Blessed Weather

Is this better John? The post above was 4 hourly intervals at 5 frames/second and, below, the same intervals but at 1 frame/second.

A very windy few days (Sun to Weds) coming up as this sequence of maximum wind gusts forecasts from Arpege highlights. Hardly an area of the UK escaping from seeing a gust of 50 mph+ at some stage, although for a change the far north of Scotland might turn out to be the least windy place to be! Wednesday is looking a particularly windy day nationwide.

No disagreement amongst the GEFS members in the overnight output (0z 28th Dec), with all 21 members now forecasting a stronger-than-average Vortex (10hPa 60N) by 12th Jan. The zonal mean zonal wind is currently 43.8 m/s and the forecast for 12th Jan is 59 m/s. Today: 12th Jan: Wave 2 activity forecast for around the 8th Jan, but on this occasion this doesn't seem enough to disturb the upper strat at 10hPa? (Any comments/views on this last point would be welcomed please). Charts http://weatheriscool.com/

What a wet 24 hours! It's such a shame to be so close to a major snow event but just end up with a spell of wet snow that quickly turns to slush (and that was if you were lucky! Nothing IMBY). Look at these rainfall totals for eastern areas - well over an inch for many. With a tweek of the synoptic pattern we could have been digging ourselves out!!

Here's what the UK Mountain & Hill Walking website says re the drop in temp with altitude. So you can see that in marginal rain/snow situations like today, being at 300m elevation could make all the difference to what falls and whether it settles. Under normal atmospheric conditions, as altitude increases, air temperature drops between 1°C and 3°C for every 1,000ft (300m) height gained. For dry air the temperature drop is higher, saturated air the drop is more likely to be 1°C. In practice, this means that the temperature at the top of a 3,000ft (900m) mountain will be at least 3°C cooler than the valley, but could be up to 9°C colder! A good rule of thumb is to assume 2°C temperature drop per 1,000ft (300m). http://www.mountainsafety.co.uk/Weather-Temperature.aspx

Ian Fergusson tweet with insight into Euro4 and ECMWF snowfall forecasts:

The set-up for this Weds is SO frustrating! The tweet below from the Met Office (about 1927) shows what can happen if it all goes right. In the case below there was a high pressure block over Iceland giving a very cold NE/E'ly flow, so the slider turned southern Britain into a winter wonderland. If you want to torment yourself, the full blog makes good reading..... https://blog.metoffice.gov.uk/2017/12/25/90-years-ago-parts-of-england-were-getting-buried-in-snow/

Met Office animation of snowfall in the Alps and Pyrenees this week (Tues through to coming Saturday):

Whilst the rest of us relaxed on Christmas Day, Dr. Cohen was busy updating his weekly blog! His final sentence below is not what many of us want to read, but atm model output seems to support his thinking. The latest GEFS (26th Dec 0z) have 15 out of 21 members with a stronger-than-average strat vortex by 10th Jan. I also note CFS has backed off from its' thoughts about a January SSW. Here's some extracts: The dynamic event that I am most focused on is the predicted increase in poleward heat transport or increased vertical component of the Wave Activity Flux (WAFz) activity for the end of December and the first week of January. But the critical question in my mind is will this predicted WAFz pulse and possibly subsequent pulses be of sufficient magnitude to disrupt a strengthening stratospheric PV? If not then the stratospheric PV will likely remain relatively strong for much of January and exert increasing influence on the tropospheric circulation with similar strengthening of the tropospheric PV and an increasingly mild pattern across the mid-latitudes of the NH. Alternatively, if the predicted WAFz pulse and possibly subsequent pulses are of sufficient magnitude to disrupt the stratospheric PV, then the weakened stratospheric PV will exert increasing influence on the tropospheric circulation with similar weakening of the tropospheric PV and an increasingly cold pattern across the mid-latitudes of the NH. My interpretation of the model trends is that the models favor the former milder solution. Full blog: http://www.aer.com/science-research/climate-weather/arctic-oscillation

Here's this morning's BBC/Met Office forecast for Weds. The biggest 'take' from the sequence is that the area of snowfall dwindles as the system moves east, so by the time it reaches eastern coastal counties it looks as if we end up with a few wet flakes. But looking very interesting for the western half of the Region! Just seen your post @Mark wheeler and AROME is certainly far more bullish about a decent area of falling snow making it to the far east of our Region. Just goes to highlight the uncertainty! Here's the beeb sequence for 01.00 hours, 05.00, 07.00 and 11.00 hours Weds:

Just sneaked a peep at the radar whilst Mrs Blessed watches Christmas Strictly. That's a beauty of a squall line moving east! Gusty winds heading our way!! 19.20

A very Happy Christmas everyone. I hope you have a wonderful day. I'm hoping Santa brings me a new weather station that only reads 'very cold and snowy'! But meanwhile, look....... Arpege joining in the festive mood and forecasting 15 flakes of back-edge snow for us on Weds!!

Our Region's turn to be stuck under persistent grey - although I notice @Ed Stone has managed to wangle a clear patch over Beccles!! Never mind, at least the models all agree we'll see a change from nothing to something by Boxing Day!

So we appear to have an interesting variance in forecasts for January. GloSea output a week or so back switched to saying no to a SSW in Jan, but now we have the latest CFS output saying yes. Today's Weatheriscool chart shows the CFS (pink and green plots) forecasting negative Zonal Mean u-wind at 10hPa 60N, meaning a reversal: And today's GEFS output right at the end of the forecast period (6th - 7th Jan) is not without interest, showing Wave 1 activity returning. All out in the unreliable at the mo, but something to watch. Charts from http://weatheriscool.com/

Just before the all-important Christmas/New Year holiday period it's wonderful to be reading reports like this from snow-forecast.com. And interesting that the correspondent correlates snowy seasons in the Alps with La Niña years. Extracts: Snow-Forecast Data Shows This is The Best Start to the Season in The Alps for 21 Years Research in to early season snow stats has revealed that this is the snowiest start to the season for 21 winters “Although 1998, 2011, 2012 and 2008 were just as snowy in some Alpine resorts, we have to go all the way back to 1996 to find a ski season that was notably better in terms of early season snow depths across the whole of the Alps,” says Snow-Forecast’s Robert Davies....... Why so good this year? Davies says that first, we avoided a weather event is usually the cause of our worst ski seasons: when the Azores high takes up residence over Western Europe in Autumn and then stays there into January. Second, really snowy ski seasons, including this one, tend to be La Niña years. Although La Niña describes a low-temperature anomaly in the Pacific Ocean, it affects the whole globe: for example, by causing slightly cooler than usual global temperatures. Full article with some lovely pics: http://www.snow-forecast.com/whiteroom/snow-forecast-data-shows-best-start-season-alps-21-years/ P.S. To everyone heading for the Alps this weekend - have a great holiday!!!

Absolutely drab, dreary weather at the mo. But how about this fantastic cloud formation photographed over Lincolnshire on Tuesday of this week. Wonderful. P.S. Oops! Is Lincolnshire in our Region?? Well if not it should be and it's close enough to allow me to post this!!

Hopefully long rangers GloSea & ECM are onto something for blocking mid-Jan. Then it just needs to be in the right place! https://twitter.com/fergieweather/status/943787865791713280 https://twitter.com/fergieweather/status/943787865791713280 https://twitter.com/fergieweather/status/943787865791713280

Hi. All looking good for Chamonix from what I can see. The official depths are 60cms lower slopes and 120cms upper slopes. http://www.ledauphine.com/meteo/meteo-neige And the forecast from Meteo-France for 1,050m suggests a lovely week's skiing. Above freezing by day, but below at night so the pistes can be put back into good shape!! (Pic below shows each day to 2nd Jan with an hourly breakdown for today. To see the daily breakdown for each day go to the website and click on the day.) Have a great holiday and try and post some pics! http://www.meteofrance.com/previsions-meteo-montagne/chamonix-mont-blanc/74400

While we wait for some 'proper' (cold!!) charts to turn up I thought I'd look at tonight's GEFS 12z spread for 10 days out (31st Dec). It appears to be a case of good news and bad news. Interestingly, the biggest area of uncertainty in the NH at month end is over the UK. So the good news is the UK might be under a cold trough..... Pert 14 ...but then again, maybe it'll be a mild SW'ly flow. Pert 13 But I suspect the real bad news.... if you look back at the first chart, the GEFS don't show much spread over the Greenland/Iceland area. So as suggested by tonight's Op run, it's looking a rather potent PV to our North to end the month. But hey, all my post is only based on today's 12z output, so let's continue to hope for better tomorrow!!!

Fair point Paul - certainly exact track not set in stone. But generally speaking, a strong jet exiting the eastern seaboard is not good news for deep cold prospects here in the UK. IMO better to have a weak jet meandering about with 'stuck' patterns and blocking..... as long as we get stuck in the cold sector!

Nice morning with a sharp frost. Down to -2.5C overnight. And absolutely zero, zilch fog here..... and by the sounds of it nowhere.... lol.

Last Thurs 14th Dec I posted a tweet from Dr Butler with a forecast of a promising spike in heat flux. The latest tweet (Mon 18th) now showing a forecast of the opposite - a drop off in heat flux.

Thank you @bluearmy and @Mattias for your comments. Hot off the press this evening is the latest blog from Dr Cohen with his thoughts on how things have developed so far this season and where we might end up going forward: Taking a broader view and looking at the latest polar cap geopotential height (PCH) and vertical Wave Activity Flux (WAFz) plots, a troposphere-stratosphere-troposphere (T-S-T; Figure i) coupling event is underway (Cohen et al. 2007). The first stage was the tropospheric precursor with warm PCHs in the troposphere only during the first half of December and ended this weekend. During this stage cold temperatures dominated many regions of the NH including the Eastern US, Western Europe and East Asia. This is followed this week by active energy transfer from the troposphere to the stratosphere all this week and peaking this weekend. PCHs are predicted to turn warm in the stratosphere while turning colder in the troposphere. The warming of stratospheric PCHS is related to a PV disruption and displacement towards Eurasia with a strengthening anticyclone or high pressure near Alaska and northwest Canada. This stage is dominated by a turn to milder temperatures in the Eastern US, Europe with the possible exception of East Asia where temperatures are predicted to warm but could still remain below normal. The final stage is the downward propagation of the circulation anomalies from the stratosphere to the troposphere. This includes northerly flow across much of North America favoring relatively cold temperatures but westerly flow across Eurasia favoring relatively mild temperatures. This latest predicted PV disruption looks to be minor. Further, with the predicted weakening of Ural blocking subsequent WAFz or poleward heat transport will likely be weaker than the activity predicted for this week but something to watch. Given that the PV disruption looks to be minor, I expect that the subsequent related tropospheric circulation will last on the order of three weeks or about half that following a major disruption. The important question is what to expect after this T-S-T coupling event ends. I think three different scenarios are most likely. One, the stratospheric PV rapidly strengthens favoring a mild pattern for much of the NH from mid-January on. Two, a more robust PV disruption takes place favoring an overall cold mid- to late- winter across large parts of the NH. And third, additional relatively minor PV disruptions occur that favor more regional cold. Given that the greatest sea ice anomalies this fall were in the Chukchi and Bering Seas, most likely favors North America for cold air outbreaks. I continue to favor the second and third scenarios for the same reasons that I have been discussing since October. And based on the trends that I am seeing in the stratospheric PV, for now I favor the third scenario the most with the winter of 2013/14 being the closest analog. I have been hesitant to jump on the 2013/14 bandwagon based on an easterly quasi-biennial oscillation (QBO) but so far there are no signs of a sizeable and prolonged disruption of the stratospheric PV. Full blog: http://www.aer.com/science-research/climate-weather/arctic-oscillation

Dramatic looking tweet showing the 850hPa temp anomaly on 25th Dec over Canada/US. Today's ECM Op 12z 500hPa anomaly chart for Boxing Day looks in full agreement, with a steep temp gradient set to fire up a strong jet stream exiting the Eastern seaboard. ECM Op 12z 500hPa anomaly for 26th Dec: GEFS Jet stream 26th Dec: Edit: Just a quick aside - does anyone else think this sort of tweet should be allowed in the Model thread when supported by charts? It seems relevant to model output discussion and impact on the UK.

A very interesting tweet by Dr Cohen based on GEFS 0z run but I must say I'm slightly puzzled by the Wave 1 observations because looking at the GEFS charts I see on Weatheriscool.com, based on the 12z run yesterday and today, the Wave 1 activity fades by the start of Jan 2018. My other observation is that if there is downward propagation, with the Strat Vortex u-wind speed forecast to rise to 49 m/s (which is above average) by 01/01/18, it suggests not such good news for favourable mid-latitude cold patterns in the trop?? As a 'learner' in this thread I'd again be interested in the views of others. Here's the tweet. Then the Weatheriscool GEFS Wave 1 charts from 12z today. Geopotential Wave 1 forecasts at 10 hPa 60N: 24th Dec 1st Jan