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Short range model discussion - into 2018


Paul

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth

Latest HIRLAM for snowfall by Wednesday 12Z. Disruptive snowfall to the east of the Pennines and down the east coast, perhaps North Downs too. Also localised falls for S Devon and S Cornwall, and places in the south that virtually never see snow are covered (Isle of Portland, Ventnor, etc). Snow falling out of the sky at some point for everyone?

hirlamuk-45-48-0.png?26-17

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Posted
  • Location: Edinburgh
  • Location: Edinburgh
13 minutes ago, Man With Beard said:

Latest HIRLAM for snowfall by Wednesday 12Z. Disruptive snowfall to the east of the Pennines and down the east coast, perhaps North Downs too. Also localised falls for S Devon and S Cornwall, and places in the south that virtually never see snow are covered (Isle of Portland, Ventnor, etc). Snow falling out of the sky at some point for everyone?

hirlamuk-45-48-0.png?26-17

Thats going to be carnage for the Scottish Central belt ...

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Posted
  • Location: Nuneaton
  • Location: Nuneaton

With regard to the front tonight aka the polar low, just been looking on the latest satellite images from Norway and to my eye it seems to be tracking slightly south of where the models have been showing it. Any thoughts?

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Posted
  • Location: Bournville Birmingham
  • Weather Preferences: Hot n cold
  • Location: Bournville Birmingham
19 minutes ago, Matthew Gill said:

With regard to the front tonight aka the polar low, just been looking on the latest satellite images from Norway and to my eye it seems to be tracking slightly south of where the models have been showing it. Any thoughts?

Keeping an eye on it. Looks like it's moving sw landing Lincs?

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Posted
  • Location: Camborne
  • Location: Camborne

The updated fax charts for midday Tuesday-1200 Weds showing the wave over Wales and the convergence zone through the channel. Thus the snow showers may impinge more along the south coast.

PPVE89.thumb.gif.313250f23d03a4c38f7e173bdc54c02a.gifPPVG89.thumb.gif.26a47d55f0fd7b22258ac982d052e07b.gifPPVI89.thumb.gif.d3f87760114f8d5d7c5860f828920d7e.gif

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Posted
  • Location: winscombe north somerset
  • Weather Preferences: action weather
  • Location: winscombe north somerset
49 minutes ago, Sweatyman said:

Keeping an eye on it. Looks like it's moving sw landing Lincs?

yes it does look to be taking a track further south ,time will tell , but a very interesting feature ,cheers all .

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Posted
  • Location: Abingdon - 55m ASL - Capital of The Central Southern England Corridor of Winter Convectionlessness
  • Weather Preferences: Winter: Snow>Freezing Fog; Summer: Sun>Daytime Storms
  • Location: Abingdon - 55m ASL - Capital of The Central Southern England Corridor of Winter Convectionlessness
9 minutes ago, knocker said:

Some nice convergence zones at 1800 and the upper front in the Channel 1200 Thursday with warm front northern France

PPVA89.thumb.gif.87a4e87094ebb090b5ca91e5c6426448.gifPPVK89.thumb.gif.03b3ab5d8349d6ca61550ed689e3ca6d.gif

Two questions:

1. Will showers forming over those convergence zones continue to track in a line moving in a south-eastward direction?

2. What is the difference in relation to snowfall between the upper front and the warm front?

Cheers,

TE

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Posted
  • Location: Camborne
  • Location: Camborne
11 minutes ago, The Enforcer said:

Two questions:

1. Will showers forming over those convergence zones continue to track in a line moving in a south-eastward direction?

2. What is the difference in relation to snowfall between the upper front and the warm front?

Cheers,

TE

1.Sorry not following the south-eastward direction bit. More south west tending towards the west depending on the low level flow more likely.

2. A lot less, if any, if any on the upper front assuming of course that everything else is conducive to snow which looks likely. But I'm open to correction on this by JH who is much more knowledgeable than I on the subject. :)

EDIT

But thinking about it it may modify the upper air a tad which may impact on snowfall from the following warm front. On the other hand that might just be waffle.

Edited by knocker
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Posted
  • Location: Bridge, Kent
  • Location: Bridge, Kent
4 hours ago, knocker said:

As for accuracy i've no idea but as they are official sites I doubt you will get better. If you change the filters you get a much bigger coverage,

A bit late to the party on this conversation but I can confirm anyone with a station can upload to this site. I know because I connected my station last week!

But most amateurs who have added their sites (just like Wunderground I suppose) tend to state what equipment they have and where it is located so you can make a judgement.

I guess from a Met Office perspective they get access to ‘big data’ akin to crowd sourcing and can make use of that.

keep up the good work on this thread guys. I’m just starting an Open University course on the weather so I hope to be able to contribute soon!

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Posted
  • Location: Abingdon - 55m ASL - Capital of The Central Southern England Corridor of Winter Convectionlessness
  • Weather Preferences: Winter: Snow>Freezing Fog; Summer: Sun>Daytime Storms
  • Location: Abingdon - 55m ASL - Capital of The Central Southern England Corridor of Winter Convectionlessness
42 minutes ago, knocker said:

1.Sorry not following the south-eastward direction bit. More south west tending towards the west depending on the low level flow more likely.

Apologies, I don't know my east from west either. So, it's reasonable to assume a south-westwards to westwards extrapolation of showers out from the line of the convergence zone.

Ok, so the upper front is bad news for snowfall and ideally it should go away.

Edited by The Enforcer
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Posted
  • Location: Camborne
  • Location: Camborne
1 minute ago, The Enforcer said:

Apologies, I don't know my east from west either. So, it's reasonable to assume a south-westwards to westwards extrapolation of showers out from the line of the convergence zone.

Ok, so the upper front is bad news for snowfall and ideally it should go away.

Yes I would think so. And a sat. image from 10 minutes ago

ch4.thumb.jpg.a8de46c838a70e4e5ce2dbc48d956bdf.jpg

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Posted
  • Location: Camborne
  • Location: Camborne

No huge change in this evening’s anomalies so will keep this brief. The high pressure/ridge still over NE North America into southern Greenland and signs of the second coming of an old friend over Banks Island, The main vortex lobe still N. Russia with the associated trough running all the way west through Scandinavia/UK and across the Atlantic ending south of the ridge.

This gives a pretty slack gradient over much of the UK, more particularly the north with a moderate westerly jet running into France and Iberia and just about impacting southern Britain and it’s along this path that any systems will travel. Precisely how and if they impact the UK is for the det runs to sort and this will also dictate the temps but probably a reasonable call the they will remain below average.

ecm_eps_z500a_5d_nh_11.thumb.png.8beb26d4aea4771059577f5e2f00d2d5.pnggefs_z500a_5d_nh_41.thumb.png.d2057525822281c755751288d8868579.png610day_03.thumb.gif.bd0dd82d275ea8ee222f5556881f361e.gif

gefs_t2ma_5d_nh_41.thumb.png.0f8c275aaa03124db90ba71bf166d3b9.png

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Posted
  • Location: Abingdon - 55m ASL - Capital of The Central Southern England Corridor of Winter Convectionlessness
  • Weather Preferences: Winter: Snow>Freezing Fog; Summer: Sun>Daytime Storms
  • Location: Abingdon - 55m ASL - Capital of The Central Southern England Corridor of Winter Convectionlessness

Here's how the faxes have developed Friday's conditions so far:

T+120:

20180225_2132.PPVO89.thumb.png.56519ddb542b8a593cbe60653b479287.png

T+96:

20180226_2205.PPVM89.thumb.png.1c93114a9c6dc5da1b7996521828df3d.png

Summary: Low further south-east and flatter. Frontal boundary further south in the south-west and further north in the south-east, occlusion slower. 528DAM line further north.

Edited by The Enforcer
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Posted
  • Location: Work: Near Glasto Home: near Puriton
  • Weather Preferences: Hot and sunny or cold and snowy. Nothing inbetween.
  • Location: Work: Near Glasto Home: near Puriton

Thanks both for the fax updates. Can you please elaborate on what the Low is doing in them? Thanks 

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Posted
  • Location: South Norfolk, 44 m ASL.
  • Weather Preferences: Varied and not extreme.
  • Location: South Norfolk, 44 m ASL.
24 minutes ago, knocker said:

And the latest for Friday/Saturday - problem solved :)

PPVM89.thumb.gif.1c77fd5477ea0efa369b597c3185ad2b.gifPPVO89.thumb.gif.e308202efb6ed3c970b43f6095bbc91a.gif

Still liable to small changes in frontal positioning having a significant influence on surface conditions.  Do you think that upper warm front will increase the risk of freezing rain on Friday?

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Posted
  • Location: Camborne
  • Location: Camborne
5 hours ago, chrisbell-nottheweatherman said:

Still liable to small changes in frontal positioning having a significant influence on surface conditions.  Do you think that upper warm front will increase the risk of freezing rain on Friday?

I've no idea to be honest Chris but it may well help forming a 'warm nose' Does this ring a bell?

A freezing rain event

Quote

The map below shows the area which was affected in this particular event. High pressure over Northern and Eastern Europe had been controlling the weather with cold easterly winds affecting the UK. On the evening of the 23 January an area of low pressure moved slowly northwards across the south of England and gave outbreaks of rain. In some areas the rain turned to snow but in the areas marked on the map the snow turned to freezing rain with outbreaks through the night and intermittently through the 24 January.

https://www.metoffice.gov.uk/learning/learn-about-the-weather/weather-phenomena/case-studies/freezing-rain

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Posted
  • Location: Camborne
  • Location: Camborne

After the excellent summation by Nick above it's really a question of attempting to dot the eyes and crossing the Ts a bit.

Out little wave feature has been busy tracking south west overnight bringing more consolidated snow showers to many areas and by 00 it is SW of Ireland.There have been some hefty snowfalls in many areas in the east, north the Midlands and north Kent. Behind a rather perturbed low level flow with some hefty convection going on as the UK comes under the influence of even colder air.

PPVA89.thumb.gif.a36fa76675f69aa7a2bc9fb1fc787e42.gifPPVE89.thumb.gif.5213195f5e5e657c0086873215bb14ac.gif5a94e7eebe167_shower1.thumb.JPG.b49e8677250bdcf9fe12108a86084764.JPG

5a94e7f85ce23_shower2.thumb.JPG.ec0a7f2d6f28350fd2b9ff7228f16c74.JPG

And talking about colder air the UK is now entering what is likely to be the coldest two or three days of this cold spell so worth a quick glance at the forecast wind chill over the next 36 hours according to the GFS-WRF

5a94e8cfe2ea1_chill1.thumb.JPG.3d21b888ff1992f164f7c062cc3bd695.JPG5a94e8d6be10a_chill2.thumb.JPG.00fac5b0603600b9af2088f4983f072c.JPG5a94e8de67c76_chill3.thumb.JPG.6fc3bc05c12a30bb6d3b6e56d0050739.JPG

As the depth and intensity of cold increases it serves to boost convection and perhaps it's no coincidence that tomorrow there are likely to be some steep 850mb-500mb lapse rates in the north and much showery activity in the same area, according to the GFS-WRF anyway The showers will continue through the day with strong winds along the north east coast, and later in the south, perhaps reaching gale force, thus feeling bitterly cold.

lapse.thumb.JPG.cf5b7df4335f357807ddc2c0aba28a7b.JPG5a94e9fc367d9_showerschill.thumb.JPG.d14d41d5ce512c05be5354d4ac491d96.JPG

Thursday starts with a severe frost in many areas and feeling bitterly cold in the strengthening E/ESE wind touching gale force but changes are afoot to the south.

gfs_t2min_c_uk2_10.thumb.png.624a97d419f99c7b04f38527e6cb7dea.pnggfs_ptype_slp_eur2_10.thumb.png.9b745413b4990603e6ccd7e68e0e2e23.png

So the key question remains how will the breakdown in the south materialize and will it produce copious amounts of snow in southern and western areas? It remains unanswered but as to the latter looking leas likely but the best way to illustrate the problem is to post a few charts from this morning's gfs.following on from the one above.

gfs_ptype_slp_eur2_11.thumb.png.ac19f3616e0aa91d68697f537b2e7915.pnggfs_ptype_slp_eur2_12.thumb.png.0613429eab1f2e2e4736941341c11a42.pnggfs_ptype_slp_eur2_13.thumb.png.45964fb107355cef658411a7a7b19af8.png

And then on Friday the warm front does push north but there does not appear to that much snow on it and freezing rain is still being bandied about (keep an eye out for the warm nose) so as mentioned previously the detail of this is still not sorted and it is certainly questionable as to how far north the 'warmer air will reach without 'mixing out' as for most areas, apart from God's Little Acre, Friday remains a bitterly cold day.

gfs_ptype_slp_eur2_15.thumb.png.1ff40b7cc3e9f0b430f3fe2029c0ca80.pnggfs_ptype_slp_eur2_16.thumb.png.e96ff4854ebb76b868cc4ad0bc5347b0.pnggfs_t850a_eur_16.thumb.png.19edb328c62991808638c6f012bb32f6.png

gfs_t2max_c_uk2_16.thumb.png.778224fea814c890fc1f403b1961d462.png

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

Since going to press the fax charts have updated. Interest one for Weds showing convergence zones and a trough over the north east coast, Might support my waffle above of increased shower activity in that region.:)

PPVG89.thumb.gif.cc58e7fc1e3af0867a37f1bbc7832105.gifPPVI89.thumb.gif.e256d646cab60969a2fd38917f9c7982.gifPPVJ89.thumb.gif.a9d4781426327d7bb3001a0f692d7003.gif

PPVK89.thumb.gif.5e8dc99a679634ee1825c347ce522d46.gif

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

Many are wondering, including myself, why given the upcoming scenario of warm air approaching very cold air we aren't getting the snow ploughs on standby. I did some very simplistic musing about this whilst perusing this morning's ecm, And simplistically it appears me down to the position of the deep upper low to the south west and the formation and track of the surface lows and fronts associated with it. Because moving within the former's circulation does not facilitate a direct confrontation between the warmer and colder air, rather a sliding and much slower approach which has within it a SE-NW component as well as northerly, which allows a certain amount of upper air mixing. I can't post the most relevant charts but these will do.

ecm_z500_anom_natl_5.thumb.png.21fc9fbf3abd0b0847698afd880bc60b.pngecm_t850_anom_natl_4.thumb.png.58f18cac52f9c61170e5a31e1ba7e7c3.pngecm_t850_anom_natl_5.thumb.png.8d7df41ccde45bfdd2668297e420d420.png

ecm_mslp_uv850_eur_3.thumb.png.e60e0548c2accd90e282434ec74bfaf9.pngecm_mslp_uv850_eur_4.thumb.png.a45cf6ad13872890c09f498a1f824cda.pngecm_mslp_uv850_eur_5.thumb.png.0b89236dd16a2bf865193b6a41abed32.png

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Posted
  • Location: Camborne
  • Location: Camborne

I've been trying to find a forecast sounding to illustrate the possibility of freezing rain later in the week to no avail. Got close with this but it requires a bigger 'nose' of warmer air to be above 0C,

sounding.thumb.jpg.06ecb2d9ae7d868f2cc305677d7d14a0.jpg

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