Stratosphere Temperature Watch

[chionomaniac]

The vortex split is still forecast by the ECM this morning. At the 100hPA level it is due to commence around T+144 with two separate vortices by T+192. (This forecast is delayed by a day as well)

The split is now showing signs of working up to the 10 hPa level - the Canadian daughter vortex looks to be the stronger section.

c

[mountain shadow]

It seems that if the PV is over Greenland we get mild and wet. According to Brickfielder above a split vortex over Canada and Siberia also brings us wet and mild. This cannot be right surely?

[AtlanticFlamethrower]

Looks to be a warming coming. This page (re: "heights" and "temperatures" to f240) suggests split vortex over Canada and Siberia rather than high pressure near us...

Edited December 3, 2009 by AtlanticFlamethrower

[chionomaniac]

When one gets a split vortex SSW, the heating of the stratosphere completely wipes out the strength of the vortex and zonal winds reverse throughout the whole length of the atmosphere. The event, even though it may be tropospherically led by wave breaking, tends to be led from the top of the stratosphere propagating downwards. What appears to be forecast in the next week is a cold vortex split that is led from the troposphere and is radiating upwards. There are strong negative mean zonal winds forecast, that are propagating upwards in a completely different fashion to the negative mean zonal winds associated with a SSW (eg last January's).

These negative mean zonal winds are best illustrated on the cross sectional view of the NH atmosphere:

Forecasts are suggesting that the separate vortices, that extend far up into middle stratosphere, will maintain a certain amount of strength and I guess the reformation of one vortex is the next most logical step after (ie no SSW type stratospheric mean easterly winds). How long two separate vortices remain in the troposphere is probably important. The longer the split vortices remain, the better the chance that global teleconnections may become well aligned, and proper cold may reach our shores. So this will be well worth watching.

[bluearmy]

When one gets a split vortex SSW, the heating of the stratosphere completely wipes out the strength of the vortex and zonal winds reverse throughout the whole length of the atmosphere. The event, even though it may be tropospherically led by wave breaking, tends to be led from the top of the stratosphere propagating downwards. What appears to be forecast in the next week is a cold vortex split that is led from the troposphere and is radiating upwards. There are strong negative mean zonal winds forecast, that are propagating upwards in a completely different fashion to the negative mean zonal winds associated with a SSW (eg last January's).

These negative mean zonal winds are best illustrated on the cross sectional view of the NH atmosphere:

Forecasts are suggesting that the separate vortices, that extend far up into middle stratosphere, will maintain a certain amount of strength and I guess the reformation of one vortex is the next most logical step after (ie no SSW type stratospheric mean easterly winds). How long two separate vortices remain in the troposphere is probably important. The longer the split vortices remain, the better the chance that global teleconnections may become well aligned, and proper cold may reach our shores. So this will be well worth watching.

both GFS fi runs show the reformation of a large siberian vortex a week to ten days beyond the split.

[chionomaniac]

both GFS fi runs show the reformation of a large siberian vortex a week to ten days beyond the split.

Interesting ba. Stratospheric forecasts don't run out that far, but have tended to keep the Canadian vortex the dominant one!

30 hPa at T+240

[Guest North Sea Snow Convection]

Interesting ba. Stratospheric forecasts don't run out that far, but have tended to keep the Canadian vortex the dominant one!

30 hPa at T+240

What price to have a SSW Santa x mas present special next!

An initial split (as upcoming and as you describe) leading into the full whammy!

Stormchaser C on eastern wx was looking at a December major warming event I seem to remember!? If ever there was a time for a forecast to verify!!

Edited December 4, 2009 by North Sea Snow Convection

[chionomaniac]

What price to have a SSW Santa x mas present special next!

An initial split (as upcoming and as you describe) leading into the full whammy!

Stormchaser C on eastern wx was looking at a December major warming event I seem to remember!? If ever there was a time for a forecast to verify!!

Yes indeed. Jim Hughes hasn't given anything away yet has he?

[Guest North Sea Snow Convection]

Yes indeed. Jim Hughes hasn't given anything away yet has he?

His most recent comment I read was 'the time for the 10 and 30mb levels will come'!

[cooling climate]

If you look at the pressure charts for say t120 the high pressure over Alaska is most

pronounced at the higher levels of the stratosphere then working its way down.

IE rosby wave breaking = SSW event from the top down.

10hpa t120

100hpa t120

The warming area expands due to the lower density of the air as I understand it but then

radiative cooling acts to address the anomally.

Edited December 4, 2009 by cooling climate

[chionomaniac]

Well, the splitting of the vortex is forecast to occur in around 72-96 hours.

This will create a large area of negative zonal wind anomalies around 60-90ºN. These are already showing up at around T+120 and increasing significantly around T+192

Looking at the 100hPa profile we can work out where high pressure is most likely to form.

Here we can see that upper level pressure rises are favoured directly above the UK. Where we go from here hasn't yet been decided.

I am quite encouraged by the height rises extending to Scandinavia on a stratospheric point of view. Episodes of blocking are often precursors to SSW type events. Before this winter started, my hunch was for a displacement type SSW to occur around the New Year, and any Atlantic blocking around mid month would fit in nicely with that time frame. ( I looked at Jan 1987 as a comparative event ) We shall see!

c

Edited December 5, 2009 by chionomaniac

[Glacier Point]

This will create a large area of negative zonal wind anomalies around 60-90ºN. These are already showing up at around T+120 and increasing significantly around T+192

Quite good support for the start of the upwelling wave going on there I think. Add to that, I'm starting to think around December 20th for a large warming at 10 and 30 hPa layers based on where Wave 1 progression which could well be a record amplitude for this time of year.

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_WAVE1_MEAN_OND_NH_2009.gif

[chionomaniac]

Quite good support for the start of the upwelling wave going on there I think. Add to that, I'm starting to think around December 20th for a large warming at 10 and 30 hPa layers based on where Wave 1 progression which could well be a record amplitude for this time of year.

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_WAVE1_MEAN_OND_NH_2009.gif

That fits in nicely with my 'guess'.

[Gavin P]

Quite good support for the start of the upwelling wave going on there I think. Add to that, I'm starting to think around December 20th for a large warming at 10 and 30 hPa layers based on where Wave 1 progression which could well be a record amplitude for this time of year.

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_WAVE1_MEAN_OND_NH_2009.gif

So Dec 20th for a big warming could lead to major blocking mid-late January?

[cooling climate]

Quite good support for the start of the upwelling wave going on there I think. Add to that, I'm starting to think around December 20th for a large warming at 10 and 30 hPa layers based on where Wave 1 progression which could well be a record amplitude for this time of year.

http://www.cpc.ncep....OND_NH_2009.gif

Surely its this now that is causing the vortex to split.

A SSW is already or about to take place.

[bluearmy]

Surely its this now that is causing the vortex to split.

A SSW is already or about to take place.

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

i'd wait to see the 10hpa temp forecast on the rise before calling a SSW. the temps lower down positively tropical in the next week.

[chionomaniac]

Surely its this now that is causing the vortex to split.

A SSW is already or about to take place.

The vortex split currently modeled does not appear to be as a result of a SSW. Classically, the prolific warmings of SSWs occur before the polar vortex disruption. There has been no prolific warming and even though the vortex has a partial split it appears that this could be as a result of tropospheric disturbances on an already weakened vortex, after a series of minor warmings. The vortex net strength is maintained throughout the height of the stratosphere despite the split.

The necessary requirements to achieve a SSW are that the zonal mean zonal winds become easterly at 10hPa and 60ºN. This has not occurred yet and is not forecast to do so in the immediate future.

c

Edited December 5, 2009 by chionomaniac

[Guest North Sea Snow Convection]

The vortex split currently modeled does not appear to be as a result of a SSW. Classically, the prolific warmings of SSWs occur before the polar vortex disruption. There has been no prolific warming and even though the vortex has a partial split it appears that this could be as a result of tropospheric disturbances on an already weakened vortex, after a series of minor warmings. The vortex net strength is maintained throughout the height of the stratosphere despite the split.

The necessary requirements to achieve a SSW are that the zonal mean zonal winds become easterly at 10hPa and 60ºN. This has not occurred yet and is not forecast to do so in the immediate future.

c

Yes E - that is what I was referring to on the model thread. We need the big full reversal!

[chionomaniac]

Today, I am going to look at the ECM forecast charts for the period of the vortex split.

The polar vortex is forecast to split from the troposphere upwards in the next couple of days. The zonal mean winds are currently situated over the North Pole as can be seen from the following chart (the oranges extend upwards above 90ºN to show westerly winds):

However, following the split, the mean zonal winds are significantly weakened with negative anomalies (blue) stretching throughout a significant part of the stratosphere between 60-90ºN:

So what happens to the temperature in the troposphere in the northern hemisphere during this time? The following chart shows a cross section of the mean current temperature profile of the northern hemisphere:

We can see that the coldest temperatures are at the North Pole by the dip at 90ºN at the tropospheric level (1000hPa). However, following the vortex split the profile changes somewhat. Now we can see that there is a dip of temperature that has translated further south - look at the dip between 60-80ºN. This is as a consequence of the cold Arctic air flooding south - one of the prerequisites needed in order for mid latitude areas to receive deep cold.

So again, we now look at the forecast for the area of the vortex split to see where ridge building is likely from stratospheric influences. Both the 100hPa and 400K potential vorticity charts are suggestive of height rises north of the UK. Will tropospheric influences override this?

c

[BrickFielder]

I am not sure high pressure in the stratosphere gives high pressure in the troposphere. The key point is the vorticity and the effect of winds in the lower stratosphere (100hpa) on the upper troposphere.

My take on the 400K vorticity charts would be as follows.Remember the troposhere has its own drivers which can over ride or shift signals from the stratosphere.

The interesting thing about wave 1 being strong and wave 2 being weak is that this would tend to give a shift in the vortex rather than a split. For me a persistent deep low towards Iceland sets things up for another warming but one more favourable towards cold weather in the UK.

What I do expect to see from the coming vortex split is cross pole wind flows which should enhance ice production and will allow cold air to be spilled out from the pole (just not towards us). This will give a very strong jet stream in places and globally this winter may play out giving some unusual weather.

[chionomaniac]

The lower stratospheric pressure patterns correlate very well with the upper tropospheric pressure patterns as can be demonstrated from todays charts.

Surely, (and correct me if I am missing something here) the stronger the stratospheric vortex, the lower the pressure and the lower the corresponding tropospheric heights? Otherwise we would be praying for a strong stratospheric vortex come winter.

I would have also thought that the orange areas on the 400K pv chart show where the vortex is strongest with the lowest pressure - not where ridging will occur? You have suggested this previously here post 62

Edited December 6, 2009 by chionomaniac

[BrickFielder]

What you don't want is a positive NAO which is linked to a strong vortex.

http://www.atmosp.physics.utoronto.ca/SPARC/index.html

[chionomaniac]

What you don't want is a positive NAO which is linked to a strong vortex.

http://www.atmosp.physics.utoronto.ca/SPARC/index.html

I think that I may have misread your first vorticity chart. The H's that you have highlighted are for higher vorticity not pressure!

[cooling climate]

I think that I may have misread your first vorticity chart. The H's that you have highlighted are for higher vorticity not pressure!

That is the way I understand it also. It is a vorticity chart and the greatest vorticity will be centered around the

vortices's.

[chionomaniac]

We still have great mean zonal wind forecasts which are now negative into the reliable timeframe.

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

We have a lovely strat 100hPa profile at T+192 - the kind that I would have liked to see after last winters MMW- the only annoying thing is that the ECM forecasts are delayed a day so things may have changed by the time we look at them!

Looking further afield I am looking for evidence that the strong amplitude wave 1 may be ready to cause another warming. There are signs, with a severely distorted vortex shape at the 10hPa level that this could occur. Even though the mean zonal winds are forecast to increase dramatically I feel that the stratospheric vortex is there for the taking!

It's like a squeezed balloon ready to pop!