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Nick F

Senior forecaster
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Everything posted by Nick F

  1. Some warming at the top of the stratosphere showing on yesterday's Berlin EC strat diagnotics, uncertainty whether it will propagate downwards, but I suppose worth keeping an eye on in the bleak January days ahead with the formidable strong sPV/tPV
  2. Happy New Year all! The best we can salvage from the strong westerly onslaught, as the strong jet and low heights of the PV over Greenland shunt increasingly south over the Atlantic is some cold zonality. GFS ops been advertising this over recent runs, albeit in the medium range - which it has a well-known cold bias in that timeframe. If UK can get north of the jet, as T+198 shows below, then we may at least get some snow potential for the north, particularly hills. But, we need to get the jet south and also wary of the GFS op cold bias. Otherwise little in the way of crumbs of comfort for snow lovers for now.
  3. GFS on its own against UKMO, EC, GEM and ICON with regards to how far south it gets the Europe bound cold plunge this weekend, models other than GFS barely get -5C T850s across Scotland. So will be a triumph for GFS if it proves nearer the mark. That said, we are chasing a very brief cold shot, only likely to bring snow to Scotland and northern hills briefly, if there's ppn, before it warms up again.
  4. I think, if you’ve not already, that we will have to lower expectations for January re: cold and snow, history indicates that once a strong +AO along with +NAO sets in by the New Year, it could last for the rest of the winter. We only have to look at real stinkers of winters for cold and snow with +AO/+NAO most of the winter to be worried: to name a few 2013/2014; 2007/2008; 1999/2000; 1997/1998; 1989/1990; 1988/1989. Once the +AO/+NAO combo sets in, the models generally tend to perform better over longer time frames than when these indices are negative. Although the MJO briefly orbits through 7-8, it does so at low amplitude, so will likely have little effect on changing the wavelengths over the N Atlantic, furthermore there is strong support for the MJO to swiftly die into COD then emerge into the Maritime Continent, phases 4-5, which are warm phases, so there will likely be no help from the MJO through much of January. Though it is possible that the MJO will progress onwards to colder phases by mid-January – but the lag of this probably not having an effect until towards end of the month. The AO flipped suddenly from -2 to +3 in a space of a few days recently in December, so I suppose there’s chance that it may flip back –ve later in January or February – though it’s not quite clear what the precursor for this would be. But there is also every likelihood that it could remain +ve through much of the rest of the winter. The QBO has only recently turned easterly, so unlikely this will have an impact on the PV until later in winter, when the PV would normally start to wane anyway. So we are kind of reliant on tropical forcing over the Pacific changing the patterns at high latitudes, of which there is unlikely to be much help from for a few weeks at least. There is EAMT and GLAAM to consider, but that’s not my forte, so cannot really suggest if these will have positive impacts.
  5. Yes, no signs of the coupled strat-trop strong polar vortex weakening anytime soon, certainly not in the stratosphere anyway. Was reading on another forum that SSWs don't normally happen when the Indian Ocean Dipole (IOD) is positive so a SSW is probably unlikely over next month at least. With regards to the strong IOD recently, this has been hindering the MJO orbit and even when it starts to move it tends to go through the colder phases of the MJO quickly / low amplitude and spends longer in the warmer phases. eQBO descending may put stress on the sPV eventually, but it seems not anytime soon. It's going to be a struggle to shake off the influence of a raging PV over coming weeks, but too early in the winter to give up hope that it won't dominate all winter.
  6. Interesting the divergence between models for the degree of amplification in the upper flow this weekend. GFS and GEM ops going for a brief coldish N/NWly, EC and UKMO not amplifying the ridges and troughs so much so cold plunge not reaching the UK. Yesterday morning's 00z output consensus of building a ridge over the UK in the medium range seems to have evaporated in the EPS means, with quite a flat, zonal / cyclonic picture now. GEFS seems to want more ridging though, but not far enough north to stem a mild maritime flow. Models chopping and changing more than usual, but you kind of get that niggling feeling any hints of colder incursions, albeit brief, will be watered down or gone as we draw nearer when they are originally shown.
  7. I'm not suggesting any wind direction is likely, the ens mslp certainly not best guide for knowing where high pressure may set-up at that range, but if high pressure is over parts of UK and the flow is slack, day time temps may struggle if skies have been clear overnight sllowing frost. Cold Pm flow into Europe preceding the ridging helping in any surface cold. All conjecture for now, pressure may not build as much northward.
  8. I guess the building high traps cold polar air that sweeps SE across UK on day 6
  9. Well, the op is out of kilter with the GEFS mean
  10. 00z EPS 10-15 day H500 indicates ridging N over UK here to stay. Whether it can gain enough latitude to allow a cold easterly undercut remains to be seen though. But it at least it offers potential for surface cold to build. Think raging mild zonality is increasingly being shunted out of the picture. We could be seeing the effects of MJO passage through 7-8 being increasingly picked up by the models through more and more amplification showing up over recent runs with the forcing of MLB over northern Europe.
  11. The models could be underestimating the amplitude, given they seem to be playing catch up on the MJO's progress. Clutching straws I know, but a possibility. However, given the lag of 10 days or so of the impacts of more favourable 7-8-1 for HLB, we are unlikely to see the models showing anything for a week at least. In the meantime, not a good look from the operationals if it's snow you want.
  12. Tough model watching at the moment for those wanting to see some snow, particularly with the AO forecast to go strongly positive combined with a +NAO, probably because a strengthening stratospheric PV is coupling with the troposphere. 18z GFS no exception to the continued horror show output for snow lovers. This very cold upper air vortex tightening up over the arctic can take a while to shift and can last through much of the winter (hopefully not the rest of this winter though). However, there's a few glimmers of hope, carrying on from s4lancia's mention of the MJO above. Aswell as the Indian Ocean Dipole beginning to weaken, the SOI is tanking through -ve (ENSO neutral towards El Nino-esque tropical Pacific pressure pattern), and also it appears the models have been struggling to predict the MJO progression and are playing catch up, latest GFS and EC RMM plots seem to increasingly be trying to orbit through colder phases of 7-8, when previously the orbit has gone from the current warm phase of 6 back into COD then back out into warm phases. So we could see more coherent progress through 7-8-1, so after the usual lag we could see some sort of pattern change favouring blocking as we head through Jan. however, it's just a glimmer of hope for pattern change, remains to be seen if tropical Pacific forcing will have any impact on the pattern becoming deeply entrenched over the N Atlantic and Europe caused by the strengthening tPV over the arctic.
  13. UK Severe Convective & Storm Forecast - Issued 2019-12-23 18:22:46 Valid: 24/12/2019 00z - 25/12/2019 00z CONVECTIVE / STORM FORECAST - TUES 24 DEC 2019 Click here for the full forecast
  14. Yes, very hard to see where any deep cold will come from in the next few weeks, unless the upper pattern suddenly flips over the northern hemisphere. The general direction of the ensemble guidance of teleconnections important for us not really pointing in the best direction for now. After a spell in negative, both the AO and NAO are indicated to head north into positive in the last few days of the year and to start January. This indicates generally deep cold air bottled up at high latitudes in our part of the world. This not helped by a longer term shift shown in the ensembles of the tPV from north of Alaska to Greenland and possible coupling of a strong strat PV with the troposphere too. The only saving grace is the modelling of the MJO has been jumping around a lot between the models, so this may be why we see differences between GFS and EC with modelling the troughs and ridges over the Atlantic, but even if the position of these become more favourable for us synoptically, we may still have the issue of a lack of deep cold air to tap into. Don’t want to sound too negative, but don’t think there’s great deal for coldies to get their teeth into for a bit until the pattern changes.
  15. Interesting stuff. Here was the Netweather radar image around the time of the reports
  16. Following a month's worth of rain in the last week across the south and further rain Saturday & Monday, the risk of flooding will continue this weekend. But high pressure by Christmas Day with bring a drier respite View the full blog here
  17. Model RMM plots finally roughly agreeing on the MJO moving out of COD into phase 7 then maybe towards 8 by end of the month, so we could start to see more blocking in the 'right' places in Jan to better deliver deep cold Meanwhile we are now into the easterly phase of the QBO - which will help too But hard to see the pattern changing much before the New Year IMO, we might get lucky on a local level with transient cold shots, but not widespread luck. Looking very low pressure dominated in next few weeks. Jet southerly tracking, but because of west based -NAO we are on the wrong side of the low pressure in the means, so deep cold is kept way out of reach.
  18. One thing's for sure, with low pressure close by for much of the run, going to be a lot more rain to come up to the New Year Whether or not we get on the right side of these lows to get in some deep cold, with a better lowland snow potential, remains to be seen and is well out of reach for now, particularly given there is a west-based -NAO developing now Want the -NAO to become more east-based Good news is the QBO has turned easterly
  19. Cold or Mild? A look at what the weather has in store in the run up to Christmas View the full blog here
  20. Closer-up charts of 00z EC for noon Monday, you would never guess snow possible with those 850mb temps
  21. I wouldn’t have much confidence in model ops past day 6 at the moment, seem to be quite noticeable intra-model differences in the track of the jet into Western Europe and expansion of higher heights eastwards from the Greenland upper ridge later next week. 18z GFS and earlier 12z GFS lowering heights more into Central Europe than EC - which goes on to merge the far N Atlantic upper vortex with the vortex over Barents Sea thus raises heights over SW Europe. Deep cold still way out of reach, but we could get ‘faux’ cold continental flow instead in run up to Christmas.
  22. Given there is such large differences between EC and GFS with Friday night's low track, Ec has it track across S England GFS across N England, wouldn't even consider snow potential as far away as early Sunday for now. 00z EC doesn't even show GFS's low for early Sun, though has a frontal wave or trough moving NE, which brings snow to Wales and N England for a time. This far off, could change ...
  23. UK Severe Convective & Storm Forecast - Issued 2019-12-11 09:00:50 Valid: 11/12/2019 0600 - 12/12/2019 0600 CONVECTIVE / STORM FORECAST - WEDS 11TH DEC 2019 Click here for the full forecast
  24. Nothing particularly inspiring up to day 10 on GFS, unless it’s wet and windy you like. Trouble is, secondary lows keep forming out west due to deep cold coming out of Canada causing a steep temp gradient over NW Atlantic, these lows forming to SW of parent low north of Scotland holding back the coldest PM air, so zonal flow not really cold enough to bring any snow away from high ground in the north. Just going to have to wait for the strengthening trop PV to weaken or at least dig further southeast into Europe; no signs atm of any real shake up of the zonal pattern for now.
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