Stratospheric Warming event on the way?

[MoeWx]

I am not by any means an expert on ssw 's but I read a paper on it and as I recall it said there was a 2 to 4 weeks lag time from the time is the event took place until the cold reached north america. Plus, it needed time to propagate downward. I will have to look for the paper and I'll post it

I would be interested in reading it as well. I have not read too much up on stratospheric warming, though I am aware of it implications...

[QVectorman]

I would be interested in reading it as well. I have not read too much up on stratospheric warming, though I am aware of it implications...

To be honest, I have looked all over my computer and can't find it. I think it was on the SSW page from columbia.edu and the link is broken now. Sad too because they had awesome 3D animations of the polar vortex breaking down for 5 or 6 major SSW events since 1960 as I recall.

[Weathergun]

The ECMWF now forecasts 10hpa and 30hpa warming to about average, in 10 days. Particularly at 90N. Good sign for changes in the high latitudes to begin at the end of this month:

[showmethesnow]

Most of what I have heard from the pros on this site as well as elsewhere are of the opinion that SSW can not be predicted. That being said I found an interesting paper from 2009 that seems to suggest that blocking in the troposphere actually can be a precursor to a SSW and with different blocking locations will result in either a PV split or a PV displacement. I was wondering if any of the pro-mets had seen this article and/or had an opinion of any validity to it's assertions.

http://www.columbia....es-GRL-2009.pdf

[usedtobe]

Most of what I have heard from the pros on this site as well as elsewhere are of the opinion that SSW can not be predicted. That being said I found an interesting paper from 2009 that seems to suggest that blocking in the troposphere actually can be a precursor to a SSW and with different blocking locations will result in either a PV split or a PV displacement. I was wondering if any of the pro-mets had seen this article and/or had an opinion of any validity to it's assertions.

http://www.columbia....es-GRL-2009.pdf

Interesting, I hadn't seen the paper and have seen others that suggest just the opposite.

[usedtobe]

The ECMWF now forecasts 10hpa and 30hpa warming to about average, in 10 days. Particularly at 90N. Good sign for changes in the high latitudes to begin at the end of this month:

I saw that but also saw that the 1 mb winds are forecast to increase and that the ep flux will be working to increase the 1 mb winds in that same time frame. I'm not sure what that means but the forecasts of the NAO and AO on the GEFS ensembles are pretty robust in the longer time ranges.

[donsutherland1]

The ECMWF now forecasts 10hpa and 30hpa warming to about average, in 10 days. Particularly at 90N. Good sign for changes in the high latitudes to begin at the end of this month:

Hopefully, the forecasts for warming will grow more impressive in coming days. In early December, portions of the stratosphere saw moderation for a period, but then reverted back to below normal anomalies. Right now, the modeling still does not really indicate a possible SSW event.

[showmethesnow]

Interesting, I hadn't seen the paper and have seen others that suggest just the opposite.

I found it interesting as well. The paper basically goes against everything I have heard from the pro's throughout the years. I am basically clueless when it comes to SSW so I was hoping to get some feedback from those pro-mets familiar with SSW as to whether there may be any validity to these claims.

[usedtobe]

I found it interesting as well. The paper basically goes against everything I have heard from the pro's throughout the years. I am basically clueless when it comes to SSW so I was hoping to get some feedback from those pro-mets familiar with SSW as to whether there may be any validity to these claims.

My guess is that it can work either way. In 2009-2010, the stratosphere certainly led the blocking early in the season and then there was a second warming event in Jan that also helped nudge the AO back into the strong negative range. Last year, I think an upwelling event (blocking in the troposphere) led the way and was a mjor contributor to the severe negative nao we had last year. Like you, I'm no expert. Certainly at times, the tropical forcing seems to lead to amplification that then leads to an nao down the line.

[usedtobe]

Hopefully, the forecasts for warming will grow more impressive in coming days. In early December, portions of the stratosphere saw moderation for a period, but then reverted back to below normal anomalies. Right now, the modeling still does not really indicate a possible SSW event.

Exactly and the 1 mb zonal winds are forecast to start building again do to EP flux according to the Berlin site. That makes me think the ao will probalby strengthen again if it ever actually falls to close to zero (I've got my doubts about that).

[donsutherland1]

My guess is that it can work either way. In 2009-2010, the stratosphere certainly led the blocking early in the season and then there was a second warming event in Jan that also helped nudge the AO back into the strong negative range. Last year, I think an upwelling event (blocking in the troposphere) led the way and was a mjor contributor to the severe negative nao we had last year. Like you, I'm no expert. Certainly at times, the tropical forcing seems to lead to amplification that then leads to an nao down the line.

That's my understanding, as well. SSWs can lead to the development of blocking, but sometimes they can be a response to strong blocking and tend to "perpetuate" the blocking for lack of a better term.

[bluewave]

My guess is that it can work either way. In 2009-2010, the stratosphere certainly led the blocking early in the season and then there was a second warming event in Jan that also helped nudge the AO back into the strong negative range. Last year, I think an upwelling event (blocking in the troposphere) led the way and was a mjor contributor to the severe negative nao we had last year. Like you, I'm no expert. Certainly at times, the tropical forcing seems to lead to amplification that then leads to an nao down the line.

Right, that was a great thread that you started back on the old forum around the end of November in 2009.

[okie333]

Exactly and the 1 mb zonal winds are forecast to start building again do to EP flux according to the Berlin site. That makes me think the ao will probalby strengthen again if it ever actually falls to close to zero (I've got my doubts about that).

Every model is showing the AO [weakly] negative in about 3 days. IMO it will remain near neutral until the SSW affects things. Euro still not going out far enough for me to see if it's major... on the GFS it's not (I used GrADS myself to check it... 10mb zonal wind goes down to 24 and stays there on the 6Z... far from a reversal but it's definitely a minor SSW from the temps).

[CoastalWx]

Exactly and the 1 mb zonal winds are forecast to start building again do to EP flux according to the Berlin site. That makes me think the ao will probalby strengthen again if it ever actually falls to close to zero (I've got my doubts about that).

Wes are you talking about EPV flux?

[wxmx]

Wes are you talking about EPV flux?

I think he's talking about Elliasem-Palm flux, which is indeed EPV (V for vector)

[CoastalWx]

I think he's talking about Elliasem-Palm flux, which is indeed EPV (V for vector)

Ok, because I was reading it from the page. I see what he is saying. I'm not familiar with the EP flux so I'll have to read up.

[donsutherland1]

Every model is showing the AO [weakly] negative in about 3 days.

I believe the 12/14 0z ECMWF kept the AO > 0 throughout the next 10 days. It will be a close call, but this near-term forecast isn't the first time strong model consensus argued for a brief period during which the AO was negative. At this time, especially when one considers the historic statistics with strong AO+ regimes in December, I share Wes' doubts about a negative AO anytime in the next 10 days.

[CoastalWx]

I believe the 12/14 0z ECMWF kept the AO > 0 throughout the next 10 days. It will be a close call, but this near-term forecast isn't the first time strong model consensus argued for a brief period during which the AO was negative. At this time, especially when one considers the historic statistics with strong AO+ regimes in December, I share Wes' doubts about a negative AO anytime in the next 10 days.

And likely longer than that. I see no sign of a -NAO on the EC ensembles, unless you count the 6hr lasting fleeting ridge.

[tacoman25]

I think most of the evidence indicates that a sustained period of -AO is unlikely until at least mid January.

[donsutherland1]

And likely longer than that. I see no sign of a -NAO on the EC ensembles, unless you count the 6hr lasting fleeting ridge.

I agree with you.

[Jefflaw77]

So as it looks right now- the consensus is that the overall weather pattern won't be changing much until PERHAPS the January 10-15th time frame..

[OKpowdah]

I think he's talking about Elliasem-Palm flux, which is indeed EPV (V for vector)

Careful though, not Equivalent Potential Vorticity lol. Best to just say EP

[Isotherm]

So as it looks right now- the consensus is that the overall weather pattern won't be changing much until PERHAPS the January 10-15th time frame..

I think it could occur as early as the first week of January, but we'll see.

[NJwinter23]

So as it looks right now- the consensus is that the overall weather pattern won't be changing much until PERHAPS the January 10-15th time frame..

You dont need a raging reversal to negative in the AO regime to get a pattern change before then. Sure I dont think were going to see the winter pattern we all dream of anytime soon, but I also dont see November and December style warmth continuing into the New Year.

I'm part of the camp that thinks the AO will at least flirt with 0 over the next 10+ days, probably staying on the positive side throughout, but nothing like the +5 values we've seen. That high pressure feature over in Eurasia is here and wants to creep towards the polar regions somewhat, getting that AO towards neutral. If you believe the ensembles, this wants to be a permanent feature throughout the run. That doesnt mean we get consistently cold or anything in the east per se, but the cold is readily available on our side of the globe. The NAO does look hopelessly positive in the meantime though.

10 day

Fantasy land

[blizzardof09]

The way its looking we may get to the middle to end of january before the east coast sees any sign of sustained winter weather i.e cold, snow storms, storm threats. What a difference a winter season makes

[usedtobe]

Wes are you talking about EPV flux?

I ahd responded yes but the answer is no. It is not EPV flux but is EP flux which stats for Elliassen Palm Flux

http://www.rsmas.miami.edu/users/isavelyev/GFD-2/Eliassen-Palm%20Theory.pdf

http://www-k12.atmos.washington.edu/~dennis/Limpasuvan_etal_JClim_04.pdf

http://center.stelab.nagoya-u.ac.jp/cawses2005/PDF/yamazaki_koji.pdf

Sorry, my brain went dead for awhile.

[chionomaniac]

To be honest, I have looked all over my computer and can't find it. I think it was on the SSW page from columbia.edu and the link is broken now. Sad too because they had awesome 3D animations of the polar vortex breaking down for 5 or 6 major SSW events since 1960 as I recall.

The SSW site is down at the moment (frustratingly) due to server issues but I believe that a revamped website will be available after Christmas.

My guess is that it can work either way. In 2009-2010, the stratosphere certainly led the blocking early in the season and then there was a second warming event in Jan that also helped nudge the AO back into the strong negative range. Last year, I think an upwelling event (blocking in the troposphere) led the way and was a mjor contributor to the severe negative nao we had last year. Like you, I'm no expert. Certainly at times, the tropical forcing seems to lead to amplification that then leads to an nao down the line.

There are different types of SSW's and stratospheric warming events. The early winter 2009/2010 blocking was in response to 'local' wave breaking. That is when waves from the troposphere enter the stratosphere through the centre of the polar vortex. I believe that this is more likely if the stratospheric vortex is weak to start with. At the time the vortex split upwards from the troposphere into the middle stratosphere and this was seen well with the charts at the time.

This is completely different to 'remote' wave breaking. The forecast warming of the stratosphere is a good example of remote wave breaking. This is caused by deflected planetary wave riding the stratospheric surf zone up to the top of the stratosphere before breaking downwards trying to break into the centre of the vortex and causing the entailing disruption.

Currently we are seeing a series of waves trying to 'remotely' break into the vortex.

Look at the increased momentum flux forecast - this has rocketed over the last few days

These waves appear to be forecast to be successfully breaking into the vortex at the 1 hPa level. Note that the temperature charts are not the same as the potential vorticity or polar vortex geopotential height charts.

The warming at the 1 hPa chart appears to be forecast to propagate down to the mid stratosphere according to the GFS but less so according to the ECM. So far we are led to believe that there will be some pressure on the vortex but will that be enough to create a SSW?

Well, at present we do not know. There has been a lot of talk of a SSW in January this year and that is still my bet. My thoughts are that we are in an interesting tropospheric / stratospheric feedback period each wave that 'knocks' the stratospheric vortex feeds back to the troposphere leading to another stronger wave to knock again and so on and so forth until we see a SSW and a more meridional troposphere flow pattern.

The ECM charts ( which are from the previous days 12Z run) tomorrow morning will be important to see haow the ECM is forecasting the projected warming . My guess is that the vortex will take a severe knock but not enough to cause a SSW, but these are very difficult to predict accurately.

However the current projected warming will already have consequences on this seasons strong vortex reducing the strength and leading to weakened jet stream. With the ozone levels rising, the residual westerly QBO flushed out, I think we will have seen the worst of the strong zonal conditions before the month of December is out and the AO will start dropping as we enter the New Year.

c

[Isotherm]

The SSW site is down at the moment (frustratingly) due to server issues but I believe that a revamped website will be available after Christmas.

There are different types of SSW's and stratospheric warming events. The early winter 2009/2010 blocking was in response to 'local' wave breaking. That is when waves from the troposphere enter the stratosphere through the centre of the polar vortex. I believe that this is more likely if the stratospheric vortex is weak to start with. At the time the vortex split upwards from the troposphere into the middle stratosphere and this was seen well with the charts at the time.

This is completely different to 'remote' wave breaking. The forecast warming of the stratosphere is a good example of remote wave breaking. This is caused by deflected planetary wave riding the stratospheric surf zone up to the top of the stratosphere before breaking downwards trying to break into the centre of the vortex and causing the entailing disruption.

Currently we are seeing a series of waves trying to 'remotely' break into the vortex.

Look at the increased momentum flux forecast - this has rocketed over the last few days

These waves appear to be forecast to be successfully breaking into the vortex at the 1 hPa level. Note that the temperature charts are not the same as the potential vorticity or polar vortex geopotential height charts.

The warming at the 1 hPa chart appears to be forecast to propagate down to the mid stratosphere according to the GFS but less so according to the ECM. So far we are led to believe that there will be some pressure on the vortex but will that be enough to create a SSW?

Well, at present we do not know. There has been a lot of talk of a SSW in January this year and that is still my bet. My thoughts are that we are in an interesting tropospheric / stratospheric feedback period each wave that 'knocks' the stratospheric vortex feeds back to the troposphere leading to another stronger wave to knock again and so on and so forth until we see a SSW and a more meridional troposphere flow pattern.

The ECM charts ( which are from the previous days 12Z run) tomorrow morning will be important to see haow the ECM is forecasting the projected warming . My guess is that the vortex will take a severe knock but not enough to cause a SSW, but these are very difficult to predict accurately.

However the current projected warming will already have consequences on this seasons strong vortex reducing the strength and leading to weakened jet stream. With the ozone levels rising, the residual westerly QBO flushed out, I think we will have seen the worst of the strong zonal conditions before the month of December is out and the AO will start dropping as we enter the New Year.

c

Excellent post, agree with all of it.

[blizzard1024]

How do the stratospheric conditions this December compare to December 1999 and also December 2006 both mild which were followed by a pattern change.

December 2006 was mild in the east until mid-late January 2007...then winter hit hard. December 1999 and the first 1/2 of January 2000 were mild

and then wham...winter hit hard for almost 5 weeks. December 2001 was also mild but was followed by a mild January and February. No major change.

Obviously, (unless major changes occur real soon), this month will be mild in much of the northeast U.S. How does this December compare

to these recent Decembers? That would be interesting. My gut is telling me mild the rest of the winter...with just a short period of real winter

cold (2-4 weeks at best). Below normal snow, below normal lake effect.

[Ottawa Blizzard]

JB is really honing in on the 1984-1985 analog and seems to be implying that winter will hit hard by mid January. Personally, I have my doubts.