Stratosphere and Polar Vortex Watch

[Blessed Weather]

GEFS ensemble mean going for a zonal wind reversal around 14th/15th Feb. Presumably this was today's (Wed 31st Jan) 06z run.

 

[bluearmy]

[Hammer50]

8 minutes ago, bluearmy said:

Wow

[starstream]

12 minutes ago, bluearmy said:

@bluearmy is that a portion of PV sitting above the UK?

[karyo]

Just now, starstream said:

@bluearmy is that a portion of PV sitting above the UK?

No, the opposite.

Great to see consistency developing regarding the SSW and the split. 

[Daniel*]

Now that is a split vortex beyond salvation. Severe winter conditions are definitely set to remain to affect the mid latitudes if this is anything to go by North America could be in this for long run. 

[Man With Beard]

I don't think the GFS is going to back down on this one.

[Glacier Point]

On 11/01/2018 at 12:06, Glacier Point said:

This isn't new, but reanalysis of 10hPa temps after passage of strong Indian Ocean MJO events underlines the potential relationship between tropical forcing and the stratosphere.

I reckon we peaked tropical signal in phase 2 around the 8th or 9th Jan.

For years with strong MJO signal centred in phase 2, 10 hPa temps:

Rolled forward, by day 15, displacement starting to occur:

By day 39/40, we get peak warming signal:

The surprising thing is the duration of the warming signal (days 20-40+) but this is more likely a result of the large number of dates used smoothing out the warming signal.

Now, current during the same peak in MJO phase 2:

Much more perturbed with wave 2 already in evidence from previous forcing. Different location of warming being forecast, much more aligned through 260 - 180 W rather than Asia to the Atlantic.

Suggestion: warming and substantive weakening of the vortex likely to occur given the scale of the MJO wave passage, timings probably more advance given the state of the vortex at onset. Whether a trigger for a SSW or MMW are sufficient will be worth monitoring but not guaranteed.

This feels like a long time ago now.

GFS advertising around the 13th February as key date. That's 36 days after Indian Ocean coupled convective wave passage, so the timeline bang on and yet again another example of the slow time scales for stratospheric - tropospheric events.

[ghoneym]

I wanted to ask the Start experts on here if there is any correlation between the Antarctic stratosphere conditions and the Artic stratosphere conditions? From what I can see from the conditions back to the 17th of January the Antarctic Stratosphere is very organised and entered over the pole, down below the antarctic jet stream appears strong zonal. Move forward in time over 2 weeks and the stratosphere winds almost disappear completely from the Antarctic land / ice mass and seem to move towards the equatorial regions and strengthen there. The jet stream weakens and starts to meander. As this all happens you can see the Artic Stratosphere winds start to buckle presummably due to them also being dragged toward the equator due to atmospheric momentum strengthening the equatorial winds? 

Are these conditions typical for a Southern Hemisphere at this period of the year?

 

Images below are for the 17th of January then the 24th, then the current day and lastly the projected conditions for the 4th of February

Again the 17th of January, then the current day and then the projected conditions for the 4th of Feb

And same again for these images.

 

[Kentish Kiwi]

9 minutes ago, ghoneym said:

Are these conditions typical for a Southern Hemisphere at this period of the year?

Unsure how relevant this is, but it may be worth noting that New Zealand has just experienced its warmest month on record, and might be on track for its warmest summer on record if February continues the trend.

[Nick F]

Anthony Masiello illustrates nicely the wave breaking over Scandi, GIN corridor and Barents Sea aka wave no. 2 - to which the models have been indicating may split the vortex.

 

[KyleHenry]

1 hour ago, Glacier Point said:

This feels like a long time ago now.

GFS advertising around the 13th February as key date. That's 36 days after Indian Ocean coupled convective wave passage, so the timeline bang on and yet again another example of the slow time scales for stratospheric - tropospheric events.

Who is willing to predict the NH Tropospheric scatter from this reversal. If the GFS is reading to split correctly and both lobes are hit with down welling it is effectively a continuous atmospheric shotgun blast. 

[mountain shadow]

29 minutes ago, Nick F said:

Anthony Masiello illustrates nicely the wave breaking over Scandi, GIN corridor and Barents Sea aka wave no. 2 - to which the models have been indicating may split the vortex.

 

Nick,

Given the progged cold spell next week is occurring before any stratospheric impacts, would you think that any model output showing a breakdown of the cold in the T+240 area is probably not to be trusted?

In other words, the cold spell starting next week could be quite long lived?

[Interitus]

Just minded that GFS/GEFS forecasts have been shown to have a bias towards the earliness and strength of warmings (where's @Recretos?) and at the moment they are showing greater wave heights and wind deceleration than ECM & GEOS for same forecast times (though more recent runs of course).

Of closest analogues for 30mb temperature gradient (MERRA2 data) to GEOS forecast for 8th Feb -

21/02/05 gradient reversal 5 days - was too weak, second gr 19 days with eventual wind reversal also 19 days

13/01/87 gr 5 days, wr 10 days

15/02/79 gr 6 days, wr 7 days

13/02/07 perhaps the closest analogue for a range of metrics, gr 10 days, wr 11 days

Gradient reversal typically occurs ahead of potential wind reversal, the earliest SSW from these instances would be 15th.

[bluearmy]

1 hour ago, mountain shadow said:

Nick,

Given the progged cold spell next week is occurring before any stratospheric impacts, would you think that any model output showing a breakdown of the cold in the T+240 area is probably not to be trusted?

In other words, the cold spell starting next week could be quite long lived?

An SSW may not have any immediate impact in the trop and any quick trop response may not affect nw Europe anyway. 

[karlos1983]

2 minutes ago, bluearmy said:

An SSW may not have any immediate impact in the trop and any quick trop response may not affect nw Europe anyway. 

Hi BA, is that a generalised statement, or due to thoughts on how the split is being forecast?

TIA

Karlos

[bluearmy]

Just now, karlos1983 said:

Hi BA, is that a generalised statement, or due to thoughts on how the split is being forecast?

TIA

Karlos

Generalised 

[Interitus]

Case in point, see the Andrea Lang vortex forecast charts - from today's 00z the GEFS splits the vortex in advance of the GFS with mean wind reversal at 65°N 2 days earlier -

http://www.atmos.albany.edu/facstaff/andrea/webmaps/GFSellipseFcast.html

http://www.atmos.albany.edu/facstaff/andrea/webmaps/GEFSellipseFcast.html

 

[Nick F]

3 hours ago, mountain shadow said:

Nick,

Given the progged cold spell next week is occurring before any stratospheric impacts, would you think that any model output showing a breakdown of the cold in the T+240 area is probably not to be trusted?

In other words, the cold spell starting next week could be quite long lived?

Looking at the forecast GPH/temps for the different pressure levels of the stratosphere and upper troposphere, to me looks like the forecast strat warming over Scandi is linked with the trop blocking developing over Nern Scandi and Barents next week, before any impacts from the potential SSW / SPV split.

Whether the block to the NE will hold out for any reinforcement later in the month from a SSW remains to seen though, have yet to see any other models back GEFS/GFS for the SPV split as well.

[Interitus]

5 hours ago, Interitus said:

Just minded that GFS/GEFS forecasts have been shown to have a bias towards the earliness and strength of warmings (where's @Recretos?) and at the moment they are showing greater wave heights and wind deceleration than ECM & GEOS for same forecast times (though more recent runs of course).

Latest GEOS to 9th has increased wave 2 heights but no significant wind or temperature changes by this time. However, this twitter thread started by Amy Butler reiterating the GFS differences to GEOS & ECM suggests that changes are afoot in these other models also -

 

Edited February 1, 2018 by Interitus

[Interitus]

Fantastic animation downthread showing a plume of low pv air from the subtropics advected northwards and hurled at the vortex at time of splitting

Edited February 1, 2018 by Interitus

[Snowy L]

2 hours ago, Nick F said:

Looking at the forecast GPH/temps for the different pressure levels of the stratosphere and upper troposphere, to me looks like the forecast strat warming over Scandi is linked with the trop blocking developing over Nern Scandi and Barents next week, before any impacts from the potential SSW / SPV split.

Whether the block to the NE will hold out for any reinforcement later in the month from a SSW remains to seen though, have yet to see any other models back GEFS/GFS for the SPV split as well.

Would also explain the ridiculous strength of the vortex in Greenland/East Canada and the widespread -40 uppers in those regions. The vortex gains strength as it is squezzed and contracted by warmings. Pressure at the center of the vortex is expected to lower further sometime next week before the warmings finally take their toll. Purely hypothetical now, but looking at the strat charts after the forecast split, the biggest lobe of the vortex stays over Greenland too, so I think we will have a January 2013 type tropospheric pattern where the atlantic is still very active but Scandi heights manage to stop the lows one week, but fail to the next week.

[Allseasons-Si]

Nice

i don't know much about the strat/trop but i do know these tweets look good to me.

 

[Nick F]

12z EC heading for the split at day 10

[Daniel*]

I don’t think I’ve seen anything like this incredible, I’m sure there would be a ‘quick’ response.

@Recretos where you been? your absence is sad to see.

Edited February 1, 2018 by Daniel*