Snowy L

Good shout, Greenland High building based on t168

GFS gone shortwave crazy again, it's sending way too much energy over the top of the high. That high pressure is looking very weak, I hope this is just a poor run from the operational and we see it changed at 18z. One alternative is that we could see a Greenland high earlier than expected of course...

We have the classic elongated west Atlantic Low setting up, could be seeing a Greenland High in FI.

To be fair I don't think anyone could have called the bulk of the high sinking towards South Russia and then a tiny part of the High cutting off and going on a 1 man crusade against the vortex It just highlights the uncertainty in the models and I'd like to point out again that I don't think we will see such an intact vortex in 8 days time like the ECM is showing.

I should add though that I don't buy this run at all. There is no way the vortex will be that much intact in 10 days time. We will see gaps appear which will aid our high pressure to stay to our North, unlike the end of todays 12z run.

It's being drawn in by the Southern Russian high

PV is still very much intact, the last 2 frames aren't going to be nice imo, I can see that high sinking.

ECM makes it, surrounded by lows to the south so it can't sink.

Also good WAA towards Greenland on that 144 chart.

Looks like it's going to make it based on t144...

We have retrogession

That's a nice line of lows building up in the Atlantic, I hope that aids the retrogression of high pressure to our Northwest.

ECM and UKMO still keep some form of link between the Atlantic High and North Pole High. GFS in typical fashion says no to that and ramps up the low pressures to the North of our block.

Looks like we're going to get high pressure moving into Greenland in FI again. We need to keep an eye on that Atlantic high that joins in after our toppled high of the initial cold spell.

Stronger Iberian low, could be so important for a reload.

Well I didn't see that one coming...

Weird looking 18z, high pressure in the Atlantic is very weak but low pressure doesn't seem to want to claim the area either.

Hmm, I'm not sure if this is an error, but the ECM has suddenly picked up on a massive increase in wave-2 breaking in 7-10 days time. I'm skeptical because this was nowhere to be seen in forecasts in the previous few days. Can't post images yet sorry: http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/eczm.php?alert=1&forecast=f240&var=ha2&lng=eng

Storm of the century in FI GFS, those isobars over Greenland have formed a solid white line

I'm quoting Chionomaniac on this but the stratosphere did indeed play a part in that cold spell: "There is still a lot to learn about this subject and on the surface the stratospheric conditions were nothing too out of the ordinary in late autumn in 2010. However, at that time of year, the vortex is yet to gain the kind of strength that a prolonged winter cooling would lead to and so is vulnerable to attack. And this attack came in the form of the rare tropospheric led Greenland wave break, which broke into the lower reaches of the stratosphere creating a split, which in turn reinforced the Greenland high. Later on in the season, these types of tropospheric waves will be suppressed by the vortex if it has cooled and strengthened sufficiently. So enhanced tropospheric wave activity was enough to split the lower stratospheric vortex before the stratospheric vortex had increased to it's full winter strength. Quite rare." In fact it bares a few similarities to what I think is our current situation. The vortex is strengthening and will continue to strenghten with strong zonal winds, however wave breaking is expected to begin next week, which some models, the GFS in particular, are forecasting to affect the lower stratosphere. There was an interesting GFS chart posted in the strat thread which shows a split in the lower vortex, albeit in FI, which if becomes reality we could be looking at some form of Northern blocking. This of course being started by the big height anomaly in the Aleutian Islands in the troposphere. The stratosphere isn't the main contributor to winter weather, but I think the troposphere>stratosphere>troposphere is by far and away the main cause of winter set ups.

GFS has picked up on this a lot more than the ECM models. Still too early to say but that massive enhancement of wave-2 breaking thanks to the Aleutian High was always going to have some sort of effect. It won't affect the higher strat but you would expect it to make an impact in the strat lower down. The whole idea of Canadian Warmings is that the higher strat continues to cool whereas lower down we see a warming in Canada that shifts the lower vortex east of the North Pole, as seen in those GFS charts. The fact that it's forecasting a smaller section to split away over North America ties in nicely with the fact that it's caused by wave-2 rather than wave-1.

Yeah it can be seen in the PNA it's expected to dive into a strong negative phase, which suggests strong blocking over the North Pacific. Anomalous high pressure over this region brings enhanced wave-2 activity and this can be seen for the first time on the Berlin models. We're looking at some pretty strong wave breaking in 7-10 days just after the wave-1 activity begins to weaken. http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_ha2_f216.gif Some small bursts of warming over Canada in the lower stratosphere have already put wobbles into the the lower vortex and I'm guessing they're the reason for the change to cool zonal, even very brief meridional patterns. Edit: Can we not post picture files from our computer anymore?

Any figures on how this year's index performed and how it compared to good years like 2009?

The attack on the stratosphere continues...wave 1 activity expected to increase in 10 days combined with an increase in wave 2 activity. Is this combined effort the reason why there's a credible rise in temperatures forecast for the other side of the north pole in a couple of weeks? Hopefully we get a minor warming out of this and we see a situation similar to early December last year, though with us being on the right side of blocking this time!

I know I'm not using it to forecast storms I'm using it for stratospheric forecasts.