yes the PV has split -

[DTWXRISK]

 REALLY  FOLKS??  

 

REALLY?

 

[leo2000]

 REALLY  FOLKS??  

 

REALLY?

 

t-23.jpg

 I agree with you DT, just a lot of misleading information going on. If I am correct a split brings about a ssw event?. If so, that usually lasts for a long long time. 

[Jim Marusak]

just looked at the 500 hemispheric loop week or so back from the latest. You're right on the split. it also looks like the PV was weakening the last few days, but the trigger to the split was the Icelandic bomb. now just a matter of how cold until we can re-combine them, right DT?

[donsutherland1]

The polar vortex has clearly split at the tropospheric level. Sometimes what happens in the troposphere works its way up to the stratosphere and vice versa. For now, this split is just another ingredient strengthening the case that we're in a transition away from the brutally warm December pattern toward what could become a generally cold one with snowfall opportunities.

 

I'll also add that if a SSW event occurs (none appears on the guidance right now), it would much more likely be a bottom-up response to the deep blocking that is forecast on the GEFS and EPS, even if it propagates downward afterward.

[ayuud11]

The polar vortex has clearly split at the tropospheric level. Sometimes what happens in the troposphere works its way up to the stratosphere and vice versa. For now, this split is just another ingredient strengthening the case that we're in a transition away from the brutally warm December pattern toward what could become a generally cold one with snowfall opportunities.

 

I'll also add that if a SSW event occurs (none appears on the guidance right now), it would much more likely be a bottom-up response to the deep blocking that is forecast on the GEFS and EPS, even if it propagates downward afterward.

 

STRAT_K (02/02-02/07)

In this week’s forecast, we are forecasting a new event, named as STRAT_K, to occur during the period of 02/02-02/07. STRAT_K appears to be a major aftermath PULSE event right after the major breakup of the stratospheric polar vortex. The associated cold air outbreaks will occur over both North American and Eurasian continents.

 

The stratospheric polar vortex may break completely following STRAT_J (in the last week of January, 2016).

 

We are continuing to forecast that the stratospheric polar vortex will be weakened significantly twice in the month of January of 2016, one after STRAT_H and the other after STRAT_J. The latest forecasts indicate that STRAT_H will be mainly driven by stronger wave activities of wave number 2. The warm air transported by wave number 2 will not only fill in the polar stratosphere with anomalously large amount of warm air but also split the stratospheric polar vortex into two.

STRAT_J is also a strong PULSE event due to stronger wave activities of wave number 1 and 2. STRAT_J will give the already weakened vortex another powerful punch, leading to a breakup of polar vortex in the period 01/27-02/03. As forecasted above, there will be a major PLUSE event right after the breakup of the polar vortex. As a result, the polar vortex may not be rebuilt till middle of February. Associated with STRAT_H, J, and K are continental-scale cold air outbreaks over both continents.

http://www.amccao.com/

[donsutherland1]

http://www.amccao.com/

Interesting, but I don't know anything about this group.

 

While the group has a chart for Arctic air transport (trillions of tons per day), it provides no definitions of how it defines Arctic air masses, etc. Saying a cold air mass will move into Eurasia doesn't provide much information, as the enormous Eurasian landmass typically sees such air masses on a regular basis, though in differing regions. 

 

If one looks closely at the details related to the cold air transport idea, it appears that verification is poor despite what the group's graph shows (and that raises questions of its own).

 

For example, 12/21 was "verified" to have among the highest amounts of Arctic air being transported into the middle latitudes while 12/30 had among the lowest. Yet, if one examines temperature anomalies for those dates between 30N and 50N (boundaries offered because the group doesn't actually specify middle latitudes) one finds about the same amount of below normal temperatures during both dates.

 

IMO, if the group seeks to make a contribution to forecasting, it needs to become specific in its definitions, replace trillions of tons of Arctic air with more conventional measures e.g., geographic coverage of cold anomalies, etc. It also needs to begin to verify its forecasts.

 

In the end, I'm not sure whether this group's ideas have merit. At a minimum, it has a lot of work to do to gain credibility starting with specification of its terms and actual verification of its forecasts using reliable datasets e.g., NCEP.

[Amped]

When people said "The PV hasn't split" they were talking about the stratospheric vortex, not the tropospheric one.

 

So we all agree:

Troposphere 500mb vortex:      Got sliced and diced and tossed about.

Stratospheric 10mb  vortex:      Strong as ever and has hardly budged

 

Misunderstanding clarified, next.

[Ginx snewx]

Interesting, but I don't know anything about this group.

While the group has a chart for Arctic air transport (trillions of tons per day), it provides no definitions of how it defines Arctic air masses, etc. Saying a cold air mass will move into Eurasia doesn't provide much information, as the enormous Eurasian landmass typically sees such air masses on a regular basis, though in differing regions.

If one looks closely at the details related to the cold air transport idea, it appears that verification is poor despite what the group's graph shows (and that raises questions of its own).

For example, 12/21 was "verified" to have among the highest amounts of Arctic air being transported into the middle latitudes while 12/30 had among the lowest. Yet, if one examines temperature anomalies for those dates between 30N and 50N (boundaries offered because the group doesn't actually specify middle latitudes) one finds about the same amount of below normal temperatures during both dates.

IMO, if the group seeks to make a contribution to forecasting, it needs to become specific in its definitions, replace trillions of tons of Arctic air with more conventional measures e.g., geographic coverage of cold anomalies, etc. It also needs to begin to verify its forecasts.

In the end, I'm not sure whether this group's ideas have merit. At a minimum, it has a lot of work to do to gain credibility starting with specification of its terms and actual verification of its forecasts using reliable datasets e.g., NCEP.

http://www.amccao.com/#!underlying-science/c24gx

[DTWXRISK]

 then perhaps those  making such a  argument should of  stated it as such?
 after all the  REASON why the PV split has recvd so much attention was  that it signal a pattern change


 

When people said "The PV hasn't split" they were talking about the stratospheric vortex, not the tropospheric one.

 

So we all agree:

Troposphere 500mb vortex:      Got sliced and diced and tossed about.

Stratospheric 10mb  vortex:      Strong as ever and has hardly budged

 

Misunderstanding clarified, next.

[donsutherland1]

http://www.amccao.com/#!underlying-science/c24gx

Thanks Ginx snewx. While the underlying science seems to have some merit, the group's forecasts are overly general and not verified. Indeed scanning the forecasts around a few notable dates for the last winter and so far this one, argues that verification is poor. 

 

For example, from the 11/26-12/04/2014 discussion:

 

STRAT_D1, first forecasted last week, is still expected to peak between December 18 -24 with peak intensity of more than 700 billion tons per day transported into the polar stratosphere. Therefore, this is going to be a strong circulation event.  Associated with STRAT_D1 are wintery precipitation and major cold air outbreaks over a large portion areas over the east coast of North America and East Asia, and Europe in the week before Christmas, which has a high potential in impacting pre-holiday travel.

 

Actual outcome:

 

 

And then from this winter:

 

STRAT_F (12/19-12/24), is also expected to be on time, which was first forecasted on November 12. STRAT_F is expected to be a long-lasting stratospheric pulse event, which could lead to major cold air outbreaks over both North American and Eurasian continents, which may affect the Christmas holiday travelers.

 

Actual outcomes:

 

 

 

The excessive warmth on both continents around the Christmas holiday event speaks for itself.

 

In sum, the group needs to verify its forecasts. At least several high profile forecasts were far off the mark. Unless the group begins to verify its forecasts, it may be unaware of whether its forecasts have merit. IMO, from the randomly checking a few of the forecasts from winters 2014-15 and the early part of 2015-16, there seems to be little skill.

[WXeastern]

Why worry more about the stratospheric PV than the tropospheric one when the tropospheric one has more impacts on our weather?

[ayuud11]

Thanks Ginx snewx. While the underlying science seems to have some merit, the group's forecasts are overly general and not verified. Indeed scanning the forecasts around a few notable dates for the last winter and so far this one, argues that verification is poor. 

 

For example, from the 11/26-12/04/2014 discussion:

 

STRAT_D1, first forecasted last week, is still expected to peak between December 18 -24 with peak intensity of more than 700 billion tons per day transported into the polar stratosphere. Therefore, this is going to be a strong circulation event.  Associated with STRAT_D1 are wintery precipitation and major cold air outbreaks over a large portion areas over the east coast of North America and East Asia, and Europe in the week before Christmas, which has a high potential in impacting pre-holiday travel.

 

Actual outcome:

 

 

And then from this winter:

 

STRAT_F (12/19-12/24), is also expected to be on time, which was first forecasted on November 12. STRAT_F is expected to be a long-lasting stratospheric pulse event, which could lead to major cold air outbreaks over both North American and Eurasian continents, which may affect the Christmas holiday travelers.

 

Actual outcomes:

 

 

 

 

The excessive warmth on both con

tinents around the Christmas holiday event speaks for itself.

 

In sum, the group needs to verify its forecasts. At least several high profile forecasts were far off the mark. Unless the group begins to verify its forecasts, it may be unaware of whether its forecasts have merit. IMO, from the randomly checking a few of the forecasts from winters 2014-15 and the early part of 2015-16, there seems to be little skill.

It does look like their director Dr. Ming Cai wrote several articles in regards to the same subject, if you have subscription to the ams journals online database you can check it out there.

• Yu, Y-Y, M. Cai, R-C Ren, H. M. van den Dool, 2014: Relationship of Warm Air Mass Transport into Upper Polar Atmosphere and Cold Air Outbreaks in Winter. J. Atmos. Sci., 10.1175/JAS-D-14-0111.1.

• Cai, M., and C-S Shin, 2014: A Total Flow Perspective of Atmospheric Mass and Angular Momentum Circulations: Boreal Winter Mean State. J. Atmos. Sci., DOI:10.1175/JAS-D-13-0175.1.

• Zhang, Q., C-S Shin, H. van den Dool, and M. Cai, 2013: CFSv2 Prediction Skill of Stratospheric Anomalies.   Clim. Dyn. DOI:10.1007/s00382-013-1907-5.

• Ren, R-C and M. Cai, 2008: Meridional and downward propagation of atmospheric circulation anomalies.  Part II: Southern Hemisphere cold season variability. J. Atmos. Sci., 65, 2343-2359.

• Ren, R-C, and M. Cai, 2007: Meridional and vertical out-of-phase relationships of temperature anomalies associated with the NAM variability. Geophys. Res. Lett. , 34, L07704, doi:10.1029/2006GL028729.

• Cai, M., and R-C Ren, 2007: Meridional and downward propagation of atmospheric circulation anomalies.  Part I: Northern Hemisphere cold season variability.  J. Atmos. Sci., 64, 1880-1901.

[donsutherland1]

 

It does look like their director Dr. Ming Cai wrote several articles in regards to the same subject, if you have subscription to the ams journals online database you can check it out there.

• Yu, Y-Y, M. Cai, R-C Ren, H. M. van den Dool, 2014: Relationship of Warm Air Mass Transport into Upper Polar Atmosphere and Cold Air Outbreaks in Winter. J. Atmos. Sci., 10.1175/JAS-D-14-0111.1.

• Cai, M., and C-S Shin, 2014: A Total Flow Perspective of Atmospheric Mass and Angular Momentum Circulations: Boreal Winter Mean State. J. Atmos. Sci., DOI:10.1175/JAS-D-13-0175.1.

• Zhang, Q., C-S Shin, H. van den Dool, and M. Cai, 2013: CFSv2 Prediction Skill of Stratospheric Anomalies.   Clim. Dyn. DOI:10.1007/s00382-013-1907-5.

• Ren, R-C and M. Cai, 2008: Meridional and downward propagation of atmospheric circulation anomalies.  Part II: Southern Hemisphere cold season variability. J. Atmos. Sci., 65, 2343-2359.

• Ren, R-C, and M. Cai, 2007: Meridional and vertical out-of-phase relationships of temperature anomalies associated with the NAM variability. Geophys. Res. Lett. , 34, L07704, doi:10.1029/2006GL028729.

• Cai, M., and R-C Ren, 2007: Meridional and downward propagation of atmospheric circulation anomalies.  Part I: Northern Hemisphere cold season variability.  J. Atmos. Sci., 64, 1880-1901.

 

I will definitely see if I can get the articles. From Ginx snewx's link, I was able to learn more about the group. The transition from theory to operational forecasting can be challenging. At least from what I've seen more work remains to be done. There were some successes and also some big misses. Hopefully, over time, the forecasting skill will improve, as it would mark a pretty significant advance in subseasonal forecasting.

 

IMO, one has seen similar "growing pains" of sorts with the SAI, as the last two winters produced different outcomes from what had been expected in terms of the predominant state of the AO. This winter's outcome remains to be seen. Even if the SAI's correlation is weaker than initially thought, it can still add value, especially if additional variables are considered and added to the mix. I believe this year there has been a greater emphasis on sea ice than last winter. It's still too soon to be confident about what will wind up to be the predominant state of the AO, as we're only 35 days into meteorological winter and sustained strong blocking could well eliminate the positive average to date and also result in the majority of days seeing AO- values.

 

In any case, the long-range is extremely challenging to forecast. I strongly support the initiatives that are underway to improve such forecasts even if at least some of such initiatives are not yet ready for reliable operational forecasting. SAI is probably farther along than this group's methodology, but still in need of refinement.

 

In any case, I hope that my thoughts that the group's work does not seem to provide much skill right now is not seen as overly negative toward its efforts. It just reflects the current state of where things stand right now. I do think more rigorous and specific verification could begin to lead to stronger conclusions related to the methodology's performance to date, as well as necessary adjustments to that methodology. Maybe the whole body of evidence will be evaluated at some point in time and then we'll learn more once that happens.

[scottmartin49]

Why worry more about the stratospheric PV than the tropospheric one when the tropospheric one has more impacts on our weather?

Maximal heat dispersal versus simple displacement; http://www.aer.com/science-research/climate-weather/arctic-oscillation