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Stratosphere and Polar Vortex Watch


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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

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2 hours ago, Blessed Weather said:

It's worth capturing the sequence of 3 tweets from strat expert Amy Butler this afternoon (24th Dec). Fascinating stuff. With ECM superior at modelling the very top of the strat, would this help explain the variance with GFS?

1773576885_AmyButlertweet24Dec14_45.thumb.jpg.f4beaf2b13a68c0bde59c6f83eea2560.jpg1099095500_AmyButlertweet224Dec14_45.thumb.jpg.aaccfc98d26c68b66660393f063eef72.jpg1724866063_AmyButlertweet324Dec14_45.thumb.jpg.0d07ccf197defa60fba77cb6f5cdb867.jpg

Nice spot, this is what I said about a week ago; internally driven in a manner that requires good stratosphere resolution - which GFS lacks but ECM possesses.

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3 hours ago, Blessed Weather said:

It's worth capturing the sequence of 3 tweets from strat expert Amy Butler this afternoon (24th Dec). Fascinating stuff. With ECM superior at modelling the very top of the strat, would this help explain the variance with GFS?

1773576885_AmyButlertweet24Dec14_45.thumb.jpg.f4beaf2b13a68c0bde59c6f83eea2560.jpg1099095500_AmyButlertweet224Dec14_45.thumb.jpg.aaccfc98d26c68b66660393f063eef72.jpg1724866063_AmyButlertweet324Dec14_45.thumb.jpg.0d07ccf197defa60fba77cb6f5cdb867.jpg

Just a quick comment, there has been a lot of criticism of the GFS but note the FV3 has been showing quite similar forecasts. The ECM itself has been solid but has retreated in time a few days. It would be interesting to compare models if they ran with exactly the same initial data assimilation. Regarding the heat flux, little surprised that Amy focuses on the 100 hPa flux quite so much - yes it has been shown for a number of years to be related but is it causative? - one of her collaborators on the SSW compendium, Jeremiah Sjoberg has in a couple of papers questioned the significance of this. Also nearly everybody looks at the 10 hPa temperatures / heat flux - it is a matter of simple observation from the data to see that reversals at 10 mb are actually closer linked to 30 mb temperatures oddly enough.

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looking at the 00z ec op run, the split at 10 hpa wasn’t there .... the vortex became very stretched by day 10 and a split would probably have come but it wasn’t there by day 

there was a split at 50 hpa and 30hpa .... contrary to previous runs, the split worked up ....would have been good to see the upper levels 

The noon run restores the split from top down route but it’s delayed until the latter stages of the run .....it is a quick imprint from 10 hpa down to 50 hpa which is encouraging but today has seen a change back time wise in the split timescale ( perhaps 18/24 hours) and the reversal looks to be early New Year’s Eve on this run. the splits on this run look better but the fact that the consistency we had been seeing has gone removes the confidence that had been there in the ec solution 

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Seems to me that nobody truly knows what's going on ?.

It's tricky to assess the ECM trends as we don't really know much about historical bias in the mid-upper stratosphere, we can't go looking at the tropospheric patterns for help, and the most available model to compare with (GFS) has many other known shortcomings.

IMO the best that can be done for the time being at least is to look at the historical data and the patterns that have preceded the most impactful SSWs, note the similarities with how Dec 2018 has evolved, and draw conclusions from there.

 

On the face of it, it seems the atmosphere has played things largely by the book with respect to producing a major downwelling split SSW event. So odds are, it'll happen one way or another - but the timing does seem unusually difficult to pin down for some reason. Mysteries regarding just how well or not models resolve the downward propagation make it difficult to have much confidence in any given date; it could equally as well be sooner than the latest model runs, in line with the current consensus, or even later in time. The last of those options is more likely to be trop-driven as the tropical cycle delivers another potent punch. GFS has been seeing this on and off for a number of runs now.

For some time, I've been viewing the faster, 'top-down' outcome as the more likely but that was assuming ECM was getting the upper level developments right - this delay does indeed lower confidence in the model, though it's still a long way from being threatened by GFS in my mind. 'Removed the confidence' is a bit strong a phrase IMO!

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will Chris tweet the updated data which brings that split forward again?  it doesn’t fit his apparent agenda which is to try and keep a lid on the ‘anticipation’ ........ 

it has drifted back a day or so when compared to a few days ago but the gfs height charts are also showing plenty of splits now 

 

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2 minutes ago, bluearmy said:

will Chris tweet the updated data which brings that split forward again?  it doesn’t fit his apparent agenda which is to try and keep a lid on the ‘anticipation’ ........ 

it has drifted back a day or so when compared to a few days ago but the gfs height charts are also showing plenty of splits now 

 

Quite so.Although I respect Mr Fawkes as a BBC weatherman. I,d give more credence over the strat to You and GP anyday of the week Blue.

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9 minutes ago, snowblizzard said:

Better late than never!

Merry Christmas to everyone on Netweather  ?

Another late start to winter ,can't see this current block in the wrong place giving Europe a cold  2 weeks and us a mild 2 weeks changing  unless we see a dramatic flip in the models, merry crime everyone 

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2 minutes ago, Broadmayne blizzard said:

Quite so.Although I respect Mr Fawkes as a BBC weatherman. I,d give more credence over the strat to You and GP anyday of the week Blue.

Don’t include me in that !  Chris has access to lots of ec data we don’t ... I expect there is something behind what he says but he can’t show the charts he would like to. With uncertainty re downwelling, he is just playing devils advocate .......

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12 minutes ago, bluearmy said:

Don’t include me in that !  Chris has access to lots of ec data we don’t ... I expect there is something behind what he says but he can’t show the charts he would like to. With uncertainty re downwelling, he is just playing devils advocate .......

My views en

 

14 minutes ago, bluearmy said:

Don’t include me in that !  Chris has access to lots of ec data we don’t ... I expect there is something behind what he says but he can’t show the charts he would like to. With uncertainty re downwelling, he is just playing devils advocate .......

No problem Blue. I,m not trying to speak for you just giving my view. I would only point out you can have all the data you want but it's down to interpretation and Mr Fawkes seems to me to always interpret from a mild standpoint.

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17 minutes ago, Broadmayne blizzard said:

My views en

 

No problem Blue. I,m not trying to speak for you just giving my view. I would only point out you can have all the data you want but it's down to interpretation and Mr Fawkes seems to me to always interpret from a mild standpoint.

Erring on the side of climatology seems like a wise thing to do for a professional forecaster and that climatology of course is mild

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