weather eater
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Posts posted by weather eater
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On the whole, awesome charts again tonight if you want snow. Several days coming up where snow cannot be discounted pretty much anywhere, except for a few hours tomorrow. Even as we head into FI, the return to mild keeps getting pushed back, though caution needed on anything beyond T120 in a UK cold spell as a slightly wrong track on a slider low could make many more places soggy rather than snowy.
The MO via the BBC seem to be edging towards the mainly dry after tonight/tomorrow morning, that of course will be subject to much revision. As for the models we feel a bit stuck at the moment waiting to see whether we are heading towards something less cold or whether they are going to pull a rabbit out of the sack. The ECM a case in point it looks as if it's going somewhere interesting but doesn't really manage it.
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No, they just need to viewed I a different way. I treat them and the new opp run as different models.
All output should be considered in the round. Even minor models
That just sounds a recipe for more confusion to me, it's bad enough just trying to way-up the pros and cons of the GFS vs the UKMO and the ECM. You can see that confusion caused by the kitchen sink of models, runs and their attendant ensembles just about every day of the year on the model thread, peaking in winter, sometimes I feel less is the new more.
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Fair enough. On that point I suspect you will be right. The mid term is getting more interesting though, especially as the old GEFS usually want to revert back to westerlies ASAP. Shame we don't have new ensembles yet.
Doesn't that make them next to useless,, the ensembles are supposed to be guidance for the OP but the OP is the new GFS and the ensembles the old.
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This mornings gem is consigned to the bin in the short term.
It was never a starter with no other op support at such a short timeframe.
I will get shot down for this but I haven't seen any polar lows on any models. That will generally be because they tend to form at short notice and are not picked up by the nwp at more than a day or so out. A low that forms over the polar field can clearly be called a polar low but it's not in the classical definition .
Yes the GEMs cunning plan appears to have gone the way of the pear. As for the polar low there is some debate whether this was modelled or is just a feature that has appeared on satellite imagery, from what I gather the MO think it is a PL.
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I wonder if the express are paying attention, bet nobody there has ever heard of a polar low before. A new buzz weather phase to drop into their snow sensation stories, JM are you watching, repeat after me Polar Low, could in the right hands be snow measured in metres not centimetres.
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A long way to go for the mid-term solution to come into focus although I still don't see it being this morning's GEM solution, unfortunately. Much will depend on the modelling of the low and lobe of vortex north of Newfoundland early next week.
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Out of all the shouts we have seen over the years claiming to be polar lows, this one looks as close to be one, as anything. Perhaps the upper temps of -35C could be a tad lower, but the sea may be a touch warmer than average, so it's all relative.
I think that it is....
Good call by Daniel then. My guess is that, if it was off the English east coast then that might create some consternation for the MO. As it is off the NW coast of Scotland and as they are supposed to be short lived affairs then it may not even get a mention.
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Is that a Polar Low forming to the North-West of Scotland? Just skirted over a few models and can't see a low that extensive being forecasted anywhere
certainly looks like some of these but I'm no expert
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Oh dear. I was really hoping the slightly improved 0z ensembles would reflect in the 6z, with tightening of the scatter and the others being more in line with the operational. Instead the opposite has occurred, and the control has even gone off on an FI cold outlier.
Of course, the op could be right, but to have it this much out from the mean and median of members is not brilliant:
Screen Shot 2015-01-29 at 12.30.09.pngUntil or unless this ensemble situation improves any evolution towards further cold beyond Sunday continues to look a tad precarious to me (I'm putting it as gingerly as I know how).
And all of that should be pointing you at the fact that the ensembles are producing no more of a guide than the operationals, its one thing today, something else yesterday and tomorrow. Obviously all of this stuff is here to discuss and it's good to do so but I don't think there is much of an overwhelming case as yet for a long term continuation of the cold or a quicker return to something less so. And even if there was then any of us who have been doing this stuff for years know that trends have a habit of changing tack. My own view on the ensembles suites and I've said so for years, is that much of the time they makes things more confused and not less so.
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I have to say as well, hats off to the GFS it has done really quite well with this spell, except for over complicating the LP for a time, it certainly picked up the slider low early.
The 06z after toying with an easterly has reverted to the idea of the MLB close or over the UK that we saw from a number of runs a couple of days ago, I still think this looks like the most likely solution with the possibility of a reload thereafter.
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Well the 06z is not the GEM but it's not a million miles away either, this evenings runs could be quite interesting to say the least.
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Incredibly difficult for the MO, small synoptic changes are making big differences in precipitation, will it won't it, amounts and type they will keep their cards close to their chest so as to give the best advice as soon as they are sure.
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GEM does also have a decent degree of support within its ensembles. There is a lot of scatter but there is enough support for an easterly for it to be considered a coherent signal. Coupled with some support in the GEFS its well worth watching.
Well we can live in hope but some ensemble support doesn't mean much, there is support of other options as well, I would have a lot more faith in the GEM if it had some other operational support. Remember the operational is the models best guess, the ensembles are just a guidance for the operational they are not alternative forecasts as such.
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If I understand this correctly the Ensemble members have modified starting conditions for each member of the set to promote divergence, is that correct? The main point I think being to promote a spread of solutions, if the spread is wide and varied then that provides doubt on the main model solution, but if the spread is tight and not very divergent then that implies that the operations solution is along the right lines. Not an expert but from what I have read in the last few years that seem to be to way these sets are analysed. Do the Ensemble set have the same alteration to each member in their starting conditions every run?
There are deterministic models and statistical models, again if I understand correctly the deterministic models are the operation models and they solve a set of fluid dynamic equations to predict surface flow and other conditions. However, I wondered if the statistical models have "a priori" information added in the form of historic outcomes for similar situations and they use a set of Earth Science equations to measure the deviation from the mean of any outcome. I am familiar with this type of model in the Earth Science area where the a priori knowledge is the "Ground truth in my terms" and is used to calculate the probability of an particular pixel belonging to a set of similar values. The main difference being that in the Earth Sciences satellite example the pixels are measurement of the spatial reflectance of an area on the ground measured in a particular wavelength from a geostationary satellite and in the weather model the pixel would be the value of a cell within a 3 dimensional matrix. Sorry for the questions I am trying to understand the basic working of the weather models in terms that I understand Earth Sciences satellite analysis.
There is no historical data its pure climate science mathematics and yes I think the same set of starting conditions are run, remember these are global models so trying to work from historical data from all over the world would be next to impossible.
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Unfortunately the GEM stands alone and if it comes off I may have to start believing in the super natural. However the changes from the big three happens really early into the run and it is similar to last night output, so maybe that gives it some credibility. Then again none of the big three have shown any sign of backing that evolution at any stage. I want it to be right but I feel it's a wild goose chase, can anybody remember the last time it trumped the GFS, ECM and UKMO at 96-120hrs.
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I would agree with WIB in regards the fact that at least one run would have to show something more shall we say progressive but it is one operational run and a possible breakdown in 5/6 days is a long way off in synoptic evolution terms. However, there is no getting away from the fact that it has credence if little support yet.
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If anyone wants a good indication of how difficult it is to know what's likely just three to four days away in any detail, look at the three fax charts T96/T84/T72.
All issued within the last 24 hours and all different. Not for the first time, the T72 is closer to the T96 than the more recent T84!
You can see that in the BBC forecasts , they are not that far off now casting such is the MO uncertainty.
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Me I rather suspect though I was looking for something closer to home, while its just for fun and far out from the GFS this from the GEM is not. Shame the GEM is not reliable enough and shame its really still only MLB and not HLB. all the same its tasty.
Someone complained that there were only tentative hints from the Ops of pressure over Scandi.. well.. GFS 12z heard you, and raised you this
(Way, way out. Posting for fun)
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Indeed that's pretty sensational and that's what I keep hoping the GFS UKMO and ECM would offer some hints at. But I guess given the time scales then jam today will be gone before we get to taste it, that's what usually happens. Better for those sorts of chart to appear at 96hrs.
GEM is going to excite some members.
http://modeles.meteociel.fr/modeles/gem/runs/2015012812/gem-0-150.png?12
Steve M will appreciate this run as beyond could be tasty!
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Can't believe how quiet this forum is. We're about to go into the coldest spell of the season, where is everybody?
It's always the same Daniel as soon as the cold begins to bite everyone leaves for the regional's, which rather proves the point that in winter this thread is just a snow chasing one and very few are that interested in synoptic models unless snow is in the mix. Nothing really wrong with that I guess and I suppose (and I include myself here) we just hate to admit we are still all little kids at heart and snow brings that out in us.
Mean while in model land we have some of the best continuity I have seen for a cold spell modelled by the operational runs since 2010. The only disappointment for those of us who want to see a really prolonged and bitter cold spell is that we cannot seem to get the ops to do more than give some faint hints at possible heights to our NW.
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Holy mother of god..
It's pretty much horizontal, almost true blizzard conditions and i usually call people up for using the word.
Ha me too but if you want to see the real power of snow its at its worst when combined with wind especially in the countryside.
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BBC very reluctant to go much further than tomorrow morning and I don't blame them. As for the showers the weather graphics are pretty meaningless and they are just a generalisation. some areas that look like they are being missed could get plenty and others the opposite. Radar much more useful in this instance
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Snow here in East Lindsey district, rather wet horizontal snow it has to be said and very windy.
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Which rather supports the idea that the operational is considered far more important and trusted even without the support of the ensembles. Sometimes they are a guide and sometimes not and frankly they are subject to as many vagaries as the operationals. They are run from the same data as the operational but tweaked. Subsequently if an operational run differs quickly and substantially from the previous run because of big data changes from the previous run then its ensembles will also reflect a big change from the earlier runs ensembles. In other words an ensemble set is only relevant to its operational or at least only to the point of divergence between operational runs.
They didn't, that upgrade is due later in the year.
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Tracking the potential Polar Low - Thursday into Friday
in Spring Weather Discussion
Posted
Looks to me on the radar that it will track Cheshire gap, Birmingham then London although I doubt it will amount to much by then