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Author Topic: Atmospheric connections, structure, and long range weather forecasting  (Read 257 times)

sark

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Opening this new thread in response to long range weather forecasting discussions in the main melt season thread.  From pages 14-15..  Anything goes.

I would propose a 'Long Term Weather Forcast Thread'.

There are obviously people not interested in this kind of content. By having it in a separate thread they could easily avoid it. And the ones interested wouldn't feel restricted and could post freely.

and I'll open with my "Autosquint" 500mb anomaly 21 day comp mean, with one of today's GFS runs tacked on to the end

This could use a synopsis of the SSW style final warming of 2019, with the ensuing coupled barotropic polar atmosphere that has beaten into the high north.  Analogues, models, papers

I feel like it'll calm down once the snow melts, but 2019 is a continuation of a really disappointing trend.  I spent 3 days curled in a ball last week.  I'm not a scientist and I don't play one so I can say this: The polar cell is failing.  It has been for years.  The trend is not your friend, but it's still a trend... and the emerging trend has to be indicative of the drastic, faster-than-expected breakdown of the polar cell.

What the hell is even happening?
« Last Edit: May 19, 2019, 12:37:59 AM by sark »
I am not a scientist

FishOutofWater

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I wrote about what's happening over at a fading political blog the other day. Intense end warmings in the stratosphere have consequences. The sudden warming of the region from 60N to the pole from the surface to the top of the stratosphere is what I was referring to by the description "atmospheric convulsion." There's likely to be a horrific tornado outbreak on Monday and Tuesday as the storm that's now giving California a very late soaking reforms on the east side of the rocky mountains.

Zach Labe understands the physics of this situation better than I do - he's studying it for an advanced degree. I doubt he's reading this but I wouldn't mind being corrected if I made a mistake.

https://www.dailykos.com/stories/2019/5/15/1857911/-Atmospheric-Convulsion-Will-Cause-Historic-Disasters-of-Arctic-Melt-U-S-Storms-Next-Week

vox_mundi

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Long-term weather starts to get into tele-connections ...

Hot Arctic and a Chill in the Northeast: What’s Behind the Gloomy Spring Weather?
https://blog.ucsusa.org/brenda-ekwurzel/hot-arctic-and-a-chill-in-the-northeast-whats-behind-the-gloomy-spring-weather

... It may seem counter-intuitive, but the story of the strange weather unfolding this spring in the US is related in part to snow last October in Eurasia. This indicator—the Eurasian October snow cover extent indicator—is proving to be worthy of additional attention by US weather geeks. The good news is that the scientists who were paying attention to the Eurasia snow extent behavior during October, along with a host of other indicators, gave advanced warning of the emerging US winter and spring weather pattern for 2018/2019. 

... I encourage those who want to know, to spend some time clicking on the links here or links in earlier blogs that point to even more information (see here, here, here, and here). These describe the details regarding how Arctic sea ice decline, particularly in the Barents-Kara sea ice, north of Scandinavia and Russia, contributes to ocean and atmosphere behavior. Which contributes to Eurasian snow cover extent behavior. And ultimately a wavy jet stream with episodic cold outbreaks over winter and spring in the Northern Hemisphere, including the US.

... Here is an example of the science as Judah Cohen explains, “There is a growing consensus that it is Barents-Kara sea ice in the late fall and early winter that has the greatest impact across Eurasia.  Therefore, low Barents-Kara sea ice in November for example, favors a strengthened Siberian high, increased poleward heat flux, a weak stratospheric Polar Vortex and finally a negative Arctic Oscillation. An important point regarding the Siberian high is that it strengthens or expands northwest of the climatological center.  For low snow cover and/or high sea ice the opposite occurs.”  Translation, a weakened polar vortex means more cold outbreaks deep into US territory like this past winter and spring. ...

North Atlantic Warming Hole Impacts Jet Stream
https://phys.org/news/2019-04-north-atlantic-hole-impacts-jet.html

The North Atlantic warming hole (NAWH), a region of reduced warming located in the North Atlantic Ocean, significantly affects the North Atlantic jet stream in climate simulations of the future, according to a team of researchers.

... To investigate how the development of the NAWH impacts the jet stream, the team conducted a series of large-ensemble, atmospheric model experiments in the CESM with prescribed SST and sea ice levels over three different time periods.

Their results indicate that the NAWH plays an important role in midlatitude atmospheric circulation changes in the model's future climate simulations.

"We found that it's really quite important for that region," said Gervais. "The NAWH seems to be elongating the jet even further and shifting it a little bit north. Instead of just thinking about how the tropics and arctic amplification are influencing the jet, we now also need to think about how this warming hole is going to influence the jet. These local changes in the North Atlantic jet are of a similar magnitude to the full climate-change response in the region, indicating that the North Atlantic warming hole could be an important additional factor in the tug of war on midlatitude circulation, that has received little attention."

Melissa Gervais et al, Impacts of the North Atlantic Warming Hole in Future Climate Projections: Mean Atmospheric Circulation and the North Atlantic jet, Journal of Climate (2019)
https://journals.ametsoc.org/doi/10.1175/JCLI-D-18-0647.1
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late