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Showing content with the highest reputation since 09/01/19 in all areas

  1. 98 points
    It's all good folks - we are about to get slammed Think March 2013 imprinted on the middle of winter - what's not to love ! The slider solutions are dialled in as the wave guide changes, NW SE sliders will be the key feature of the next 6 weeks as the canadian vortex drains itself via downwelling. No it's not 62 or 47 or 2010 But what it actually is an SSW which we all now respect and have learned from, and have the nuance to watch in real time, spilling its arctic cold guts all over the mid latitudes. I am sorry for those of you who think , nope this is not a driver, nope AAM isnt a driver, MJO isnt a driver, Nino - isnt a driver - you get me? Simply put - they are - and always will be and GWO and AAM possibly the most reliable of the lot! Do not discourage in weather that which you have yet to understand - this science is difficult, no one is ever right, no one is ever perfect, no one on here alludes to that What I want to say is- for us afficiandos of cold, us dedicated individuals, hunting, searching, wanting looking and dissecting everything. We are all good Its near solar min, monster SSW, monster Split. NWP - Bring IT !
  2. 85 points
    All roads lead to Rome - or in this case a cold spell. There have been some odd comments on here today, given we are on the cuspy of only our second significant cold spell since 2013, and so I'm going back on my last post - and instead of looking only at short range charts from here it might be good to make some connections and map out the road ahead. Strat first of all. We have seen a slow downwell - no doubt about that - and a fairly chaotic displacement/split event that was uncertain for a while. But the mists have cleared, and the downwelling is finally going to impact more substantially on the trop pattern in the coming days. The atlantic profile for midweek is still fairly flat but the split has worked in our favour, with the Canadian lobe remaining in situ but the more substantial Siberian shard pushing back east towards the pacific. The 150hpa forecast 5 days later quite clearly shows this and you can see the push of energy at 30hpa moving away from Europe over the eastern Siberia with the Canadian shard sitting in place The signal for a resurgent midatlantic ridge up to the N/NW is quite clear. Picture those EC46 images showing more robust northern blocking by month's end - part of downwelling strat forcing. But we have a pacific signal that looks to be marrying up. Our current high has been resilient, but at too low a latitude for our liking. No getting away from that - forecasts a month ago saw the blocking, but saw it further north. The slow speed of strat impacts probably wrecked this possibility. Now torque effectis, apart from in the tropics, have been on their way down....but before long the bounce back up will begin again, and lag effects will time perfectly with maximum impact of strat downwell So we have the beginning of strat impacts to come in 7 - 10 days followed by GLAAM support 7 - 10 days after that. All good. But the story does not end there - the MJO, which on its own was not enough in early Jan to override other factors, is heading swiftly back around to phase 6 - 8 in time for February....so that just as the atmosphere needs a bit more of a bump to keep blocking in place - it gets it. Note also that the MJO is remaining generally active, and poleward wave activity is therefore going to remain a factor in preventing any flat pattern from getting a hold once again. Ventrice filtered plots remain quite impressive So - this takes a pattern of parallel forcings supporting a meridional signal and anything but a westerly atlantic pattern well into February. But let's finish on the strat…..because of all the factors that drive our weather it is becoming increasingly clear that impacts on the vortex that downwell to the trop are dramatic and forceful. The warming that started well over a week ago is just past its peak, but winds at 10hpa are set to remain easterly until the back end of the month, give or take At the same time westerly winds will return at the top. Bad news? Not at all. A return of westerly winds at the top will form part of the ongoing downwelling process - and just as we had a flushing process of westerlies pushed down into the trop round about now, helping neutralise attempts at mid atlantic to greeny height rises, so this flushing out of easterlies will serve to force them onto the trop pattern. Given that the 10hpa pattern will have been reversed for the best part of 4 weeks, we are facing a long process in this regard...and so the gradual recovery of the vortex will actually sustain a reduction in tropospheric westerlies for a long time also - I'd suggest most of February. And then in March the vortex is fading anyway. Will we get anything like enough westerly momentum to change the pattern out of the entrenched cold cycle? I'm not sure we will.....but that is a bit far off to be discussing in detail now. So - forget op runs in 8 or 9 days time that are making it look as though a resurgent trop vortex driven from Canada is about to fire through the atlantic. It isn't. a Canadian trough will remain in place as the strat image is imposed upon it - but the door in the atlantic is going to be slammed shut, and cyclonic energy will have to circulate around the edges. Cold northerlies or undercut scenarios. And if we can get slices of that cold Canadian vortex firing moisture down into Europe over the top, or later on potentially underneath, the block then we get the precipitation we want in a cold phase. This on top of the impacts of deep European snow cover that will help provide a very cold feed off the continent at times when the winds turn E/SE. Long post - apologies - but everything is in place for something a bit special. Stop worrying about NWP. It doesn't get a handle on all these processes well....and while there is no way I would want to call the microscale specifics at anything more than 72/96 hours (and always from UKMO and ECM) - we can sleep easy knowing that the macroscale factors are lining up in favour of snowy goodness for the second half of winter.
  3. 83 points
    New EC weeks 3 and 4 as you were. High pressure in all the right places.
  4. 77 points
    Pondering evolution and longevity today. It's taken it's time in coming - and I will do a longer post later tying in the thoughts of December and early January into what is happening now - but the gloom of 5 days ago seems a distant memory as the blocks begin to drop into place. In Dec 2010 we got a very swift transition to a deep scandy trough supported by a very sharp and strong greeny high - but it wasnt particularly long lived. It started to fade within a week because all the drivers were moving things back to a mobile pattern, and then the rest of the winter was unmemorable. This time around we have a much slower evolution - but the blocks are in place for a much more sustained affair. The initial cyclonic euro/scandy blast wont be quite as severe or swift as 2010 because we havent got the same strong block surging up over greeny BUT we are in the heart of winter rather than at the outer edge and with pacific signals remaining on track and a slow strat process suggesting slow but positive evolutions ahead we could find ourselves in a pattern that sustains the cold and, at this time of year, brings plenty of snow from this predominantly cyclonic signal, at least in the medium term. Might we see mention of blizzards in parts? Quite possible. Longer term more entrenched cold, maybe a bit less precipitation. The potential for a noteworthy spell of weather that can be mentioned in the same sentences as Dec 10, Jan 13, March 18 looks on the cards. I'm breathing a sigh of relief and putting the knitting needles away - for a short time doubt began to creep in as to whether synergy of pacific and strat would work out as all instincts and understanding suggested - but today all is clicking nicely. I wouldnt bother wondering or asking where it will snow for a good while yet - but with a bit of luck and a half decent roll of the synoptic dice we can get at least one solid front to cross the country to give everyone a shot, and plenty of convective action pushing inland. Window of opportunity from Friday next week - but probably midway through the following week for maximum chances. And dont expect this pattern to return anywhere close to mild (or even average) for a while. For a little bit we can afford to put the teleconnective charts away and forget macroscale pattern drivers, and instead enjoy a bit of fax chart scrutiny, weather radar updates and even some lamp post action. Lovely.
  5. 48 points
    Bloody hell, what is wrong with some people tonight! Those continuing to post personal comments aimed at other members will be stopped from posting for a period of time. And if you want to moan because a particular run doesn't have snowmaggedon in your backyard at t+3000 or whatever it may be, please go to the banter thread, no-one who wants to read about the model output is interested in pointless moaning and the bickering which follows it.
  6. 48 points
    Cracking ICON / UKMO !!! GFS hot on the heels as well at day 6-7 - just slightly flatter but can correct- Best start to the day in a while ... Easton Luna boys = Ian Brown ?
  7. 48 points
    I am estimating a mean CET of -2.5 from day 9 to day 16 from the 12z charts (realizing this is speculative but that's what those charts would produce), certainly cold enough for snow by about the 22nd to 24th with the northeast winds. As the run ends, another Atlantic assault is mounting what looks like a high-energy slider, that could be interesting to monitor as it moves into range of later model runs. It was encouraging to see the GEM losing its zonal theme from the previous runs, and joining the consensus. As to what we consider reliable, I think when there is broad model consensus past day six, it's a lot easier to feel at least reasonable optimism (or pessimism) for an outcome than if you have a wide range or two camps. Also, with these arctic outbreak scenarios, I recall last February we were tracking a strong high moving very slowly across the polar region towards Franz Josef Land and that was inspiring confidence because there was a real feature in play, that had to end up somewhere, as opposed to scenarios where developments have to take place days from now. This signal for much colder weather has been sustained now for about a week and is no longer being moved back every day or two, so that also begins to build confidence. There is such a thing as cold moving forward in model timetables too, we've seen that happen once or twice in the past ten years. The thing to remember about polar weather patterns is that distances from one longitude to another are very small and 20 degrees north of 80 N is, well, 80 N on the far side of the north pole. Some feature retrogressing through Siberia into Russia could take an age, but if it's moving from north of Wrangel Island and the other Siberian islands, it can appear very quickly north of Scandinavia. I'm thinking retrograde because the first half of February should see a peak in retrograde motion this winter, according to my research, and some analogue years include very deep cold in late January into February. If we can get this pattern to develop and begin a retrograde when high pressure is in northern Scandinavia, then a cold pattern could lock in for weeks.
  8. 45 points
    I actually think that is a reasonable question. It would be good if folk who post charts where no model or date is shown on the chart kindly provide this info in their post. Please.
  9. 44 points
    Again.. Canadian lobe will begin to drain-and migrate as she does.. No matter the current modeling...shes a breast feeder-...and the baby is becoming healthy!!!
  10. 44 points
    This next 'evolution' is all about the speed & deceleration of the pacific jet & how far east the Low at 168 gets & how the 'tilt' of the low supports the cold Not sure where this cold for +10 days or 12/15 days is coming from. Its day 7!!!!!! The UKMO ( as already highlighted ) has been performing much better than the GFS in terms of non bias Eastwards, & as we stand tonight would be poised for the greatest advection of cold @168- Ive annotated the 144 charts to show the differences showing why they may or may not 'project east' hint hint.... In Order -UKMO/ ECM/ GFS The UKMO is the slowest & most amplified with a negative tilted low & support for a greater blocking wedge ahead of the low pressure, this run would project the coldest outcome @168 >192 with the most amplified trough axis & a high likleyhood of the mild 'bump' of warmth hitting the UK 192/216 - or at least seeing more of a glancing 'slider' impact across Ireland / SW. GFS is positive in the tilt indicating more forward speed & less block, which to a certain extent is supported by ECM with its neutral position, ( Glancing at the ECM 12z mean - looks more UKMO ish ) Expect ECM op to be mild outlier day 8/9/10 So tonights summary would be similar to the forecast from 3-4 days ago where we say the UKMO day 6 chart almost spot on- Which is..... UKMO / ECM blend with the low, maybe UKMO to negative, ECM to neutral so the middle ground- GFS to far east with its 'positive tilt' look for that to correct... The upshot of all this will mean the -8c line is further south & west 168-192 & also atlantic inroads into the UK less progressive. At the moment the model theme ( from 120 ) is more indicitive of cold zonality with the treasure at the end of the rainbow day 9/10 however UKMO indicates that the day 8> 9 blip could actually be a slider snow scenario... Have a good one S
  11. 43 points
    And yet, 10 days ago, this ECM chart was being 'boomed' left right and centre, with the GFS apparently playing catchup / incorrect for whatever reason at that point too. The GFS at that time was way closer to where we've ended up though.. I'm not saying that because of this the ECM is rubbish and the GFS great, and the model scores certainly don't have the GFS beating the ECM or Meto right now, but just ignoring a major model which albeit behind isn't stupidly behind, is as worthless an exercise as taking any run from any model as gospel.
  12. 42 points
    Not sure what all that business days 6-10 was all about on the 12z GFS, but UKM and GEM advertising well the early stage development of the cold pattern. GFS does show loaded potential days 8 onwards with shallow long wave troughs running through the southern tier of the US off the Eastern Pacific. Their interaction with the polar trough once again bringing about significant downstream (cold) ramifications for NW Europe in the extended, as per ensemble broad ensemble guidance. FWIW and purely for fun, days 16-20 on the GFS op would be a redux of 1987.
  13. 42 points
    Blocking features are not necessarily Greenland Highs. Within the context of a deep cold trough across NW Eurpe, you don't need strong blocking features. These are however still potentially on the table for the week 3 period, and would represent the icing on the cake. We go below average on the 16th, and remain there after.
  14. 42 points
    Extended EPS T2s and T850s dipping at the very end of the run, which would be against model bias to drift back to climatology. I'm struck at the moment by the Scandinavian trough and daughter vortex over Canada. Perfect mirroring of the stratospheric pattern. This is a clear influence which does not fit troposheric drivers. Between the two features, uncertainty abounds, but you can't escape the model trend for deep cold uppers forecast within the Canadian vortex. That should, against other signals, continue to remove the Greenland High option. I think more +ve height anomalies and a more likely mid Atlantic ridge rebuilding but not necessarily Greenland Highs are of the order, and tonight's EC run will be viewed with interest - there could well be a very slow downwell of the stronger -U wind anomalies from the warming to come which might be the trigger, although I'd like to see some more NAM plots to get a proper handle on this. The tropical wave signal is moving extremely fast. By week 3, we could well be back to Dateline convection and Eastern Pacific. Again, good signal for sustained cold. Other features catching my eye: the deeply negative state of the Arctic Oscillation (not unexpected for the second half of the winter); and, related to this, the ridge extending into the Arctic from Alaska modelled to break off and move towards Siberian sector. With the clockwise rotation developing in the Arctic lower tropospheric flow, this shows signs of moving towards Svalbard by month's end. With the European trough embedded, that makes for some interesting permutations for February.
  15. 41 points
    SSW Down welling will over ride the MJO signal the resurgence of the upper level westerly regime will flush down the 'burrowing easterlies' referred to in Scaife Meto vids Simply put this SSW is new - its a monster displacement - so strong - its split the vortex - no long range model saw this. The physics meant it went strong into canada, then strong into siberia - it literally has been sheared QBO is irrelevant now - this is important as upper strat advertises differing regime from lower the split means the trop is influential - and the trop players arrive from the tropics - the nino base state and the mjo transition Where we are .. the dilution of the IO development for the MJO today after the coupling of the lower TSV over the pacific means the MJO can move again - its sessions stalled in COD - we can see more modes ahead... It's going to cycle with AAM into phase 5 .. EC week 5 regresses these.. and we have the winter lock
  16. 41 points
    Don’t know why some are moaning about the ECM . Nothing notably cold is expected until at least 12-15 days down the line and ECM only goes to day 10 . I give up in here sometimes.
  17. 40 points
    Extreme cold has developed in Yukon territory similar to early phases of 1947 event. It is also colder than normal in most parts of the arctic islands of northern Canada. These are good building blocks because any polar northerlies will be sucking air out of those regions to feed the flow. Given that the models are now in a catch-up mode a week after the SSW event, I think we are getting into territory where the odds of the GFS being too conservative are catching up to the recent trend of it being too aggressive (in medium range to end of 16 day runs). Therefore it's legitimate to speculate that the 12z run could verify at least verbatim, which would be a great outcome, it is modified winter from 17th to about 21st then full on winter after that with one very good snowfall scenario around the 22nd-23rd.
  18. 39 points
    Can we open an IMBY 1 please.. The very annoying...we'll get snow at my house nonsense has already begun!.. C, mon- its gonna come down 2 microscale...as per on our maritime island..with the slightest tweak/adjust..having massive ramifications.... Gets my goat something bad!!!!
  19. 39 points
    I posted this table over in banter and perhaps a lot of more serious onlookers don't go in there, so as it's not really banter I am taking the liberty of posting it here also. Basically it's a summary of all major cold spells in the daily records of the CET from 1772 on (the first one caught being 1776, and there must have been some stonkers before 1772 but we have no way of knowing the daily details of them, 1740, 1684 and 1709 for example must have produced long cold spells. The bottom line is that one fifth of all winters have produced a cold spell of at least ten days (where the mean daily temperature stayed below 0.0). A few others produced ones that failed that test but were very significant (eight or nine very cold days, or just being a bit too late into March and getting the inevitable daytime boost). Also what this table reveals is that one cluster of cold spells started on dates in late December and early January, with another cluster preferring February. There was a bit of a half-time phenomenon in late January. However, I did note that some of the major February cold spells had a good start in that period of late January and just failed to attach by one or two days getting briefly above zero. I'm sure you would experience the 1947 cold spell as starting 24th January for example. But in the table it shows up later. So here's the table, I have reduced it to quite a small size to make the seasonal profile easier to see visually, but if you want to examine the details then go to a higher magnification. The table is arranged in order of duration of these cold spells and when several are tied, the mean temperature they achieved is used to sort them. Days _ Duration of Days 0.0 or lower ______________________________ Coldest ____ Average ______[] __DECEMBER__ [] __JANUARY__ [] _FEBRUARY_ [] __MARCH______ 32 ... ... ... ... ... ... ... ... 27 Dec 1813 - 27 Jan 1814 ....................................... -- 6.7 ...... -- 3.2 26 ... ... ... ... ... ... ... ... ... ... 7 Jan - 1 Feb 1776 ..............................................-- 7.5 ...... -- 3.0 22 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... . 5 - 26 Feb 1947..................-- 6.7 .... -- 2.5 **** 20 ... ... ... ... ... ... ... ... ... ... 8 - 27 Jan 1881 .................................................. -- 8.1 ...... -- 4.6 20 ... ... ..(+12d see below) .. 7 - 26 Jan 1963 .................................................. --8.4 ...... -- 3.6 *** 18 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 6 - 23 Feb 1855 ................. -- 7.5 .... -- 3.7 18 ... ... ... ... ... ... ... ... ... ... ... 9 - 26 Jan 1823 ................................................. -- 8.9 ...... -- 3.0 18 ... ... ... ... ... 9 - 26 Dec 1890 ........................................................................ -- 6.8 ...... -- 2.1 17 ... (very cold 31 Dec - 7 Jan).10-26 Jan 1795 ............................................. -- 8.9 ...... -- 4.0 15 ... ... ... ... ... ... ... 21 Dec 1870 - 4 Jan 1871 ............................................... -- 6.9 ...... -- 3.6 15... ... ... ... ... ... ... ... ... ... ... 10-24 Jan 1940 ...(+11d later) ......................... .. -- 7.1 ...... -- 3.3 15 ... ... ... ... ... ... ... .. 24 Dec 1892 - 7 Jan 1893 ....................................... ..... -- 5.0 ...... -- 3.3 15 ... ... ... ... ... ... ... ... ... ... ... ... ... 18 Jan - 1 Feb 1784 ................................ . -- 3.7 ...... -- 2.1 14 ... ... ... ... ...(+10d earlier) . 8 - 21 Jan 1838 ............................................. ... -- 11.9 ...... -- 5.1 14 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 5-18 Feb 1895 .......................... -- 8.3 ...... -- 4.8** 14 ... ... ... ... ... ... ... ... ... 3-16 Jan 1820 ................................................... ....... -- 8.5 ...... -- 3.6 14 ... ... ... ... ... ... ... ... ... ... ... ... ... ... 21 Jan - 3 Feb 1780 .......................... .... -- 3.6 ...... -- 1.0 13 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 26 Jan - 7 Feb 1954 ........................... -- 5.0 ...... -- 2.5 13 ... ... ... ... ... ... ... 17 - 29 Dec 1860 ........................................................ ........ -- 3.7 ...... -- 2.1^ 13 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 6-18 Feb 1986 .......................... ... -- 4.6 ...... -- 1.6 13 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 14 - 26 Feb 1956..................... -- 3.2 .... -- 1.6 13 ... ... ... ... ... ... ... ... ... ... 29 Dec - 10 Jan 1811 ............................................. ... -- 3.6 ...... -- 1.5 12 ...... ... ... ... ... ... ... ... ... ... ... 6-17 Jan 1987 ................................................ ..... -- 7.7 ...... -- 2.6 12 ... ... ... ... ... ... ... ... ... 23 Dec 1962 - 3 Jan 1963 .(plus 20d ^^).......................... -- 3.6 ...... -- 2.2 *** 12 ... ... ... ... ... ... ... ... ... ... ... ... ... 18 - 29 Jan 1880 ......................................... ..... -- 4.3 ...... -- 2.1 12 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 3 - 14 Feb 1991 ............................. ... -- 4.7 ...... -- 1.9 12 ... ... ... ... ... ... ... ... ... .. 25 Dec 1853 - 5 Jan 1854 ........................................ ..... -- 5.0 ...... -- 1.8 12 ... ... ... 30 Nov - 11 Dec 1796 .......................................................................... ..... -- 4.7 ...... -- 1.8 12 ......... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 17 - 28 Feb 1955 .......... -- 3.3 ... -- 1.7 11 ...... ... ... ... ... ... ... .17 - 27 Dec 2010 ............................................................. ...... -- 7.0 ...... -- 3.9 11 ...... ... ... ... ... ... ... ... ... ... ... 11 - 21 Jan 1867 ................................................. .... -- 5.0 ...... -- 2.9 11 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 1 - 11 Feb 1917 ................................. ...... -- 7.2 ...... -- 2.8 * 11 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 9 - 19 Feb 1985 ........................ ... -- 4.1 ...... -- 2.7 11 ... ... ... ... ... ... ... ... ... ... ... 2-12 Jan 1879 ..................................................... ........ -- 4.8 ...... -- 2.3 11 ... ... ... ... ... ... ... ... ... ... ... ... ... 6-16 Jan 1850 .............................................. ........ -- 2.8 ...... -- 1.4 11 ... ... ... ... ... ... ... ... ... 25 Dec 1820 - 4 Jan 1821 ............................................ ........ -- 3.3 ...... -- 1.3 11 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 11 - 21 Feb 1853....................... -- 3.2 ...... -- 1.2 11 ... ... ... ... ... ... ... ... ... ... ... ... ...(+15d earlier ^^) . 9 - 19 Feb 1940 .......................... --2.5 ....... --1.1 10 ...... ... ... ... ... ... ... ... ... ... ... ... 6-15 Jan 1982 ..................................................... .... --7.6 ...... -- 4.0 10 ... ... ... ... ... ... ... ... ... ... ... ... ... 8 - 17 Jan 1826 .......................................... .............-- 6.9 ..... -- 3.7 10 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 20 - 29 Jan 1945 ............................ ........ -- 7.6 ...... -- 3.5 10 ... ... ... ... 5 - 14 Dec 1844 ................ .............................................................. ............-- 5.5 ...... -- 2.7 ... see below Mar 1845 10 ... ... ... ... ... 8 - 17 Dec 1878 ............................................................................. ......... -- 5.3 ...... -- 2.9^^ 10 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 16 - 25 Jan 1829 .................................. ....... -- 4.8 ...... -- 2.8 10 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 14 - 23 Jan 1809 .................................. ........ -- 5.1 ...... -- 2.4 10 ... ... ... ... ... ... ... ... 24 Dec 1836 - 2 Jan 1837 ................................................ ........... -- 3.3 ...... -- 1.3 10 ... ... ... ... ... ... ... ...23 Dec 1837 - 1 Jan 1838 ..(+14d later) ............................. .......... -- 2.7 ...... -- 1.4 10 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 21 - 30 Jan 1917 .(1-11 Feb^)................. -- 1.8 ... -- 1.1 * __________________________________________________ ^ Most of the period 1-16 Jan 1861 was also subzero, the 31-day period 17 Dec 1860 to 16 Jan 1861 averaged -1.3 C. ^^ This cold spell extended from 7 to 26 Dec, 20 days in which the mean CET was --2.4 C. The interval 20-25 Dec was --3.7 C. * Except for +0.3 on 31 Jan 1917, a 22 day spell avg --1.8 C lasting 21 Jan to 11 Feb. ** A longer spell of 24 days with +0.4 as warmest, 26 Jan - 18 Feb 1895, avg --3.7 C. *** Although there were only two spells in winter 1962-63 that qualified for this list, note that the period of 35 days that includes the two, 23 Dec to 26 Jan, averaged -2.7 C and 70 days 22 Dec to 2 March averaged -- 1.5 C. **** The 45-day period 23 Jan to 8 Mar 1947 averaged --1.9 C. <<>> RECENT NEAR MISSES & EXPANSION OF 1986 FROM LIST <<>> 25 Nov to 4 Dec 2010 averaged -- 1.7 C and 25 Nov to 8 Dec averaged -- 1.7 C but these periods failed by a slight margin to make the list (25 Nov was +0.3 and 5 Dec was +0.4). The 26-day period from 6 Feb to 3 Mar 1986 averaged -- 1.2 C. The 15-day period from 5 to 19 Jan 1985 averaged --1.7 C. (11th not subzero so it has no ten-day interval) 1 to 10 Jan 2010 averaged --1.9 C but failed to make the list because 2 Jan was +0.3 C. 16 to 25 Jan 2013 averaged --0.9 C but failed to make the list because 24 Jan was +0.7 C. 8-26 Dec 1981 averaged -- 2.3 C. ___________________________________ honourable mention should be given to 11-20 March 1845, there were two days in that 10-day interval slightly above zero but the average so late in the season was --1.7 C and contains the coldest March day (-6.5 on 13th). Also, in terms of a sustained cold anomaly, 21 March to 1st April 2013 (12 days) had a mean of +1.2 C. 1785 was even colder at the same time of year, 13 days from 22 March to 3 April had an average of +0.8 C. In terms of early winter season sustained cold, the interval 11-16 Nov 1919 averaged --0.3 C. ________________________________ ANALYSIS of starting dates for 10-day or longer cold spells Of all the 51 spells (in 47 winters, roughly 19% of the years surveyed) including the later ones in March, but excluding those that just missed during the winter season, this is the frequency count for starting dates: xx Nov to 10 Dec __ 4 11 to 20 Dec ______ 2 21 to 31 Dec ______ 9 01 to 10 Jan ______13 11 to 20 Jan ______ 6 21 to 31 Jan ______ 3 01 to 10 Feb ______ 8 11 to 20 Feb ______ 3 21 Feb or later ____ 3 For whatever reason, there is a period from 21st January to start of February when these spells are less likely to commence. A second cluster then emerges around first week of February often lasting longer than 10 days. We have now reached the point in the winter when half of these significant cold spells had begun. The three-quarters point is around 8 February. Not that length is the only important point when comparing cold spells, last winter's late bloomer lasted about five days but "did the business" for snowfall and set a daily record on the 1st of March. Not all of the above set daily records, about two-thirds did (and sometimes quite a few, for example 1776 set five in a row). You will find examples of winters with a cold spell listed and some other memorable cold or snow outside that interval, for example, in Dec 1796 a later but shorter cold spell produced the coldest December day. February's coldest day in 1816 was embedded in a seven-day subzero stretch which was about a week after an earlier five day interval at end of January. The spell listed for 1956 is not the most memorable cold of that month, that happened in the first few days of February. But that spell only ran to five days. Will this winter join the list? If so, likely to be 23 January or so before it begins. The 1947 subzero cold spell began on 24th, the interval to 2nd averaged -1.7 but fell one day short of this list (and by 0.1 C on 23rd). Two days of 0.7 separated that from the main cold spell shown in the table and it then stayed very cold to about the 10th of March.
  20. 37 points
    No cautious optimism from me, time to get the ramp out at long last!! Of course i jest, i think, upgrades is todays buzzword, i missed the 6z but it has for sure followed EC 00 det with its progression.. From the perspective of someone living in the NW with reasonable altitude its quite exciting, i do hope the easterly comes off , its a pretty perfect time of winter for it to be coming really,so hopefully the NW gets some action later next week and then those in the south and east get in on the action thereafter .. Fingers crossed.. In some respects i feel a bit guilty ramping away with the horrible news about Diane Oxberry- i really hope she is up in Heaven looking down smiling on us crazy people.. RIP Diane.
  21. 37 points
    Putting some index figures to the EC weeklies, AO mean is forecast to tank negative by early Feb late Jan for the week 3 - 4 period (mean -2.5SD) with the NAO also moving to around -1SD. Both remain negative for the entirity of the run. For that week 2 to 3 evolution, which must see a developing Arctic ridge most likely in combination with enhanced sub-tropical flow across North America to displace the lobe of the polar vortex further south and west from its current modelled position. Week 3 could still be a bit wobbly on that, given what we know about the stubbornness of the vortex in this location. On the plus side, good reasoning to think tropical wave development will swing back rapidly to a positive forcing forcing for -NAO during this period. I also think there is a good case for suggesting the downwelling of -U wind signal from the SSW will finally be realised during this period.
  22. 37 points
    ECM 00Z individual ensembles are - BRUTALLY - cold by 25th January. From a synoptic point of view, on that date only, I judge: 32 members are definitely cold enough for snow (for the majority of the UK, usual caveats apply re: coasts / SW extremities) 10 members are not cold enough for snow 9 members are potentially cold enough for snow but not completely clear. I also checked for upper temperatures; 37 members had the minus 5C uppers line through most of the UK, but in truth most of these were far colder than that, and out of the remaining 14 members, it was still very cold in some parts of the country, or it looked like cold had just left or would be coming shortly after. Truly mild runs were scarce. It's becoming a very strong signal indeed.
  23. 37 points
    They have been bloody consistent ..... week 6 is now week 2/3................
  24. 37 points
    Good afternoon... Ahem ^^^^ Anyway.. The GFS mean is great @-6c *BUT* expect westward corrections where the reality is going to be probably be -8c UKMO / ICON look like a good blend to me - Jet axis allignment day 8-10 could bring plenty of snow.
  25. 37 points
    ECM individual ensembles - it's starting to go "boom" - by 24th January, the number of runs with a favourable block to the N, NW or W is now well into the majority. I expect an even colder ensemble set than last night when the summaries come out.
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