Stratosphere Temperature Watch 2011/2012

[geoffw]

is an MMW the same as an SSW?

[weatherjunkie]

GFS shows 12z shows 2 warmings, second bigger than the first

http://176.31.229.22...nh-10-96.png?12

http://176.31.229.22...h-10-336.png?12

Is that looking good?

The location of these warmings doesn't appear to bode well for the N. Atlantic. Again, I know the propagation of the warming doesn't translate directly from level to level, but this still doesn't appear to be good for a -NAO, am I right?

is an MMW the same as an SSW?

MMW = major midwinter warming, but I'm unsure if the criteria is the same

[chionomaniac]

is an MMW the same as an SSW?

Yes.

The location of these warmings doesn't appear to bode well for the N. Atlantic. Again, I know the propagation of the warming doesn't translate directly from level to level, but this still doesn't appear to be good for a -NAO, am I right?

I think it is far too early to tell due to the centres of potential vorticity that change throughout the levels of the stratosphere. Also if we get a SSW then tropospheric factors could have a large deterministic effect of where blocking is most likely.

[ITSY]

I'm so confused

[cooling climate]

The location of these warmings doesn't appear to bode well for the N. Atlantic. Again, I know the propagation of the warming doesn't translate directly from level to level, but this still doesn't appear to be good for a -NAO, am I right?

MMW = major midwinter warming, but I'm unsure if the criteria is the same

I may well be completely wrong here but if you consider where the warming

has started and where it is most intense at the 1 and 5 hpa level I would

guess blocking in the north Atlantic (- NAO) becoming east based (block

transfering to Iceland, Scandanavian area. The reason I say this is that

over the last couple of winters the warming has initiated much further east

with the block being more -NAO west based.

Of course the warming my not propagate ( although it is showing signs of

doing so) and any effects to the troposphere will be at least 2 weeks down

the line (Jan 7 onwards).

As I say I could be completely wrong though.

[damianslaw]

I may well be completely wrong here but if you consider where the warming

has started and where it is most intense at the 1 and 5 hpa level I would

guess blocking in the north Atlantic (- NAO) becoming east based (block

transfering to Iceland, Scandanavian area. The reason I say this is that

over the last couple of winters the warming has initiated much further east

with the block being more -NAO west based.

Of course the warming my not propagate ( although it is showing signs of

doing so) and any effects to the troposphere will be at least 2 weeks down

the line (Jan 7 onwards).

As I say I could be completely wrong though.

Your thoughts would appear to support GP's thoughts of heights building over scandi and ridging towards Iceland as opposed to Greenland. A block in such a position would deliver easterlies rather than northerlies/northeasterlies and if anything is a much better position for sustained long term cold east based negative NAO being much better than a west based negative NAO - the latter often gives rise to lower heights moving into southern parts enabling milder air off the atlantic to creep in (we saw this happen to some extent in Feb 2010). Whereas a high over iceland/scandi locks in the cold longer and deeper - see charts for Feb 86.

Have to say given the poor current synoptics for cold, the prospects of a warming strat are keeping us cold lovers happy. I do think regardless of whether we do see a strat warming, the second half of the winter will see a much weaker PV and therefore generally much colder conditions than during the first half.

[weatherjunkie]

Yes.

I think it is far too early to tell due to the centres of potential vorticity that change throughout the levels of the stratosphere. Also if we get a SSW then tropospheric factors could have a large deterministic effect of where blocking is most likely.

That is what I had suspected. As always, your input is greatly appreciated.

I may well be completely wrong here but if you consider where the warming

has started and where it is most intense at the 1 and 5 hpa level I would

guess blocking in the north Atlantic (- NAO) becoming east based (block

transfering to Iceland, Scandanavian area. The reason I say this is that

over the last couple of winters the warming has initiated much further east

with the block being more -NAO west based.

Of course the warming my not propagate ( although it is showing signs of

doing so) and any effects to the troposphere will be at least 2 weeks down

the line (Jan 7 onwards).

As I say I could be completely wrong though.

Yes, I see what you are saying. It looks like we'll just have to wait and see. At the very least it gives us something to monitor other than lack of cold and snow.

Wave breaking potential also on the increase given the wave 1 amplitude (and forecast strengthening). Also seeing signs from forecasts of wave 2 strengthening.

[chionomaniac]

This mornings update - there is a lot to take in.

Firstly, we are about to see a large wave 1 induced warming that is going to disrupt the stratosphere for the first time this winter. We have been waiting a long time to see the below average cold conditions driving the strong polar vortex be threatened.

So this wave breaking into the upper stratosphere is large enough to give a forecast reversal of mean zonal mean winds at the upper levels of the stratosphere. The vortex though is not forecast to break up completely. It is close and probably on a knife edge, but I suspect that we will need another wave break and subsequent warming to break the vortex.

Moving down the warming does propagate down to the 10 hPa level and propagation is supported by a poleward EP flux. However it is insufficient to give us a SSW currently - so still no SSW.

However, what is forecast to occur is very encouraging and will have some effects on the vortex positioning in the troposphere. In fact I suspect that a Pacific based ridge will build which will be a preconditioning building block to an eventual SSW. We are most certainly heading in the right direction, but frustratingly for cold lovers more patience required.

c

[lorenzo]

Here are some charts in relation to Chionos update that illustrate the changes. Chi, Phil please edit if incorrect still finding my way in this subject.

Current Heat Flux

Projected

10hpa Height / Temps

Zonal Wind reversal

[sebastiaan1973]

At this site http://www.wzforum.d...096#msg-2320096 I read today 'Momentan haben wir einen der stärksten Polarwirbel seit 1948, also seit Aufzeichnungen des Archivs. Die extrem negative Geopotenzialanomalie zieht sich wie ein Faden bis in die Bereiche der Troposphäre und beschert uns letztendlich auch das westgeprägte Wetter seit Ende November.' (written in german)

So I wonder is this true. Do we have the strongest polar vortex since 1948 and an extreme negative geopotential anomoly?

Edited December 23, 2011 by sebastiaan1973

[chionomaniac]

At this site http://www.wzforum.d...096#msg-2320096 I read today 'Momentan haben wir einen der stärksten Polarwirbel seit 1948, also seit Aufzeichnungen des Archivs. Die extrem negative Geopotenzialanomalie zieht sich wie ein Faden bis in die Bereiche der Troposphäre und beschert uns letztendlich auch das westgeprägte Wetter seit Ende November.' (written in german)

So I wonder is this true. Do we have the strongest polar vortex since 1948 and an extreme negative geopotential anomoly?

If that is for November then it is possible - December - I wouldn't be too sure

[weathe20]

Why are people suggesting they can see the effects of SSW already in the Model Output thread? This event hasnt even happend, nor is it forecast? It has been picked up on some models are MIGHT happen. Is that true?

[Aceman]

Why are people suggesting they can see the effects of SSW already in the Model Output thread? This event hasnt even happend, nor is it forecast? It has been picked up on some models are MIGHT happen. Is that true?

I think its the warming of the stratosphere not a SSW which people are seeing in the models.

[phil nw.]

Why are people suggesting they can see the effects of SSW already in the Model Output thread? This event hasnt even happend, nor is it forecast? It has been picked up on some models are MIGHT happen. Is that true?

If you read back a little in this thread then you can see from the daily updates that Chion has posted that a Strato.warming is forecasted at the upper levels within the next 7days now.

We need to see this warming propagate down to lower levels before any real effects are likely on the Polar Vortex.This may show up in the Strato forecasts in the next few days or the warming on this occasion may not permatate down far enough--it`s a wait and see situation with no gaurantees for a cold spell in the UK at this stage.

If the Strato.warming forecasts do start to show warming at the lower levels then the models should start to highlight changes to the strength of the vortex in the far reaches of it`s output.

We are all still learning W20 and this thread is simply monitoring any effects of Strato warmings on the Trophospheric patterns--it comes with no promises and i for one has said this on more than one occasion in the Model Discussion Thread.Unfortunately some members on the MOD thread do get a little impatient and see things on the charts and misinterprate them as a sign of a big change towards a cold pattern.

Anyway have a read back over the thread and you can see the latest state of play.

[mountain shadow]

Why are people suggesting they can see the effects of SSW already in the Model Output thread? This event hasnt even happend, nor is it forecast? It has been picked up on some models are MIGHT happen. Is that true?

I believe we are already seeing an influence but way out in deepest FI. Keep and eye on the H500 northern hemisphere for sign of a warming over the pole with a build in pressure. I believe or hope that we will start to see some decent cold runs through boxing day.

Edited December 23, 2011 by mountain shadow

[bluearmy]

ecm 12z T240 spreads have a cluster of runs raising heights over the pole. there is little else of interest from any current nwp wrt to events in the strat as far as i can see.

[Glacier Point]

... wrong area I think Nick, based on ozone forecasts which, allied to composite analogues for a dipole warm - cold profile to the stratosphere (30-50C difference across the North Pole). I would suggest height rises over Canada as being the key area to look, and only from mid January onwards. Based on that, we are some way off this being within model range.

[The PIT]

If this comes off I suspect the models won't pick it up until last minute last minute being 14 days. Prior to that a lot of jumping around in FI then suddenly wham.

[January Snowstorm]

... wrong area I think Nick, based on ozone forecasts which, allied to composite analogues for a dipole warm - cold profile to the stratosphere (30-50C difference across the North Pole). I would suggest height rises over Canada as being the key area to look, and only from mid January onwards. Based on that, we are some way off this being within model range.

And bang on queue the 18z suggest this in FI

[Kentish Kiwi]

What kind of weather patterns can we expect to experience in the UK with height rises over Canada?

[mountain shadow]

... wrong area I think Nick, based on ozone forecasts which, allied to composite analogues for a dipole warm - cold profile to the stratosphere (30-50C difference across the North Pole). I would suggest height rises over Canada as being the key area to look, and only from mid January onwards. Based on that, we are some way off this being within model range.

I disagree a wee bit with the last sentence Chino, if only because some ensembles members will show the effects of the warming quicker than is likely to happen.

What kind of weather patterns can we expect to experience in the UK with height rises over Canada?

Obviously Canada is a huge country. The best outcome would be height rises in north eastern Canada ridging into Greenland which would see the Uk on the cold side of the high pressure in a more northerly flow.

The worst would be a more central Canadian high which would see lower heights over Greenland and the Uk in more westerly atlantic flow.

[sebastiaan1973]

Although it's far away it seems to me the zonal wind reversal is less strong than earlier was predicted (?)

[karyo]

Today's update has downgraded a bit the stratospheric warming! http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php

As you can see, the mean zonal winds are not expected to reverse. The 30hpa level also shows a smaller rise than yesterday.

Karyo

[chionomaniac]

It certainly looks that way- GFS forecast a little better. I seem to remember the ECM going overboard with a forecast last year that was then reduced.

Though GFS has been consistent with another warming in early January.

I suspect it may need a couple of waves to knock our sandcastle over.

Edited December 24, 2011 by chionomaniac

[sebastiaan1973]

It's only 1 run, so from that perspective we don't have to worry. Besides that 'always' we needed a second wave to disrupt the vortex even more to get a more favourable situation at a lower altitude.