settled side. (Maybe less so for the north on the gets)

gens-21-1-216.png

EDM1-216.GIF

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I really like the way the ECM 0z is trending from a settled point of view, here’s the day 10 mean and op respectively..lovely stuff!!!!😜☀️..indeed I have drank to this..drunk actually..a tad early but I am an alcoholic..at weekends!!!!!!!..hiccup:shok:😉:drunk:

CD47FBA7-1AFC-45AD-A997-70F4D941AC93.thumb.gif.e03e488f90f8d44fa20ed9f2115165ac.gif0B2730B8-73D0-44EA-BC50-3A8FE36F4533.thumb.png.9c07da3b7308e2aba212edd8d7bd273a.pngEA6DF0C6-C493-48CE-9E83-4C50ADB6E5D8.thumb.gif.ae9299fe0ad2b8a086982e397d2717a0.gif

Edited by Jon Snow
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Quite a few tropical disturbances modelled over the Atlantic over the next fortnight ......that’s never a good sign for nwp reliability ....

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11 minutes ago, Jon Snow said:

I really like the way the ECM 0z is trending from a settled point of view, here’s the day 10 mean and op respectively..lovely stuff!!!!😜☀️..indeed I have drank to this..drunk actually..a tad early but I am an alcoholic..at weekends!!!!!!!..hiccup:shok:😉:drunk:

CD47FBA7-1AFC-45AD-A997-70F4D941AC93.thumb.gif.e03e488f90f8d44fa20ed9f2115165ac.gif0B2730B8-73D0-44EA-BC50-3A8FE36F4533.thumb.png.9c07da3b7308e2aba212edd8d7bd273a.pngEA6DF0C6-C493-48CE-9E83-4C50ADB6E5D8.thumb.gif.ae9299fe0ad2b8a086982e397d2717a0.gif

Getting to that time of year where it would be still warm by day but under that sort of high pressure some cold nights are to be expected!

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The GEFS 6z mean certainly has an air of respectability about it for a time in terms of pleasant surface conditions, especially across southern u k so it’s certainly not all doom and gloom during most of early September!!!😉..in the meantime, we have an improving Bank Holiday long weekend as a ridge builds in from the west bringing more in the way of sunshine and light winds but a few chilly nights..a gentle reminder that we are on the cusp of the meteorological autumn!:shok:😁 🥶 🍂 

B381588A-AD28-4FA7-A435-83929A385605.thumb.png.29b0ce2178e5a3fcb7b14e40d424ce0e.png0678DC9E-ECA5-408F-8544-03776E01CD39.thumb.png.b2adf3c056b6f00cb3878e272f3041f9.png998BD7F3-DAE0-49F1-92F4-15EC58CB5569.thumb.png.0479a35bcad02ea62e059c9625717010.png

Edited by Jon Snow
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Looks to me like a bit more consistency on a settled spell beyond next weekend on the 12s. 

ICON T180:

4FEE261F-9E94-48CA-B39E-2EB0112DB696.thumb.png.ce730b16d95966ccd8457db530b1b1e2.png

GFS T204, and the parallel 6z at same time T210:

19F983B1-36AE-4BA8-976C-2A711D37BB4B.thumb.png.be60690197b3b2cb7b1170bd6bf3ff3e.pngE35E9E41-C516-484C-88A0-5227982C7862.thumb.png.aa0239843f2dc4d125ecce3d129bf329.png

How warm is not in any way a done deal, but high pressure close to UK looking the form horse now, this would be hardly unusual for September.

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10 minutes ago, Mike Poole said:

Looks to me like a bit more consistency on a settled spell beyond next weekend on the 12s. 

ICON T180:

4FEE261F-9E94-48CA-B39E-2EB0112DB696.thumb.png.ce730b16d95966ccd8457db530b1b1e2.png

GFS T204, and the parallel 6z at same time T210:

19F983B1-36AE-4BA8-976C-2A711D37BB4B.thumb.png.be60690197b3b2cb7b1170bd6bf3ff3e.pngE35E9E41-C516-484C-88A0-5227982C7862.thumb.png.aa0239843f2dc4d125ecce3d129bf329.png

How warm is not in any way a done deal, but high pressure close to UK looking the form horse now, this would be hardly unusual for September.

horrid precip chart though on GFS

ukprec.png

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ECM doubling down on yesterdays 12z, and the 0z, here it is in full:

anim_wgq5.gif

Classic September pattern I would say, and I also think that this is the time of year that can most be banked on for settled weather, nowhere near 100% of course, but I would rate the second week in September as the most likely for a high pressure out of all weeks of the year...models increasingly indicating it this year now.  

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Apologies if this is the wrong thread but I think this will interest a few people

 

Edited by Zak M
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57 minutes ago, Zak M said:

Apologies if this is the wrong thread but I think this will interest a few people

 

It’s the right thread, Zak, this old chestnut again!  😁 If you look at the verification stats over a long period there is no statistical difference between the 4 GFS runs.  They are all equally bad! Currently at day 5 and day 10:

A583F36F-027B-4B58-A9A2-8563981737C4.thumb.png.30361d63277bef984d08b2293a56cc94.pngC800EC5F-BFBF-4D94-BFDF-C038CE7F84C6.thumb.png.946990cc7e773c636d628f314f26cbd1.png

Pub run actually doing best at the moment!

Why does the 18z go crazy?  Maybe because we view it with the beer goggles on!

Edited by Mike Poole
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43 minutes ago, Mike Poole said:

It’s the right thread, Zak, this old chestnut again!  😁 If you look at the verification stats over a long period there is no statistical difference between the 4 GFS runs.  They are all equally bad! Currently at day 5 and day 10:

A583F36F-027B-4B58-A9A2-8563981737C4.thumb.png.30361d63277bef984d08b2293a56cc94.pngC800EC5F-BFBF-4D94-BFDF-C038CE7F84C6.thumb.png.946990cc7e773c636d628f314f26cbd1.png

Pub run actually doing best at the moment!

A now age old observation-notion..1 that we have EVERY winter ‘mostly ‘12z is king..or queen if ya like... throughout public modelling suites...

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This morning's GFS 00Z op not looking too bad, I guess... but, the general slide into autumnal gloom is getting underway:😷

image.thumb.png.b2af6063d6f17889531a57fa71c79b74.png    h850t850eu.png

h500slp.png    h850t850eu.png

h500slp.png    h850t850eu.png

h500slp.png    h850t850eu.png:shok:

PS: Ensembles are playing up!

 

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Euro this morning suggests the outlook is quite pleasant and dry but not overly warm. Hints by day 10 of retrogression. Potentially cool nights with a good durinal range.

https://www.wetterzentrale.de/en/topkarten.php?map=1&model=ecm&var=1&time=240&run=0&lid=OP&h=0&mv=0&tr=24

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The models continue to be summed up as 'low pressure to the north, high pressure to the south, the UK in the bland transition zone in between'. Never particularly warm, or settled, or unsettled. Signs of something more unsettled later on beyond the 10th as high pressure gets forced out into the Atlantic with low pressure coming over the top.

Nothing unusual for September of course, with the Atlantic in autumn mode now. Could do with a rogue ex-tropical storm to send a summer high our way.

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On 30/08/2020 at 09:09, johnholmes said:

All 3 suggest a coolish and rather changeable/unsettled 6-10 days coming up with the 8-14 carrying this on, possibly a touch more in the way of height rises. The usual caveat at this time of year=tropical storms/ex hurricanes will not show on these mean charts and if they do occur will cause havoc with all models and all time scales.

Nothing to me suggests any outlook for warmth or indeed more than the odd settled day or two under any transient surface high.

Very interested in your analysis. Feels like we've been looking at different charts for a while now. NOAA and EC/GFS anomaly charts have gone roughly where it seemed to me they were going, and seem to suggest positive anomalies over the UK. Meanwhile even NWP is consistently producing relatively persistent high pressure dominated scenarios for the UK.

Admittedly the signs are that we might end up under the eastern end of any HP cell and generally retain a westerly flow, but with Tamara's analysis in mind, these details seem ripe for upgrades...

Anyhow, even if there is cloud mixed in, it looks pretty pleasant, especially compared to the last week or two. I'd agree it doesn't look warm, but it looks pretty settled to me. Wondered whether it was a question of our respective locations, but even with that in mind and following a quick check of some Northern cities, it looks decent from some time later this week.

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