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Kentish Kiwi

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  1. Kentish Kiwi
    The cold on the 00z looks like a pretty good example of what a toppler can offer with a complete lack of any heights to our north. A potent low pressure system moves in from the NW and stalls to the NE of the UK dragging down powerful northerly/north-westerly winds sourced directly from the pole. If such a synotpic set-up were to occur in mid-January things could be looking quite severe.
  2. Kentish Kiwi
    Probably worth noting I hadn't seen the 18z operational at the time of writing that post. The 00z seems like a possible upgrade on last evenings run and would certainly qualify as cool/cold zonality, also the strength of the NW/Nerly winds is a significant factor in what the temperature will actually feel like. The cold that moves in at around the +141h mark looks to be rather significant as far as early season topplers go. Strong north-westerlies sourced directly from the pole. Would imagine it could bring snowfall to sea level in Scotland and parts of northern England. Exposed northern high ground will certainly be in the firing line with full-blown blizzard conditions a real possibility. However before the cold air moves in there is a significant wind event for the NW of the UK, which has upgraded slightly on the 00z GFS, from a pretty potent storm system that moves in from the north-west.
  3. Kentish Kiwi
    A solid air and ground frost this morning with a low touching -3. The first proper frost I've seen this year and probably the second significant one we've had. Currently its slightly overcast and cold at 0C.
  4. Kentish Kiwi
    Very typical of a zonal pattern. The mean hovers just below average so could be described as cool zonality, but it's more that average will feel 'cool' compared to the mild weather we have experienced throughout autumn and the expectation of mild/warm that has come to be associated with zonality in recent years. Crucially not many of the ensembles drop much below -5C in terms of 850 hPa's, which would indicate snow will be mostly limited to higher ground in the north, particularly given the early season and Pm airmass associated with any cold.
  5. Kentish Kiwi
    The December 5th frame seems relatable to our current situation, however the 15th and the 25th both feature a split or at least disrupted vortex and northerly blocking, something that would be unlikely this year until the stratosphere warms a reasonable amount. I had completely forgotten the famous Jan 1987 event. Got a bit of a shock looking through the archive past the 10th again.
  6. Kentish Kiwi
    It depends how much it was to warm and how the warming impacted the different layers of the stratosphere and troposphere, if it was a split or displacement warming etc etc... An SSW (sudden stratospheric warming) can having remarkably rapid impacts on the troposphere, the lowest part that affects our weather directly, while other warmings can have no impact whatsoever. There's a lot of variation in it. In general though, from what I've read from Chiono, there is usually a lag time of around a month between warming and impact, give or take a week or so.
  7. Kentish Kiwi
    Actually on a second viewing it looks as though the important 1985/86 warming that actually caused the cold February was from an already average state. And the stratosphere throughout 1990/91 was already very erratic, not a sustained deep period of below-average temperatures, and had undergone a rather substantial warming during January. Still, it's all academic anyway and the 1985/86 analogue (I believe that's the one a few members have mentioned in terms of ENSO?) looks to have decent support from a range of factors.
  8. Kentish Kiwi
    Cheers for the reply LS, that '85/'86 record is pretty much exactly what I was hoping to see. Illustrates just how rapidly the stratosphere can warm after an extended and deep period of 'negativity' and just how quickly the troposphere reacts to this warming. It's also encouraging given the amount of comparisons people have drawn between 1985/86 and the current state of the atmosphere, background signals and analogues such as ENSO. I do fear though that for every example someone can provide of a very cold stratosphere early in the winter leading to a 'cold winter' (although the cold is quite understandably concentrated in the final half/third of the season), there are ten more where the stratosphere has failed to recover sufficiently and the PV has remained in an organised and powerful state throughout. It would seem reasonable to say that from the two above examples it would be worrying if the stratosphere doesn't recover and warm to some extent by or around the New Year period... However, I suppose on both occasions the SSW's in question rocketed the temperature upwards from an already very negative state and the temperatures preceding an event such as those are irrelevant?
  9. Kentish Kiwi
    Worryingly it looks as though the Stratosphere continues to cool, and rather rapidly too. Surely we must be close to record cold levels by now? We truly will be in a desperate state if it continues to cool at the same rate through the end of November and into the first five or so days of December (I estimate it would be below -85 by that time at this rate). I wonder how much colder the stratosphere could physically become... A question for Chiono or Mr Data - are there any 'cold' winters in the records that featured a very cold stratosphere through the majority of November and into December? The only positive that could possibly be taken from this is what seemed like a throw away comment from GP about us wanting the vortex to spin faster now that it is already in a very well organised state, as this would apparently aid any SSW that happened to eventuate? (Or something very vaguely along those lines...)
  10. Kentish Kiwi
    Beaut day here. Unbroken sunshine and a bit of a breeze. Chilly.
  11. Kentish Kiwi
    I had the problem you describe a few weeks back, but thought nothing of it at the time as I managed to sign in on my computer eventually and hardly ever post while on my iPhone. Can see how it could be frustrating. Guess it's one of the many teething problems associated with an overhauled forum.
  12. Kentish Kiwi
    To be honest, this isn't even a particularly good chart as far as extreme FI eye candy goes. Complete lack of heights to our north. Not sure what the cold pooling over the UK would be like either...
  13. Kentish Kiwi
    Which you believe is less conducive to sustained blocking in areas that impact the UK then a vortex split like the last two? (in terms of bringing colder weather)
  14. Kentish Kiwi
    Interesting to note that on the GFS 06z the 528 dam line resides over some part of Scotland from 159h through to 300h. Obviously uncertain at such a time frame but it certainly illustrates the change to cooler conditions in the north that is becoming more of a likelihood.
  15. Kentish Kiwi
    Very good idea for a thread. Will hopefully help clean up the main MOD thread too. Just a thought Chiono, do you think you could possibly edit your original post to ask people to include 850hPa temperatures too if possible? It's always a little frustrating looking back at posted charts and not having a clue what the cold pooling is like and if it is actually as good as the pressure makes it out to be; the colours associated with the heights often mislead people into thinking they are a direct translation to temperature.
  16. Kentish Kiwi
    Hmm, quite the opposite of what many of the experienced forecasters on this forum are expecting.
  17. Kentish Kiwi
    Can you really call it a bartlett though? By +240 its pretty much disorganised into an area of slack high pressure of 1020hPa. I though one of the prerequisites of a bartlett was its longevity?
  18. Kentish Kiwi
    Do you mind refreshing our memories as to what the winter that followed was like Mr D? I get the feeling from your post that it was a cold one...
  19. Kentish Kiwi
    And the two warmest Aprils and presumably two of the warmest springs (I know this Spring was the warmest on record but not sure about 2007).
  20. Kentish Kiwi
    Certainly provides hope for the second half of winter. Would it be possible to produce something similar in terms of NAO?
  21. Kentish Kiwi
    To be fair, it's not impossible that the high pressure cell retrogresses NWwards towards the 'vacuum' of 1020 pressure over Greenland, but given the current pattern and background signals it would be extremely unlikely and probably requires the PV to split perfectly for us - again unlikely and against background forecasts. +240 on the ECM looks quite odd to me, with those two small but potent depressions to the west and south-west of the UK forming rapidly and apparently out of nowhere. http://www.wetterzen...cs/Recm2161.gif to http://www.wetterzen...cs/Recm2401.gif It seems unlikely we'll see these features continued to be modeled on ensuing runs, although I suppose there is a reasonable temperature contrast between the plume of Tm air over the UK and the Arctic air from southern Greenland which could aid cyclogenesis.
  22. Kentish Kiwi
    Would you mind explaining why this is a positive note? I note that the sea's surrounding southern Greenland were also anomalously warm at the end of last October and I take it this was a factor in promoting the intense and prolonged blocking in that area? It's probably been explained many times in this thread or the SST one, but I don't really understand how/why warm anomalies such as that promote blocking... I would have thought increased warmth would lead to increased evaporation and therefore more rising air and lower pressure, in which case I was lead to believe that colder sea temperatures/negative anomalies would promote blocking. However this appears to be the opposite of the reality. Is it because warmer seas in the north of the North Atlantic and cooler seas in the south lead to a smaller temperature contrast and therefore contribute to a weaker Jet Stream (by taking away the fuel that is the natural contrast in temperatures)?
  23. Kentish Kiwi
    Love how -27C only qualifies as 'cold' to them.
  24. Kentish Kiwi
    In general it does seem things have been like that since January. However all of summer has to be excluded from that, otherwise we'd have seen something much more interesting in terms of warmth!
  25. Kentish Kiwi
    Bit of an obscure question but could anyone provide me with an idea of the deepest recorded snowfall in lowland Southern England? We had between 40-45cm at its deepest during November/December 2010 but I was just wondering how deep that actually was compared to records and if there's much chance I'll see any deeper in the next 3-4 years I'm living in the UK.
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