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The Sudden Stratospheric Warming 2011/2012
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GFS update trends are good as well this morning.
The only drawback is that it is not until T+240 that the vortex show signs of leaving Greenland.
However, we see a forecast of significant warming at the 30 hPa level for the first time.0 -
A look at the mean zonal winds at different layers of the stratosphere highlights both the strong polar vortex conditions that we have seen and the changes already encountered in upper to mid levels of the stratosphere.
First we see that the 10 Hpa temperature is now running above average.0 -
Excellent stratosphere forecasts this morning from the ECM.
If these forecasts verify then I would say a SSW would be
imminent. Looking through the height charts IE 10mb,
30mb,50mb etc good downwelling seems to be occurring
and the profile of where the heights and vortex is likely to
be look very good for the UK and Europe from a cold
perspective.0 -
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ECM update:
Starting from the top af the stratosphere, we see a warming forecast for a considerable time that leaves us with the following picture at T+240.
This chart show a considerable warm upper stratosphere with a reducing vortex that looks to be soon overwhelmed by the warming. The forecast mean zonal mean winds are very negative ( -30m/s). During the record breaking SSW of 2009 the mean zonal winds, at this level, bottomed out at around -40m/s, so that gives one an indication of how strong this event could be. The vortex is not completely forecast to disintergrate yet though.
Moving lower now, into the middle stratosphere we see that there is a displacement of the polar vortex forecast at the 10 hPa level that is being recharged by considerable warming.
We have yet to see reversal of the mean zonal winds at this level, but with this type of warming (and if the forecast verifies) then that would be the natural progression.
We see further propagation at the 30 hPa level which continues the theme.
The trend at the lower stratosphere on the ECM is for a complete displacement of the vortex to the Eurasion half of the hemisphere leaving a small area of weaker vorticity that has dropped into East America.
This suggests Atlantic blocking but is the most unreliable part of the forecast. Small shifts in the vorticity centres can lead to very different tropospheric pattern for our small island. We best wait until we have some cross model agreement before establishing where exactly any High latitude blocking will establish. ( An Aleution high looks a safe bet though).
The next chart sees the negative mean zonal winds becoming established in the upper polar atmosphere. Hopefully in the coming days we will see these blues lower further towards the troposphere.
GFS update to follow later.0 -
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SUDDEN STRATOSPHERIC WARMING (SSW) + COLD HEALTH WARNING
I see that it's now very likely that we will be seeing a SSW.
1hpa Upper strat winds are forecast to greatly reverse.Even if it backs off somewhat like the previous warming that never actually made the reversal as forecast, I still think that the warming is too great and the polar vortex is past the point of rescue and so the effects will propagate down to 10hpa and completely reverse the upper westerly flow to easterly.
It only becomes a SSW when winds reverse at 10hpa level so will be watching this part on graph with great interest.
The Temps are shown to rise well above average at the 30 hpa level which is very encouraging.
Now this all disrupts/splits the PV ,so greatly enhances any chances of super cold periods down the road.However there is no guarantee any future blocking will set up in the perfect place to drag Arctic conditions to our back yard. Canada,USA could favour from this and we could be on the wrong side so hang fire on the excitement until the models get their head around what's happening because they don't handle situations like this well.
That is all for now. Tis very encouraging to say the least0 -
If the PV splits and if it heads the right way, then were going to have great fun watching the models and seeing what does or doesn't appear in FI.
If it splits the wrong way, I think I might start following cold/snow developments on the US weather forums. I usually only read those forums during hurricane season. Could be interesting.
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Just a little look at what the ECM predicted at 30hpa 9 days ago.
This is what happened.
Very good verification.. the only marginal difference is the high, with the +216 predicting lower heights and slightly cooler temps. The flow was almost perfect. I'd say it gives a lot of confidence for those forecasting using the tool.0 -
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Randomly came across this so might as well stick it here.
From about 1:00 in the video.0 -
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Unrelated to the the thread in most respects but I thought those reading this thread might appreciate it.
Interesting one from NASA
See How a Stronger Arctic Oscillation Has Shifted the Flow of Russian Runoff
An interesting new study published in Nature points out that an increase in the strength of the Arctic Oscillation between 2005 and 2008 caused winds in the region to grow more cyclonic and shift ocean currents in ways that drew more upper-surface freshwater from Russian rivers toward the Canada Basin and the Beaufort Sea. To see the shift in the animation above, look for the tightening of the wind patterns (shown in blue) over the Canada Basin that begins about 13 seconds into the video.
Notice how the stream of less salty water from river runoff in Russia (shown in red) begins to loop westward toward Canada in sync with the circulation of the wind rather than continuing toward Greenland as it typically would. The purple arrows show the transpolar drift, a current that generally pushes water toward Greenland. NASA's Jet Propulsion Laboratory has a press release with more details, and a number of news outlets have written stories about the study. In the image below, the altered path of the freshwater current is shown in red.
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One thing I find is that weather forums have a great difficulty in 'getting' the extremely lagged timescales involved with the stratosphere.
Agressive, sharp warmings can have a shorther propagation time but generally 20+ days is considered the most likely duration for an event at the top end of the stratosphere to work its way down.
With that in mind, the warming event over Christmas was centered in the Pacific sector.
Wind forward to GFS ensemble mean H5 anomaly projection for the 18th January:
There may be some tropospheric factors at play which inclined the blocking signal to this region, however this does provide some additional weight to the evidence around tropospheric influence from the stratosphere.
Two further warming episodes are forecast in the next 15 days from around day 8 through day 14. I wouldn't be suprised to see these two merge as they are relatively close together:
The first of these is also being modelled by the ECM. The second of these being a rapid injection of warm air into the core vortex.
I'm still not totally convinced that the 1st warming has come onto the radar yet, particularly if it's a nodal propagator which by nature would appear to come and go as it descended. Factor in the possible height rises early February in those areas where warming is forecast, and the whole polar field becomes infinately (more) problematic to model.0 -
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Sponge Bob wrote: »Forgive me Pete, I cannot make out where these are oriented on the Instant weather maps generated pics of yours above....can you add continental outlines or thicken them or display Longitudes ?
Im afraid bob as I have said in the title of the post these were taken from netweather ,
But looking at the site you might find the info you are looking for here ,
http://www.instantweathermaps.com/GFS-php/showmap-strat.php?run=2012010612&var=TMP&lev=10mb&hour=039
Not sure if this will help u but I have marked Ireland and UK which might give some orientation
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https://www.youtube.com/watch?v=F1xoO2kZC_c
https://www.youtube.com/watch?v=y8diuqAI6YA
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