Stratosphere Temperature Watch 2011/2012

[johnholmes]

a life away from Net Weather, tut tut young man. Since when. As one of our resident experts your input is required each and every day!

The simple baramoter of the Stratosphere that I use, the 30mb temperature pattern does look to agree with your post. No surprise there, its played about around the normal curve for some time, with most of the largish changes being above the average curve. Its done so again after looking to dive down below it. So the other tc's may well start to show something in a few days time?

perhaps the MJO first then the AO, or am I totally talking garbage?

[chionomaniac]

a life away from Net Weather, tut tut young man. Since when. As one of our resident experts your input is required each and every day!

The simple baramoter of the Stratosphere that I use, the 30mb temperature pattern does look to agree with your post. No surprise there, its played about around the normal curve for some time, with most of the largish changes being above the average curve. Its done so again after looking to dive down below it. So the other tc's may well start to show something in a few days time?

perhaps the MJO first then the AO, or am I totally talking garbage?

I am of the opinion that currently I can see no high latitude blocking in a region that is likely to deliver cold, from the current stratospheric output. Even though weak the polar vortex is still situated enough to the north to prevent Northern blocking from occurring in the next 10 days (both the GFS and ECM support this).

Further weight is given from the MJO forecasts. Currently we are in a MJO phase 8 scenario which supports blocking towards Greenland.

That is why the Azores high has displaced to the north but the door has shut, maybe also due to the positioning of the stratospheric vortex, before anything substantial has become established.

The forecasts tend to suggest that the MJO will move into phase 1 next before perhaps stalling.

.

This is not a phase that we would want to be stuck in for too long!

However, I have noticed over a period of time that when we see a period of stalling it is quite often followed by a backwards step to the previous phase and we will need to check whether this is true this time.

So nothing of note for the next 10 days or so other than the possibility of topplers affecting the usual areas.

[picog]

Chiono, why would we not want to be stuck in an MJO phase 1 for too long?

[johnholmes]

Chiono, why would we not want to be stuck in an MJO phase 1 for too long?

take a look at the 500mb chart he also showed, +ve heights just SW of the UK?

[phil nw.]

Plenty of evidence to show the weaker vortex is unlikely to suddenly find new life at this stage.

Although zonal mean winds are still strong at the top(1hPa)- here

the graph shows a slowing at 10 and 30hPa and as we look further down at the bottom of the Strat(100hPa) we see there is almost nothing at high latitudes over the next 6 and 10days.

The stronger zonal winds at the lower (trophospheric levels) are further south around 40-50 deg N and at the 200-300hPa level where the jetstream is modelled

So in conclusion little energy forecasted in the northern arm of the jet and as recent modelling has shown the trend is for the main jet to go south.

The chances of some late winter northern blocking is still there but as ever we need some luck wrt it`s placement.

[damianslaw]

Plenty of evidence to show the weaker vortex is unlikely to suddenly find new life at this stage.

Although zonal mean winds are still strong at the top(1hPa)- here

the graph shows a slowing at 10 and 30hPa and as we look further down at the bottom of the Strat(100hPa) we see there is almost nothing at high latitudes over the next 6 and 10days.

The stronger zonal winds at the lower (trophospheric levels) are further south around 40-50 deg N and at the 200-300hPa level where the jetstream is modelled

So in conclusion little energy forecasted in the northern arm of the jet and as recent modelling has shown the trend is for the main jet to go south.

The chances of some late winter northern blocking is still there but as ever we need some luck wrt it`s placement.

Whilst the strat profile may not appear conducive to northerly blocking in the medium term - it isn't the be all and end all for cold and snow prospects. Indeed with a southerly tracking jet - those heights over russia could very easily advect west again with undercutting. Indeed I see such synoptics unfolding later this month.

[Weather-history]

The overall picture suggests a continuance of the weak vortex conditions at least until the end of the month. I am of the opinion that the increase in mean zonal winds at the 1hPa level is unlikely to affect the troposphere until much later in spring. The remnants of the westerly QBO have now been extinguished from the tropical stratosphere which will assist in keeping the polar stratospheric mean zonal mean winds reduced for the rest of winter. This in effect means that tropospheric considerations will have an enhanced affect during the rest of winter and into early spring.

Edit: just to clarify what I mean by that. Early this winter the tropospheric wave pattern and flow was dominated by the strong stratospheric vortex - this prohibited any chance of HLB's from occurring and prevented local wave breaking events into the centre of the stratospheric polar vortex. We are now in a position where that stratospheric dominance has been removed and tropospheric wave patterns can influence the polar patterns without being immediately squashed by a strong polar vortex.

The turnaround in mid January is impressive.

Are you disappointed though that the warming didn't have a greater impact? Look how long the temperatures at the 10hpa were above the average and indeed the 30hpa as well and yes the zonal winds reversed at the 10hpa level and slowed at the 30hpa level but taking it at face value, it looked as though it should have had a big impact than it did.

[chionomaniac]

One would always hope for a greater impact Mr. D. I am not disappointed with the stratospheric forecast that I gave back at the start of November, but would always hope for more sustained northern blocking over Greenland. However this was never likely to occur once the displacement of the vortex held the upper vorticity in the Atlantic Arctic sector. That meant that we were never going to see local wave breaking in this region. Personally for me this winter has delivered enough for me to be happy. My expectations were for no chance of sustained blocking occurring in the first half of winter and that has occurred. We could have had more if the vortex displacement had been more favourable for the second half though.

[mountain shadow]

Would it be correct to say that we are scientifically in a position now to predict Stratospheric warmings perhaps two or three months in advance but that we cannot yet forecast with a degree of accuracy whether that warming will impact the troposphere, and if it does where in the troposhere will be impacted until perhaps 15-30 days before?

[chionomaniac]

Would it be correct to say that we are scientifically in a position now to predict Stratospheric warmings perhaps two or three months in advance but that we cannot yet forecast with a degree of accuracy whether that warming will impact the troposphere, and if it does where in the troposhere will be impacted until perhaps 15-30 days before?

I do not think that we can predict stratospheric warnings 2-3 months in advance with certainty, however, we can predict when we think conditions will be more likely for them to occur. This winter was a case in point. The January warming wasn't a lucky punt- there were a number of factors that pointed towards this occurring. However, there will be times when conditions look right and warming doesn't occur!

[Glacier Point]

One of the most notable aspects of the warmings this year has been the relationship with Asian mountain torques.

We have 3 traceable warmings, all occuring within three weeks of a +ve Asian mountain torque (but only after the cold vortex event faded)

Positive mountain torques are reasonably predicatble, being a product of increasing tendency in angular momentum and movement of tropical convection from the western through the eastern Indian Ocean.

Edited February 14, 2012 by Glacier Point

[chionomaniac]

One of the most notable aspects of the warmings this year has been the relationship with Asian mountain torques.

We have 3 traceable warmings, all occuring within three weeks of a +ve Asian mountain torque (but only after the cold vortex event faded)

Positive mountain torques are reasonably predicatble, being a product of increasing tendency in angular momentum and movement of tropical convection from the western through the eastern Indian Ocean.

And I think that this part is critical!

[karyo]

Once again it has been interesting to follow this thread this autumn/winter. Quite a few areas are still not explained like why such significant warming didn't lead to more long lasting northern blocking. Stratospheric temperatures at the 30hpa level are still above average so you would expect northern blocking to continue for several more weeks. However, as we can see in the models that's far from what is happening.

Karyo

[mountain shadow]

Once again it has been interesting to follow this thread this autumn/winter. Quite a few areas are still not explained like why such significant warming didn't lead to more long lasting northern blocking. Stratospheric temperatures at the 30hpa level are still above average so you would expect northern blocking to continue for several more weeks. However, as we can see in the models that's far from what is happening.

Karyo

Stratospheric warming does not always lead to warming in the troposphere.

[La Bise]

A big thank you to the main contributors on this thread. Not only for the insight into possible weather scenarios but also for the explanations, sometimes often repeated. The reasonning and science behind it is fascinating and leaves me with the impression of some real investigative work being undertaken. No arcane musings, no nebulous allusions to hidden drivers, no obsessive hopecasting just good solid science and a great read for anyone with an interest in weather.

[johnholmes]

Yes this thread is very probably the success story for Net Weather for the autumn-winter 2011-12 and my thanks to those who have contributed so much to it; no need to name them they well know how much effort they have put into this thread-a very big thank you.

edit

The main thanks of course must go to chio-a huge effort-I've learnt a lot this autumn-winter so my personal thanks for all your work and the patience shown when we have asked what probably, to you, seem obvious.

Edited February 14, 2012 by johnholmes

[BLAST FROM THE PAST]

Stratospheric warming does not always lead to warming in the troposphere.

And that leads to the fact that there are other drivers and possibly 'external' forcings that override this fact. A response rathert than a leader?

BFTP

[Partholon]

And that leads to the fact that there are other drivers and possibly 'external' forcings that override this fact. A response rathert than a leader?

BFTP

Perhaps a crucial difference this year, was the strength of the vortex prior to the warmings compared to previous years. An additional consideration might be that the ep flux didn't go poleward, which, if i recall correctly, the experts said was not a very good sign.

Edited February 14, 2012 by Partholon

[johnholmes]

Perhaps a crucial difference this year, was the strength of the vortex prior to the warmings compared to previous years. An additional consideration might be that the ep flux didn't go poleward, which, if i recall correctly, the experts said was not a very good sign.

yes something else I had never even heard of until this autumn-winter-totally absorbing thread

[Isolated Frost]

Stratospheric warming DID cause high-latitude blocking- take the notable Aleutian blocking ridge that formed during January as a response to the breakdown of the cold vortex.

You also just need to look at GPH anomalies around the arctic to see that from mid-jan onwards, a cold vortex turned to a very much displaced vortex with blocking heights around the arctic at times.

Indeed the blocking occurred at the wrong place- but despite this, the retrogressing russian block allowed a very cold first half of the month for much of Central and Eastern England.

Just the wrong place really, hit and miss, although there are many factors that contributed to the placement of blocking heights around the arctic.

You would also think GLAAM and MJO had a large influence on the positioning and strength of the vortex and resultant blocks.

From a neutral POV- the prediction was for a warming of the stratosphere allowing mid-troposherical blocking as we progress into late January and February, after the first half of winter is dominated by an active, cold vortex. The reality is this has been correct and the northern hemisphere witnessed a large pattern change as January progressed.

We could be defaulting now, with all the background signals possibly around static bar a few, and with +AO possibly to return for at least a few days- a milder period is likely in the scheme of it all.

Well done to chiono, lorenzo, GP etc, brilliant and definitely the best, most informative thread on NW this year, and next year I'm sure!

[TEITS]

Stratospheric warming DID cause high-latitude blocking- take the notable Aleutian blocking ridge that formed during January as a response to the breakdown of the cold vortex.

You also just need to look at GPH anomalies around the arctic to see that from mid-jan onwards, a cold vortex turned to a very much displaced vortex with blocking heights around the arctic at times.

Indeed the blocking occurred at the wrong place- but despite this, the retrogressing russian block allowed a very cold first half of the month for much of Central and Eastern England.

Just the wrong place really, hit and miss, although there are many factors that contributed to the placement of blocking heights around the arctic.

You would also think GLAAM and MJO had a large influence on the positioning and strength of the vortex and resultant blocks.

From a neutral POV- the prediction was for a warming of the stratosphere allowing mid-troposherical blocking as we progress into late January and February, after the first half of winter is dominated by an active, cold vortex. The reality is this has been correct and the northern hemisphere witnessed a large pattern change as January progressed.

We could be defaulting now, with all the background signals possibly around static bar a few, and with +AO possibly to return for at least a few days- a milder period is likely in the scheme of it all.

Well done to chiono, lorenzo, GP etc, brilliant and definitely the best, most informative thread on NW this year, and next year I'm sure!

Yes overall this thread has been excellent and I shall eagerly be following it again. I do agree with your comments with regards to Dec, Jan, early Feb. However if we read the comments 2 weeks ago and what is now predicted by the models then in my opinion its gone a little pearshaped.

I have no doubts a warming of the stratosphere has an impact on the PV. However its also clear to me that how this affects the PV and the impact it has on the UK is very uncertain and the projections from the models can quickly change. Still to be fair to CH he doesn't say a warming of the stratosphere is a guarantee for the UK to experience a cold spell.

So thanks to everyone especially CH.

[MisfitDog3]

It's been a good thread but I do wonder if it's in the right place? Doesn't seem a logical category to me.

[bluearmy]

Yes overall this thread has been excellent and I shall eagerly be following it again. I do agree with your comments with regards to Dec, Jan, early Feb. However if we read the comments 2 weeks ago and what is now predicted by the models then in my opinion its gone a little pearshaped. I have no doubts a warming of the stratosphere has an impact on the PV. However its also clear to me that how this affects the PV and the impact it has on the UK is very uncertain and the projections from the models can quickly change. Still to be fair to CH he doesn't say a warming of the stratosphere is a guarantee for the UK to experience a cold spell. So thanks to everyone especially CH.

dave, ed pointed out a week or so ago that ncep was forecasting the vortex to split in an unfavourable way for us to receive cold as it placed a lobe of the p/v near greenland and split straight across to siberia. (as opposd to ecm ). this forecast changed somewhat, day to day but did then settle on the greenland lobe which has led to what we now see in the models for the next week or so. lower strat height fi forecasts are also prone to swings, but not quite as much as the trop ones.

[TEITS]

dave, ed pointed out a week or so ago that ncep was forecasting the vortex to split in an unfavourable way for us to receive cold as it placed a lobe of the p/v near greenland and split straight across to siberia. (as opposd to ecm ). this forecast changed somewhat, day to day but did then settle on the greenland lobe which has led to what we now see in the models for the next week or so. lower strat height fi forecasts are also prone to swings, but not quite as much as the trop ones.

Yes I know he did but only a few days before this the ECM was showing the most exciting charts of the winter. This is why I said the forecasts can change very quickly.

[Partholon]

Yes I know he did but only a few days before this the ECM was showing the most exciting charts of the winter. This is why I said the forecasts can change very quickly.

Indeed. The ecm 32 dayer, which was considered very accurate with regard to the blocking events of the previous two years, was very misleading this year. I recall Matt Hugo referencing it in his tweets, because blocking to the northwest was depicted by it on several occasions.

Ian Brown rightly receives criticism for some of his posts on here, but in saying that he was right when he mentioned several weeks ago that the vortex split this winter might not be favourable for blocking over the UK and Ireland. He cautioned people not to get carried away at the time. So This winter has shown me it's best not to get carried away by t-240 stratosphere profile charts from now on. Also that a split vortex does not guarantee blocking will occur in the right area for us to benefit from, even if some of the models suggest so in late FI.

Edited February 15, 2012 by Partholon