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Climate change and severe tornado outbreaks (1 Viewer)

Is climate change leading to fewer big outbreaks?


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Severe Tornado Outbreaks
defined as outbreaks with:
≥ 2 long-tracking tornado families
each family w/ ≥ 2 (E)F3+ tornadoes
each of these w/ path lengths ≥ 25 mi
these families over wide geographic area

Examples:
19–20 February 1884
28 March 1890
29–30 April 1909
28 March 1920
9 May 1927
21–22 March 1932
16 March 1942
21–22 March 1952
2–3 April 1956
11–12 April 1965
3–4 April 1974
5–6 February 2008
27 April 2011

I think that the overall warming of the Pacific basin over the past decade, coupled with recent -AMO trends (weakening AMOC) in the North Atlantic, has made low-amplitude, progressive patterns less likely, even during -ENSO/-PDO setups, hence the dearth of major, widespread tornado outbreaks, for the most part, since 2011–12, especially over the Plains. So events like Palm Sunday 1920/‘65, Super Outbreaks ‘74/‘11, Super Tuesday ‘08, et al. will be harder to come by for the most part, due to AGW being reflected in the absorption of heat and fresh water by the major ocean basins, especially the Pacific and the North Atlantic.
Source

Climate change is leading to forces that make widespread, violent tornado activity—that is, outbreaks with multiple long-tracking supercell tornado families over a wide geographic area—less likely than it was prior to 1965 and especially prior to 2013. Certain models, including mesoscale such as the NAM/HRRR, still struggle to account for climate change’s impact on wavelengths vis-à-vis the warmer Pacific and the weaker AMOC signal in the Atlantic. Significant tornado outbreaks can still occur, but they are becoming less frequent, more limited in aerial coverage, and more confined to one (or two) big supercell that thrives more due to mesoscale quirks than large-scale synoptic factors vs. the past.
Source
 
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andyhb

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Why exactly are we talking about mesoscale models capturing climate signals here? There is a lot of basic meteorology/climatology that is being ignored. Number one that climate forcings are on entirely different time and spatial scales than models like the HRRR and NAM (or even the GFS and Euro) are meant to forecast for.

There’s a reason we use GCMs instead of operational NWP to forecast changes in the climate. Do climate signals feedback onto the shorter term? Absolutely, but operational NWP is effectively separate/independent from that because the initial conditions and length of the forecasts are already within the current climate regime.

Also, until you can show me proof that severe weather outbreaks are becoming less common with time, this is a lot of conjecture. As someone who has studied this stuff for years and read papers on it, I can tell you that the conclusions you draw here are at best conflicted in the scientific literature and at worst disproven by the scientific literature.
 

pohnpei

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I was focus on this subject for such a long time and used to read literally any paper or findings that I can find. But I still find myself know so little about this topic. I may have many ideas want to share about but I also don't know how to start it or what kinds of conclusion I can make.
So, first I want to talk about the trend we have already know or quite sure about. That is even with the the development of detection technology, the trend of fewer and fewer tornado days every year was apparent. The reason is that as jet retreat early and early because of the golbal warming, tornado activity in summer was reducing rapidly through last 30 years. This conclusion was already back up by either obsevation or statistics calcuation or climate model. Also I think Grazulis noticed this change long time ago.
Some finds about this change:https://www.sciencedaily.com/releases/2018/08/180806104253.htm
But I know the most important question must be how about the change of tornado activity in spring? Even in relatively cold era, spring was the most prolific time to produce tornados, especially violent tornados.

I don't know if you have ever watched this, but Dr.harold had some insightful ideas about this topic. In his model, it seems that the tornado activity was largely increasing in spring. But I will also recommand you to read this paper last year:https://journals.ametsoc.org/view/journals/bams/aop/bamsD200004/bamsD200004.xml
This suggests that despite increasing instability, thunderstorms in a warming climate may be less likely to develop due to stronger convective inhibition and lower relative humidity. (also higher and higher LCL)
So they may give a hint to a opinion that fewer and fewer tornado days due to higher and higher CIN but more violent tornado if stroms succeed to fire up.
full-BAMS-D-20-0004.1-f6.jpg

103_15264_d01c8e3bb7f7546.jpg 103_15264_b32fc8eab84ceb8.jpg

Another great paper I recommand to read and I believe you must already read before was this one:


The spatial trends in tornado environments and tornado frequency showed in this findings was obvious, but something more interesting was this statistics they made. It seems that the Annual accumulated STP had quite good correlation with the annual tornado counts.


QQ截图20210319212937.jpg

Also some interesting trend about 500 Height and EF2/3 tornado numbers :

We know that global warming increase the 500 Height as time goes by.

After reading all those papers, I think we still can't make any certain conclusion about this topic. One thing that have been discussed these days in the March 17 severe weather trend was did high ceiling event bust more often now? It seems to be true in last few years and some of the bust of high ceiling conditions even find hard to figure out the reason of it. But was there really a clear statistics to show that we bust more often than before? I think the answer is no. SPC used to issue high risk more frequently. For example, 1990 and 1991 were all very active year, but did anyone remember what happened on 1990/2/1, 1990/5/9 1990/5/29, 1991/3/28, 1991/4/28? These were all high risk days and they all bust very hard. People don't seems to remember those bust 20 or 30 years ago. Also, what contribuate to the decresing high risk days over last 30 years? It seems that the criterion of the high risk day was largely on rise.
So there was many uncertainties about this topic. Like many people said before, the next super outbreak can happen 1000 years later or it can happen in next month. We‘ll ’never know, so keep you mind open as much as possible. Hope the answer is helpful to you.
 

thundersnow

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For years, the thought was that climate change/global warming increases volatile/severe weather. Previous decades showing upticks in severe weather were supposedly bearing that out. Now that trends have gone quieter for a few years, it's climate change that's lessening it?

This shouldn't come across as being skeptical or outright denying climate change, but I think climate change has now become the perennial go-to scapegoat for just about ever weather occurrence... when really so much can be explained by cycles, and just the right ingredients coming together at the right time.
 

warneagle

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For years, the thought was that climate change/global warming increases volatile/severe weather. Previous decades showing upticks in severe weather were supposedly bearing that out. Now that trends have gone quieter for a few years, it's climate change that's lessening it?

This shouldn't come across as being skeptical or outright denying climate change, but I think climate change has now become the perennial go-to scapegoat for just about ever weather occurrence... when really so much can be explained by cycles, and just the right ingredients coming together at the right time.
I think the issue is that it's difficult to suss out exactly how large-scale processes like climate change will affect small-scale events like tornadoes. It's relatively easy to figure out the deterministic and stochastic effects of climate change on bigger features (e.g. tropical cyclones and winter storms) but much harder to figure out whether there are deterministic effects on things like tornadoes which are more random, which also means that it's easier to attribute trends to climate change for those bigger processes than it is for tornadoes.

We might be able to draw some general conclusions about whether climate change makes the overall climatology and synoptic patterns more or less favorable for tornadoes (and even then it might be tough to separate what's resulting from anthropogenic climate change vs. the natural changes in the background state), but I don't think we can really say whether certain things that evolve on the mesoscale are being driven or altered by climate change at this point, especially since our understanding of the process of tornadogenesis is still incomplete. There are just too many confounding variables to draw firm conclusions at this point, imo.
 

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