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Model output discussion - proper cold spell inbound?


Paul

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Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth

Looking through the 20 gefs on gfs there are 14/15 going for an easterly flow in the t+300 time. That is a growing trend. Blocking in different places as you would expect. 

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Posted
  • Location: leicester
  • Location: leicester
Just now, That ECM said:

Looking through the 20 gefs on gfs there are 14/15 going for an easterly flow in the t+300 time. That is a growing trend. Blocking in different places as you would expect. 

The thing is though every single easterly that is being shown over the last 72 hours is stayin around 300 hours and not getting any closer!!by now you woild expect it to be around 240 hours!!there have been positive changes early on though so it might show up suddenly a lot earlier!!

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Posted
  • Location: Waddingham, Lincolnshire. (9m asl)
  • Weather Preferences: Anything newsworthy, so long as it's not in the Daily Express
  • Location: Waddingham, Lincolnshire. (9m asl)
8 minutes ago, shaky said:

The thing is though every single easterly that is being shown over the last 72 hours is stayin around 300 hours and not getting any closer!!by now you woild expect it to be around 240 hours!!there have been positive changes early on though so it might show up suddenly a lot earlier!!

240 you say....

8F69944B-E87E-43D7-A66B-5A035F056D92.thumb.png.e0baedfadac22f26733729500777a4aa.png

And I guess an Easterly is soon to follow this ECM chart with heights shooting up to Greenie.

255BAD17-D7E9-4234-9E01-8996A3971A90.thumb.png.502b8a3c2c64af58c1a33f46eb495bb4.png

Might still be all you’re hoping for Shaky :D

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North
19 minutes ago, That ECM said:

Looking through the 20 gefs on gfs there are 14/15 going for an easterly flow in the t+300 time. That is a growing trend. Blocking in different places as you would expect. 

That's great news, yesterday there were 7/8...I can feel the anticipation growing..could be a cracking late winter / early spring for coldies!!:cold::D

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Posted
  • Location: Bournemouth
  • Weather Preferences: Dry mild or snow winter. Hot and humid summer.
  • Location: Bournemouth
13 minutes ago, shaky said:

The thing is though every single easterly that is being shown over the last 72 hours is stayin around 300 hours and not getting any closer!!by now you woild expect it to be around 240 hours!!there have been positive changes early on though so it might show up suddenly a lot earlier!!

All at t240 this is growing trend as well. Not nailed of course but a much greater chance than normal. The amount increases as you go further out, some not responding to the ssw as quickly? JFF we should set up a thread and pick your gef for t300 and see who is near the mark.

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Posted
  • Location: Redhill, Surrey
  • Weather Preferences: Southerly tracking LPs, heavy snow. Also 25c and calm
  • Location: Redhill, Surrey

ECM trending better but for me the UKMO is looking even better.  Definite hint that the trough will disrupt and undercut into the near continent.  Another good start to the day.

I see my post has disappeared....hope no offence was taken as none was meant...

BFTP

 

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Posted
  • Location: st albans
  • Location: st albans

This mornings gem evolves how I would expect things to  

if we head the more ecm route, then I expect more se movement of the trough than ene as per the output. Ukmo is further south by day 5/6 anyway. 

Gfs on its own and perhaps makes the gem a bit more feasible 

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Posted
  • Location: portsmouth uk
  • Weather Preferences: extremes
  • Location: portsmouth uk

Ok all I can say is the GFS brings in some exciting cold from the west northwest.

And shallow heights to our northeast building with each run especially on the GFS.

Also looking at the stratosphere event on going you can see clearly a huge split with European section of the vortex spinning from the east to west over the south of the uk.

This paves the way for lower heights to our south and by God opens the door to some pretty impressive northern blocking.

As the vortex takes one last gasp of energy and then explodes spewing out cold air already bottled up in the northern hemisphere.

In fact I'm actually blown away by the intensity of cold around.

Most certainly some snow events showing up.

Of coarse still us roasting south coast crew still awaiting a event.

but seen some snowflakes so not all bad.

And from past events I really believe this will be a quick response to the stratosphere this time.

Vortex absolutely ripped apart.

 

Continued from yesterday we have cold outlook firming up.

Quick response from stratosphere warming with a number of cold options gem wants Greenland block ECM wants Greenland,

GFS and gefs want Scandinavia block best option would be Greenland straight northerly or northeasterly.

But then GFS would be easterly but either is good.

GFS has shown Scandinavia block repeatedly since yesterday morning.

I expect to see these exciting charts to continue.

Very exciting and extremely interesting.

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Posted
  • Location: uxbridge middlesex(- also Bampton oxfordshire
  • Weather Preferences: blizzard conditions. ice days
  • Location: uxbridge middlesex(- also Bampton oxfordshire

Lets just throw these in here....

MT8_London_ens (3).png

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Posted
  • Location: Horsham, West sussex, 52m asl
  • Location: Horsham, West sussex, 52m asl
21 minutes ago, shaky said:

The thing is though every single easterly that is being shown over the last 72 hours is stayin around 300 hours and not getting any closer!!by now you woild expect it to be around 240 hours!!there have been positive changes early on though so it might show up suddenly a lot earlier!!

actually shaky, on the 00z, we do indeed have an eastlerly flow established by 240 hrs-

gfsnh-0-240-5.thumb.png.3d838cb0a4e29b78e4a7f7f73ecc22d2.png

this continues right to the end of the run with some decent snow events thrown in

gfsnh-0-324-1.thumb.png.02ca79ac746bf83f68acb27f526351ed.png

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the trend is your friend....

unless its skinny jeans. that trend is not my friend...

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Posted
  • Location: Hull
  • Weather Preferences: Cold Snowy Winters, Hot Thundery Summers
  • Location: Hull

Delete

 

 

 

Edited by Quicksilver1989
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Posted
  • Location: Crymych, Pembrokeshire. 150m asl
  • Weather Preferences: Extremes of all kinds...
  • Location: Crymych, Pembrokeshire. 150m asl
23 minutes ago, Sky Full said:

Ever colder uppers being drawn east from the continent:

image.thumb.gif.3427511232324b3f5427ee57327d6aa5.gif

 

Correction (unable to edit) - should of course have read: "....being drawn west from the continent".   :fool:

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Posted
  • Location: Isle Of Lewis
  • Weather Preferences: Wild!
  • Location: Isle Of Lewis

Well well well... getting blasted by cold both directions!

Its Fl territory for the more reserved peeps on the forum but and this is a big but the trend is their for an easterly. At this stage of SSW in 2013 it was projecting this far in advance with a huge amount of confidence.

It will do so again. 

Enjoy ( I will enjoy a cold crisp sunny early spring (and dry). 

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Posted
  • Location: Wyke regis overlooking Chesil beach.
  • Weather Preferences: Snowfall
  • Location: Wyke regis overlooking Chesil beach.

Everything seems to be ticking along nicely to the wintery set up caused ny the SSW. I'm with Chiono on this in that I'd rather see quite good charts slowly up grading to stellar output nearer the time. Seen to many snowy nirvana charts at 300+ melt away or downgrade to one day with a few flurries. Far better to gradually build the Scandie or Greenie or Icewegian high and then see stalling fronts come into play nearer the time.

 

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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.

Friday morning could be interesting. The ECM shows a fairly heavy and large area of precipitation crossing parts of Wales and the Midlands and down towards the SE in the early hours. -6 to -8 uppers at that time.

Hirlam model shows something similar.

4C430F5A-C131-4CBA-9489-29C7F92BA1B2.jpegparys 

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Edited by MattStoke
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Posted
  • Location: Nutts Corner
  • Location: Nutts Corner

Charts like this should cheer a few people up.

West looking good for this evening into tomorrow and then another event on Sunday for the white stuff.

For the 21st of the month the south to the midlands could get in on the action.

All positive outlook and hopefully the months of model watching for the easterly pay off.

prectypeuktopo (1).png

prectypeuktopo (3).png

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Posted
  • Location: Longton, Stoke-on-Trent.
  • Location: Longton, Stoke-on-Trent.
4 minutes ago, bluearmy said:

Maybe above 600 feet could be some interest Matt 

Ex raw shows 2mm precip (sleet) at 350 feet for me 

I'd have thought with those uppers, occuring in the early part of the day and the precipitation looking quite heavy, snow could fall widely to low levels?

I'm at 146 m. About 480 feet.

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Posted
  • Location: Redhill, Surrey
  • Weather Preferences: Southerly tracking LPs, heavy snow. Also 25c and calm
  • Location: Redhill, Surrey
17 minutes ago, TEITS said:

Unsurprising to see the ECM now showing some interesting charts because the date of change has always been around the 19th Feb..I also continue to back the idea of a Greenland High influencing our weather at first rather than a Scandi HP (like GFS) and todays +240 ECM is heading that way.

ECMOPNH00_240_1.png

One thing I will mention after BFTP commented on the UKMO +144. I cannot see the potential N blocking, cold spell being brought forward in the NWP. This is simply a case of being patient and waiting for the SSW to have its impact on the PV. The date for when a real blast from the N or E or NE will arrive has always been from around the 18th - 20th Feb onwards and in my opinion continues to be the case.

Hi Dave

I particularly mentioned the UKMO as it brings the trough in for midmonth on the angle I have spoken about and several days for it to hopefully pass and undercut. I don’t anticipate a speed up either but I think it won’t be straight forward and clean either

 

BFTP

 

BFTP

 

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Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL
33 minutes ago, Quicksilver1989 said:

Well lets see what the science says about it all shall we?

There is considerable evidence that SSW's have an impact on atmospheric circulation patterns, indeed many studies have confirmed this. It provides a significant increase in forecasting skill.

But first what in an SSW event?

This refers to a warming of upto 50C in an area of the atmosphere 10-50km above the earth's surface. High up in the atmosphere we have the polar night jet, which can bend if we get blocking features in the lower atmosphere. If enough pressure is placed, the jet can break. In these scenarios air in the stratosphere collapses leading to a warming in our stratosphere. The easterly winds begin sinking from the stratosphere into the atmosphere and we start seeing the changes in atmospheric circulation, but this can either take place over days or weeks.

A recent paper by the Met Office (Scaife et al 2015) sheds some light on the impacts, here is a key figure:

image.thumb.png.a4d72ca35792e95c1bea823b3d82f5eb.png

What is this showing? Well its comparing the forecasting model of the winter NAO with and without taking SSW's into consideration. We can see that factoring in the probability of an SSW increases the forecasting skill of the model dramatically. This underlines how useful understanding our stratosphere can be.

How likely will that translate into surface cold here in the UK? and how negative did the NAO actually go? Here I look at 2 key events:

1) The most obvious example of an SSW directly impacting the UK is the 24th January 2009 event. Some similarity to what we are seeing now.

26th January 2009                                       Early February 2009
NOAA_1_2009012618_1.pngNOAA_1_2009020218_1.png

Quite an impressive transformation but outside of early February did it really do much? The rest of February was mild and the NAO was only neutral for that month.

5th January 2004                                        21 January 2004
NOAA_1_2004010518_1.pngNOAA_1_2004012118_1.png

This one was not really noteworthy in the UK or western Europe, its effects were far harsher over the eastern USA.

Out of the 22 SSW events since 1981- I'd say only 50% have led to UK cold spells at varying times after they occurred though. Hence my caution. You can see the impact it has on NH temperature anomalies in this figure by Deser et al (2014)

image.thumb.png.babd0a9232d7e621342ebeb0ab74b068.png

Of course its over 60 days but generally the main areas are more the eastern USA and Scandinavia extending out to Eurasia for more increased cold air outbreaks.

Finally we are getting to the time of year where easterlies do not always equate to cold. Look at the SSW event of February 1999 for example:

NOAA_1_1999031118_1.png

After a brief cold spell a few days earlier it actually turned very mild despite some fantastic northern blocking. So I think my post is a valid one. Increased chances of cold? definitely. Snowy cold spell? More likely but absolutely no guarantees. Prolonged cold? Again even more ambiguous. Not pessimistic, just realistic.

As for nothing has changed well... it has. Why do you think the 1740s to 1890s, 1940s to 1960s and 1980s saw far more cold spells then what we see now? Climate change. That is why. If we were in the 1800s, don't you think a lot more colder solutions would be verifying compared to what we see today? Here is an interesting paper from 2003, detecting anthropogenic influence on SLP. The clear trend to our south has remained.

image.thumb.png.f1aa8d259c1cf8049ec8ee4e2b7524a7.png  Trend in winter SLP

Why was 2010 so blocked then? Well that was to do with a slowdown in the overturning circulation that has been well documented. In general though I expect the trend in the above Figure to continue. Indeed the Atlantic cold blob has been a defining feature in recent years. Hopefully that will go away. However this is something predicted by the climate models and also in global surface temperature trends.

                           Grrr                                          Temperature trend from 1900-1912
image.thumb.png.a2e9c95f724c794f73389dc4046b24d0.png1900-2012-temp-trend-lrg.png

Sneachtastorm  - 1 hour ago

What upper nonsense


Any claims to back that statement up, I believe I am in some position to have a say given I am a PhD climatologist. What about you?

Overall, increased chance of a cold outbreak over the next 1-4 weeks, especially from the east but don't be so certain of a snowy solution or a notably cold one for our area...

 

I don’t think you can use a ‘normal’ SSW as a benchmark. So I’m told this one has some uniqueness. 

Dr Cohen likes to 1985/1991 as anologues of upcoming split of which both winters delivered some spectacular winter weather the latter much less prolonged and perhaps more arguable in resultant conditions considering cold peaked relatively early in the month perhaps the efffects of SSW were instantaneous. I don’t think anyone should be certain. However, it’s clear to see, we stand a much greater chance GFS has consecutively being putting out very good FI charts. And the last day it’s picking up in semi reliable timeframe as below easterly in 10 days time.

GFS 00z gives an easterly within the next 10 days technically, and it turns into a snowy one too. No doubt MJO imo is why we’re seeing interest in a Scandi high but the SSW will decrease perhaps substantially the zonal westerlies across the Atlantic which are often the nail in the coffin, meaning we stand an increased chance of a prolonged easterly cold spell. I’m absoloutely no expert but even I see considerable potential. 

E8554BF1-581C-4401-B154-8F95664BC18D.thumb.png.24f5255b06f48d7faef110dbb4f4a142.png4E9B883C-6D16-48F2-8AFE-91C7603016B2.thumb.png.fded4fcb56554435fd97cda08b4a137e.png

From his latest blog..

Impacts

The predicted stratospheric PV split and the tropospheric response is likely to dominate the weather across the Northern Hemisphere through the end of winter. Most model runs predict that the PV disruption will qualify as a major mid-winter warming (where the winds reverse from westerly to easterly at 60°N and at 10hPa) though I don't consider it critical for the forecast. The PV disruption is unusual in that it is predicted to result in one primary stratospheric PV over North America. I also find it unusual that both sister vortices advect/transport significant amount of heat towards the equator simultaneously even after the split. Thanks to Twitter peeps Jonathan Wall (@_jwall), Swaginator457 (@BruenSryan) and Zac Lawrence (@zd1awrence) for their help identifying the best analogs for the predicted polar vortex split. I would say that the best analog was early January 1985 (central date of January 2) followed by early February 1991. Two weeks following the January 1985 PV split one of the greatest historical Arctic outbreaks was unleashed into the Eastern US (January1985cold). This contrasts with February 1991 that was an overall mild month though the end of the month was slightly below normal temperatures across the Eastern US with more significant cold in Eastern Canada. The temperature response across northern Eurasia was more consistent including Europe. For both January 1985 and February 1991 cold was widespread across much of Europe.

https://t.co/LahzvNZ6yj

There’s so much potential :D

 

Edited by Daniel*
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