Ruben Amsterdam
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Posts posted by Ruben Amsterdam
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36 minutes ago, Glacier Point said:
Unbelievably strong sceuro ridge on this morning's EC EPS from Boxing Day onwards (gaining strength at end of run). If that is anywhere near the mark, wave 2 would be serious player and very troublesome for the vortex 10th Jan onwards.....tick tock
Repeated on both yesterdays 18z and todays 00z. Just a wild idea: this sceuro ridge is the result of wave action we are seeing now, only to develop a tropospheric pattern that will annihilate the vortex from the bottom up. Dream mode off.
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8 hours ago, chionomaniac said:
At first glance with the ECM Berlin data it appears that the wave 2 is far stronger than the wave 1, but that is not the case at all. The scales surprisingly and confusingly are different so that the wave strengths are the same for both. I put this in the lower end of moderate category. The wave 1 shows through most because it has the wave 2 element on top of the wave 1 reinforcing it.
I remember reading here one day that wave-2 geopotentials can be more disruptive at lower m' values? Hence maybe the different color scales: 1200 m' is more impressive for wave-2 than it is for wave-1.
Speaking of wave-2, just checked the 2008/09 thread and check out the EPV and heat flux on some of these historical forecasts!
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Wave-2? Didn't see that one coming... More interesting things this morning: quite a significant difference between EC and GFS at 1 hPa +240hrs. GFS forecasting height increases in the Japanese sector, EC in the European (hence the wave-2 I think). EC does show the "Japanese" high in the levels below (2,3,5 hPa), is it hinting on something starting from the top? I must say the +21C in the EC forecast is quite impressive.
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What to say? GFS is forecasting some sort of minor event now within the +240hr range. At the same time, it appears that this will not at all be enough to bring the vortex down. Any thoughts/calculations on how this will affect zonal wind speeds and whether we can expect any tropospheric responses?
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In Holland we have the famous Elfstedentocht, a 200km ice skating tour/competition. It has been held 15 times since 1904, most often in February but only once in December (1933). So yes, February can produce extreme cold when the continent is snow covered and SSTs are at their lowest...
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9 minutes ago, CreweCold said:
Exactly why I said 'any warming' instead of THE warming or words to that effect. No chicken counting, just a hypothetical question in all honesty.
Personally I think any predictions more accurate than "higher change of northern latitude blocking" are speculation, especially since warming has not occurred and the specific type of event is not yet known (apart maybe that a wave-1 event is more likely).
But maybe one of the semi-pro's has some interesting thoughts, yes. I am all ears.
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12 minutes ago, CreweCold said:Does any of the more learned on here know how any warming is likely to manifest i.e would we be looking at a fairly rapid trop response or are we going to be waiting around? I only ask because I don't fancy using up the best (first half) part of January waiting for any effects to be felt. February cold is never the same in my opinion.
Don't you think we have to wait before warming actually happens, before making statements on the possible effects of such a warming? Warming may or may not have implications (positive or negative) for Western-European weather. For all we know downwelling may not even occur. Count your chickens after they hatch, not before (in Dutch we say "don't sell the hide before you shoot the bear").
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7 minutes ago, chionomaniac said:
Check out the trop led split...
Yes, indeed. But trop. led and thus likely to vanish next run?
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Latest GFS06z seems a bit more progressive with the continuation of wave-1 activity than previous runs. It appears to start somewhere around the +168hrs mark but remains rather insignificant for considerable time. At the end of the run wave activity intensifies. Let's hope for an even more amplified signal in runs to come.
Edit: the 12z seems pretty consistent with max and min heights a little higher than in the 06z at the +384hr mark.
Edit 2: just as you think there's a consistent signal, GFS reduces the pressure on the vortex.
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Actually, this is the graph that Recretos made last thursday. By comparing it to the present one, one can only conclude that slowing down (is this English or Dunglish?) of the vortex did not really get in closer range. We need to see warming come into the +240hrs range really to get more excited (I think better charts will come in the EC range the coming days, but that's me being optimistic maybe).
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The point Singularity raises I think is valid: significant warming so far only appears beyond +300 hrs. Although promising, we really need these charts to slowly but surely move to into the 240-300 hrs range. Recretos, any chance you can make us one of those artistic plots of the ensemble members one of these days? Then surely we can see whether warming/mean u decreases come closer or not.
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29 minutes ago, Recretos said:
I Like this graph! Let's see if in two-three days time the yellow and green colors get more dominating and closer to +144hrs.
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Ryan Ashoka? If this is the Ryan Ashoka (winterexpert?) I think it is, this may not be a reliable source...
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The January 2013 SSW is a nice example of how powerful wave 1 can be.
Link to youtube: youtu.be/EjGcvtxlh1s
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Here is some long range magic from CFSv2 daily ensembles, which I finally managed to average the right way, and they seem to be doing a good job, continuing with the promotion of the vigorous wave1.
Gonna add the NASA model, which I find to be very interesting, and going to 240h, it has forecasting potential together with ECMWF, FIM-9, GFS, JMA and ensemble guidance.
Nice graphics again Recretos! However, I have the sneaky suspicion that CFS is still thinking "Siberian High" while this has already vanished from GFS FI.
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Hello from Amsterdam, and thanks for all the solid info posted here!
I am surprised how quiet it is here. Surely today's 12z isn't too bad, right?
Can someone elucidate to what extend the (imo) unusual high over the Kara and Barentz Sea has something to do with the (minor) warming we see at 10 hPa?
One more, maybe stupid, question: is this a wave-3 pattern (temperature wise) developing?
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With tropospheric driven wave 2 activity, it will take some to get a SSW. I know that there is a lot of chatter tonight on twitter regarding some fantastic ensemble strat means from day 10 that are showing a split. Brilliant news, because if they verify it is very likely that we will see a great block develop to our northwest along the line of the split, and, from what I have seen the -ve NAO would not be west based like tonights ECM op.
In January 2009 we saw a large strat warming that led to a split SSW - but that event was a downwelling split powered from the top of the strat.
What we much prefer to see are the upwelling wave 2 split that tend to occur following a previous ( normally wave 1 attack) warming of the vortex, and (without being able to see the restricted charts) that appears to be what is being forecast here. This type of scenario occurred with the weakened vortices of early winter 2009/10 and 2010/2011 and these wave 2 splits are without doubt the better for more guaranteable cold. If these forecasts of the wave 2 splits verify, then we could once again be on the cusp of some special winter synoptics.
Yes, you are very right. Wave 2 is what we need. But I'm just playing devils advocate here. In case that wave-2 warming is trop. based (i.e. Greenland high), it is only as certain as the tropospheric output is. And we all know that the operational models do not perform well in these situations. Early december 2013 (edit: 2012!) springs to mind. I think in these cases extreme caustion is required re. any tropospherically induced strat. splits.
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This particular Atlantic secondary height wave is not resulting because of the Eurasian temperature wave as WSI is saying, but it is tropospherically driven.
And I think this is why we should not jump into any conclusions about any potential SSWs. We know how reliable tropospheric Greenland blocks are in FI.....
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Yes GFS is biased towards the end. Warming is there at +240hr though. I prefer the FI warm, even if we know it is positively biased it is better than no forecast warming at all.
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Also the gfs ops are much more positive in the FI after a few days of mainly runs with insufficient warming events.
I also regard the continuous roasting of the upper start in GFS FI a positive thing. At least it is not waning, or disappearing completely. It might be biased, but it is a warming none the less.
Does anyone have any info about the performance of GFS-P regarding the stratosphere? Judging by the meteociel 10hpa temp maps it seems a bit too generous. Any other charts available?
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Me again. Although not as fancy as the impressive (!) 3D modelling of the strat above, the map below shows that GFS12z increases heating at the top-strat even further. Where I thought the 6z might be a freak outlier, the 12z solidly confirms. Not only are temperatures at the 1mb level in FI now above 40 degrees Celsius, it also results in (in my eyes) promising geopotential maps. Surely if this materialises it must have an impact on the mid and lower levels of the stratosphere?
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GFS06z heats the top-strat to body temperature!
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Thanks again for an excellent post, Recretos. Perhaps we sometimes tend to forget that a part of the tropospheric response might just be an intensified Atlantic/Greenland vortex.
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GFS at 190 hrs, looks good to me. You'd think that a warming like that would have to condition the troposphere. What do you think?
That is a decent warming, and yet a bit stronger on the 12z it seems.
The thing is that the vortex reforms quickly after the split. Let's hope this improves so we can actually see some proper disturbances at 30hPa and lower.
Edit: it's a proper BOOM chart, even within the high res. And still I'm very sceptical, not whether it varifies, but what the impact lower down will be. Any thoughts on this, guys (and girls)?
Thursday 17th December 2015 - General Weather Chat.
in Weather reports
Posted · Edited by Ruben Amsterdam
Mild indeed. The (official, measured in De Bilt, central the Netherlands) all-time maximum temperature record for December (and winter) in the Netherlands has now been equaled. 15.3 to beat. Will we make it?
Average temperature predictions for December '15 are now 9.7ºC. That is 6º above average. The old record is from '74: 7.3ºC.