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Nick F

Senior forecaster
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Everything posted by Nick F

  1. 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.
  2. 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.
  3. 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.
  4. I guess the building high traps cold polar air that sweeps SE across UK on day 6
  5. Well, the op is out of kilter with the GEFS mean
  6. 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.
  7. 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.
  8. 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.
  9. 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
  10. 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.
  11. Interesting stuff. Here was the Netweather radar image around the time of the reports
  12. 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
  13. 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.
  14. 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
  15. Cold or Mild? A look at what the weather has in store in the run up to Christmas View the full blog here
  16. Closer-up charts of 00z EC for noon Monday, you would never guess snow possible with those 850mb temps
  17. 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.
  18. 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 ...
  19. 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
  20. 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.
  21. Well, it looks like a rampant zonal jet is in the driving seat for the foreseeable future until something weakens the strengthening and expanding low heights / trop PV to our N and NW - but model ensemble teleconnections forecasts point to a +NAO for the 1st half of Dec for now. So often windy, sometimes wet, alternating Tm and Pm airmasses. GFS and EC hinting from late next week and through weekend some cold zonality, though often the coldness of the uppers in a W or NW flows tend to be toned down as we drawer nearer the potential. We've already seen a cold arctic northerly downgrade then vanish for Election Day. The one thing that may help in lessening the moderation of the cold zonal Pm flows sources from deep cold air over Northern Canada is Atlantic SSTs that are below average to the west of British Isles according to SST anomalies below:
  22. The low leaving southern tip of Greenland Tuesday, which goes on to be the potential ‘trigger’ for an arctic northerly on Thursday and Friday next week on previous runs, deeper on this run and thus forcing the low on a more northerly trajectory towards the UK. This more northerly track could delay the colder sub -5C T850 air sinking across all of the UK, though fortunately again on the 18z it gets the -5C line to the south by Friday. Not quite so much upper flow amplification upstream following this trigger low either. But no huge downgrades for now, remarkably fairly consistent up to the end of next week with the evolution, given the timeframe.
  23. Although it's still 9 days away, and subject to change, the weather models have have several runs indicating a cold Election Day Thursday next week, even with a risk of snow. View the full blog here
  24. If high pressure doesn't build in too quickly, always potential for troughs or slider low in the cold N or NWly flow to bring more organised sleet/snow inland away from the usual windward or coastal areas which see showers in these arctic or polar flows. Then of course there is a southerly tracking jet near the south coast shown that could bring secondary lows along the south that may interact with cold air draining down from the north. Not saying these scenarios are on the cards, as too far off still to say we will even get a northerly, but highlights routes for wintry precipitation almost anywhere in such a setup.
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