johnholmes

I think the first idea was to keep it as simple as possible. There are about 8 paramaters if anyone wants to check all those that affect will it be snow or rain, see the Guides for that.

It is probably a better idea to see what the 850 wind directions are as the low tracks ? SE, along with what 850mb temperatures it suggests over you?

a nice post for new folk, the only other parameter I would add is your height above sea level, that can be significant in marginal conditions.

And what does the Met O web site show at the same time? It would not be the first time if they show a different set up.

here here

These are my daily comments after looking fairly closely at the anomaly charts I use, links as usual below SAT and changes between ec-gfs, ec back to trough-ridge-trough and flow over uk=n of w but gfs not=much as chart above=about s of w! (chart not shown in this post) Noaa 6-10 and 8-14 show no marked change from charts above=suggests cold spell lasting into 19 January at least. Latter part looks dominated by upper ridge which presumably will have a surface high somewhere beneath it. ec-gfs not in agreement, and although they led the way (ec especially) in predicting the pattern change, I am more inclined to believe noaa than the other two. http://www.cpc.noaa.gov/products/predictions/610day/500mb.php http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

For sure there is doubt amongst the various outputs, be that longer term links, anomaly charts, mean charts or synoptic outputs. However, the overall idea initially of a change from the relentless wet weather causing so much havoc and discomfort to so many is going to change. The cold outbreak is showing signs of developing much as suggested 2-3 maybe as much as 5 days ago. It is a slow process due to the reluctance of the upper trough, for whatever reason, to move east. This ensures that the surface features beneath it also take a longish time to edge east to allow the more polar type air to move south. Just how this cold burst was able to develop with so many longer range teleconnections against it is a mystery to my simple mind. But develop it has and was well predicted, from my point of view, by the anomaly charts. They are now not consistent with one another, chiefly the EC-GFS outputs with NOAA staying with its idea of, perhaps, 8-10 days of an upper ridge west of us, and a relatively shallow upper trough east of it, before a more westerly upper flow returns. There is, as yet, no signal for any major deep cold outbreak in my view. usual links http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Dry but cloudy after slight rain overnight, a low of 3.8C

Not sure that they have yet proved to be wrong; the original forecast from them was for a cold spell of 3-5 days. That is still going to occur. What is now in doubt is any longer spell. At no point, but correct me if you feel I am wrong, did I suggest it was to be an intense deep cold. Originally, again, they showed the upper ridge over the UK by about the 3rd day of the cold spell. This appears, on the synoptic models, to ne what may well happen?

sod it, spent 5 m typing a post and its gone, no idea where, so brief repeat. Until the output this morning from EC especially, less so GFS, the anomaly charts for at least 3 days had been showing very similar charts for the 6-10 day period. With NOAA also on its 8-14. This morning, see below, EC left the consensus, indeed looking very closely, it had started to do that yesterday. I am not sure if it is the correct idea on things 6 days or more hence or it will come back to the NOAA chart. 2 years ago I would have backed NOAA every time against it but the last 12 months or so and it, sometimes with GFS, has led NOAA to what turns out to be the correct solution for the upper air pattern. This whether it is for the status quo to remain or for a pattern change. Nor am I sure just how much effect the probable arrival in the North Atlantic of an ex Sub Tropical storm will have. They rarely get picked up correctly by any model for several days as far as position, track and intensity. We are going to get cold (by definition of that word), indeed the far NE is already so. How much snow for anyone will not be sorted probably until 12-18 hours prior to its prediction. How long the cold lasts is not clear at the moment, at any rate not to me, using the anomaly charts. IF NOAA shows any inclination to follow EC then 4-6 days, if not then perhaps longer. I would not back either way for 1-2 days so enjoy what the weather does for the next week. And hopefully much less will fall from the skies for those folk unable to live or work in their properties. http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

no correction needed you are pretty much spot on with what the AA and NAO are.

Sub tropical lows are well known for any model having great difficulty in dealing with them. Whether this is having an effect on the synoptic models I don't know, it may be. What eventual effect this may have on the cold spell starting Monday if not earlier further north is also unknown I would suggest.

Dry and mostly cloudy after clearer skies allowed the temperature to touch 2.6C briefly, now on 3.5C

12.6mm of rain here, cleared early pm with cloud breaks by dusk and a sharp drop in Td making it feel pretty chilly!

so easy to criticise and sometimes without all the facts. The first solid evidence to me, using free data, was 3 days ago when the first of the anomaly charts showed the evolving pattern. Not sure what UK Met have, for sure one heck of a lot more data. The problem then is for each senior man to shuffle through the piles of data that come in several times each day, then try to decide which is the most reliable and likely to give a reasonably solid basis for a forecast, be it 24 hours ahead 6-15 or 30 days or a season. The Met model data, available to us, has consistently shown the winter to be about average to mild but trending a touch below in the latter part. What their model did not show, the seasonal one that is, although I have not kept the issues, was the huge rainfall totals for parts of the western half of the country.

To answer one or two negative ideas about the upcoming cold spell. Yes it is coming, yes it will be cold and yes some will see snow. The synoptic models almost always change from run to run as they converge on the actual weather. It happens throughout the year but is highlighted during the winter as folk search for their ideal cold and snow set up. My use of the anomaly models does draw criticism at times but not to worry. As a retired professional I feel that using these, never on their own but looking at everything we have available on the free web, does allow for a more balanced view at times. They, the 3 I use, have consistently, cross model and with each of their own outputs shown what the upper air pattern will be from about this weekend and, initially, for 3-5 days beyond that. Over the past 48 hours they have extended this slow moving pattern to suggest ‘cold’ may well last out to at least 21/22 January. I never attempt to predict beyond 2 weeks or so. Detail of this will not really come from the anomaly charts although careful use over a long period does allow fairly decent forecasts to be put together. Currently NOAA 6-10 and 8-14 shows a fairly stationary wavelength, the ridge out west around 35-40 west with the trough fairly well east of the UK. This does look like not allowing any Atlantic breakthrough, as a few suggest will happen, well into January. Once this type of block sets up then with quite deep cold air only moving slowly any attempt to push through it is often slower than any model or human prediction suggests. Not always the case of course and the clever bit will be getting that breakdown correct. In the meantime the series of Fax charts from UK Met shows that the arrival of ‘cold’ is a rather complex feature, (link below as are those for the anomaly charts). Their latter ideas T+120 onwards may well undergo some changes as is always the case with any weather pattern. How much snow, how cold are questions to gleen from the models and Fax charts or indeed DIY using some of the tools available if we use ideas from the learning area on Net Weather. I have lost count of the number of times I have urged caution in trying to predict snow falling. It is immensely complex with the first one getting PPN over your back garden to start. There are then approximately 6 maybe 8 other variables to factor in. Fun trying it so have a go. I cannot remember the Guide I posted in the learning area but I am sure someone will post it. To repeat, don’t worry in the near time frames, say out to 120 hours of the models, upgrading/downgrading, they do it all the time throughout the year. The Atlantic will not roar in for 10-14 days at least, so enjoy the weather if you like cold and keep your fingers crossed you get some snow. Showers/frontal, whatever. Cheers Fax charts http://www.weathercharts.org/ukmomslp.htm#t96 Anomaly charts http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html some of you may like to try this?

Your post is not a true reflection on what any model is showing in the broad scale pattern of things. Please pm me if you wish to discuss my post further. John

Rain overnight, overcast with the odd spot at the moment, 8.2mm so far since midnight, a low of 5.2C, up to 6.3C now

true and the 00z and the 12z yesterday and the 00z, in fact using the anomaly charts back 3 days for consistency.

this NOAA anomaly shows that little marked change is likely out to at least 20 January, ridge and trough positions http://www.cpc.noaa.gov/products/predictions/814day/500mb.php NOAA and ECMWF-GFS have been consistent with this idea now for around 3 days. It is rare when they show this consistency cross model and timewise that the predicted upper flow does not occur over the time scales shown.

As some might say, 'it's been a funny sort of day'. Cloud, brief sun, fog, rain and drizzle, a high of 8.6C now on 7.3C

You seem to have a very blinkered view of UK Met from your position abroad Nick. I suggest you have a close look at what they use and how on their web page. Get the facts rather than what you think happens. Sorry if it sounds a bit OTT but I like facts not fiction. Of course any model USA, UK, European will get it wrong at times, or rather, perhaps the man part of it will not get their interpretation of the models correctly. It is easy to be critical.

I still think that 'cold' will be around for 8-10 days. As always beyond 14 days from now I do not go, starting over this weekend and out to at least 15-16 January probably beyond. Becoming high pressure dominated after 3-4 days from the start.

foggy here now, sky obscured and 3-400m visibility