Twin Cities Experiences Mini-Boulder: #WeatherWhiplash

Over the last 48 hours or so a weather system slowly moved across the southern Dakotas, Nebraska, Iowa, and Minnesota. It was in part shaped and positioned by the jet stream, and it was so slow moving because of the unusually curved nature of the jet stream. This is very much like what happened a few weeks ago in Colorado, but with less of an effect. Nonetheless, there was a damage and injury causing tornado in Nebraska and Iowa, and nine inches of rain in Winona, where there was some very inconvenient flooding. The huge multi-foot snow storm in the Dakotas was part of this system. People died in that storm.

And yes, folks, this is global warming. A warming earth meant a warming Arctic. The Arctic warmed to a certain point and then runaway feedbacks caused the Arctic to suddenly grow much much warmer than it was, and more importantly, the Arctic became relatively warmer compared to the rest of the plant, a phenomenon called "Arctic Amplification." This changed the way extra heat in equatorial regions moves towards the north pole, and this in turn caused the jet streams to change their configuration so they get all bunched up (in these things called "Rossby Waves") which causes large weather systems, usually either very dry or very wet, to stall in place or move very slowly. We were getting a mini-flash drought while Boulder and environs were getting flooded. And now we are getting flooded while our neighbors are being buried under three feet of snow. The rapid back and forth between extremes, and the more extreme nature of the extremes, has been termed "Weather Whiplash" by meteorologists.

Welcome to the new normal! Most of the time it will just mean a change in when you water your lawn. Other times it will mean footing the bill to rebuild all the roads, and a death here and there. Sometimes it will mean much more. Stay tuned.

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In 2007, Winona was nailed by over a foot of rain within 24 hours. The exrtreme is becoming normal.

New normal?…

"... key statements from the IPCC AR5 WGI Chapter 2 on extremes"

"Precipitation extremes also appear to be increasing, but there is large spatial variability"

"In summary, there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale."

That's one of the reasons we are asking the IPCC process to be sped up. The AA-jet stream effects are very recent (in their frequency). There isn't any argument that they are not real, and are not the reason for the wacky weather. There is a very good argument that AA causes the Rossby waves. We know for certain that the AA is caused by sea ice collapse and decrease in snow and ice cover, and we know this is caused by AGW.

I'm not sure if speeding up the IPCC process is the answer. To me the answer is to wait decades to see if observations match predictions. Climate science by it's very nature appears to be science in slow motion.
Sometimes a 30yr signal will disappear if you go back far enough. For example, using the 20th Century Reanalysis V2 U-wind and V-wind datasets, I calculated the average yearly heading of the winds between 40N and 50N. The recent headings have become more meridional compared to the 1960's, but are similar to the early 20th century. Just an amateur computation with potentially lots of uncontrolled variables and resulting biases. I still think it would be a challenge though for a professional to falsify the hypothesis that today's Rossby waves are similar to those in the early 20th century.

" Just an amateur computation with potentially lots of uncontrolled variables and resulting biases."


Indeed the chances that an amateur finds a spurious signal is greater than would a pro, so I won't state that what I found is the gospel. In this case, however, there seems to be corroborating evidence.
I performed a separate computation of NH summertime land temperature variability from 1900 to present using GISTEMP data. This was similar to Dr. Hansen's probability density plots published last year, except my line plots were of standard deviation for all 11yr rolling periods. My plot showed the same as Dr. Hansen's for the 1950-present periods; lowest variability in the 1960's, highest in the present. However, my extended plots showed the early 20th century variability was similar to the present. I also limited my computations to those grid cells reporting at both the beginning and end of the periods and the same pattern was found.
So until a profession study is done dating back to 1900, I'll stick to my opinion. The new normal in weather variability looks a lot like the old normal. Hopefully a professional study will be performed in the not so distant future. Science must hate a vacuum. Maybe the IPCC community can prioritize this?

I'm sure there will be such a study, I think it is being worked on. Meanwhile we have this:

Petoukhov, V., Rahmstorf, S., Petri, S., & Schellnhuber, H. (2013). Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes Proceedings of the National Academy of Sciences, 110 (14), 5336-5341 DOI: 10.1073/pnas.1222000110

which I summarize here:…

and here:…

It is quite possible that there are periods of more curvy jets, and you may be on to something. But you can't ignore the physics. Arctic Amplification is a thing, and it seems to have a cause (AGW) and an effect (Rossby waves being more common).