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New Study Finds That Outbreaks Of Multiple Tornadoes Becoming More Common

March 8, 2016

By Paul Homewood  




As we all know, global warming makes everything worse, and now there is another junk study out which tries to persuade us that we are getting more tornadoes when there is an outbreak.



Tornadoes cause loss of life and damage to property each year in the United States and around the world. The largest impacts come from ‘outbreaks’ consisting of multiple tornadoes closely spaced in time. Here we find an upward trend in the annual mean number of tornadoes per US tornado outbreak for the period 1954–2014. Moreover, the variance of this quantity is increasing more than four times as fast as the mean. The mean and variance of the number of tornadoes per outbreak vary according to Taylor’s power law of fluctuation scaling (TL), with parameters that are consistent with multiplicative growth. Tornado-related atmospheric proxies show similar power-law scaling and multiplicative growth. Path-length-integrated tornado outbreak intensity also follows TL, but with parameters consistent with sampling variability. The observed TL power-law scaling of outbreak severity means that extreme outbreaks are more frequent than would be expected if mean and variance were independent or linearly related.


WUWT does a good job of shredding any credibility the paper might have had, but I’ll add my twopennorth.




It is absolutely established, and widely accepted, that many more tornadoes get to be reported these days, simply because of changes in reporting technology, as NOAA explain:


Today, nearly all of the United States is reasonably well populated, or at least covered by NOAA’s Doppler weather radars. Even if a tornado is not actually observed, modern damage assessments by National Weather Service personnel can discern if a tornado caused the damage, and if so, how strong the tornado may have been. This disparity between tornado records of the past and current records contributes a great deal of uncertainty regarding questions about the long-term behavior or patterns of tornado occurrence. Improved tornado observation practices have led to an increase in the number of reported weaker tornadoes, and in recent years EF-0 tornadoes have become more prevelant in the total number of reported tornadoes. In addition, even today many smaller tornadoes still may go undocumented in places with low populations or inconsistent communication facilities.

With increased National Doppler radar coverage, increasing population, and greater attention to tornado reporting, there has been an increase in the number of tornado reports over the past several decades. This can create a misleading appearance of an increasing trend in tornado frequency. To better understand the variability and trend in tornado frequency in the United States, the total number of EF-1 and stronger, as well as strong to violent tornadoes (EF-3 to EF-5 category on the Enhanced Fujita scale) can be analyzed. These tornadoes would have likely been reported even during the decades before Doppler radar use became widespread and practices resulted in increasing tornado reports. The bar charts below indicate there has been little trend in the frequency of the stronger tornadoes over the past 55 years.


It is only since Doppler became comprehensively established in the late 1990s that we can make proper comparisons. To be fair to the Tippett study, it recognises this factor and excludes the weaker EF-0 tornadoes.

However, what NOAA fail to explain is that it is not just EF-0 ones that are affected. We find a very similar pattern with EF-1s.




When we exclude these EF-1s, we see that there is a very clear decline in the number of tornadoes. This can only mean two things:


1) The increase in EF-1s is a reporting anomaly

2) The intensity of tornadoes is decreasing on average.





Another factor is that Doppler technology often allows multiple tornadoes to be spotted, which previously would have been counted as one.


NOAA also advise above that we look at the trends of the stronger, EF-3+ tornadoes, which they show as:  




The reality is that tornado numbers are not increasing, and that violent ones have been decreasing since the 1970s.


There is also a further issue with the Tippett paper, as it begins its analysis from 1954. Tornado experts are clear that the data prior to 1970 is utterly unreliable. McCarthy & Schaefer, in their paper “TORNADO TRENDS OVER THE PAST THIRTY YEARS”, started their analysis in 1970 for this very reason, explaining:


This period [their chosen period is 1970 to 2002] does not include the tornado growth period that occurred as official records began to be kept in Tornado Data (through 1957) and Storm Data (in subsequent years.) Also, the years 1950-1969 were a growth period because it was the start of the public awareness and communication revolution that gave tornadoes increased publicity due to television news coverage and graphic depictions of tornadoes and tornado damage.


No serious scientist would attempt to compare trends with the 1950s and 60s.



This is not the first study which tries to prove that tornadoes are somehow getting worse, and each one has subsequently been demolished.

One Comment
  1. April 4, 2016 1:33 am

    Reblogged this on Climate Collections and commented:
    With the advent of WSR-88 NEXRAD Doppler Radar, detecting rotation became simple. Previously the WSR-57 (Mil: AN/FPS-41) displayed blobs on a scope. It was a fun toy, er system, to play with, but an operator had to manually adjust range, tilt, and sweep, and only then might be able to see a hook echo or V-notch.

    So, Paul Homewood is spot on here. There are more lower intensity tornados detected now than before–merely because of the tools available. Forensic work, inspecting damage hasn’t changed much.

    Here’s a piece from the AMS on Weather Radar history:

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