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Paul

Mid-winter - models, teleconnections and nowcasting

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The detail regarding this weekend is tricky and I suspect will remain so. The overview is that on midnight Saturday the country is in a strong westerly flow but over the next 48 hours this becomes meridional, thanks to amplification of the subtropical zones, which results in the upper trough re-orientating to a neutral tilt over the UK

gfs-deterministic-natl_wide-z300_speed-6281600.thumb.png.dacd05f8e1077547c9b8ac1a7261ffe6.pnggfs-deterministic-natl_wide-z300_speed-6454400.thumb.png.33db0ebef33aec54cde48729c0a1be08.png

All of which means that small surface features developing in the complex area of low pressure are not going to be easy to pin down as can readily be seen on this morning's fax updates

PPVK89.thumb.gif.c0a01361e895eb018b0b813b2320a3e1.gifPPVM89.thumb.gif.39a0eed4123b79b9d220af4575bc291d.gifPPVO89.thumb.gif.77dd50e8400b6911950ce7cb13588603.gif

So futile say anything other than it will be unsettled with showers and some longer periods of rain which will fall as snow on the high ground in the north

ecmwf-deterministic-uk-t2m_c_max6-6346400.thumb.png.069520d9cb30e75239362e98e726d263.pngecmwf-deterministic-uk-t2m_c_max6-6432800.thumb.png.46a32cc0e08de16bcdbfe2c0c55c437e.png

Edited by knocker

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The ext GEFS this morning is not dissimilar to last evening's EPS with the trough a tad further east in the negatively anomalous Atlantic with the European high not quite so intense, albeit still significant

gfs-ensemble-all-avg-nhemi-z500_anom_5day-7232000.thumb.png.d138c6f1a1394133a82a38f25320f180.pnggfs-ensemble-all-avg-nhemi-t850_anom_5day-7232000.thumb.png.7d89ca3b688673e2e3241658a0dd0f34.pnggfs-ensemble-all-avg-eur-t2m_c_anom_5day-7232000.thumb.png.7898868967712b28060fb94ded64814c.png

 

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After the brief interruption of the eastbound energy at the beginning of next week, normal service is then resumed, to a point. The intensification of the European high is now acting as quite an efficient block

ecmwf-deterministic-nhemi-z500_anom_5day-6864800.thumb.png.51f526d55f50841c3043de638a109836.png

144.thumb.png.55c8d30fbf6490ad8c3680a300a0349e.png168.thumb.png.aaba29106c85611ed3abfa0ae40118c8.png192.thumb.png.28e2f1d99fa972867b2a6c7d604f2288.png

 

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Quite a lively day in Scotland with frequent squally showers in the strong westerly wind which could well reach gale force in coastal areas, with thunder and lightening in the mix. The precipitation will fall as snow on the high ground. Frequent heavy showers in western regions further south also and in particular a band will track east through the day, courtesy of the feature to the west on the 0600 chart. Quite a cold day

PPVA89.thumb.gif.6bd30057127b2888a3e179742818803a.gifmean2mtemp_d02_15.thumb.png.e28eeaecd38c000db7a13991592222e2.pngmeanreflec_d02_9.thumb.png.c66218e719f27a3cc7345a060c9931c7.pngmeanreflec_d02_12.thumb.png.aee20f3b44bbb81e52834745cd8007b4.pngmeanreflec_d02_15.thumb.png.0e0d1d1e2a9a97345fee8dc30ab5d1aa.pngmeanreflec_d02_18.thumb.png.cb434294c71ecbe6044837ca5caac7d1.png

 

Edited by knocker

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Gfs seems to want to develop quite a major system for Friday night.. With a very strong jetstream riding over the top of it with a marked temperature differential its worth keeping an eye on. 

EUROPE_PRMSL_TMP850_54.thumb.jpg.e8a23ac9373bb12f4bc0bca07778be1d.jpg

1625825106_EUROPE_PRMSL_72(3).thumb.jpg.b7e265439744909a31559ebf549662a9.jpg

1180929107_EUROPE_PRMSL_78(3).thumb.jpg.670db1146f098a5be5953c2e39464d93.jpg

Wind gusts at 10m..

EUROPE_PRMSL_2MWIND_66.thumb.jpg.0a09e00903f9f5ba1e2461e551670efc.jpg

EUROPE_PRMSL_2MWIND_72.thumb.jpg.29607b87d57dc6395ed10c79b6afaea3.jpg

EUROPE_PRMSL_2MWIND_78.thumb.jpg.d5c078fee37d45bfe7dc31d3a3fe033c.jpg

Jetstream forecast from the Gfs.. 

40861821_EUROPE_JETSTREAM_36(2).thumb.jpg.2ebaa7e36265badf3b103f419abd0138.jpg

1074456351_EUROPE_JETSTREAM_60(1).thumb.jpg.e64955f5e69de0a6052b8c78b5cdb835.jpg

Gem has something somewhat similar.. 

EUROPE_PRMSL_66 (1).jpg

1477366974_EUROPE_PRMSL_72(4).thumb.jpg.1d9d3d3cd49f1df364dea82b255eda2c.jpg

Edited by jordan smith

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I was looking at the FAX charts last night.. I don't think I have ever seen that many upper troughs on one chart before?

BRAEU_120.thumb.gif.d1b146fcf2d4b30e281fa2c2a734f6fb.gif

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55 minutes ago, Mapantz said:

I was looking at the FAX charts last night.. I don't think I have ever seen that many upper troughs on one chart before?

BRAEU_120.thumb.gif.d1b146fcf2d4b30e281fa2c2a734f6fb.gif

I'm not sure I follow that Mapantz as it's a surface chart

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25 minutes ago, knocker said:

I'm not sure I follow that Mapantz as it's a surface chart

Yes, you're right there, knocker. I shouldn't have added 'upper'.

Certainly abundant on that particular chart!

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1 minute ago, Mapantz said:

Yes, you're right there, knocker. I shouldn't have added 'upper'.

Certainly abundant on that particular chart!

Yes indeed and as I said this morning sorting the detail is a bit of a nightmare

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Upstream with the ext GEFS is not without interest this evening with the Alaskan ridge extending into the Arctic alongside the east Pacific trough which,with some help from the Canadian vortex which isn't cooking with gas, and some height rises in the southern States, results in a strong westerly upper flow exting the eastern seaboard and running across a very much negatively anomalous Atlantic It does start to back as it reaches the trough over the UK, courtesy of the European high pressure. Still portending unsettled but tending towards a N/S split but warming up nicely

gfs-ensemble-all-avg-nhemi-z500_anom_5day-7275200.thumb.png.67ce2d5fe6352b9da9f4b186ce98f722.pnggfs-ensemble-all-avg-nhemi-t850_anom_5day-7275200.thumb.png.16054539f2df9081a0ec94674b41d9f4.pnggfs-ensemble-all-avg-eur-t2m_c_anom_5day-7275200.thumb.png.38318404fb22f2a0a2f73e335201b89b.png

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Just an idea how messy the surface analysis can get when the upper trough is caught, albeit briefly, between amplifying subtropical zones. Mind probably a quite welcome respite

ecmwf-deterministic-natl_wide-z500_anom-6497600.thumb.png.234bbbde67a357a1d8091f06b098b6c0.pngecmwf-deterministic-natl_wide-z300_speed-6497600.thumb.png.0d675c20c9d4b9d7da08cd2e358ba10e.png

96.thumb.png.31860e2f3e683b7be29f8c6f9e959cc1.png120.thumb.png.d17c9b4f779fe8f9d0a6301c43f57b2d.png144.thumb.png.fd2763d4965b2f7fdd6624b01aaaa145.png

Edited by knocker

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The upstream structure of the ext EPS is markedly different to the GEFs so until this is sorted caution is required. As it happens the upshot of this is not that different downstream with a strong westerly upper flow running south of the vortex extension and increasingly influential ridge into east Greenland. The flow backing quite sharply in the vicinity of the UK courtesy of the amplifying European high

ecmwf-ensemble-avg-nhemi-z500_anom_5day-7275200.thumb.png.2080af6df88e685efc85db6d43cb7508.pngecmwf-ensemble-avg-nhemi-t850_anom_5day-7275200.thumb.png.07673094674d0f4d43a6b5c9ed9e2b3d.pngecmwf-ensemble-avg-eur-t2m_c_anom_5day-7275200.thumb.png.0de215bb44199f5edb088f8aa07eac0c.png

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6 hours ago, knocker said:

I'm not sure I follow that Mapantz as it's a surface chart

 

5 hours ago, Mapantz said:

Yes, you're right there, knocker. I shouldn't have added 'upper'.

Certainly abundant on that particular chart!

There can be troughs (shortwaves) located above the boundary layer depicted on those charts as well, for example when representing small scale vorticity/ascent aloft. They are synoptic charts. Upper cold/warm fronts are depicted all the time when they arise, too. 

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Outlook - unsettled and quite cold

The North Atlantic 300mb wind field and surface chart for midnight

gfs-deterministic-natl_wide-z300_speed-6108800.thumb.png.a470a0b255f92d024322bb0e59590eef.pngPPVA89.thumb.gif.ea1d049885c3a38252078cd16fe6419f.gif

A deep low is tracking east towards the UK and the associated complex frontal system will cross the country today. Whilst the east of the country has started dry with frost, cloud and rain from this is already into N. Ireland and the south west and this will move quickly north east through the day, clearing the east coast by 1800 with only the far north of Scotland escaping. Some snow over the high ground in wales, northern England and Scotland. Frequent heavy showers following over western regions

PPVE89.thumb.gif.304c8d32b5f13fd57e09b1c51a8469e8.gif2mtemp_d02_20.thumb.png.2c28306c5b1daa7d4dedf1fdb7f03c5e.pngmeanreflec_d02_15.thumb.png.d80a839fdf90b54af75d7212b12d42c3.pngmeanreflec_d02_18.thumb.png.f2a179f0f5f21ad53043242c2d6375f7.pngmeanreflec_d02_21.thumb.png.719e75682a5cef1e5b6925efb889531c.pngmeanreflec_d02_24.thumb.png.b0df5d7ccec21b51986336b612eb22f7.png

By tonight the country is in the circulation of the low 966mb just west of Scotland so a windy night, particularly in the south west with coastal gales, and quite wet with showers and longer periods of rain, courtesy of troughs running around within the circulation

PPVG89.thumb.gif.85a0061ed7a5ed221fe68b93720239d8.gif

The country remains in the circulation of the low on Friday as it tracks into the North Sea so a day of decreasing showers in the now north westerly wind, But further fronts and rain are arriving in the south west by dusk from the low pressure dominated Atlantic

gfs-deterministic-natl_wide-z300_speed-6238400.thumb.png.b36bd44353a836145f0c71c99e573686.pngPPVI89.thumb.gif.a14901e302c64207e3bc0ceb29ae252d.gif2mtemp_d02_44.thumb.png.d15f839bf3e3a3ce2a00f1aed6f5d8e9.png

By Saturday a complex upper trough covers the eastern Atlantic and north west Europe so another cold and unsettled and quite windy day for the UK with frequent showers and a band of rain moving north on the occlusion which will fall as snow to quite low levels

gfs-deterministic-natl_wide-vort500_z500-6346400.thumb.png.c705ea2e525c67c6759445f9aedc5ac5.pngPPVJ89.thumb.gif.cecade0ed54c03d8391555ed620e65db.gifPPVK89.thumb.gif.3fa4e177af4bd8233c73497ed29d725b.gif

gfs-deterministic-uk-precip_6hr_inch-6346400.thumb.png.cfbd16c00c8e3eb5f16e56ffccf7b214.pnggfs-deterministic-uk-t2m_c_max6-6346400.thumb.png.4af710234e032213435fc5c3289d9427.png

The only significant change on Sunday is the orientation of the trough, courtesy of the subtropical zones amplifying

gfs-deterministic-natl_wide-vort500_z500-6411200.thumb.png.13fda74a9a638d63c8925e76a0304757.pngPPVM89.thumb.gif.c81722bfc83ed861de63c6da13eedb09.gif

gfs-deterministic-uk-precip_6hr_inch-6432800.thumb.png.17886a0a0d084fac40e04746b7d7474c.pnggfs-deterministic-uk-t2m_c_max6-6432800.thumb.png.d12a962b7eadd904f1b26fcdbbb62261.png

The re-orientation process continues on Monday but at least this results in a much quieter day with sunny intervals and a few showers

gfs-deterministic-natl_wide-vort500_z500-6497600.thumb.png.b69a53554f6820e8c2c292e9810f0245.pngPPVO89.thumb.gif.e366dc444e181f8c9f0d2e1110e14b06.gifgfs-deterministic-uk-t2m_c_max6-6519200.thumb.png.b43a2aed6b64035ae83df7077a0a254d.png

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What of the rest of the week with the gfs? This has been covered in previous posts but after another quiet and relatively pleasant day on Tuesday the energy exiting the eastern seaboard has blown away the ridge in the west and another intense trough has arrived in mid Atlantic.And the surface fronts associated with this will impact the UK on Wednesday.

gfs-deterministic-nhemi-z500_anom-6627200.thumb.png.737c353bb9118a564d13d3357698e1c3.png156.thumb.png.44d734ca48d2af09db88d6c7cf75fb85.png

But the European high is solid and during the latter part of next week the emery hits the buffers and the upper  troughs deconstruct so still changeable, nut not intensely so, an becoming warmer

gfs-deterministic-nhemi-z300_speed-6843200.thumb.png.4bd6d8f340f6b0ca2d7c3d01ae417571.png204.thumb.png.10b22dd3fcb915046e6081412e6f18a2.png

Edited by knocker

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The salient points of the ext GEFS this morning

Alaskan ridge/east Pacific trough

Twin vortex lobes NW Greenland/NE Canada with heights building over the southern US States

Resulting in a strong westerly upper flow exiting the eastern seaboard across the Atlantic

To the trough over the UK where it backs, courtesy of the European ridge

gfs-ensemble-all-avg-nhemi-z500_anom_5day-7318400.thumb.png.4c9907734213b54f002986dacb90fda5.pnggfs-ensemble-all-avg-nhemi-t850_anom_5day-7318400.thumb.png.ab18b5af29141fd8dfc8979ef85a5fa3.pnggfs-ensemble-all-avg-eur-t2m_c_anom_5day-7318400.thumb.png.58f9e8d8c654bf648a3e4df1ebbe64df.png

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The theme from the ecm next week is initially similar to the gfs but the energy quickly gains the upper hand leading to more cyclonic wet and windy weather

ecmwf-deterministic-nhemi-z300_speed-6843200.thumb.png.b2aa2a5c7a28f591a1193a7766e4d655.png

156.thumb.png.0a34f8b33f19ee45c548a5d3d00cb674.pngindex.thumb.png.c8fde35c79d5d8333e735879f47fa444.png204.thumb.png.b683f60c29690df4cf4539b342b36a99.png

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Still major differences between the ext GEFS and EPS vis the upstream and Arctic profiles so this still needs to be resolved. One thing that is similar is the strong westerly upper flow exiting the eastern seaboard south of the vortex extension. This backs sharply in the vicinity of the UK, courtesy of the European ridge which is now extending into the Arctic

  ecmwf-ensemble-avg-nhemi-z500_anom_5day-7318400.thumb.png.62a2f77065ce7045a43296c9a5dceef9.pngecmwf-ensemble-avg-nhemi-t850_anom_5day-7318400.thumb.png.bec8364a219561297bf284d12e7dcef6.pngecmwf-ensemble-avg-eur-t850_anom_5day-7318400.thumb.png.281507b37a199fd1102c0c85f20d38f1.png

Some downwelling?

ecmwf-deterministic-nhemi-z50_anom-6972800.thumb.png.3cadfda98be559b0067bb2d5b1a49568.png

 

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No real change to our wet and unsettled weather through the next few days.

The latest T72hrs fax and raw UKMO 500 hPa pattern shows the UK surrounded by surface lows and fronts circulating within a broad upper trough


1147351089_fax72s(1).thumb.gif.1f887ef5c69fa5d0ea250d1cead1513a.gifUN72-21.thumb.gif.8efb5adebeab5824ed7654f737811c85.gif

so continuing rather cold especially further north with snowfall quite likely at imes in elevated areas as we continue to sit in a mainly polar maritime air mass. 

Signs of a change appear around day 6 as all the main models show pressure rising from the south which in consequence  has the trough on the retreat- at least for a while.

  gfsnh-0-138.thumb.png.8f0f310aeb3b98ee9fc26cde9ce1ab7d.pngECH1-144.thumb.gif.f208ce50a4b8b72e42cb834be4c2b5cd.gifUN144-21.thumb.gif.aab0a97c3442f1f336ac402f31e13f14.gif

so as we pick up a more south westerly flow we can expect a bit of a warm up with maybe a drier period especially towards the south east.The latter depending on the positioning of the Euro heights of course which will no doubt be determined in a couple of days.

London combined ens.

ensemble-tt6-london.thumb.gif.14dc939e6db25f943011341cbb4ce613.gifensemble-rrrcum-london.thumb.gif.7b05c812d5b955c645821beea1754084.gif

 

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