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Model output discussion-mid Autumn and beyond


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Thanks knocker. Useful to come over to this thread for a dose of reality rather than seeing P14 of the 18z GFS run which shows cold weather at 300 hours, when we all know that it's standard wet, windy

Hi Malcolm, I just saw your post after doing mine above. Yes this thread seems under used which is a shame.The idea of this one as you probably know is for any members to post what hopefully

Finally getting time to check how the 500 mb anomaly charts have been over the past week. They have not consistently but generally gone from suggesting trough domination to one that now has ridging as

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43 minutes ago, Man With Beard said:

And in non-cold weather news ...

81-582UK.GIF?13-6

A nice BBQ after work on Friday perhaps (if you finish early enough)!!

yes, with a top on one could toast the excellent summer most had and toast the hoped for early start to winter next week.

I do hope ut happens, even some snow, thus avoiding an early toys out of pram and playground tantrums!

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The energy flows with this evening's ecm are not as conducive to transporting colder air around the high cell west/south west as on the morning run as it is aligned further east and cuts this route off in favour of plunging the colder air south over eastern Europe. But this was always going to be moveable feast given the energy at play.

t132.thumb.png.d54f340498c174277acdad03b3e5be57.pngt162.thumb.png.0b8a5651f10fa4931f8de6499b41e416.pngt204.thumb.png.1d3dc4c7389673f0e7d34065a65453ae.png

 

 

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So what are the ramifications mentioned in the other thread? Just over the next three days, I don't feel inclined to venture further than that, the overall scenario, according to the gfs, is for low pressure to form over central and eastern Europe and move east to western Europe including the UK. This distorts the Scandinavian high cell and thus the quite strong easterly winds are cut off. In that quite strong easterly it has turned a lot colder, particularly in the south and east where frequent rain showers will occur, possibly of sleet/snow on the higher ground. But with the interruption it could become colder in the light winds with widespread frost. For a change the NW is out of the firing line.The detail in this developing situation could be very tricky to pin down

gfs_z500_vort_eur_25.thumb.png.0db892cacd4e5fe49b437069a64536b5.pnggfs_z500_vort_eur_29.thumb.png.6ffce863c23547cc440a5e9c264eaa17.pnggfs_z500_vort_eur_33.thumb.png.e8a281c0d26fdd29cfd2e7e876b789a1.png

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Surprisingly the ecm is not a million miles away from the gfs next week and by T192 has progressed the low into the southern North Sea which backs the strong easterly and pushes it north whilst introducing colder air the south/south east, which could also impinge on southern regions of the England All very interesting

t192.thumb.png.e1d09461b98c22f18498ed24badb9db1.png547636696_t192s.thumb.png.a3764928dd336b34f8cb921ea4776a38.png

Edited by knocker
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I'm not entirely sure why this sudden loss of the very cold weather comes as a surprise. It was after all very dependent on the high cell migrating NW and it wouldn't take much adjustment of the energy flows to interrupt this as has appeared to have happened. And of course this is not necessarily a done deal either. It's the perennial problem of people looking too far ahead, particularly when tricky patterns are on the go. Just my opinion of course

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6 minutes ago, knocker said:

I'm not entirely sure why this sudden loss of the very cold weather comes as a surprise. It was after all very dependent on the high cell migrating NW and it wouldn't take much adjustment of the energy flows to interrupt this as has appeared to have happened. And of course this is not necessarily a done deal either. It's the perennial problem of people looking too far ahead, particularly when tricky patterns are on the go. Just my opinion of course

Though slightly ironic that you are using that same long-range forecasting as an example of people looking too far ahead?

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7 minutes ago, Optimus Prime said:

Though slightly ironic that you are using that same long-range forecasting as an example of people looking too far ahead?

Always with the caveat that it is susceptible to correction, and I normally attempt to say why. I'm merely attempting to point out that it shouldn't be surprising. But hey it's no great surprise that people disagree with me.

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EPS Mean not so different to the 12z yesterday, out to day 10 or so. Slight shift west for the high. 

Lots of options in the clusters, one suspects. Although if this potential cold weather doesn't hit western Europe, I'm just wondering about a split in this high and part of it sitting over Western Russia and the other part ending up just below Greenland. Getting quite cold out that way. Not exactly a classic Easterly, but it would certainly deliver.

Of course, that's probably at least 15 days away and a lot could happen in that time.

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Wed 14th Nov

Ec-gfs Closed upper high with closed upper low beneath it, similar, well yes but positions have changed with the high now n of uk and the low/trough further n and into the s’ern half of the country. Not sure what the surface weather would be, coldish but any ppn more like rain than snow, ? hills, best peek at noaa

The high is centred between Iceland and nw Scotland as is the c of g of +ve heights with no 500 mb flow at all s of the border but no actual low/trough shown. The 8-14 is very similar, no actual high but v marked ridge and again no 500 mb flow se of the contour for the ridge.

Again what the surface weather will be is far from clear, how cold, how much cloud, any ppn, where, what sort. The only totally definite weather 6-14 days is no wind of any note and for colder than average temperatures.

usual links below

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

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

 

Edited by johnholmes
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The ecm tonight is once again the story of the energy flows and the pressure field in the eastern Atlantic and Europe. Initially at T96 the high cell centred over Scandinavia gains influence and the temps cool down in the UK under the fresh south easterly wind that this initiates but also a much sunnier day for most.

By T120 this has changed somewhat with low pressure being promoted in central Europe putting pressure on the high cell and backing the still very fresh wind to easterly over the North Sea and thus frequent showers in the north and eastern regions.Temps around average but feeling cooler.

By T144 the low pressure area has moved west to be south of the UK bringing colder into France and the far south of England whilst increasing the easterly wind and thus the showers become more frequent and general

This then goes on to establish a low pressure area to the south west troughing north east over the UK..

t96v.thumb.png.a349aa137fd18184f6db00fb1ae35fce.pngt120v.thumb.png.3624b2d5fc015b257609233c03dd8c41.pngT144.thumb.png.77ef02e85609dffc8da405bf7a1030e2.png

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Looking at the EPS, GEFS and NOAA 5-10 anomalies this evening is certainly not going to shed much light on the detail vis the weather over the UK but does illustrate the problem with pinning anything down at this range.

Twin vortex lobes with the Canadian one displaced south east into the Atlantic and an intense high cell somewhere north of the UK. Thus a very strong westerly upper flow exiting south of the trough diverging in mid Atlantic around the high pressure and south east towards low pressure to the south west of the UK. This is complicated by another flow west across Europe sustained by the initial jet around the north of the high, aided by the lobe/trough in eastern Europe. Resulting in a very slack pressure area over the UK and the tricky business of sorting the detail.

But what appears to be the percentage play moving forward from here is the weakening of the trough area in the north west allowing high pressure to build further west and the vortex/trough in eastern Europe becoming more influential allowing colder air to flood into Europe

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Slack pressure pattern for the north next week could mean lots of frost and fog, with wintry showers / precipitation in the south - quite an unusual set of circumstances for late November.

There will be a wintry feel to things.

In blocking set ups, it becomes difficult to pinpoint exact details, subtle shifts in the position of core heights will make a difference between whether you see sunny calm frosty conditions or dank cold wet conditions.

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Well well well, the first signs of the ECM backing down on a prolonged cold outlook? The 12Z run only really shows 2 cold days next week, with the high pressure slipping to our east eventually, allowing a warmer continental flow.

Fingers crossed that this cold spell is a blink and you'll miss it affair.

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Just viewing the nwxtra model tracker in which i focused on the expected pattern for Monday next on the last 4x12z runs on both GFS and ECM We can see how small changes have enhanced the pattern change to an easterly showing quite a robust block to our north east by then..(Oldest charts first)

GFS

viewimage.pbx?date=20181111;time=12;ext=viewimage.pbx?date=20181112;time=12;ext=h500slp.pngh500slp.png

ECM

ecm500.192.pngecm500.168.pngecm500.144.pngecm500.120.png

More energy modeled to go under the block than a few runs ago with lower pressure also across Europe.The link to the Azores ridging to our high further north now severed helping to support the Iceland/Scandi high.

Finally tonight's T120 fax

fax120s.gif?1

showing a brisk easterly well established by Monday with temperatures falling off to daytime single figures. Our first easterly of this season arriving quite early when the Atlantic is normally gearing up.

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Moving on from the short range the key question is where does the gfs go from here over the rest of next week. The answer is it develops the low pressure area over eastern Europe and tracks it north east as a fully developed surface low into the UK where it phases with the trough to the south west. Forming a general area of low pressure over western Europe with the high cell now north of Scotland

All of this tends to continue to back the surface wind with plenty of showers and it also drags some colder into France which will also impinge on the south of England before more general unsettled weather arrives by Thursday/Friday

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The ecm evolution next week rather seems to illustrate where the differences on the influence of the different energy streams can result in quite a  different surface analysis. It also has low pressure to to the SW > SE developing over western Europe, including the UK, but also quite extensively in the eastern Atlantic which puts a lot of pressure on the high cell which becomes elongated along a NW >SE axis which cuts off the colder air into Europe. But prior to that it does bring colder air into France/Germany which will also impinge on the south west and the south of England with plenty of unsettled weather next week. Quite unpleasant if you on a break in Skeggy. Or anywhere for that matter

t144.thumb.png.1e422c91808c448409a836b7b7bba253.pngt174.thumb.png.e9cf3947f900ec16e04dade606234438.png

 

Edited by knocker
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And as mentioned in the anomaly post last evening the ecm has the colder air flooding south into Europe in the ext period with a west > east bias

5-10.thumb.png.f92eac3254555a245c326f478a4ffb2c.png

 

Edited by knocker
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14 hours ago, Scorcher said:

Well well well, the first signs of the ECM backing down on a prolonged cold outlook? The 12Z run only really shows 2 cold days next week, with the high pressure slipping to our east eventually, allowing a warmer continental flow.

Fingers crossed that this cold spell is a blink and you'll miss it affair.

eh? normally agree with your posts, have done for last 6 months or so, but don't agree with this! any cold spell is shown after 25th deepest FI, and why would anyone want it as a blink and miss it? I hope it's a 2010 repeat, almost to the date

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