Stratospheric Warming event on the way?

[Alpha5]

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.

Looks like that winter did a 360 around new years....

Dec

Jan-Feb

[Alpha5]

NAO went from +1.5 in Dec to -2.5 and -1.5 in Jan and Feb respectively

[weatherwiz]

Could someone please provide model links to where you can see forecasts for temps/temp anomalies for 1mb through 100mb and zonal wind forecasts and such.

[okie333]

Could someone please provide model links to where you can see forecasts for temps/temp anomalies for 1mb through 100mb and zonal wind forecasts and such.

GFS (new site, much better than the NOAA one):

http://www.instantwe...S-php/strat.php

ECMWF:

http://wekuw.met.fu-...alert=1&lng=eng

[weatherwiz]

GFS (new site, much better than the NOAA one):

http://www.instantwe...S-php/strat.php

ECMWF:

http://wekuw.met.fu-...alert=1&lng=eng

Awesome!

Thanks!

[donsutherland1]

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.

I do, too, even as I suspect that January might wind up the coldest month relative to normal this winter for many parts of eastern North America, including the Ottawa area.

1984-85 was very blocky beginning in the fall. December was a pause in the blocking. The following are the percentage of days on which the AO was negative (1984-85):

October: 54.8%

November: 73.3%

December: 29.0%

January: 100% (including -6.226 on 1/19/1985)

February: 64.3%

In contrast, there has been very little blocking since autumn:

October: 19.4%

November: 10.0%

December: 0.0% (through 12/14)

In terms of ENSO, the 1984-85 La Niña peaked in December and faded in January and February. In contrast, both the ECMWF and CFS forecast the current La Niña to continue to strengthen through January. The stage could be set for a very warm February if some of the guidance is right.

[weatherwiz]

I did have 1984-1985 as one of my analogs for the winter, however, I only used December of 1984 which is why I went with a warmer for Dec. I did go colder for Jan/Feb in my original winter outlook I did in October but when I did an update a few weeks ago I went warmer for Jan/Feb.

[Ottawa Blizzard]

I do, too, even as I suspect that January might wind up the coldest month relative to normal this winter for many parts of eastern North America, including the Ottawa area.

1984-85 was very blocky beginning in the fall. December was a pause in the blocking. The following are the percentage of days on which the AO was negative (1984-85):

October: 54.8%

November: 73.3%

December: 29.0%

January: 100% (including -6.226 on 1/19/1985)

February: 64.3%

In contrast, there has been very little blocking since autumn:

October: 19.4%

November: 10.0%

December: 0.0% (through 12/14)

In terms of ENSO, the 1984-85 La Niña peaked in December and faded in January and February. In contrast, both the ECMWF and CFS forecast the current La Niña to continue to strengthen through January. The stage could be set for a very warm February if some of the guidance is right.

I'm afraid I don't have much hope for this winter Don, particularly in Toronto, where I am this winter. I recall jokingly saying a month or two ago that this could end up like 1931-32, and look where we are. A mild snowless November tends to herald a warm winter in Ontario.

[icebreaker5221]

GFS (new site, much better than the NOAA one):

http://www.instantwe...S-php/strat.php

ECMWF:

http://wekuw.met.fu-...alert=1&lng=eng

Looks good okie! Any plans to add geop. height anomalies for the stratosphere as you did in the troposphere? I think that would be really useful, if you have background climatology available.

[uncle W]

the only time the AO was negative this fall the Halloween snowstorm followed...1992-93 was very positive most of the first part of that winter with more blocking February and March...The AO was at its lowest around the beginning of March 93 and the super storm came a week later...I'm still expecting some blocking in February...When it comes the snow will follow...

[okie333]

Looks good okie! Any plans to add geop. height anomalies for the stratosphere as you did in the troposphere? I think that would be really useful, if you have background climatology available.

It's not my site... it's my cousin's friend. He doesn't have ready access to any background climo though.

[Lee]

I do, too, even as I suspect that January might wind up the coldest month relative to normal this winter for many parts of eastern North America, including the Ottawa area.

1984-85 was very blocky beginning in the fall. December was a pause in the blocking. The following are the percentage of days on which the AO was negative (1984-85):

October: 54.8%

November: 73.3%

December: 29.0%

January: 100% (including -6.226 on 1/19/1985)

February: 64.3%

In contrast, there has been very little blocking since autumn:

October: 19.4%

November: 10.0%

December: 0.0% (through 12/14)

In terms of ENSO, the 1984-85 La Niña peaked in December and faded in January and February. In contrast, both the ECMWF and CFS forecast the current La Niña to continue to strengthen through January. The stage could be set for a very warm February if some of the guidance is right.

Don, if we get lucky and get and hold onto some decent blocking into February, the predicted solidly moderate nina then, may have it's affects muted, as was proven last winter, can be the case . I still think a 1971-72 analogue fits for this winter.

[usedtobe]

The stratospheric temps according to the euro model may have peaked and the u-winds are forecast to strengthen again as the ep flux and its vector gets going.

Now look at what is happening to the 10 mb temps. They also start to rise. I don't see a big breakdown as early as some here, I suspect it will take a couple more warming events before the pattern breaks which would mean no real breakdown until mid jan even if we get the ao to go negative for a day or two around xmas. Either way, the pattern does not look good for snow anytime soon for dc.

[chionomaniac]

The stratospheric temps according to the euro model may have peaked and the u-winds are forecast to strengthen again as the ep flux and its vector gets going.

Now look at what is happening to the 10 mb temps. They also start to rise. I don't see a big breakdown as early as some here, I suspect it will take a couple more warming events before the pattern breaks which would mean no real breakdown until mid jan even if we get the ao to go negative for a day or two around xmas. Either way, the pattern does not look good for snow anytime soon for dc.

One has to be careful when looking at the ECM temperature charts as they quite often do not tell the whole story.

It is far better looking at the combined geopotential and temperature charts to get a better idea.

The recent Asian MT event has been followed by a NA MT event which in effect has given the stratosphere a double whammy wave break.

So looking at the 1 hPa chart we see the effects of the second blow - more dramatic than the first and the all important surf zone is forecast to be broken.

These waves do not always propagate down but there is a chance that this one will but the long range forecasts do not suggest a SSW before the end of the year.

At 30 hPa when looking at the temperature charts there is an impression that not much is occurring. However when looking at the combined geopotential charts we see an increasing warm zone that has yet to break the surf zone

This will not have registered on the temperature scale 60-90N but is certainly present and possibly ready to break the surf zone.

I suspect that it will be the next wave already showing below at the end of the month that will give us a SSW.

[usedtobe]

One has to be careful when looking at the ECM temperature charts as they quite often do not tell the whole story.

It is far better looking at the combined geopotential and temperature charts to get a better idea.

The recent Asian MT event has been followed by a NA MT event which in effect has given the stratosphere a double whammy wave break.

So looking at the 1 hPa chart we see the effects of the second blow - more dramatic than the first and the all important surf zone is forecast to be broken.

These waves do not always propagate down but there is a chance that this one will but the long range forecasts do not suggest a SSW before the end of the year.

At 30 hPa when looking at the temperature charts there is an impression that not much is occurring. However when looking at the combined geopotential charts we see an increasing warm zone that has yet to break the surf zone

This will not have registered on the temperature scale 60-90N but is certainly present and possibly ready to break the surf zone.

I suspect that it will be the next wave already showing below at the end of the month that will give us a SSW.

You certainly know more abou tit than I do. If we get a ssw event, how long until we see it get to the trop?

[chionomaniac]

You certainly know more abou tit than I do. If we get a ssw event, how long until we see it get to the trop?

That's the question that we all want to know the answer to!!

As you may be aware some SSW's are good propagators to the troposphere and others not so. I believe that there is a Japanese study somewhere that I have read that highlights the criteria for this.

In the case of late January 2009 we had a rapid split of the vortex - the split was felt immediately at the troposphere which in the UK resulted in a snowy easterly. The prolonged mean zonal reduced and negative zonal winds that followed, propagated down to the troposphere slowly and surely for upto 6 weeks later, but on our side of the Atlantic disappointingly did not lead to Northern blocking - just a very weak jet stream - great for those flying west!

So not only do we need propagation we also need a troposphere ready to play ball. Having reviewed a number of stratospheric warmings I would class two types of tropospheric responses:-

1) immediate and direct

2) delayed and indirect.

The split vortex is an example of an immediate response and HLB's are good examples of delayed and indirect responses.

The indirect response to a SSW can take between 2-6 weeks to be felt and can last for a similar period of time.

[usedtobe]

That's the question that we all want to know the answer to!!

As you may be aware some SSW's are good propagators to the troposphere and others not so. I believe that there is a Japanese study somewhere that I have read that highlights the criteria for this.

In the case of late January 2009 we had a rapid split of the vortex - the split was felt immediately at the troposphere which in the UK resulted in a snowy easterly. The prolonged mean zonal reduced and negative zonal winds that followed, propagated down to the troposphere slowly and surely for upto 6 weeks later, but on our side of the Atlantic disappointingly did not lead to Northern blocking - just a very weak jet stream - great for those flying west!

So not only do we need propagation we also need a troposphere ready to play ball. Having reviewed a number of stratospheric warmings I would class two types of tropospheric responses:-

1) immediate and direct

2) delayed and indirect.

The split vortex is an example of an immediate response and HLB's are good examples of delayed and indirect responses.

The indirect response to a SSW can take between 2-6 weeks to be felt and can last for a similar period of time.

Here's the Japanese study, it concentrates on the direction of the EP vectors.

http://center.stelab...mazaki_koji.pdf

That's part of the reason I posted the euro EP figure as right now that model is not showing the ep as being favorable for slowing down the vortex but as you say, it might be misleading.

[chionomaniac]

Here's the Japanese study, it concentrates on the direction of the EP vectors.

http://center.stelab...mazaki_koji.pdf

That's part of the reason I posted the euro EP figure as right now that model is not showing the ep as being favorable for slowing down the vortex but as you say, it might be misleading.

Thanks, I need to read it again.

I was under the impression that we want the EP flux to be poleward (but will need to complete further research to confirm this)

[usedtobe]

Thanks, I need to read it again.

I was under the impression that we want the EP flux to be poleward (but will need to complete further research to confirm this)

The poleward idea is what I took from the article.

[wxmx]

Yep, I had also read the article before, and the poleward vector is what we want. So far it has been unfavorable(equatorward), but stuff like that can change, obviously, so we would have to wait until a SSW to look at the EP flux.

[usedtobe]

Yep, I had also read the article before, and the poleward vector is what we want. So far it has been unfavorable(equatorward), but stuff like that can change, obviously, so we would have to wait until a SSW to look at the EP flux.

Cool figures, where did you find them? I've seen something like them on the Berllin site but have not seen one that shows consecutive days in that format.

[wxmx]

Cool figures, where did you find them? I've seen something like them on the Berllin site but have not seen one that shows consecutive days in that format.

Here you go!

[chionomaniac]

From here:

http://ds.data.jma.g...x.html#monit_nh

Beaten to it but note the latest stratospheric flux direction.

[wxmx]

From here:

http://ds.data.jma.g...x.html#monit_nh

Beaten to it but note the latest stratospheric flux direction.

Though, the tropospheric part of the EP flux is the key for propagating events, not the stratospheric, which is more than an order of magnitude weaker (the stratospheric graphs are a zoom of the tropospheric and stratospheric graphs I posted)...but I think the stratospheric flux doesn't hurt if it's poleward also. Equatorward direction for Dec 13th (the latest day in the graphs) is not as strong, and there's an enhanced upward motion, which I think is good for planetary waves traveling towards the stratosphere...probably it helped with the MT events you mentioned.

[showmethesnow]

Great stuff here. Now if I just knew what all of it meant.

[wxmx]

Great stuff here. Now if I just knew what all of it meant.

This might help.

We are discussing if an SSW were to occur, whether it would propagate to the troposphere... referencing the paper Wes linked to, we started talking about the EP flux. According to that paper, the vector direction of the EP flux has a good correlation with whether the event propagates to the troposphere or not. Lately, it has been equatorward, which means, that if an SSW were to occur soon (1-10 days), the EP flux would argue for a non propagating event, since it's clear the mean direction is equatorward in the image I posted above. Compare those images to what the paper linked showed in their research:

Warm->propagating, Cold->non-propagating, average EP flux from 1 day to 10 days before an SSW happens. I noted that lately it has been a little less equatorward, and a little more upward, which is a good signal if the EP flux directionality is about to change...but obviously a day or two do not a trend make.

[VAwxman]

Good stuff in here. So far not one model run I have seen shows an actual major SSW. There is a good deal of warming courtesy of the Asian pattern / MT spikes, which may be able to to a little more and more as the QBO falls (50mb still pretty + right now), but for the next 2 to probably 3 weeks, there probably is not a major SSW in the cards, and in fact, warming in the regions we are seeing it modeled has occurred in many recent Decembers (different intensities of course). Bottom line is that I don't think we can expect to see a tanking AO anytime soon.

[chionomaniac]

Though, the tropospheric part of the EP flux is the key for propagating events, not the stratospheric, which is more than an order of magnitude weaker (the stratospheric graphs are a zoom of the tropospheric and stratospheric graphs I posted)...but I think the stratospheric flux doesn't hurt if it's poleward also. Equatorward direction for Dec 13th (the latest day in the graphs) is not as strong, and there's an enhanced upward motion, which I think is good for planetary waves traveling towards the stratosphere...probably it helped with the MT events you mentioned.

Thanks wxmx, I hadn't quite grasped the importance of the tropospheric aspect of the EP flux but have now. But that's why we come on these forums - to learn some more.

[Amped]

Nice, We need a second hich on the oposite side of the pole if it's really going to pry this vortex apart.

[Geos]

Very interesting subject here. Enjoying all the information! Did a SSW turn the switch on the late starting winter of 1998-1999?