SSW on the 3rd?

[scottmartin49]

[donsutherland1]

I have my doubts, especially as the high and relative warmth are not stacked at 1 mb and 5 mb. This look has appeared a number of times since late November. Each time, the area of warming was shallow. No SSW materialized.

 

Far more importantly, Dr. Judah Cohen doubts that there will be an early January SSW. He thinks there's a better chance in late January.

 

Of course, SSWs are very difficult to predict, so all of this is speculative.

[JoMo]

Still chasing the mythical SSW? I gave up on that and Dr. Cohen in mid-December after his predictions kept ending up wrong. 

[scottmartin49]

I have my doubts, especially as the high and relative warmth are not stacked at 1 mb and 5 mb. This look has appeared a number of times since late November. Each time, the area of warming was shallow. No SSW materialized.

 

Ah, the stacking! Forgot about that...

 

Thanks, Don- more experience is what I was looking for.

[donsutherland1]

Ah, the stacking! Forgot about that...

 

Thanks, Don- more experience is what I was looking for.

No problem. Of course, 10 mb is the standard location at which one looks. Even in such cases of stacking (which hints at a large-scale warming), there is still a lot of uncertainty. Forecasting skill for SSWs is low. Moreover, there is, on average less than one such event each year. Hopefully, forecasting skill will improve in the future.

[donsutherland1]

On a more positive note, I just saw that Mike Ventrice posted an EPS ensemble chart of a possible 10 mb warming. That chart looks far more impressive than the GFS idea, so we'll see what happens.

[GaWx]

  I recently did a study of the dates of the 11 strongest SSW's. Criteria: strong SSW based on a warming to an anomaly of +28+ as per this:

 

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

 

I'm sure others would have different criteria/sources.

 

Dates in calendar order of the strongest SSW's since 1979 starting with Dec.: 7, 12, 17, 23, 23, 29, Jan: 1, 9, 14, 22; Feb.: 9

 

 So, based on this list, late Jan. would be kind of on the late side to get a strong SSW though still quite doable.

 

 Regardless, though it would be helpful, a strong SSW is absolutely not required to get a strong -AO (about half the sub -2 AO months had none that month to two months earlier).

[Weathergun]

Euro forecast to 12/29. Temps are rising, zonal winds dropping. But nothing huge at 10hpa yet:

 

 

[Amped]

Kind of unusual to see the max wave2 height  at 25mb.

 

 

Zonal winds still haven't reversed and EP flux vectors don't go poleward until day 10.

[DTWXRISK]

 not happening... 

[weatherdude]

https://www.aer.com/science-research/climate-weather/arctic-oscillation

[donsutherland1]

https://www.aer.com/science-research/climate-weather/arctic-oscillation

The prior blog entry dismissed the early January SSW (I mentioned it in post #2 in this thread) and favored later in the month. Now the current blog favors the early event.

 

Unfortunately, as things currently stand, barring some meaningful changes, the forthcoming event will likely wind up having been a minor to perhaps moderate warming event. The Berlin site (http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html) isn't posting the images for the zonal wind and fluxes or temperature and temperature differences, so some important pieces of data aren't available.

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2014.gif

 

For purposes of comparison, January 2009 and 2013 featured SSW events.

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2009.gif

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2013.gif

[weatherdude]

The prior blog entry dismissed the early January SSW (I mentioned it in post #2 in this thread) and favored later in the month. Now the current blog favors the early event.

 

Unfortunately, as things currently stand, barring some meaningful changes, the forthcoming event will likely wind up having been a minor to perhaps moderate warming event. The Berlin site (http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html) isn't posting the images for the zonal wind and fluxes or temperature and temperature differences, so some important pieces of data aren't available.

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2014.gif

 

For purposes of comparison, January 2009 and 2013 featured SSW events.

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2009.gif

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_ALL_NH_2013.gif

 

So back on December 19th, you believed that Dr. Cohen's opinion was most important, and now you are disagreeing with his assertions from two days ago?

 

Dr. Cohen, et al:  "The strong wave driving will result in a sudden stratospheric warming (SSW) and a splitting of the polar vortex.  In the near term this will help build ridging across Western North America and cold temperatures across the United States after the New Year." 

[donsutherland1]

So back on December 19th, you believed that Dr. Cohen's opinion was most important, and now you are disagreeing with his assertions from two days ago?

 

Dr. Cohen, et al:  "The strong wave driving will result in a sudden stratospheric warming (SSW) and a splitting of the polar vortex.  In the near term this will help build ridging across Western North America and cold temperatures across the United States after the New Year." 

Not really. I view is unchanged: one should be very cautious about proclaiming an imminent SSW event until there is consistent strong data for such an assertion. Forecasting SSWs is very difficult (at least according to the literature).

 

My point at the time of the earlier blog entry was that I had doubts about a SSW event, as the data at varying levels (pressure and temperature) suggested a shallow and weaker event. Moreover, I noted that such a situation has appeared a number of times on the guidance since late November. Each time, the area of warming was shallow and no SSW materialized. Most warmings at some level of the stratosphere do not result in SSW events.

 

I found the earlier blog entry useful, because it took a more cautious stance on a difficult-to-forecast event. As I noted then, SSWs are very difficult to predict (at least according to the literature). In the very near-term, they become more predictable, but even then there is uncertainty. There's no assurance that we'll see a SSW event this winter, though such events are a little more common during El Niño events. Nevertheless, the average is still less than one per winter even during El Niño events.

 

All said, the measure of caution from the earlier blog entry would have worked well, especially as only a single run of the ECMWF showed anything approaching a full-fledged SSW (albeit falling somewhat short, as well). This analogy might not fit perfectly, but is applicable in this situation: Would one forecast a major East Coast snowstorm, for example, if a single run of the ECMWF showed such an outcome approximately 120-144 hours away, despite all the other runs showing a lesser event? Given the difficulty of medium-range forecasts regarding possible SSW events, there's too much uncertainty, at least for me, to embrace the most aggressive model run. I'd want to see additional ones.

 

Since then, the subsequent runs of the ECMWF have consistently shown only a minor or moderate event in line with the earlier runs (with the exception of the single aggressive one). Now that the event is unfolding, it can be noted that the actual warming that has occurred so far is not very impressive.

 

IMO, the EPO, which went negative on 12/26 and is now strongly negative (prior to the minor or moderate stratospheric warming event in question) rapidly replenished cold in North America and will play the lead role in the cold start to January.

 

Finally, it should be noted that I admire and respect Dr. Cohen and his work. That I thought the last blog entry was too aggressive does not change that.

[Absolute Humidity]

"Finally, it should be noted that I admire and respect Dr. Cohen and his work. That I thought the last blog entry was too aggressive does not change that."

Very true and can't blame him either for his wording, he needs this to occur for any hope of SAI -AO verification this year.

[donsutherland1]

"Finally, it should be noted that I admire and respect Dr. Cohen and his work. That I thought the last blog entry was too aggressive does not change that."

Very true and can't blame him either for his wording, he needs this to occur for any hope of SAI -AO verification this year.

I hope that AO turns strongly negative shortly after mid-month, as happened in 2005 regardless of whether there is a SSW event. It would be a real loss if the SAI is found not to be as strong a predictor as it initially appeared, not just for all the work that has been put in, but for long-range seasonal forecasting, as well. Nevertheless, the longer-range is extremely challenging. One can only admire the scientists who put in so much research to try to push the boundaries of understanding.

[Absolute Humidity]

I hope that AO turns strongly negative shortly after mid-month, as happened in 2005 regardless of whether there is a SSW event. It would be a real loss if the SAI is found not to be as strong a predictor as it initially appeared, not just for all the work that has been put in, but for long-range seasonal forecasting, as well. Nevertheless, the longer-range is extremely challenging. One can only admire the scientists who put in so much research to try to push the boundaries of understanding.

Such turn around would surely vindicate (not that Cohen's work needs vindication) and likely save winter. The 18Z and 0Z GFS certainly agrees.

[Rainman]

At this point, is it not safe to say that even if one develops that it has nothing to do with October snow cover? Wave driving fell off a cliff in December and the stratosphere completely recovered. What happens now has no connection to October forcing anymore. If an SSW happens or if the AO goes strongly negative, it will vindicate his work statistically, but not meaningfully. It will be a coinicdence.

[Isotherm]

On the December 31st run of the ECMWF valid 240hrs/Jan 10th, it forecasted the reconsolidation of the vortex at 10mb. The latest run from January 1st, continues to split the 10mb vortex by D5, and now keeps it split through January 10th, day 9. Reconsolidates by January 11th, D10, but the ECMWF is delaying the reconsolidation compared to the previous run. This may not mean much at the end of the day, but it's also possible that the split / 10mb warming gradually becomes stronger as we move up in time. Even upon reconsolidation on January 11th, the vortex remains highly elongated / disturbed with significant warming, implicating that another split might occur shortly thereafter.

 

Point being, I'd say the probabilities are still quite high for a sudden warming event within the next 7-14 days. Whether it achieves major classification is tough to say at this point.

[Isotherm]

At this point, is it not safe to say that even if one develops that it has nothing to do with October snow cover? Wave driving fell off a cliff in December and the stratosphere completely recovered. What happens now has no connection to October forcing anymore. If an SSW happens or if the AO goes strongly negative, it will vindicate his work statistically, but not meaningfully. It will be a coinicdence.

 

 

 

Disagree. In the typical / average high snow cover case, stratospheric perturbation would occur in the first half of winter, with tropospheric H5 anomalies not being significantly affected until sometime in January or even later. So I think if a strongly negative AO does in fact finally develop for the second half of meteorological winter, it will be a solid verification for the theory. With that being said, I don't think snow cover is the only factor for SSW events for sure. The -QBO forcing increases the potential for an event as well.

 

[donsutherland1]

The stratospheric warming proved to be a moderate event. It didn't approach a major one. Moreover, the last data showed that the stratosphere was beginning to cool. That trend should continue if the ECMWF forecasts are accurate.

 

[Roger Smith]

  I recently did a study of the dates of the 11 strongest SSW's. Criteria: strong SSW based on a warming to an anomaly of +28+ as per this:

 

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

 

I'm sure others would have different criteria/sources.

 

Dates in calendar order of the strongest SSW's since 1979 starting with Dec.: 7, 12, 17, 23, 23, 29, Jan: 1, 9, 14, 22; Feb.: 9

 

 So, based on this list, late Jan. would be kind of on the late side to get a strong SSW though still quite doable.

 

 Regardless, though it would be helpful, a strong SSW is absolutely not required to get a strong -AO (about half the sub -2 AO months had none that month to two months earlier).

 I wonder if you could post those eleven dates in terms of what years they happened. Any thoughts about unusual or different characteristics (slow, fast, where it began etc) might be of interest. Thanks.

[Rjay]

http://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-96.51,72.30,462

[Rainman]

Disagree. In the typical / average high snow cover case, stratospheric perturbation would occur in the first half of winter, with tropospheric H5 anomalies not being significantly affected until sometime in January or even later. So I think if a strongly negative AO does in fact finally develop for the second half of meteorological winter, it will be a solid verification for the theory. With that being said, I don't think snow cover is the only factor for SSW events for sure. The -QBO forcing increases the potential for an event as well.

There was no Dec wave driving. October snow cover isn't doing anything right now nor did it set anything in motion that is currently in motion.

[Isotherm]

There was no Dec wave driving. October snow cover isn't doing anything right now nor did it set anything in motion that is currently in motion.

 

 

We had a very strong spike of wave activity flux in late November which IMO was largely due to the rapid snow cover advance and favorable tropospheric regime of upward propagating Rossby waves. December saw a gradual increase in heat flux. I think what prevented stronger wave driving in December was a poor tropospheric ridge / trough orientation in conjunction with heightened solar activity which tends to promote a tighter stratospheric vortex. But I disagree that wave driving was absent and/or unrelated to the October snow advance up to this point in time. If there was no wave driving, you would have seen heat flux persistently below the mean over the past 45 days which we clearly didn't have.

 

 

 

And we begin 2015 with high heat flux.

 

 

[GaWx]

 I wonder if you could post those eleven dates in terms of what years they happened. Any thoughts about unusual or different characteristics (slow, fast, where it began etc) might be of interest. Thanks.

 

Roger,

 I almost missed this post:

 

1/22/09, 1/9/06, 12/23/03, 12/29/02, 12/23/01, 12/12/00, 12/17/98, 1/14/92, 2/9/90, 12/7/87, 1/1/85

[weatherdude]

Updated through today:

[GaWx]

^Wow, impressive warming at 10 mb! Some progs had a peak around now at certain levels. I'm waiting for the following link to finally update for early Jan:

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_MEAN_JFM_NH_2015.gif

[weatherdude]

^Wow, impressive warming at 10 mb! Some progs had a peak around now at certain levels. I'm waiting for the following link to finally update for early Jan:

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_MEAN_JFM_NH_2015.gif

 

Yes...lots of missing data today...tell me its not another hack...ARGGHHH

[wxmx]

Temps are missing, but Wind is available: