Im quite new to all this weather lark and im tryin to get my head around the charts etc and the terms that go with it(don't laugh) I understand the basics ie high and lows but not sure how the colours work, being as im colourblind and find the shades blues, reds greens etc hard to see,especially when they are close together.
Ideally what should I be looking for if im hoping for cold/snow,if that all makes sense.
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Hi. Go back to the forum main page, then scroll down to the library. There are a couple of threads in there you will find useful. 

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The good news is that there is near universal agreement in the GEFS for an arctic high. The effects of course are quite disturbing for us in the medium term with the potential for a repeat of last years extreme cyclogenesis events

http://modeles.meteociel.fr/modeles/gens/run/gensnh-18-1-288.png?6

After this period of stormy weather then perhaps we can get high pressure in the right place for the end of the month

 

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No, you couldn't draw it any worse than that lol! It's like the west < east flow has been drawn with a ruler 

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do we need an SSW to get very low uppers to the uk? : no

do we need a strat profile that isnt conducive to strong zonality to get very low uppers to the uk?: no

does an SSW increase the likelihood of getting deep cold to the uk?: yes

does a strat profile that is conducive to a split vortex on a n pacific/greenland-scandi axis increase the likelihood of getting deep cold to the uk?: yes

now thats a pretty big envelope within which to have a debate!

no doubting that currently the modelled strat profile is going to be conducive to the polar trop becoming blocked and cold heading south in the NH. whether that means we get the split or displacement in a position that is good for nw europe remains uncertain. on top of that, other factors may over ride any stratospheric influence though i think a full blown upper reversal would propogate down quite quickly, given the overall weak state of the strat vortex. whether anything in the trop could override the strength of that -AO state would be questionable. in the end, unless you get a split in the greenland area, conditions for the uk are unknown and even that could result in west based -NAO. 

the jigsaw is complex but i think we have an interesting couple of weeks model watching upcoming.

 

Hi all,

Here's today's video update - Westerlies Returning For Start Of 2015;

http://www.gavsweathervids.com/

#battendownthehatches

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Not at all as heights over to the East have receded and we're a long way off from anything from the East developing going of the NH profile charts. Of course we can get a sustained cold spell without SSW as in January 84 whch delivered a two week cold spell with deep lying snow, granted the South so sod all. Until we see that lobe of low heights over Greenland subside then we'll see no HLB  in a favourable place for the UK. All talk of phantom easterlies and Scandi highs have delivered diddly squat so far and we need to look N/NW for more favourable Synoptics  and the only way that will happen is for a SSW event to take place.

Don't agree

 

As said, the models/weather "are huge jigsaw puzzles" IN FLUX and INCOMPELTE

This present weather is above what I would expect for this time of year.

Normally Xmas is dull mild and wet!

1 week cooling down and the next week warming up is the norm! Any prolonged cooling/frost in winter is a bonus!

 

 

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Cheers Gavin

Batten down the hatches indeed though I still havent bothered to fix the fence from last year!

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Yes, I agree with that mostly. My only point is that given current model output, the imminent SSW is the only straw available to clutch at. I have never said that an SSW is "THE key factor", but a decent SSW is a pattern changing event, which can change the potential for cold weather to reach our shores.

 

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No offence SC but that last sentence is total rubbish   Straight to the point Neil

 

Saying things like 'any hope of the beast from the East are dead in the water' on the 29th Dec is quite frankly ridiculous  Very true

 

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http://www.wetterzentrale.de/pics/Rtavn3121.gif

HP to our East on the 6z

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MattHugo81
@chionomaniac - Just looked through 00Z EC Clusters and not a whiff of any N blocking yet it's a zonal +AO & esp +NAO pattern throughout.
29/12/2014 09:22

Any SSW might be slow to have an impact

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Always the case - previously we have seen that it takes 8 to 10 days before any derived change shows up in tropospheric output. If the current SSW has an effect, we should start seeing an improvement in the model output within 5 to 7 days. How could the MO be expected to show improvements at this stage, when the current SSW is only just firing up? Matt Hugo is putting the cart before the horse?

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Maybe one or two of you need to learn how read a post correctly before replying as I did say on current output when viewing the NH profile. As for Matt Hugo he was the one telling us that a SSW would/should occur during the latter part of this month and like MM has said he's now putting the cart before the horse.

Is it me or have I been reading here for what seems like an age now about an impending SSW. As of yet I have seen no evidence of this showing through in the models or did the event that folks talked about earlier in the season not take place. It's the one piece of the jigsaw I confess I know little about but there seems to be a lot of knowledgeable people on here that seems to think that it's a given and what's needed for a cold spell across the UK. While it may play a part in increasing the possibility of cold it is not a given as some on here would suggest as there are a multitude of other weather paarameters which has also to fall in place for cold to take place.

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Awful. I said a couple of days ago there were some encouraging signs, they evaporated pretty damn quick to give a 2014esque pattern. The high in the arctic has no support further south so is as useful as a chocolate teapot.

Roll on February 

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The rationale behind paying so much attention to the strat. at the moment is quite simple really - with the hemispheric setup as it is, a SSW is our best bet for changing the game in our favour.

It's by no means a guaranteed path to success - there could easily be a big freeze to our east with nothing much here, like in February 2012 I think it was - but I can't see much evidence for positive changes being driven by much else in the coming weeks.

In short, what Nick said earlier (good post by the way) 

So, I'm going to be focusing on this aspect until if and when some interesting storms start coming along, by which time the week 2 model output will hopefully be showing some marked changes to our pattern.

 

Re: Martin's post above, there was a lot of warming last month but it didn't quite have the strength needed to bring about much change away from the areas beneath where the warming occurred, which were on the other side of the pole. Over there, high latitude blocking has been coming along quite often of late and looks to be doing so again during the coming 10 days or so.

As for an impending SSW, I can see strong signs of it on the latest model runs, even GFS, which has been very reluctant until today (below-left shows very strong warming focused over the SW tip of Greenland, below-right shows the impact on the vortex by day 15):

  

While GFSP remains a bit less keen, it's been trending stronger as well, while ECM has been showing the strongest warming of all, perhaps a full-blown SSW based on the day 10 00z chart (not shown as it's behind a paywall I think - I'm relying on reports by others).

The significance of having warming to our NW is that even if it doesn't go the whole hog, it will act to reduce the westerlies in the Atlantic sector and support high pressure to our NW. Just a hint of that in the latest GFS run.

As it is, the trop. impacts probably won't be seen until the second half of January.

Until then, a strong westerly flow seems likely starting 7-8 days from now with a high risk of severe wind events and large rainfall amounts. Shame we have to take this route but the wave breaking just didn't pack enough of a punch back in December to overcome what was an unfavourable origin as far as the UK is concerned (east Asia).

 

Edit: just thought I should make clear that an actual SSW remains nothing more than a possibility at the moment - we may just see some fairly strong warming to the NW, which would tip the balance toward blocking to our NW but there's no telling at this stage whether it would be enough.

Despite all this uncertainty, I'd rather analyse it in detail than spend my posts moaning about how dreadful the current NWP output is in terms of the UK's surface weather pattern.

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I think Matt actually forecast January 7th??

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I think the last couple of months have seen plenty of chat concerning warming in the strat, but none, as far as I could see, about any impending sudden stratospheric warming, which by definition is an extreme event (it wouldn't be sudden otherwise). I think it's a bit unfair of Gibby to feel frustrated with strat discussion on that basis.

On the other hand, I haven't seen any evidence that analysing modelled warming in the strat 16 days into the future is any more or less valid a method for forecasting weather than analysing modelled cold at the surface at 384 hrs. But no harm done.

One piece of evidence against putting too much weight on SSWs is the winter of 2009-10, the one recent winter which kept every coldie happy all the time, with the cold extending all the way through from mid Dec. onwards. The trouble is, the SSW that winter didn't appear until early February!
http://www.atmos-chem-phys.net/12/8115/2012/acp-12-8115-2012.pdf 

I get as puzzled as Rob K about the number of people dissatisfied with Dec. 2010: a virtually unique event for most of us in the south, with that blue light over the snowfields with the sun at its lowest.

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I will second what James has said about Nick's (nickl) post earlier which was excellent.

It is worth noting that there are several types of SSW including major and minor events as defined in a 1978 WMO commission http://en.wikipedia.org/wiki/Sudden_stratospheric_warming

For a major event to occur there must be an increase in mean temperature poleward from 60N at 10hPa or lower and an associated circulation reversal to a mean easterly flow again from 60N northwards.

For a minor event there must be an increase in mean temperature of at least 25C within a week at any stratospheric level in winter. The zonal mean wind is weakened but there is little or no reversal in the flow and the polar vortex is not broken down.

Typically a major SSW occurs about once every 2 years while a minor SSW can occur several times each winter. The warming we saw in the stratosphere back in November was nowhere near sufficient to qualify as a SSW.

The last major SSW was in early January 2013

This chart shows the sudden increase in temperature at 10hPa
http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/10mb9065_2013.gif

This chart shows the zonal mean wind changed to easterly (the green area) at the same time
http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_MEAN_ALL_NH_2013.gif

This is also highlighted by the zonal wind anomaly chart (the blue area)
http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_ANOM_ALL_NH_2013.gif

This event was followed by some cold conditions in the UK (which may have been partly a result of the SSW). From 13 - 25 Jan 2013 the mean CET was -0.6C.

The last minor SSW was at the beginning of February 2014

This chart shows a temperature increase of 25C from about -60C to about -35C in early February at 10hPa
http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/10mb9065.gif

The zonal wind was weakened but only reversed to easterly briefly and only then at 2hPa and below. At 10hPa there was still a weak westerly flow
http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_MEAN_JFM_NH_2014.gif

This event had no discernible impact on UK temperatures.

Applying the above to the current situation and what the models are showing today there are clear signs that a minor SSW is almost upon us. Given what the output is showing this could potentially become a major SSW within the next 10 days.

Warming often starts high up in the atmosphere. This can clearly be seen on the latest chart for the 1hPa level
http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/01mb9065.gif

This shows a temperature rise of about 19C in the past few days from around -31C to close to -12C. It only needs to rise by another 6C to meet the definition of a minor SSW (the above definition requiring a 25C rise within a week at any level of the stratosphere).

Looking at the model output the current temperature profile at 1hPa is as follows
http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/gif_files/gfs_t01_nh_f00.gif

This shows an area of very warm temperatures of greater than +15C but also a core of cold temperatures in places below -50C.

The forecast chart for T72 shows the following
http://www.cpc.ncep.noaa.gov/products/stratosphere/strat_a_f/gif_files/gfs_t01_nh_f72.gif

The area of warm temperatures has shrunk a bit but also there are now no areas where the temperature is below -40C. So overall the mean temperature looks like it will continue to rise in the coming days.

Significant impacts are also being modelled at the 10hPa level as per James' post above. As others have said, changes in the stratosphere probably represent at the moment our best chance of seeing colder conditions develop as we move through January. But even if a SSW does occur this does not necessarily mean we will experience colder conditions in the UK, it merely increases the probability that we might.

It is now happening and is shown correctly here:

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php?plot=temps&alert=1&lng=eng

 

It is no longer a forecast, but a nowcast.

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Let's hope that it bears some fruit as far as altering the pattern of the winter is concerned.

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Indeed. The 12Z +240 GFS has a fat Azeuro high and a flow across the UK straight from Bermuda. Pure gunk IMO.

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By the end of the week we'll start seeing some eye candy 😉

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