What a classic this is

We have in view a bunch of signals for a bit of added westerly momentum in the short-medium term as the AO increases (and AAM falls a bit, for those in the know), followed by a loss of momentum with amplification returning to most likely save the winter for some of us at least.

 - but the models are taking the first part of that to the extremes and the GFS op runs in particular are losing sight of the change in signals thereafter. It seems to happen far too often these days!

Now to be fair, the odds are indeed in favour of a westerly flow for much of the UK up until the final days of Jan at the earliest. There is just the small but not insignificant chance that the westerly momentum is being overdone to the point that a split jet event with a sliding low and an easterly are being overlooked for the latter half of next week (but look at GFSP for an exception to that rule!).

Then comes the window of opportunity, which I have been thinking to be around 28th Jan to 7th Feb, for dramatic changes to occur and set up a colder pattern with snow chances returning. I wish that period could be set in stone but as usual there is the caveat that it could take a week or so longer than that... this theoretical approach to forecasting is still rather experimental after all.

A sudden stratospheric warming or major midwinter warming may be a component in this change of fortunes, but not necessarily. The signs are that events in the tropics will be sufficient to drive the changes we desire with the aid of merely strong, sustained stratospheric warming as opposed to an actual event.

Factor in the usual smaller-scale uncertainties, and the message is that there's still a lot of reason to be hopeful for, but not enough reason to be certain of, some 'proper winter' for much of all of the UK by the middle of February.

That's starting to push it a bit for far-southerners I know, as the sun climbs higher in the sky and exerts greater influence on a larger proportion of the ground surface. The longer it takes, the more impressive the cold air import(s) need(s) to be in order to deliver sustainable lying snow. Feb 2009 does prove that it's very much possible though. Indeed some of my favourite days of weather occurred in that spell, with heavy convective soft hail and snow showers which may have been helped along by the increased solar input 

Behold the cautious optimism 

Originally Posted by: Stormchaser 

HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON WEDNESDAY JAN 20TH 2016

THE CURRENT GENERAL SITUATION A ridge of High pressure lying across the UK today will move away SE tomorrow as freshening Southerly winds and troughs of Low pressure move into the SW of Britain tomorrow moving slowly NE.

http://www.wetterzentrale.de/pics/Rtavn001.gif

CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The freezing level across the British Isles is around 2000ft apart from the far SW of England where the level is nearer 4000ft today rising to in excess of 5000ft here tomorrow. Snowfall is unlikely today.

http://www.snow-forecast.com/maps/dynamic/uk

http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow.gif

MODELS-2 WEEK HEADLINE Becoming milder and more changeable with rain at times from later this week especially towards the North and West. Mostly dry at times in the SE.

THE GFS JET STREAM FORECAST The Jet Stream currently weak across the Atlantic will ramp up somewhat and move East across the UK for a few days. Thereafter the prediction for it to locate well to the Northwest of the UK remains with High pressure close to the UK later keeping it well away from UK shores.

http://www.netweather.tv/index.cgi?action=jetstream

GFS OPERATIONAL The GFS Operational Run today is largely focused on dry and fine conditions under High pressure to the East and SE through the run. There is a couple of milder and more unsettled periods shown within the first week of the run when some rain any affect all for a time particularly this Friday and maybe again towards the middle of next week. Other than that this run shows any rain more focused towards the NW with a lot of dry, bright and possibly rather cold conditions with frost at night the more likely weather for many through the period.

GFS CONTROL RUN The theme of the Control Run today also shows quite a lot of anticyclonic weather especially for England and Wales. A milder spell is likely following a spell of rain over the weekend and this run too shows the chance of another spell of rain towards the middle of next week which is followed by a rise of pressure across the South which then extends to Europe and sets up a trend towards rather cold weather with frost and fog returning by night and more unsettled conditions threatening the UK again at the end of the run as Low pressure moves into a cold block returned across much of Europe by that time.

http://www.wetterzentrale.de/pics/Rtavn1441.gif

http://www.wetterzentrale.de/pics/Rtavn3841.gif

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=144&mode=0&carte=0

http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=384&mode=0&carte=0

GFS ENSEMBLE DATA The theme of the GFS Ensemble Clusters this morning indicate a 65% pack with High pressure either to the SW or over the British Isles itself offering fine weather with some overnight frosts and fog. The remaining 35% of members show milder West or SW winds and rain at times in association with Low pressure to the North of Britain.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

UKMO The UKMO model this morning shows an altogether milder period coming up as SW winds and occasional troughs of Low pressure move NE across the UK from Friday with rain at times for all with the heaviest and most persistent falls across the North and West but with brighter mild spells as well especially across the South and East.

http://www.wetterzentrale.de/pics/Rukm1441.gif

THE FAX CHARTS The Fax Charts today is quite representative of the raw data as the winds turn SW for all and after a series of frontal troughs bring milder air to all over the weekend. High pressure lies to the SE with a warm front moving back NE across the UK bringing further mild and cloudy weather with rain or drizzle at times especially across the North and West

http://www.weathercharts.org/ukmomslp.htm#t120

GEM GEM this morning shows milder air moving across the UK this Friday with some rain for all followed by several days of rather changeable weather with some rain in the North and West. With time though High pressure never far away to the SE realigns later as a cold puddle of air moves West over Europe and threatens the UK again with colder air later with some frost returning especially towards the South and East while the NW probably maintains the dampest and mildest weather.

http://www.wetterzentrale.de/pics/Rgem2401.gif

NAVGEM NAVGEM today prefers to fly the mild flag today as once the rain bearing trough of Friday introduces less cold air the rest of the period is shown to maintain SW winds for all with further rain at times and strong winds too as we reach the middle of next week as a more vigorous Low pressure area is shown to move up from the SW towards the SW approaches.

http://www.wetterzentrale.de/pics/Rnvg1681.gif

ECM ECM today shows the breakdown on Friday with a spell of rain for all ushering in milder Atlantic SW'lies. Thereafter pressure is shown to remain High to the SE and Low to the NW with the influence of Low pressure maintaining milder Atlantic winds with rain at times there while High pressure often very close to Southern Britain maintaining a lot of fine weather there with nearer to average temperatures at times and probably a return of some night frosts at times later.

http://www.wetterzentrale.de/pics/Recm2401.gif

ECM 10 DAY MEAN The 10 day mean chart has good agreement that pressure is likely to be Low near Southern Greenland while High pressure lies across the Azores in 10 days. Pressure patterns over Europe though look very indeterminate with a variety of options shown within members which could have implications for less mild conditions across the far SE of the UK later.

http://www.wetterzentrale.de/pics/Reem2401.gif

NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS The models show a classic NW/SE split in trend this morning with varying degrees of bias towards a dominance of influence of High pressure over Europe again this morning.

31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.6 pts with GFS edging ahead of UKMO at at 99.5 pts to UKMO's 99.4 pts. At 3 days ECM is leading with 97.6 pts to UKMO's 96.8 pts while GFS lags behind at 96.4 pts. At 5 days ECM leads with 89.9 pts to UKMO at 88.0 pts then GFS at 87.6 pts. Then at 8 Days ECM still leads at 65.7 pts over GFS's 65.4 pts. Finally at Day 10 ECM is ahead of GFS at 50.3 pts to 47.6 pts respectively.

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.png

MY THOUGHTS With temperatures not far off -8C outside my window as I type it is hard to imagine that in a couple of days time temperatures will be some 15C warmer but such as Winter in the UK this is the most likely outcome shown within the models again today. The current cold High pressure across the UK will slide away East over the next 24 hours as troughs of Low pressure move up from the SW to reach the SW later tomorrow and all areas on Friday. All areas will see a spell of rain followed by much milder SW winds and some bright weather over the weekend. There will be some further rain especially across the West and North though with the main difficulty this morning in the detail surrounding this milder phase of weather. Some output notably those from this side of the Atlantic show quite unsettled conditions early next week and possibly longer with rain at times for all and temperatures responding to near or a little above average at times. However, this is not the blanket approach by all models. There remains a cold block across Europe which although recedes East over the coming three or four days will remain poised towards Russia and the American models do acknowledge this and coupled with High pressure which never lies far away to the SE and East could come back from the East later as High pressure rebuilds across a more Northerly latitude in the second week. It may be just natural variability between model runs and this theme may disappear in the next runs but my gut feeling is that the milder weather to come will not be like the spell in December with High pressure playing a much more dominant role aided by a weaker Jet Stream than back then and if it builds sufficiently North over Europe or even into Southern Britain it wouldn't take much to throw a totally different reflection on the weather at the surface than that currently indicated. I do believe that we are not moving into a spell of prolonged mildness but rather a period of changeable weather with a slow theme to drift back into dry and anticyclonic weather with frosts returning within a week or so. So having nailed my colours to the mast lets hope that I am right and that trends continue to develop towards a colder evolution in the rest of the runs today and tomorrow.

Next Update Thursday January 21st 2016 from 09:00

Originally Posted by: GIBBY 

One thing about those Berlin forecasts - experience shows they are pretty accurate.

Originally Posted by: Maunder Minimum 

http://modeles.meteociel.fr/modeles/gfs/runs/2016012006/gfs-0-192.png?6

GFS continues its idea of more blocking

Originally Posted by: The Beast from the East 

http://modeles.meteociel.fr/modeles/gfs/runs/2016012006/gfs-1-288.png?6

Perhaps we could call it a Tomazs Shafwhatshisname run

London could get buried

Originally Posted by: The Beast from the East 

A gathering trend ? Euro's having none of it.

Originally Posted by: warrenb 

Let's hope the GFS is on the right track with developments, the 06z has shown heights develop further North than the 0z, we could be in business if the trend continues  

Originally Posted by: Shropshire 

Well the control is going witht he op but brings the cold in earlier along with about a third of the ENS.

Originally Posted by: warrenb