Wind Shear Increasing in Modern Tornado Outbreaks

[nwohweather]

Very interesting article published by Bob Henson on a research papers findings on how tornadoes are changing as the climate does. It also was talked about for quite awhile by Greg Forbes and Mike Bettes recently on Weather Underground with Bob Henson as well. 

Long story short is they're finding that over the last 50 years CAPE in severe weather outbreaks are not different at all, but the wind shear aloft is. To get more accurate information they also deleted all F0 tornadoes as to not skew the numbers due to the improvement in tornado detection in recent years. Bob Henson would go on to say of the stats...

The trends in outbreaks emerged most clearly when looking at those with at least 12 tornadoes, and when placing those 435 outbreaks into five percentile brackets (e.g., dividing each year’s outbreaks into five groups based on the number of tornadoes per outbreak). This revealed a significant increase in the number of tornadoes per outbreak, especially for the largest events. From the late 1960s to the early 2010s, the number of tornadoes per outbreak in the top fifth of outbreaks rose from around 20 to more than 35. Likewise, the size of the largest outbreak one might expect every five years roughly doubled, from 40 in 1965 to nearly 80 in 2015

I'll post the link at the bottom but was definitely intrigued by the discussion. It would explain how we've had essentially nothing in some tornado years, and then other years are just pure insanity

 

https://www.wunderground.com/blog/JeffMasters/more-tornadoes-in-the-biggest-us-outbreaksfor-an-unexpected-reason

[Hoosier]

I knew that the outbreak days are getting bigger but the part about increasing shear is very interesting.  Thanks for sharing.

[nwohweather]

I knew that the outbreak days are getting bigger but the part about increasing shear is very interesting.  Thanks for sharing.

No problem. I think it may be something as simple as greater temperature differences on land are leading to stronger low pressures, hence stronger winds aloft.

IMO it's more important to see how the climate is changing and its effects, than to worry about how warm it's getting

[DAFF]

I wonder if technology is to blame partially with the skew of increased numbers. I would have to guess many data sets were not as complete in 1965 compared to todays communication advancements. 

[bdgwx]

Thanks for posting that link. I'll read it when I get time. I believe the researchers mentioned in the article are the same ones that did a presentation at the 28th SLS conference a few weeks ago.

I've been spending more of my time reading up on the effects of climate change in the midwest and plains. In regards to tornadoes the recent academic work is really blurry on what we might expect in the future. Will there be more/less tornadoes? Will they be stronger/weaker? There doesn't seem to be a good consensus right now from what I've been reading. 

[Hoosier]

1 hour ago, DAFF said:

I wonder if technology is to blame partially with the skew of increased numbers. I would have to guess many data sets were not as complete in 1965 compared to todays communication advancements. 

Perhaps, but that is why they didn't include F/EF0 tornadoes.  I'm wondering if better detection of QLCS tornadoes may be playing a role (many of those tend to be rated EF1 and occasionally can be stronger of course). 

[Indystorm]

This is why, other parameters being conducive, I always note the surface to 1 km helicity very carefully, and sometimes give this the edge regarding possible tornado formation, particularly if strong helicity is ahead of a QLCS which seems to be breaking up into more discrete cells instead of remaining as a squall line.

[nwohweather]

This is why, other parameters being conducive, I always note the surface to 1 km helicity very carefully, and sometimes give this the edge regarding possible tornado formation, particularly if strong helicity is ahead of a QLCS which seems to be breaking up into more discrete cells instead of remaining as a squall line.

If anything it gives more credence to the prolific night time outbreaks we've seen lately. Just this week that outbreak really didn't turn it up until as the sun began to set

[IWXwx]

36 minutes ago, nwohweather said:

 

If anything it gives more credence to the prolific night time outbreaks we've seen lately. Just this week that outbreak really didn't turn it up until as the sun began to set

The June tornadoes that hit here in Huntington County at 1 AM is another example, fueled in part by an unseasonably high amount of shear.

[Nflow6]

Thanks for the link to the paper. The paper is strong on conjecture but weak on science imho.

[andyhb]

On 12/2/2016 at 10:26 PM, nwohweather said:

No problem. I think it may be something as simple as greater temperature differences on land are leading to stronger low pressures, hence stronger winds aloft.
IMO it's more important to see how the climate is changing and its effects, than to worry about how warm it's getting

But given the poles are warming disproportionately faster than the tropics, wouldn't that in theory weaken the meridional temperature gradient, thus leading to weaker baroclinicity and thus weaker cyclogenesis?

38 minutes ago, Nflow6 said:

Thanks for the link to the paper. The paper is strong on conjecture but weak on science imho.

Do elaborate.

[Nflow6]

4 minutes ago, andyhb said:

But given the poles are warming disproportionately faster than the tropics, wouldn't that in theory weaken the meridional temperature gradient, thus leading to weaker baroclinicity and thus weaker cyclogenesis?

Do elaborate.

Multiple Issues between today vs 1965.  Number of government and academic personnel conducting such surveys, changes in the importance of such surveys. Number of media, storm chasers. Explosion of inputs today of all said human influences and in determining more accurate calculations of SRH vs 1965. Number of structures today vs 1965. Changes in damage ratings, All sensing inputs, radar etc. Changes in understanding the nature of supercells,  their morphology and their cyclic nature. Multiple cyclic families of tornadoes were more likely to be counted as one long track tornado back in 1965 compared to today. Why did the authors choose EF1 not EF2 or other value characteristics like total path length?

[andyhb]

Ok good, just making sure you could back up your initial statement. I do share several of those skepticisms myself, particularly the choice for EF1 vs. EF2.