If Wishes made Weather

GFS is now suggesting 18mm precip for East Herts - assume a ratio of 1:13 for colder powdery snow which brings us to more than 20cm snow which is much for this part of the world. What amazes me though is that on the chart scales for precip we are still at the very bottom end with up to 10mm per hour.

.. and to add to that, it looks like 20cm+ is possible for some areas. The intensity is looking quite impressive in parts. Camera ready.

Yep - looks like our region is going to pull the rabbit out of the hat here, amd on the 6z NAE and GFS the 15cm mark is looking rather average. Looks like we will have snow all night into tomorrow, much of it heavy and that could give 20 cm + for some

Its teh GFS 6z - be thankful its not showing a Bartlett

"I doubt that more than 10% of the vehicles that go out on the roads will have winter tyres" Roger - this is the UK, you missed the decimal point - almost no one has winter tyres. Since we drive in Germany we run winter tyres November onwards (175 width tyre with a different tread). The compound is softer and from temperatures of +7c and below the stopping distance is significantly reduced (we run 225 width tyres in summer). The push for this came from the insurance industry in Germany. Much safer snow or no snow. As far as depths tomorrow are concerned, we are being consistantly progged for circa 15 mm precip tomorrow, so circa 20 cm for East Herts.

That would kill people here as the national grid and gas supplies would surely fail with everyones heating on full tack.

Well we appear to be in the best area for the snow staying as snow. Much nashing of teeth on some of the other threads: but we have been patient last year when nothing happened and others were on the 2 ft mark. Nothing that spectacular, but I think that for some parts of the region the 10-15 cm is a little conservative, and we may hit the 20 cm mark. Not exactly national emergency, but not to be sniffed at - and if the GFS is to be believed (and don't forget people believe the most wierd things), then we could be looking at Easterly winds setting in with the snow shower thing kicking off next week.

But remember, if precip intensity is being increased on the front, temperatures will rise making it more likely that it will be rain-snow.

-4 c in Stortford. GFS 'predicting' around 17 mm precip from the front (I think it won't be so much), but that would give 22 cm snow at the predicted dewpoints.

Probably just the rubber band snapping

Well if I could, I'd bank the GFS precip model. Of course, they will turn out wholly different, but if wishes were snowflakes ...

Shall we have a guess as to where gets the most snow? I would suggest slightly to the North and East of me - say Royston. Its (relatively) the ground for the region.

Are they in league with Croydon Council?

It really is quite astonishing how short memory is. In the 1980's (and I refuse to think that I'm old), I recall snow in the Dales where it wsa 2 feet level, and easily drifted to the height of lower barn roofs. Hard to think that 5-10 cm is heavy.

As we have often said these subjective terms by the Met don't really help. What then is "heavy"? I understand though that the Uk definition of blizzard is less, for example, than that commonly accepted elsewhere.

Met office have now got warnings out for Sat night into Sunday

Seeing as I live parly in this model thread area - amazing news and pictures coming out of Germany now. Even Alsace areas west of the Rhein are seeing windchill levels at -25c. Over in the East the inland shipping routes around the Elbe have frozen solid and ice breakers are being needed in the Baltic harbours. Just that bit colder uppers and no North Sea makes such a difference.

ECM 00z now showing a highly disrupted PV by t240.

Which seems to fit with GP's thoughts and those in the Strat warming dept. I think the points to note in the ealier parts of the run is the attempt of the ridge from the AzH to Greenland and the westward trend of the Eurasian High. Generally pleasing signs if one seeks somewhat colder weather.

Many thanks to all for the answers on this. The impression that I get on the forum here on NW is that many would like to live in a more conntinental climate; but without having actually experienced it. I recall years ago being a vastly suprised teenager on my first trip to NYC in summer at the heat levels, and the superb gardens upstate, and in subsequent business trips experiencing the New England winter (so cold it hurts to breath in, wind blowing snow so that you cannot see over a 6 lane highway, flitting from doorway to doorway to get out of the windchill for a moment when only walking a couple of blocks). I'm sure that would, just once, these conditions hit the UK for a few weeks, we would suddenly see a model forum full of those crying out for a return of the jetstream.

And look what has happened to the PV - its reduced, in the space of circa a week to half of its previous extent. And the effect: high pressure trying to ridge over from the Russian/Eurasian HIgh through Scandi to the Azores High which is pushing higher into the Atlantic. The jet though still doesn't quite be seeming to allow a full link.

Surely though on the models people must see that there are two reasons that anything remotely severe (be that wind, cold, heat, whatever) that is being indicated in F1 won't happen: 1 - its F1, meaning that the general pattern being suggested will be revised many times between +240 and +0, and, 2 - everything will always reduce to, or near to, the average. Thus, the predicted 10c above average, is most likely to end up being +2 above average etc... Thus to see that both GFS and ECM have reduced their extreme suggestions to a middle ground is not overly suprising.

Don't know if this is entirely relevant, but I remember flying from Denver to Tampa about 10 years ago on a very unstable day - multiple storms and tornados being experienced at ground level. Extremely rough ride even several thousand feet about the main action. Interestingly, on US flights it is possible to listen to the Air Traffic Control through the headphones, and the pilots were reporting back to the ATC the weather conditions/turbulance that they were experiencing and ATC were updating and updating the routing accordingly. Most unsettling when I heard our pilot reporting in and following flights being diverted from the path we had just taken.

I'm putting this question in here - but mods, feel free to move if its better placed elsewhere. In New England, most winter there are several snowstorms that would, by UK standards, be considered extreme. Typically there are -20c or colder 850 temps, very low heights (if that isn't tortological), and at the surface temps of 10 F or below, 20 to 40 knot winds and anything up to (think Jan 23 2005) several feet of snow falling as the system moves through. Are there any Northern Hemisphere larger scale patterns that could, albeit very occasionally, lead to such weather in the UK, particularly lowland UK where precipitation levels are not being sigificantly affected by topography? T

It does indeed. As I understand it, the warning system is based upon the potential frequency or extent of an event within a certain area, providing the event meets or exceeds certain criteria (windspeed, intensity of rainfall etc). Thus I think that although the charts are showing the potential for a severe, perhaps quasi tornadic event, such a storm would affect a small area. Not entirely a satisfactory system perhaps. I know from experience in other countries, where presumably the popluation are more empirical, a percentage system is used to state to people that they have today a '10% chance' of catching a severe thunderstorm and all that brings with it. Perhaps it is thought that here this translates to people understanding that you have a 100% chance of catching 10% of a severe thunderstorm?