Stratosphere Temperature Watch

[cooling climate]

http://www.esrl.noaa...lr/olr.anom.png

Tropical convection is now centred over the Indian Ocean. I think this will have an impact on the polar stratosphere through planetary waves being refracted into the stratospheric jet.

The last tropical convection centred in this region was early to mid November. 10 days from this time we saw the stratosphere warm.

Would I be right in saying that as it moves east over and to the north of Indonesia the subtropical air gets caught up in the polar westerlies which strengthens heights over western US ( +PNA) and this sends a ridge (rosby wave breaking ) into the Arctic once again.

Edited January 2, 2010 by cooling climate

[Glacier Point]

Would I be right in saying that as it moves east over and to the north of Indonesia the subtropical air gets caught up in the polar westerlies which strengthens heights over western US ( +PNA) and this sends a ridge (rosby wave breaking ) into the Arctic once again.

Could be although there is no large influx of middle or upper tropospheric warm air programmed.

I think a more likely mechanism is the upward reflection of planetary waves, shown nicely by EPV plot resulting in large heat flux at the 10 hPa and 30hPa levels:

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=fluxes&alert=1

I know Chino will be pleased with the Berlin site picking up on first indications of the increased temperatures (still well below average) with a strong wave 1 projection:

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=temps&alert=1

http://strat-www.met.fu-berlin.de/cgi-bin/ecmwfzm?alert=1&forecast=f192&var=ha1

[chionomaniac]

Could be although there is no large influx of middle or upper tropospheric warm air programmed.

I think a more likely mechanism is the upward reflection of planetary waves, shown nicely by EPV plot resulting in large heat flux at the 10 hPa and 30hPa levels:

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=fluxes&alert=1

I know Chino will be pleased with the Berlin site picking up on first indications of the increased temperatures (still well below average) with a strong wave 1 projection:

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=temps&alert=1

http://strat-www.met.fu-berlin.de/cgi-bin/ecmwfzm?alert=1&forecast=f192&var=ha1

Most definitely am, GP.

A not unexpected step in the right direction - too early to say though whether this could be a major warming though - we may need a couple of bites of the cherry to get there, but I am ever hopeful!

We are still at the primordium stage of any warming development whether major or minor.

I think we are looking mainly at wave number 1 event here. With warmings we see the heat fluxed poleward at the top of the stratosphere and then downward propagation occurs. One can see the classic poleward heat flux being 'sucked' into the vortex at the 1hPa level if you follow the following link and trace it out to T+240. The next stage should be vortex strength reduction.

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/kiruna09/index.html

c

The vortex strength is showing signs of dropping at the top of the stratosphere (by almost 20m/s) but we will need to see larger (forecast) reductions further down the stratosphere if this event is to prove significant.

[chionomaniac]

Latest GFS forecasts continue with the warming theme. Even at the 10 hPa level the polar vortex has never really settled directly over the pole this winter.

Today:

And in 10 days time:

Just a little 'push' by my reckoning and we could have a displacement MMW, and with conditions still ripe lower down the vortex there will be promise that this could alter February's expected pattern.

[beng]

Even if this doesn't develop into a major warming - it's obviously better than a continued cooling. I'd still think the chances of a decent warming are there in the next couple of weeks as the sunlight increases over the American and Asian snowfields.

Edited January 3, 2010 by beng

[cooling climate]

ECM stratosphere model continues to be very bullish about a MMW.

Edited January 4, 2010 by cooling climate

[chionomaniac]

ECM stratosphere model continues to be very bullish about a MMW.

Having looked at the model runs and corresponding upper stratospheric temperatures I am still cautious, and will probably remain so for a few days, over whether a MMW is about to occur. It is still too early to judge the extent and propagation of the warming and subsequent disruption on the stratospheric vortex. What we know so far is that a warming is forecast to occur at the upper levels and is forecast to propagate down to the 10 hPa level.

One of the winters that I highlighted last autumn that could be quite similar stratospherically was 1986/87. This was an El Nino, -QBO, low solar winter similar to this one. During that winter there was a displacement MMW (23rd January) that followed a period of Atlantic blocking similar to the period that we are currently experiencing.

With that in mind it is worth viewing the MMW from that year to see if there are any similarities to the emerging pattern this year. Previous MMW's can be viewed at the following site by clicking on view events and generating the page using the geopotential height option:

http://www.appmath.columbia.edu/ssws/index.php

There was strong wave number 1 component to that MMW and there is a similar surge in heat flux for the current wave 1 forecast.

February 1987 had a CET of 3.6ºC and after a mild start was cooler thereafter. Interestingly March was a very cold month that year.

c

Edited January 4, 2010 by chionomaniac

[BrickFielder]

Wave 1 tends to give a shifted vortex while wave 2 is more likely to give a split vortex. As GP correctly identifies the MJO pattern can produce planetary waves which disrupt the vortex, but so can high pressure systems situated in the north atlantic. At the moment I am not so keen on the vortex position forecast but looking at where the cold air is at 1hPa then I think the game may be on. In essence I think the ECM model does not have an accurate handle on what will happen at the moment.

It is worth remembering that cold air in the stratosphere is often associated with potential vorticity, which in turn is linked to low pressure systems in the troposphere. In other words I would prefer the vortex and cold stratospheric air to be shifted away from us for a cold outlook.

[weatherjunkie]

Having looked at the model runs and corresponding upper stratospheric temperatures I am still cautious, and will probably remain so for a few days, over whether a MMW is about to occur. It is still too early to judge the extent and propagation of the warming and subsequent disruption on the stratospheric vortex. What we know so far is that a warming is forecast to occur at the upper levels and is forecast to propagate down to the 10 hPa level.

One of the winters that I highlighted last autumn that could be quite similar stratospherically was 1986/87. This was an El Nino, -QBO, low solar winter similar to this one. During that winter there was a displacement MMW (23rd January) that followed a period of Atlantic blocking similar to the period that we are currently experiencing.

With that in mind it is worth viewing the MMW from that year to see if there are any similarities to the emerging pattern this year. Previous MMW's can be viewed at the following site by clicking on view events and generating the page using the geopotential height option:

http://www.appmath.c.../ssws/index.php

There was strong wave number 1 component to that MMW and there is a similar surge in heat flux for the current wave 1 forecast.

February 1987 had a CET of 3.6ºC and after a mild start was cooler thereafter. Interestingly March was a very cold month that year.

c

I'll take whatever we can get if it produces a weaker and displaced vortex and hopefully renewed potential for high latitude blocking.

Wave 1 tends to give a shifted vortex while wave 2 is more likely to give a split vortex. As GP correctly identifies the MJO pattern can produce planetary waves which disrupt the vortex, but so can high pressure systems situated in the north atlantic. At the moment I am not so keen on the vortex position forecast but looking at where the cold air is at 1hPa then I think the game may be on. In essence I think the ECM model does not have an accurate handle on what will happen at the moment.

It is worth remembering that cold air in the stratosphere is often associated with potential vorticity, which in turn is linked to low pressure systems in the troposphere. In other words I would prefer the vortex and cold stratospheric air to be shifted away from us for a cold outlook.

Looks like a +NAO and neutral AO from the images you posted and based on what I think you're trying to say.

It likes like from those images that there also appears to be potential for -PNA and some ridging along the eastern US. Ew...

Thank you both for the continued input.

OT: Does anyone know of a website that contains the GME model and its prediction for North America?

Edited January 6, 2010 by weatherjunkie

[chionomaniac]

The forecasts, both GFS and ECM have stepped back from the idea of a MMW with both modifying the vortex disruption caused by the stratosphere warming.

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=all&alert=1

c

[chionomaniac]

The forecasts, both GFS and ECM have stepped back from the idea of a MMW with both modifying the vortex disruption caused by the stratosphere warming.

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=all&alert=1

c

Having looked at the amount of warming forecast at the 1hPa level yesterday I was surprised not to see a dramatic fall in the zonal winds at that level. However today the drop is back.

Will this trend continue and will it propagate lower into the stratosphere?

c

[BrickFielder]

ECM is going for a split in the stratospheric vortex at lover stratospheric levels today.

This would suggest to me a return to the negative NAO after the high to our north retrogrades westward.

Models are likely to be a bit out from about 5 days outwards untill they accurately model this. While we definately have signs of a disturbed vortex at upper levels in the stratosphere it is a bit of a surprise that we have a split only at the lower levels. Still there is plenty opf time for the models to morph and change in the lead up. In simple words this looks like any relief from the cold spell towards the end of the week might be short lived.

[chionomaniac]

ECM is going for a split in the stratospheric vortex at lover stratospheric levels today.

This would suggest to me a return to the negative NAO after the high to our north retrogrades westward.

Models are likely to be a bit out from about 5 days outwards untill they accurately model this. While we definately have signs of a disturbed vortex at upper levels in the stratosphere it is a bit of a surprise that we have a split only at the lower levels. Still there is plenty opf time for the models to morph and change in the lead up. In simple words this looks like any relief from the cold spell towards the end of the week might be short lived.

Exactly BF, and this is the third split this winter that has extended from the troposphere into the lower stratosphere!

[weatherjunkie]

Exactly BF, and this is the third split this winter that has extended from the troposphere into the lower stratosphere!

Any concerns regarding the positive zonal winds propagating downward?

[chionomaniac]

A good morning for stratosphere watchers

Any concerns regarding the positive zonal winds propagating downward?

I think this is bound to happen at some point, I am just hoping that they hold off long enough to allow a MMW to come into play.

[picog]

A good morning for stratosphere watchers

Looks promising! Does the potential split vortex help/hinder?

[chionomaniac]

Looks promising! Does the potential split vortex help/hinder?

Hi picog,

In answer to your question we must first mention the potential split vortex. This was forecast to occur at the lower levels of the stratosphere and troposphere. However in the last 24 hours both the ECM and GFS have moved away from the idea of this vortex split instead suggesting a stretching of the vortex with two main energy components. One is initially situated over Siberia and moves eastwards whilst the other stretches out to Newfoundland. This is where main pulse of tropospheric vortex are likely to be situated with some energy in between. This situation is conducive to an initial Scandinavian ridge reforming before perhaps stretching eastwards.

The second point is the forecast warming at the upper levels of the stratosphere. This is unlikely to be affected by the lower vortex disruption unless significant propagation of an upper disrupted vortex occurs down to a lower level. At this point the unstable lower vortex is likely to assist propagation so that would be a great help IMO.

Looking at the warming forecast, we initially saw a wave 1 heat flux induced disruption at the 1 hPa level. This has not been enough to significantly disrupt the upper vortex. However we have seen forecast another surge of wave 1 heat flux which seems to have been the extra energy needed to set off a propagated warming ( all this is just a forecast please understand). This is a double whammy and may be enough to set off a MMW as propagation of the warming to the 10hPa level looks more significant. However it is still early days in these forecasts and we will need to watch in the coming days to see what actually occurs.

c

[bluearmy]

what date was the commencement of the MMW last year C ? as i recall, out early feb snow was a couple of weeks sooner than we were expecting and if we do get an MMW out of this, no doubt, any significant northern blocking with split vortex's will just seem par for the course this winter.

[chionomaniac]

what date was the commencement of the MMW last year C ? as i recall, out early feb snow was a couple of weeks sooner than we were expecting and if we do get an MMW out of this, no doubt, any significant northern blocking with split vortex's will just seem par for the course this winter.

Last year the central date of the MMW (if my memory serves me correctly) was around the 17th Jan. That MMW was a split vortex, which resulted in the early February cold snap as a direct result of the split, but the strong La Nina conditions are thought to have prevented any sustained blocking.

If we get a MMW out of the current warming then it is likely to be a different ball game. Firstly, we are more likely to have a displacement MMW which are poorer propagators. However if propagation does occur then the unstable vortex at the lower end of the stratosphere is encouraging that blocking could occur though it may take longer to establish than last year. In the meantime we have that middle stratospheric stronger vortex element to worry about. Is that going to influence late January's and February's pattern before a MMW occurs or if one doesn't occur at all.

Edited January 10, 2010 by chionomaniac

[chionomaniac]

Now this is more like it:

Setting up nicely for a displacement SSW.

[Kentish Kiwi]

Now this is more like it:

Setting up nicely for a displacement SSW.

Hi Chiono,

Just wanted to pop in and give my thanks for the effort you (and a couple of others) put into this thread and monitoring the Stratospheric conditions, with it also quite refreshing to be able to read through such an organised, succinct and 'clutter free' thread (although I'm probably not helping things by adding this). Very interesting stuff and is in my opinion critical when looking ahead during the winter. Seems things are at least slightly more promising looking towards February than they were earlier in the month, showing just how quickly things can change.

Just a quick question. From what I've gleaned, I believe that the various forms of warmings of the Stratosphere, disrupts and weakens the Polar Vortex in different ways, in relation to zonal winds and there slowing/reversal? I was just wondering what the difference between a SSW and MMW is (if any), what they actually stand for and which is more promising?

Thanks,

KK :lol: :lol:

Edited January 10, 2010 by Kentish Kiwi

[chionomaniac]

Hi Chiono,

Just wanted to pop in and give my thanks for the effort you (and a couple of others) put into this thread and monitoring the Stratospheric conditions, with it also quite refreshing to be able to read through such an organised, succinct and 'clutter free' thread (although I'm probably not helping things by adding this). Very interesting stuff and is in my opinion critical when looking ahead during the winter. Seems things are at least slightly more promising looking towards February than they were earlier in the month, showing just how quickly things can change.

Just a quick question. From what I've gleaned, I believe that the various forms of warmings of the Stratosphere, disrupts and weakens the Polar Vortex in different ways, in relation to zonal winds and there slowing/reversal? I was just wondering what the difference between a SSW and MMW is (if any), what they actually stand for and which is more promising?

Thanks,

KK

Hi KK,

A Sudden Stratospheric Warming (SSW) or Major Midwinter Warming (MMW) are both phrases for exactly the same thing. That is a stratospheric warming that causes a reversal of the usual zonal winds from westerly to easterly at 10 hPa and at 60ºN. There are two different ways that this can occur. Either the polar vortex can be displaced from the North Pole ( a displacement vortex SSW) or the polar vortex is split in two ( a split vortex SSW) These two have slightly different characteristics - for instance a split vortex normally splits right down to the troposphere whereas the propagation of a displacement vortex is less certain. The main long term effect of either is a weakened stratospheric vortex which in turn can lead to a weakened tropospheric vortex, which results in an increase in northern blocking (commonly!). This winter we have already seen the effects of a weakened vortex which has been due to the warmer stratospheric conditions this November. The vortex never really cranked up until recently and we have still yet to feel the effects of this, and therefore have benefitted from the tropospheric vortex splitting a couple of times already this winter.

c

[chionomaniac]

Latest ECM update and thoughts.

Well the latest update is promising and shows an increased possibility for a displacement MMW to occur. Strong wave 1 activity is fluxing heat polewards and we can see the effects of this with a rapid deceleration of vortex winds at the 1hPa level.

This is now forecast to propagate down to lower levels and we can see that a dramatic rise in temperatures is forecast at the 10 hPa level and the start of a rise at the 30 hPa level.

The shape of the vortex is very distorted at these levels with considerable forcing and squeezing of the vortex towards Siberia. If this continues then I don't think it will be long before we have a full displacement.

I have changed my thoughts since yesterday about how this may affect us in the short / mid term. Firstly, the planned split in the lower stratospheric vortex and tropospheric vortex looks unlikely to occur, with a banana shaped vortex taking residence instead. My feelings, having looked at the temperature and zonal wind profiles of the stratosphere, is that the push from above is initially going to drive down the positive zonal winds, that have been kept at bay in the middle stratosphere, towards the troposphere. This initially is going to reinforce the tropospheric polar vortex, which, even though it may not be situated directly over the North Pole, may give it enough oomph to hold the Scandinavian High at bay and displace it more towards Siberia. This may serve to allow a temporary spell of milder weather before the Scandi High regains strength and any effects of a MMW are felt. So in essence, the short term effects of a MMW may actually be detrimental to the pattern of winter weather that we have experienced so far. I hope I am wrong and would like to hear GP's thoughts on this.

c

[Guest North Sea Snow Convection]

The way I see it is that it is inevitable that the log jam of positive zonal winds were going to eventually get through to the surface. It is remarkable how long they have been kept at bay actually! I think GP has stated a few times that the upwelling phase was likely to reach a peak by mid January - on its own it can't be sustained indefinitely.

I think that the current developments regarding a possible MMW, give good hope for perhaps some further cold weather a few weeks down the line, perhaps during Feb, but a milder spell of weather does seem more likely now with the chances of the blocking to the north east reasserting themselves in terms of UK influence perhaps now fading somewhat for the shorter term. However we shall see. It is hard to know how much polar westerly effect there will be at this stage in terms of vortex strength regrouped back towards Greenland pushing atlantic weather past the meridian against the eastern blocking

[chionomaniac]

The way I see it is that it is inevitable that the log jam of positive zonal winds were going to eventually get through to the surface. It is remarkable how long they have been kept at bay actually! I think GP has stated a few times that the upwelling phase was likely to reach a peak by mid January - on its own it can't be sustained indefinitely.

I think that the current developments regarding a possible MMW, give good hope for perhaps some further cold weather a few weeks down the line, perhaps during Feb, but a milder spell of weather does seem more likely now with the chances of the blocking to the north east reasserting themselves in terms of UK influence perhaps now fading somewhat for the shorter term. However we shall see. It is hard to know how much polar westerly effect there will be at this stage in terms of vortex strength regrouped back towards Greenland pushing atlantic weather past the meridian against the eastern blocking

Looking at the bigger picture, February is not looking great unless we can get a MMW, so a few weeks of less cold weather may well be a price worth paying. A similar situation occurred in the winter of 86/87 after a displacement MMW then.