Mike Poole

I think the pinch point at T180 is here: If the cold is cut off here, you won’t get the Genoa low. If it isn’t you will. Knife edge on this one...

Compare GFS 18z T138 with ECM T144 from earlier (this one’s still got my scribbling on it): That NE flow round both the arctic high and our developing block is crucial. Always difficult where to look in these situations, but this is more important than the southern end at this stage for me, the GFS evolution should sort the Genoa cherry cake thing in due course?

GFS pub run, so far I think it looking OK, maybe better than 12z, T102: I wonder if the low circled yellow might help in getting some sort of connection between the developing high and arctic high to bring the cold from the NE...we will see...

That’s true, and we shouldn’t be panicking, I’ve said before that just random chance would have 6 major model runs in a 0z or 12z set give an adverse run about 1/64 of the time - so that’s about once a month. And we’re not even there - GFS and GFS // were good. So every chance it is a blip and the morning runs will be better. Mind you the MO update will be before the 12z runs.

Graupel.

If the ECM debacle is not for you, here’s tomorrow’s snow according to HARMONIE 12z:

It seems to me that there are two phases to this evolution necessary to get the real cold air to our shores properly. The first is some proper connection between the block and the Arctic high. This is shown on GFS (and also //) at T144: The 1030 hPa isobar shown by the yellow line, means advection of cold on a long draw NE’ly. ECM just doesn’t have this at same time: The second phase would be concentrating on the block closer to us (forget the arctic high at this point) to be optimally aligned to bring the cold in to the UK with sufficient disturbances in the flow to cause snow. No charts on that is it is so uncertain. Let’s get the first phase sorted, and that means the block has to be more northern than ECM shows.

Away for most of the 12z rollout on weekly pub replacement Zoom call with mates. And pages to read. So i take it the UKMO is OK as far as it goes, the GFS not as good as 6z, but sort of gets there, the // a bit better and delivers in FI, the ECM is dreadful. Sounds like standard flip flopping in a situation with high uncertainty. We won’t sort this until Sunday at the earliest. And there’s possible snow for many on Saturday. Apparently low heights in Genoa are essential, I always thought that was a cherry cake that had failed to rise in the tin. ECM mean T240 compared with 0z: It does look a bit worse, but might be only a few moire members going rogue, we will see..

UKMO uppers good over all but the far south, T144: The future potential from there is great:

Yes, that is pretty similar to how I’m viewing things at the moment. Whilst a few options are being thrown about in the models, and ensembles, the smart money seems to be on the scandi high, and from there it just about the position, as to what advects towards our shores..,.will be fun finding out.

Good post Si, Re the latest clusters, there are 6 of them but they are all blocked one way or another. Look at the borders, if you don’t want to look at the detail, at T264 all red - scandi block, by T360 two red, 3 purple (Atlantic ridge) and one green (-NAO). My feeling by T264 this uncertainty will have collapsed and we will have a scandi high. We will see...

Actually, not sure he’s showing the same thing I was, this might be the cap height? I was showing the NAM. There may be a correlation though! Not sure, I haven’t read Cohen’s blog since March, the link to it is on my office computer. I haven’t been into the office since March!

ECM clusters T192-T240, and I like these: It’s kind of what kind of blocking would you like, rather than is there going to to be blocking. The borders tell a story, it’s what ECM think the wider pattern is, green is -NAO, red is Scandi block. And red is the way they are going - this is great, at this time in late winter, a scandi block and easterly winds will deliver more than a Greenland block and northerly. It’s the other way around in early winter. Keeping my eye on the strat situation, I’ve posted the NAM chart all winter, here’s today and it gives a good visual indication of the story so far: You can see the downwelling, the blip where tropospheric conditions were not conducive, and then in the forecast the landing zone (MJO big help in that , i think) and up top the resurgent westerly winds shown in yellow will only enforce that increased likelihood of easterly winds in the troposphere for a month or more, I would expect...we will see...

We are nearly into February, and the warm anomaly shown is only up to 1C, so maybe it is something or nothing. There is certainly the potential for big convective snow if the BFTE gets going though...

Yes, absolutely. If you’ve got uppers of -10 on a brisk easterly wind, then the convective activity (not related to weather fronts) will depend on the difference between -10 at 850hpa and whatever the sea temperature is, so the the higher the better in that scenario.

Hi @Doctor96, current SSTs local to UK: A bit above average as per my post re the anomalies above. Re snowy weather for the east coast from an easterly you want warm sea temperatures and very cold uppers, for maximum convective snow showers. As we might, just possibly, be about to experience...

Aye, but that’s less likely to help with convective snow on a strong easterly here!

SSTs warmer than average, here anomaly for today: Particularly warmer than average over North Sea, which when (not if) the BFTE comes, will be significant.

I’ll take the ECM T240 mean and spread! Mean high into scandi, trough extending south and southeast into Italy. And low uncertainty about both of those on the spread. Details to be firmed up but looks great, itching to see the clusters

Yes quite, thanks, I see it the same way, Chris, the way some have reacted this chart could have been showing a Bartlett My final word on the ECM op - although milder in the middle of the run, it could lead to the jackpot - the whole cold lot coming from the NE, not big chance but it is there.

Yep, that’s the point this run won’t come off, so it is pointless worrying about what would happen. And yet we do, and it seems to me opinion split 50/50 on whether the post T240 evolution would be Narnia or a Spanish plume! I plumped for Narnia!

That we can agree on! There are aspects of this we can agree on, maybe although not sure, the engagement of the arctic high with what’s going on on our side is a plus. First time we’ve seen that in a meaningful way. The run is at the edges of the envelope of others in the 12z suite so I expect it is an outlier. I don’t see that it changes the chances in the next two weeks one iota, so I don’t understand the toy throwing.

ECM T240: I’m not really sure what the objection to this is? The high in combination with the arctic high could bring the lot from the NE? Is it more that people can see things going wrong with this than the actual evolution?

Wow, we are all looking at different parts of the NH aren’t we? My focus was on the link up with the arctic high, and such things are always poorly modelled, but if that happens and aligns, then the long draw easterly may be on, I haven’t even looked to the south! Problem is it is always all connected. What I would say is this run is probably an outlier on the 12z suite as a whole. Edit: the run is probably soggy cornflakes.

Yes ^^^ the block does seem to have migrated north on this one, but a combination with the arctic high could be very fruitful in future runs, and this one isn’t done yet!