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Model output discussion - 5th December 2016 - Into Winter we go


Paul

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Posted
  • Location: Frankley, Birmingham 250masl
  • Weather Preferences: the weather extremes in general but my favourites are snow & thunderstorms
  • Location: Frankley, Birmingham 250masl

The models are just variables of what will (should) happen, so to me let's just get that high to the west and it will end up either in a better NW location or poorer se imo. Either way it should become pretty cold with something white! That could be either the s word or the f word. Let's just enjoy whats happening and just watch the models with interest and in 24 hours things will look better or hopefully not worse. Nobody or any computer model can predict what will happen in 3-4 days let alone 10!! Just my opinion of course

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WINTER 2016/17 FULL REPORT No. 5 WITH DECEMBER 27TH INPUT

Please note that most of the charts that I refer to in this post are through “live” links which update periodically. So, if you are reading this a few days or even hours after publication (on Tuesday, December 27th at 2330), some of the charts may already have updated. My comments relate to what the charts showed at the time of this posting.

Last week I said that my next full report would probably be on Tuesday, January 3rd unless there was a significant change in the broad pattern. So, guess what – I’m back a week early! I’ll cover all my usual features including a detailed coverage of Judah Cohen’s latest Arctic Oscillation blog which should be hot off the press just after I’ve finished wrapping up the rest of my report at the end of this evening (it is better news from him). I will slightly extend my regular coverage of Arctic sea ice extent and surface temperatures as these are even more relevant than usual “should” the northerlies materialise.

Managing Expectations and a Model Watchers Health Warning:

Those who read my last report (on page 167 of this thread) will know that I felt the need to start with some frank views concerning some of the appalling behaviour on this thread by a minority of members. That was largely associated with some of the frustration and disappointment at the models showing either a zonal outlook or a bland pattern dominated by an expanse of high pressure positioned to our south and south-east. Now, just 8 days later, the mood has swung in line with the upturn in the model output. The problems, however, have not gone away. In fact, I fear that if the models start to downgrade again (and there have been rather more mixed signs today) then a huge number of posts will have to be removed by the moderators!

Now, like the vast majority on here, I am a huge snow lover. Last week I put on a brave face and tried to look on the bright side but this week it is all about not getting over excited. I do not wish to be a kill joy and pour cold water over all the enthusiasm especially as there’s a danger that this might freeze over! The amount of ramping on here in the last few days has been extreme. Even a few professionals and, dare I say, one or two moderators have joined in this feeding frenzy.

Many need to manage their expectations properly. Yes, enjoy the exciting output and the hunt for cold and snow while it lasts but do not be sucked in by the herd mentality and start fooling yourself that this is “certain to be an epic cold spell” and it is “nailed on”. This is not completely impossible but the reality is that we are highly unlikely to see a prolonged severe cold spell. There are still huge uncertainties in how long it will last and just how cold it will get quite apart from whether it really arrives properly in the first place (although it does seem probable that next weekend will see a northerly arrive). At the very time of writing this part of my report (around 1800) we are starting to see something of a downgrade (or are we?). The very marginal set-up has persisted for many weeks and there is a narrow dividing line between MLB and HLB which has confounded the models resulting in huge swings. Yes, there was a good consensus a day or so ago for a cold outlook and to some extent this was backed up by the longer range models, the ensemble charts and several of the written forecasts. The models may well see several more swings, even in the normally rather more reliable D5 to D7 range. There is still a decent chance of some cold spells during Janauary and quite possibly a colder than average month overall.  

The message is to set the bar and your expectations somewhat lower. Then take a step back, carefully digest the data, the charts, the predictions and all the commentary and opinions and then see how things pan out. This will be far better for your health. Some of the regular much more experienced posters have been drowned out during the last few days. Knocker has been ignored recently and yet he has stuck to his guns and downplayed the movement to prolonged cold. He tells it how it is with an honest appraisal of the ensemble charts. Tamara and several other highly respected regular posters actually interrupted their Christmas breaks to come on here to remind us what was going on and behind some of the swings and to reduce expectations of prolonged cold. Some of these posts were not only ignored but actually came in for some completely unjustified criticism. There have been a number of very rude comments and this has got to be stopped. It is completely unnecessary and should not be tolerated by the moderators, who seem to have given almost everyone an easy ride over the Christmas period. The thread today has been clogged up by some quite ridiculous one liners. I never mention names when I criticise but you will all know who I’m referring to. There seem to have been endless posts today about the accuracy of the models over the Christmas holiday period and alleged missing data. This has been thoroughly disproven with regular experienced posters, professionals and at least one moderator all trying to patiently explain why this is a complete myth. Some have shown verification charts and referred to earlier analyses addressing this issue. It is quite extraordinary that this poster has disagreed with all and sundry and has been thoroughly rude to fellow posters including several moderators. He has single-handedly disrupted this thread on what has been a very busy day. Why oh why is this allowed to continue? That is more than enough or me rabbiting on about this but I should say that I am seriously considering leaving the forum altogether and I know there are quite a few others who feel the same way.

Why All the Changes – What is Going On?

As always, I remind all readers that I am not a teleconnections experts and I have limited understanding in this area of meteorological science. I always try to learn and then take a simple overview in order to convey my thoughts.

Let’s look back to the beginning of 2016. The close to record strength El Nino was the dominant force throughout the Winter. We saw a consistently very strong polar vortex with all the cold locked up into the high Arctic for much of the Winter. A Sudden Stratospheric Warming (SSW) event, which is more likely in an El Nino Winter, was predicted for mid to late January. The timing of this was put back for a few weeks. Then it was realised that there had been multiple warming events in the stratosphere which had failed to propagate down properly through the troposphere to the surface. This finally occurred during March, giving us a cold first half to Spring.

During the Summer the El Nino weakened to ENSO neutral conditions and, since then, it has oscillated between a slight La Nina state and around neutral. We saw a record weak polar vortex during much of November and as we entered December. There was some talk that the stratospheric state had not fully reset from the Spring SSW. The forecast was for a pretty blocked December and we certainly had that with no prolonged period of zonality with only a week or so (even less in southern England) without high pressure nearby. Unfortunately, the blocking was mostly in the wrong areas to produce any cold spells (so far).

We have seen an extraordinary recovery in the PV to one that approached near record strength. So far this has behaved very differently to last Winter. In fact, the USA went from almost no cold to a severe cold snap last week due to a shift in the PV. The deep cold did not last for more than a few days but it was sufficient to create the huge thermal contrast between the US east and south-east coast and the western Atlantic which fired up the Jet Stream. This was predicted to produce a much more zonal Atlantic but this (again so far) barely materialised – just sufficient to generate two named storms before high pressure has re-asserted itself.    

Now we still have a strong PV albeit slightly weaker than just a few days ago with slightly uncertain forecasts of its continuing strength and position. It does seem that it is possible, at least temporarily, to maintain a strong PV but with a meandering and split Jet Stream with some blocking patterns. This does not seem to be sustainable and something will have to give sooner or later. There has been recent talk of a negative PNA (Pacific North American index), disturbances in the western Pacific, the GWO (Global Wind Oscillation) supporting mid Atlantic ridging and other factors which are beyond my capabilities to understand and explain. This is for our resident experts to explain and, for example, we had an excellent update from Tamara on page 212 of this thread. I have mentioned all this here to emphasise just what an unusual period we have been through during this year. Records and extremes in some of the teleconnections have been rife. I have not yet mentioned the record low extent of Arctic sea ice – something where I have a much better understanding  and will focus on later in this report. It is no wonder that we have seen so much uncertainty and such wild swings in the signals and the model output.

I simply do not agree with the criticism of the use of teleconnections. They are a vital part in the development of meteorological science. Understanding has improved in leaps and bounds but there is still a long way to go. Reliability has improved and they give the experts a great overview of the background signals. The computer models take account of the teleconnections, so without them, the models would be rendered pretty unreliable. I liken it to removing the fuel from a car – you would not get anywhere without it...and no, this does not mean that we should go back to the simple use of short-term pressure charts and using analogues – we all know how dangerous that can be (this Winter is not 1962-63 all over again and every Winter is different). So many factors and variables need to be considered.

Looking ahead, taking account of everything that I have just said, there does seem to be a cold spell on the way. There seems to be a greater probability of several periods of colder weather. As with December, a blocked Atlantic is predicted but as we have seen, the amount of HLB as opposed to MLB is extremely important just as is the orientation of high pressure cells. In a way, anyone with an interest in the variability of our weather should thoroughly enjoy the current conflicting picture and the fluctuations in the model output. I “hope” that we get at least some decent cold and some snow but I shall do my best to keep an open mind and not to get overly optimistic. The NetWeather long term forecast was for a “Winter of wild cards” – well 2016 has been a year of wild cards but who is going to play the joker!

Dr Judah Cohen’s Latest Arctic Oscillation Report:

Here is the link to Judah Cohen’s latest update published at 2315 on December 27th.

http://www.aer.com/science-research/climate-weather/arctic-oscillation

Now I copy his summary and impacts below.

"...Summary The Arctic Oscillation (AO) is currently positive and is predicted to slowly trend negative towards neutral and possibly into negative territory over the next two weeks.

The positive AO is reflective of mostly negative pressure/geopotential height anomalies in the Arctic and mostly positive pressure/geopotential height anomalies across the mid-latitude ocean basins, especially in the North Pacific. With negative heights over Greenland, the North Atlantic Oscillation (NAO) is also currently positive.  However with heights predicted to rise near Greenland this week, the NAO is predicted to turn negative over the weekend. 

With the positive AO/NAO, temperatures have become much milder across the Eastern United States (US) and western Eurasia, two regions sensitive to the AO/NAO phase. Cold weather remains in the Western US and Eastern Siberia, regions that are often cold when the AO is positive.

However the atmosphere is undergoing a dramatic transition as ridging/positive geopotential height anomalies currently across the mid-latitudes are predicted to migrate poleward across both ocean basins.

The North Atlantic oceanic ridge will block mild, maritime air from much of Eurasia, this should commence a cooling trend across western Eurasia including Europe.

The North Pacific oceanic ridge will block mild, maritime air from North America, this should lead to further cooling in western North America that will start bleeding into eastern North America.  Models are predicting that the two oceanic ridges will bridge across the top of North America.  This could potentially lead to a very cold period across southern Canada and the Northern US.

With relatively quiet poleward heat flux the polar vortex (PV) is now stronger than normal.  However there are signs of another troposphere-stratosphere-troposphere (T-S-T) coupling event initiating in early January and I share my thoughts below on what to expect in the coming weeks.

Impacts  In trying to use analogs to give guidance to what expect this winter I have discussed/tweeted the winters of 2009/10 and 2013/14.  I didn’t think to include last winter of 2015/16 as well but now I do.  Though last winter was mild even record mild, coupled strong PV both in the stratosphere and troposphere at the end of December was disrupted by advection of record warm air into the Arctic basin that even reached the North Pole.  That was the start of a multi week period of a negative AO and the most sustained cold across both North America and Eurasia last winter and dominated the January means.  But it was also the beginning of what I refer to as a tropospheric precursor that initiated a troposphere-stratosphere-troposphere (T-S-T) coupling event (see Cohen et al. 2007) that culminated in a record weak PV in March.  But for the winter of 2015/16 the most important impact of the T-S-T event was a very energetic and protracted period of Wave Activity Flux (WAFz)/poleward heat flux that lead to repeated northward transport of mild subtropical air across the mid-latitudes.

Though so far, this fall and early winter season have been notable for a weak PV, currently the PV has dramatically strengthened and is fully coupled between the stratosphere and troposphere.  Yet once again the transition from strong to weak PV at least in the troposphere is punctuated by unusually mild air into the Arctic basin that has reached all the way to the North Pole.  The forecast of warming tropospheric polar cap geopotential height anomalies (PCHs) in early January signals to me the commencement of a second T-S-T event this fall and winter season.  This was something that I anticipated and offered previously the winter of 2009/10 as a possible analog.  Two important differences however are that the winter of 2009/10 was an El Niño winter and the quasi-biennial oscillation (QBO) was easterly. This winter is a La Niña winter and the QBO is westerly.  So though the T-S-T event in January and February 2009/10 culminated in a major mid-winter warming (MMW where the zonal wind reverses from west to east at 60°N and 10hPa) in February, the background environment is less favorable for a MMW this winter.

Though I am less confident to how the stratospheric PV will respond in the coming weeks, I am more confident that we are at the initiation of T-S-T event that begins with a tropospheric precursor.  Tropospheric precursors last on the order of two to three weeks (or about half the longevity of the tropospheric response to a stratospheric PV disruption).  It is predicted to begin the first week of January and will likely dominate the January climate means.  The pattern is at least not initially a classic AO pattern with the strongest ridging/positive geopotential height anomalies centered over the central Arctic basin, but with strong ridging positive geopotential height anomalies predicted in the high latitudes of both ocean basins, mild, maritime air will be blocked from both continents.  Instead of westerly flow, northerly flow will advect colder air into both the US and Europe.  With the models predicting that both ocean ridges will merge creating a ridge-bridge across the North American Arctic, this will likely suppress geopotential heights further south across Southern Canada and the Northern US.  This is potentially a very cold pattern across a large area of North America.  My thoughts on how the remainder of the T-S-T event may unfold are discussed below...."  Please use the link above and refer directly to his blog for the rest of Judah's report - there is some interesting fine detail on the short-term changes plus many charts and diagrams.

BRIEF COMMENT:

Many of Judah Cohen’s short tweets are copied onto this model thread. I feel that these are rather headline grabbing and not nearly so balanced as Judah’s well considered weekly reports.

Judah was, for the first time this Winter, pretty downbeat in his report last week but he focusses on what has changed since then.

 Arctic Sea Ice News and Analysis:

The last full monthly report was published on December 6th but please note that the current ice extent map and the comparison chart to the mean are updated daily and are always of interest. Here’s the link:

http://nsidc.org/arcticseaicenews/

I refer you to my short Christmas Eve “reply post” on page 200 of this thread which is well worth a quick read if you missed it. I was very critical of the BBC ramped up story on the warmth over the North Pole. I will not repeat that here but what I argued is fully supported by my analysis below of Arctic sea ice extent and Arctic sea surface temperatures. The charts highlight the record low overall Arctic ice extent during October and the very slow recovery during November. There was a very strong recovery during the first weeks of December, then a 3 days set-back but the recovery has just resumed again since yesterday. The sea ice extent is now only just shy of the previous low set during Winter 2012-13. I still predict that with the colder forecast conditions up there for the short-term at least, 2016-17 will overtake 2012-13 within the next week. The Baring Sea and Kara Sea ice extent on our side of the Arctic has also been recovering much more quickly during December but is still well below average. The recovery is also evident across other parts of the Arctic, particularly the ice extent in Hudson Bay, around the Canadian islands  and now around Greenland too with a very rapid increase during the North American very cold snap.

Last Winter the record strong Polar Vortex sent a roaring Atlantic Jet Stream right up towards the high Arctic which greatly restricted ice build-up for weeks on end in the part of the Arctic nearest to us. So far this Winter this has not been the case, although other factors are also at play. There has been considerable speculation as to how this low ice extent interacts with the teleconnections and how it might impact on broad northern hemisphere Winter patterns. I shall pick up on this again after I have covered the other relevant parts below.

Arctic Oscillation (AO) 14 Day Ensemble Charts (updated December 27th): 

The Arctic Oscillation, which has been strongly positive for the last week or so is now trending down again. After reaching neutral there is a one day jump again before all  the ensemble members trend negative and some very strongly negative by the end of the period on January 11th.

CAUTION:  this is in line with the current GFS model output but is liable to further fluctuations. It does currently reflect the change to greater HLB in early January. Here’s the link.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml

North Atlantic Oscillation (NAO) 14 Day Ensemble Charts (updated December 27th):

The NAO is much more mixed starting off trending slightly negative with just an odd member positive and then a distinct split from January 2nd with a few members going positive but more going slightly more strongly negative. I would suggest that this slightly obscures the Atlantic set-up. The slightly NAO- is reflective of GFS modelling higher pressure to our west and the low pressure to our north and perhaps later to our east. Again subject to further short-term changes. Here’s the link:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif

Please note that both the AO and NAO charts I show are based on GFS ensembles so are indicative of their modelling and not the ECM and UKMO output.

MJO Ensemble charts:

Here are today's MJO ensemble charts for the big 4 (all updated on December 27th). 

UKMO (7 day forecast):  

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml

ECM (14 day forecast): 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml

NCEP/GEFS (14 day forecast):

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml

JMA (9 day forecast):  

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/jman.shtml

Please note that last Winter I reported on Kyle MacRitchie’s specialist MJO predictions which seemed to always differ somewhat from the big 4. I have been in contact with Kyle during the summer and he feels that his charts are not adjusted frequently enough and should not be compared to the others. So, unless Kyle improves his updating standards, I shall discontinue reporting on his predictions for the time being.

COMMENT:  The UKMO (shortest forecasting period) is now showing the MJO emerging from the COD (Circle of Death) in phase 2 at moderate amplitude at the end of the period. The ECM is confused with the MJO in the COD but swinging around between phase 6 and phase 2 The NCEP/GEFS goes on a similar COD circular tour but with a few members getting close to phase 1. The JMA ends up in phase 1 at low amplitude but with a few members getting to moderate amplitude. Overall the MJO is not particularly helpful right now (in terms of enhancing HLB) and some experts have said that there may be some masking of the signal by other factors.

Northern Hemisphere Snow Cover:

I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA).  When you go to their site you can change the date range and look at the Autumn and Winter seasons and you can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I’ve have re-set the links below to show the last 2 weeks from December 12th to December 26th but you can change these again:

a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA December 27th):

https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20161212-20161226

b) Animated Europe and Asia Day Snow Cover  (updated by NOAA December 27th):

https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20161212-20161226

COMMENT: There continues to be well above average snow cover over northern Asia and this has recently expanded southwards and south-westwards.. Much of northern Scandinavia continues to have decent snow cover but the south has lost most of its snow cover in the last few days (the high central plateaus usually have pretty complete snow cover for most of an average Winter). The snow cover currently extends to far eastern and north-eastern Europe but has receded from central Europe recently. North American snow cover had increased significantly during the recent very cold snap but has receded very slightly in recent days. The Arctic ice sheet has expanded quite quickly during the last few days on the Alaskan side but halted its expansion in the Baring and Kara seas (as described earlier) only to resume growth again from yesterday. The Hudson Bay has gone from almost ice free to completely ice covered 2 weeks ago.

Current Arctic Regional Surface Temperatures:

GFS – Northern Hemisphere Current Temperatures:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=6&mode=9&carte=1

The link to this chart updates 6 hourly with each GFS run. At the time of writing it is showing a chart for 1900 GMT today (27th December). As this is T0 to T6 hours, it should be pretty accurate. Here is a summary of the temperature readings that I will be following in future reports with comparisons to my previous readings on December 19th in brackets:

North Pole:  -28c (-20c to -28c).

Barents Sea/High Arctic:  -8c to -20c (-4c to -16c).

Scandinavia: south 0c to -4c (little change); north -4c to -8c (0c to -4c).

Northern Siberia: -32c to -40c with a wider area below -40c  (little change).

North West Russia:  around -16c to -24c.(no change)

North-east Europe: -8c  to -16c (-4c  to -16c).

Greenland: -16c to -32c (-20c to -36c).

Canadian Arctic: mostly -12c to -28c (little change).

Alaska: -8c to -16c (-8c to -24c).

Western USA: -4c to -12c (little change).

Central USA: +4c to -4c (-4c to -8c).

Eastern USA: 0c to -4c (-4c to -8c).

Please note:  For land masses I have tried to focus on readings away from the coasts and away from any mountainous areas.  At the time of posting this link it was showing 1900 GMT on Tuesday, December 27th. I will always try to show the 1900 GMT (2000 BST) charts for a consistent comparison. The charts are automatically updated 4 times a day, so the temperatures shown will be different to those I just mentioned above. We can follow the trends by looking at the latest data at any time from now on. It is vital to note the time of day to take account of daytime/night time variations. So for like for like comparisons, for example the 1900 charts for each day should be available to view from the 12z (T+6) updates which are published around 1600 to 1700 or about 4 to 5 hours later. This also applies to some of the other charts I link to in this post.

Svalbard Daily “Maximum” Temperature Forecast for 10 Days:

Here are the links to the 3 Svalbard stations that I am monitoring.

Central/West Svalbard – Longyearbyen 28 m asl:   

http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf

December 28th  -2c;    January 1st   -10c;    January 5th  -9c.

North-West Svalbard – Ny-Alesund:  

http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf

December 28th  -5c;    January 1st   -17c;    January 5th  -12c.

Central South Svalbard – Sveagruva:   

http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf

December 28th  -4c;    January 1st   -14c;    January 5th  -15c.

The “maximum” temperatures fell to between -20c and -25c  during the second week of December and then recovered to around 0c for the last few days but are falling back again steadily during the next week.

These links will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at short range. 

To put the above figures into context, here is a link to the main Longyearbyen site:  

http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html

This shows monthly means and actual highest/lowest temperatures recorded during this winter and goes back further. Svalbard has been seeing “maximum” temperatures often running at 8c to 10c above their long term average throughout most of 2016. This has been the pattern for several years and is reflective of the warming Arctic and record low sea ice cover. The very recent trend was more encouraging with temperatures falling to slightly below their long term averages for 4 days in early December  which is the longest period of below average temperatures for about 3 years! Then maximum temperatures rose to around zero but are now falling again. They will generally be around or below -10c during early January just when the predicted Arctic airstream might hit the UK. These lower Arctic surface temperatures might be the difference between rain/sleet and snow in a marginal set-up for low lying areas further south.

Final Comment:

Most of the models, indicators and forecasts that I refer to in my report do show "some" support for the predicted cold spell in early January but with a good degree of uncertainty in respect of longevity and severity. I feel that we are more likely to see several shorter cold periods with less cold interludes which might be more consistent with the weak signals and no one pattern able to dominate overall. 

Next Update:

Scheduled for Tuesday, January 3rd.

 

EDIT: @stewfox  (I am rarely able to get the member automatic link notification facility to work on these edits unless I accidentally stumble across it - i would appreciate a foolproof explanation from someone)

I see your comment (and thank you for your appreciation) but I feel that you have probably read this part of my report a little too quickly and taken the words that you highlight slightly out of context. Yes I say that we are "highly unlikely" to see a prolonged severe cold spell which clearly carries on directly from the previous sentence (where I have been emphasising the need for many readers and posters to manage their expectations and I gave examples of exaggerations that have cropped up on this thread in the last few days). Then I go on to say in the next sentence that there are still "huge uncertainties" in relation to how long the cold spell will last and just how cold will it get. I am again managing expectations which was the entire purpose of this section of my report with a clear title at the top. In respect of your final point, surely everyone accepts that cold spells "rarely" last for long in this country. 

Edited by Guest
Correcting typos and to ensure that all the links work properly.
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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

The ECM London graph looks very tasty but the GEFS are not really reading the script regarding potent cold.

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Posted
  • Location: Banbury
  • Location: Banbury
4 minutes ago, feb1991blizzard said:

The ECM London graph looks very tasty but the GEFS are not really reading the script regarding potent cold.

There is a few in the GEFS that are decent without a doubt

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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.
Just now, Banbury said:

There is a few in the GEFS that are decent without a doubt

Yes, there have been for a while now but a day or 2 back, there were more than just a few, its hard to know what to make of the ECM eps unless you can view them.

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Posted
  • Location: Napton on the Hill Warwickshire 500ft
  • Weather Preferences: Snow and heatwave
  • Location: Napton on the Hill Warwickshire 500ft
11 minutes ago, Bring Back1962-63 said:

WINTER 2016/17 FULL REPORT No. 5 WITH DECEMBER 27TH INPUT

I shall be proof reading and editing this report for the next hour or so but wanted to get the Judah Cohen good news out quickly

This is not completely impossible but the reality is that we are highly unlikely to see a prolonged severe cold spell. There are still huge uncertainties in how long it will last and just how cold it will get quite apart from whether it really arrives properly in the first place

Great report but get confused over these two comments. 

If there are 'huge uncertainties', how can we attribute 'highly unlikely' ?

From experience ? ie cold spells don't tend to last long ?

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

A quick look through the ensembles for the 18z GFS... they don't look too bad at all 

Quite a few maintain a northerly flow to T240 although most have a mid Atlantic block rather then one ridging up to Greenland. Very few ensemble members go back to the anticyclonic mild gunk we saw in December thankfully (upto T240).

I think the chances of anything really cold are quite low at the moment but I think we could well get more attempts to get things right.

And as an above post states little changes can have a big effect. AO is forecast to go negative so I'm hoping this northerly may well be sustained like this:

GFSP04EU18_216_1.png


Also of note, a fair few members go for a Scandi high later on:

GFSP05EU18_342_1.png


GFSP18EU18_342_1.png


GFSP17EU18_342_1.png

 

GFSP06EU18_342_1.png

 

In summary a northerly flow develops at the New Year, temperatures may recover to average before more potential northerlies. After that who knows? Not a bad way to start the New Year

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Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL
56 minutes ago, Dennis said:

 

If you have any old folks heading off to the likes of Barcelona and Nice to avoid the Winter's snow, you would be best advising them to stay at home.

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Posted
  • Location: BS15 8bx
  • Location: BS15 8bx
22 minutes ago, mountain shadow said:

If you have any old folks heading off to the likes of Barcelona and Nice to avoid the Winter's snow, you would be best advising them to stay at home.

Although not improbable I think the chart is highlighting possible high snow fall depths for the Pyrenees rather than Barcelona and Nice.

IMG_0682.PNG

Edited by Richard Fisher
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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire

Last 3 CFS runs for Jan

cfsnh-4-1-2017.png?12

cfsnh-4-1-2017.png?18

cfsnh-4-1-2017.png?00

Next one should be out in a couple of hours or so but fairly good continuity now....I'd like to see the height anomalies become a tad more striking but even so, I don't think we can discount some weak heights somewhere to the N of us through the month. The question is whether they'll be able to deflect the jet far enough S in our locale for us to benefit from them.

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

Yeah GFS a bit on its own but consistent with this pattern end of high res though as Steve says slight upgrades

gfsnh-0-192.png

GFS still manages to troll the netweather forum though.

gfs-1-204.png

 

I would rather go with UKMO 144 and hopefully the pattern will keep getting nudged West

UN144-21.GIF

 

GFS awful in FI losing upsteam amplification - it's like the obnoxious drunken lout in the bar that's looking for a fight.

gfsnh-0-240.png

 

GEM is more like the  buxom barmaid that just gave you an extra measure.

gemnh-0-228.png?00

 

Still seems it could be a lock in or a trip to A&E - 50/50

 

Edited by Mucka
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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

GFS slightly redeems itself with deep FI super trough.If you can't have blocking that's as good as it gets but don't hold your breath.

gfsnh-0-348.png

 

GFS parallel also disapointing day 10 but also redeems itself in deepest FI. Did I say don't hold your breath?

gfsnh-0-240.png?18gfsnh-0-348.png?18

 

GFS ensembles show little support for the Op including the control run and  though a good few solutions on the table the main theme is that the pattern has been backed West which is good news I reckon.

 

 

Edited by Mucka
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Posted
  • Location: Manchester Deansgate.
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate.

The GEFS looking much more amplified upstream even at 192 than 18z, *SHOULD* be some very cold solutions.

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Posted
  • Location: Camborne
  • Location: Camborne

For a change a quick look at this morning's lapse rate 1000mb-850mb, as an indicator of colder air in the boundary layer with low level inversions/fog, As expected in the west Midlands hardly any LR at all. The nearest 00Z sounding is Nottingham and as can be seen the 850mb temp is +2.25C, whilst at 939mb it is +6,5C and the surface +1.5C

Oh and moving to weekend the latest fax charts for the passage of the cold front

8501000lapse_d02_20.png2mmintemp_d02_20.png2016122800.03354.skewt.parc.gif

PPVM89.gifPPVO89.gif

The GFs this morning is in not bad agreement over the cold front over the weekend. After that there is another amplification burst which initiates quite a strong NW flow with the trough to the NE/E which is still phasing with the trough to the south tantalizingly close to the UK.

gfs_z500a_natl_28.pnggfs_6hr_precip_eur3_28.png

The high cell moves east stretching north which in itself is an error as it is wide open to the next attack from the energy rushing east from upstrem and more frontal systems swing and traverse the UK bring an interlude of wet and possibly windy weather.

gfs_uv250_natl_37.pnggfs_6hr_precip_eur3_36.png

So in a nutshell remaining fairly dry, particularly in the SE but the occasional interruption as fronts track in from the NW. Temps quite variable depending on which are the dominant surface features but perhaps a little below average overall.

This morning's GEFS anomaly supports the general assessment above,

gefs_z500a_5d_nh_41.png

 

 

Edited by knocker
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Posted
  • Location: Warsaw, Poland. Formerly London.
  • Weather Preferences: Four true seasons. Hot summers and cold winters.
  • Location: Warsaw, Poland. Formerly London.

An example of the 00z "going off on one"? Check out the t2m outlier. :drunk-emoji:

gefstmp2mmaxWarsaw_Poland (12).png

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Posted
  • Location: Brighton, East Sussex
  • Location: Brighton, East Sussex

The 0z charts are so close to something special but we just can't get enough amplification in the ridge, need to hope the pattern keeps backing further and further west, which is something we've seen before so entirely plausible.

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

Now there's a chart full of potential :rofl:

 

it has carried forward a similar idea to be fair. 

 

 

IMG_8100.PNG

Edited by That ECM
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Posted
  • Location: ipswich <east near the a14> east weather watch
  • Location: ipswich <east near the a14> east weather watch

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

the gfs :cold: f1  is still saying the uk can expect cold  and possible snow from jan 5   i see:cold:

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Posted
  • Location: Camborne
  • Location: Camborne

The ecm tending to ridge the HP NW and with split energy across the Atlantic. The UK generally under the influence of the high pressure except for the NW/N which is vulnerable to systems tracking around the HP. Temps a little below average

ecm_t850a_5d_natl_11.png

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Posted
  • Location: Cork, Ireland.
  • Weather Preferences: Storms frost snow heatwaves
  • Location: Cork, Ireland.
2 minutes ago, knocker said:

The ecm tending to ridge the HP NW and with split energy across the Atlantic. The UK generally under the influence of the high pressure except for the NW/N which is vulnerable to systems tracking around the HP. Temps a little below average

ecm_t850a_5d_natl_11.png

Systems tracking around the area of high pressure for those further northwest would probably suggest alright why Met Eireann in their latest update this morning are now talking about the high probability of this being a short cold snap from Sun-Tues inclusive with a return to less cold or even milder south westerlies by next Wed. 

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Posted
  • Location: Dorset
  • Location: Dorset

Not a great fan of the potential for backedge snow. The front as it moves down has embedded dps of 2-5c, despite some low 850s. Any showers once the front has moved through will likely be snow and in high ground we will see snow above maybe 300/500m. 

This might chance but the cold air is more progged to move over the front rather than under it. 

The good news is that gfs has taken a big step towards ecm and meto at the t144 range, whereas ecm and meto have taken a smaller step towards gfs. Some some agreement. This has resulted in a colder set of gfs ens. This chart yesterday had a considerable amount of green at one point. 

I still think we will see small scale changes upto t144 and the t168 and beyond could still change considerably. 

However as nick says any change will likely be around how what cold and how rather than a switch to normal or mild. 

IMG_0658.PNG

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