I’ll fully admit before I start that a inter-comparison between the ECMWF based forecast presentation from MeteoGroup and that of the Met Office’s with their own model data on a day of reasonably benign weather like today is a little bit over the top.
The ECMWF model does have a finger of showers running down the east coast but Simon King doesn’t (or forgets) to mention them in this particular broadcast at 12 am, even though he’s under no obvious time pressure (fig 1). The MeteoGroup graphics showed little or no low cloud across the southeast of England, which prompted him to say “a bit of cloud feeding into central areas, but either side of that we’ll continue with the sunshine into the afternoon” (fig 2). So nothings changed with the presenters, they believe the NWP in the graphics rather than check the latest observations, weather radar and visible satellite image. It’s as much the presenters fault as it is MeteoGroup and they now all work for the BBC and not them.
In the forecast video on the Met Office web site, Aidan McGivern does mention the showers which seem to be more obvious on the Met Office model, but then puts his foot right in it by adding that classic cliché ‘high pressure in charge’ (fig 3).
This visible image reveals how the BBC graphics have underdone the amount of low cloud across the southeast, the Met Office seem to have done better in its distribution (fig 4).
As for the light showers that are aligned along the weak cold front, both models have underplayed them, the Met Office seem to have made slightly more of them (fig 5).
In the forecast for this lunchtime, I think the Met office and their model did enough to just edged it over the BBC. Next time I do an inter-comparison between the two, I’ll have to choose a day with a bit more weather.
It would be fascinating to see a comparison between whatever mesoscale model MeteoGroup are currently using to produce the graphics with for their BBC contract, and the corresponding NWP output from the Met Office fine mesh model or whatever it’s called these days.
We live to the north of Exeter and it’s been snowing here since around 9 am this morning, it was moderate snow for two or three hours but now it’s generally slight. The top image is from last nights forecast from the BBC in Plymouth (fig 1), which has you can see has slightly mishandled the snow area that’s been affecting central and eastern Devon, and taken it westward much too quickly if you compare it with the weather radar (fig 2).
That forecast on the BBC was broadcast at 1910 UTC last night, and I’m guessing that they we are looking at the 12 UTC run of the ECMWF model (because as far as I know it’s only run at 00 and 12 UTC), and so they must have been using T+26 data (14 UTC) if there is such a time frame – if not then they must interpolate it in some way from the T+24 and the T+27 data.
I suppose it’s quite acceptable for the general public, and most will not have spotted that their forecast cleared away the snow far too quickly. Did it affect anyone? Well it may have, especially if you were a motorist trying to use the A380 near Exeter earlier this afternoon, because they had to close the road due to heavy snow, but the again I suppose that’s what amber warnings are for.
I did say last Sunday in the article return of the easterlies that it was still in the land of science fiction, well the models look to have been spot on even at T+168. The Met Office have a discrete centre of 1002 hPa on the low that seems to form on the northern edge of a warm trough that’s moving westward across France for 12 UTC on Sunday (fig 1). None of the other models, apart from the French ARPEGE seem to have pressure as low as that across the Channel on Sunday (fig 2), although it’s difficult to synchronise the validity time. It’s still 72 hours away, and we are now close to the vernal equinox, but this situation has the potential to cause a lot of disruption, especially if snow falls in the overnight period.
Today’s 06 UTC (Friday) from the GFS has a similar feel to it at T+42 (fig 3).
I wonder what the collective noun is for a number of NWP models? You know the kind of thing – a murder of crows, a murmuration of starlings, an exaltation of larks. Perhaps its simply a pile of crap? That may sound a bit harsh, but that’s the thought that ran through my mind when I compare short-range model output in this current spell of severe weather across the country.
All I really want to know is how long is it going to snow, and although they all provide you with some kind of solution, they are all quite different and not that convincing. In the early 21st century you might have least expected some commonality between them at the T+18 or T+24 range, but no that doesn’t seem to be the case, well at least not with the forecast for midnight tonight. Perhaps I am just too naïve to have thought they would have been, probably because I watch too much Star Trek. Perhaps it’s the ongoing SSW event that’s sending the models a little crazy at the moment, I would be fascinated to see just how the UKMO model is coping with the current situation, hopefully it’s better than this lot:-
Thursday is shaping up to be a real humdinger down across the southwest. The Met Office forecast charts – which are already out of date – are suggesting that the vigorous low that was forecast to be close to southern Ireland will stay much further south (fig 1). Although this will still allow much milder air to push north across the country above 850 hPa, it will find it more difficult to push down to lower levels flow as colder air is pulled in from the east, and the warm sector will slow as it comes up against the colder air and starts to occlude. This is a classic recipe for 12 or 18 hours of continuous moderate or heavy precipitation across southern areas. A period of heavy snow is possible, certainly across any higher ground and away from the coastal strip, and that’s probably why the yellow warning for Thursday across the south has just been upped to amber by the Met Office (fig 2). Let battle commence!
What happens after Friday?
It’s always difficult, even impossible and try to second guess what the UKMO model will do after T+84, because you simply can’t see it! Even what you might think is UKMO data on the BBC forecast these days may well be GFS data. Both the GFS and the ECMWF models make low Emma the dominating influence during the coming weekend and into next week as the easterly flow collapses and things become cyclonic.
There’s a cold and very wintry week ahead across the whole country according to the latest suite of forecast charts from the Met Office (fig 1). But they never extend beyond four days, which is a great pity, because that’s when the real fun and games start.
It does look like it will all end in tears though for the snow lovers amongst us though, as the anticyclonic easterly that we have at the moment is cast unceremoniously aside in the latest GFS run (fig 2), by a vigorous low that tracks northward from Biscay later on Thursday and into Friday bringing a swift return to the milder cyclonic weather that we’re used to, at least across southern areas.
Even the ECMWF is now following the GFS lead (fig 3). Of course the models beyond T+72 have been so volatile in recent weeks this may not happen exactly this way. Whatever process is behind the steering of this low might take it east a long the English Channel rather than north – we live in hope.
Just when we thought that we finally might see some winter down here in the south it now looks like two of the three main NWP models can’t agree with how things will work out in just 6 days time. The difference at T+144 between the GFS and the ECMWF models is massive, with the GFS going for a cyclonic SW’ly (fig 1), and the ECMWF for an anticyclonic E’ly (fig 2). All I can think is that it must be how each model handles the current SSW that is behind these two widely different solutions.
There is no doubt that a change of type will occur in the next week or two because of the SSW that started late last week. The next problem is where the actual block will be positioned and orientated. The two main available NWP models at T+240 have different views on that matter at the present time. The ECMWF has the block centred over the southern North Sea at the 500 hPa level and aligned northeast-southwest (fig 1), whilst the GFS has it centred over NE Greenland, and ridging more or less north-south across Iceland towards western Ireland (fig 2).
The exact position of where any block sits at the 500 hPa level, will make a big difference at the surface, because it dictates the surface flow and the source of the coldest air. As you can see the ECMWF at T+240 has higher than average 850 hPa temperatures across the UK in a strong SE’ly flow, and the coldest air over SE Europe and the Balkans (fig 3).
Meanwhile the GFS model has the coldest air at 850 hPa over Scandinavia with the UK in a much colder regime and the flow more easterly and not as strong (fig 4).
Here’s what the experts are saying down at the Met Office about the medium term (fig 5).
This short-lived easterly will soon give way and the anticyclone over Denmark will slip steadily into southeast Europe, that’s according to the latest run of the ECMWF model. Another anticyclone will form over eastern Russia though that looks like it will be more persistent. The trouble with this is that it will be too far east to bring any threat of cold air to our shores, in fact the only chance we will see of colder is air is in a strong westerly flow across the Atlantic from Canada, which obviously be moderated by the comparatively warm North Atlantic before it reaches us.
Here’s how the next 8 days pan out according to the GFS model (fig 2), as always just click on the image to see it at 100%.
Forget all the waffle that I wrote about a warm start to November, after all that was last week, and as we know “a week is a long time” when it comes to NWP output. You can’t say the latest run of the GFS isn’t meridional at the start of November (fig 1), but in completely the opposite way that it seemed to be indicating last Wednesday. Although the start of November usually marks the start of the silly season for snow, the GFS model is well supported by the ECMWF model in this northerly outbreak, although the anticyclone is over northern Greenland in the GFS model, rather than the west of Ireland in the ECMWF (fig 2).