Tornado Season Statistics Update – 'remarkably quiet'

Guest post by Paul Homewood


It does not seem long since the February outbreak of tornadoes had Joe Romm noting :-

The unexpectedly fierce and fast tornado outbreak so early in the season has folks asking again about a possible link to climate change.

And talk in some quarters of another year of extremes.

So how has the tornado season developed thus far? In fact, the data tells us it has been remarkably quiet.


Figure 1

Figure 1, from NOAA’s Storm Prediction Centre,(SPC),  shows there have been 871 preliminary tornado reports so far this year, compared to an average of 1118 at this date between 2005-2011.

(It is worth spending a bit of time explaining how the SPC calculate their tornado statistics. In their own words :-

Tornado data usually reaches SPC first from local storm reports (LSRs), warnings or other bulletins sent by local NWS forecast offices. Such reports are usually sent within the first day or two after a severe weather event, before all the information on a tornado is known. In fact, some tornado information might not be known for many weeks or months–for example, if someone who was injured dies from his injuries a long time afterward. That is why we call all tornado data “preliminary” until the National Climatic Data Center publication Storm Data is completed. Storm Data contains the “final” information on all severe weather events.

They go on to explain how they survey damage and thereby determine the Enhanced Fujita Scale.

This varies from place to place; and there are no rigid criteria. The responsibility for damage survey decisions at each NWS office usually falls on the Warning-Coordination Meteorologist (WCM) and/or the Meteorologist in Charge (MIC). Budget constraints keep every tornado path from having a direct ground survey by NWS personnel; so spotter, chaser and news accounts may be used to rate relatively weak, remote or brief tornadoes. Killer tornadoes, those striking densely populated areas, or those generating reports of exceptional damage are given highest priority for ground surveys. Most ground surveys involve the WCM and/or forecasters not having shift responsibility the day of the survey. For outbreaks and unusually destructive events–usually only a few times a year–the NWS may support involvement by highly experienced damage survey experts and wind engineers from elsewhere in the country. Aerial surveys are expensive and usually reserved for tornado events with multiple casualties and/or massive degrees of damage. Sometimes, local NWS offices may have a cooperative agreement with local media or police to use their helicopters during surveys.

In practice, this all means that it takes about three months before tornado data can be finalised and accurate statistics produced.)

So back to Figure 1!  To assure a comparison of like with like, the preliminary tornado figure for this year is compared with the preliminary numbers for previous years at the same date, and not actual numbers. (Actual numbers normally come out at between 65% and 85% of preliminary figures – this is partly due to the same tornado being spotted twice, and partly due to storms being wrongly identified as a tornado). It is clear, then, that after the early season outbreaks in February and March, the last three months have been remarkably quiet.


Figure 2

Figure 2 shows the same information as Figure 1, but compares with each year since 2005 separately. Only 2005 has recorded a lower number by the end of June.


Figure 3

Figure 3 is slightly different, as it attempts to compare with a baseline of 1954-2011. Direct comparisons are meaningless, as in the SPC’s own words – “The increase in tornado reports over the last 54 years is almost entirely due to secular trends such as population increase, increased tornado awareness, and more robust and advanced reporting networks.”. To get around this problem, tornado numbers in the earlier part of the record have been “adjusted” upwards. Also this years figure of 740 is adjusted to 85% of the preliminary LSR’s, to allow for double counting etc.

Again it appears that this year’s numbers are low by comparison, close to the 25th percentile.

June Tornado Events

According to data from the Storm Prediction Center, the count of preliminary tornado reports during June — 114 — was much below the 1991-2010 average of 243. June is typically one of the most active tornado months during the year. In terms of the number of tornadoes, this marks the least active June since 2002, when 97 tornadoes were confirmed. Once the final tornado count is confirmed, it is likely the June 2012 count will be revised lower. There were four tornado-related fatalities reported during the month — three due to a single EF-2 tornado in Missouri on June 4th and a single fatality from a tornado spawned by Tropical Storm Debby on June 24th in Florida.

A storm system moving through the Mid-Atlantic on June 1st, spawned numerous severe thunderstorms from western Pennsylvania, through the Washington D.C. metro area, and into southeastern Virginia. There were 28 preliminary tornado reports, with 12 tornadoes confirmed in and around Washington and Baltimore. The tornadoes were weak in nature, rated as EF-0 and EF-1, causing only minimal damage. The largest impact from the storms was flash flooding, with 2-4 inches of rainfall being observed. No fatalities were reported with the severe weather outbreak.


Confirmed Numbers for February

The SPC have now confirmed their figures for January and February. F1+ tornadoes totalled 78, compared to a baseline average from 1970-2011 of 33. Figure 4 shows how this year stacks up against earlier decades for tornadoes during January and February. ( Changes in recording practices, such as Doppler radar, make comparisons of the weaker F0 tornadoes with years before 1998 meaningless – for more information read here.)

TORNADO BY MONTH_htm_m57fbc005

Figure 4

While this year had a busier start than usual, this is not uncommon. Since 1970, four years have experienced more early season tornadoes during January and February.

Year F1+
2008 140
1999 122
1975 84
1971 87

Next month, we will take a closer look at the March, and hopefully April numbers. In the meantime, let us hope the summer remains quiet.


1) Detailed information is available from the Storm Prediction Centre.

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July 16, 2012 1:55 pm

So Tornado severity/frequency and climate change are in fact linked: There is no worrisome climate change and there is no worrisome outbreak of tornadoes.

Pull My Finger
July 16, 2012 1:57 pm

Too quite, must be global calming.

July 16, 2012 2:28 pm

So then, more evidence for global warming. The science is so settled.

Skeptic Tank
July 16, 2012 2:38 pm

Not to go all off-topic here, but I’d like to know when the NHC is going to update this chart:
Referenced on their Tropical Cyclone Climatology page:
It’s been 6 full seasons. Like Katrina was the last word in hurricanes.

Dickens Goes Metro
July 16, 2012 2:51 pm

Don’t forget about the record number of consecutive days without a major hurricane strike on the mainland US. How many years (or hurricane season days) has it been now?
You won’t hear about that in the news. That’s for sure.

July 16, 2012 3:07 pm

When you’re a hammer salesman, everything looks like a nail.

July 16, 2012 3:58 pm

Forgive me, I am a simple layman, and this is off topic, but, is it just me or does it seem that the seasons have “shifted?” I mean, it seems certain weather seasons and temperatures are coming earlier and leaving earlier. Has the Earth’s spin changed?

Interstellar Bill
July 16, 2012 5:15 pm

As with any climatological statistic you care to name,
reduced frequencies of tornadoes and hurricanes
are consistent with ‘anthropogenically enhanced radiative forcing of climate disruption’,
once post-hoc explanations are spun out of whole cloth.
It never seems to matter that all past Warmista predictions have crashed and burned, as have those of the population doomsayers and the peak-resources pessimists.
Imagination unattached to reality is sufficiently pliable to be consistent with whatever happens next, and post-hoc goal-post shifting can go on forever.
Models that can give very narrow, limited assistance in understanding climate
are not thereby deputized to control our economic system.

July 16, 2012 5:32 pm

First graph is interesting. If you run a visual smoothing to eliminate the random stuff, you can see the same ‘step’ in 1976 that shows on some temperature graphs. Doesn’t look like a sine curve; looks more like one flat centerline before ’76 and a lower flat centerline after ’76. Did big ’74 herald the step?

July 16, 2012 8:34 pm

The data looks a little different when looked at by day of the year (very noisy) but patterns start to develop when you look at the data by Lunar declinational patterns, for an intensive look at the pattern effects by various cyclic periods for comparison:

July 16, 2012 8:40 pm

More tornadoes, less tornadoes, more rain in UK, less rain in UK. Hot/Cool summers anywhere in the world. Mild/Cold winters again, anywhere in the world. Spring/autumn, could be mild/cold/wet/dry! All of these things are as a result of Climate Change caused by mankind!
I rest my case, we need to go back to living in caves, with small fires!

Larry Hamlin
July 16, 2012 9:11 pm

During the year 2011 NBC news carried dozens of broadcasts pushing a link between global warming and the increased number of tornadoes that year. NBC anchor Brian Williams has been virtually silent this year about the huge change and massive reduction in number of 2012 tornadoes. Now Mr. Williams is pushing the recent eastern heat wave as being linked to global warming despite the fact there is no quantitative scientific connection whatsoever to support this conjecture. It is quite clear that NBC news and Mr. Williams simply cherry pick natural weather variation changes and try to push them as being related to global warming even though there is no scientific evidence to support this conjecture. Clearly this demonstrates that NBC news is presenting biased climate fear propaganda it’s broadcasts.

Joseph Bastardi
July 17, 2012 6:06 am

I spoke on the 400 mb temp theory I have not only for tornadoes, but the hurricane season, at ICCC7. After the major march outbreak, I posted time after time on weatherbell, and even made reference here, this season would go into the tank as there is a linkage between the trend of the 400 mb temp in March and the tornado season, which those that attended ICCC7 saw me show and continue the forecast.
The Weatherbell hurricane forecast called for an ace of 70-90 with in close developments being the big problem. We had a fast in close start, publicly saying that the season would tank BUT, AND THIS IS IMPORTANT, when it came back it would not be long tracked storms but quick to develop storms near the coast, such as Belle 1976, Bob 1991, or Carol 1954, that could be a big problem. This was based on the linkage to the cold 400 mb over the tropics in spring ( while it was warm over the US!) I used the conference to show these facts.
The interesting thing is I came upon this while researching the non existent IPCC hot spot. Those of you at the conference I hope recall this and that this was ongoing research being tested in the crucible of real time forecasting, where there is no chance to hide error. The only way to go, right

Joseph Bastardi
July 17, 2012 6:08 am

By the way, there also seems to be linkage with that level and heat and drought, though I am currently looking through the years . It seems that the spring temp may be telling us where we have gone, and be an indicator of where we are going. No magic bullet, but another piece of ammo, and certainly something that debunks co2 linkage

July 17, 2012 8:38 am

Drought in the US mid-west & lack of tornadic storms go together.

July 17, 2012 10:25 am

@Skeptic Tank:
The data exists here
It looks like NNOAA has more *important* things to do than to stay updated with Inconvenient Truths.

D. J. Hawkins
July 17, 2012 1:02 pm

I’m having trouble viewing the linked graphs, I get only the gray background with a very faint impression of the various visual elements. Anyone else?

July 17, 2012 7:02 pm

Baghdad Romm

July 22, 2012 3:35 pm

“Tornado Season Statistics Update – ‘remarkably quiet’”
I don’t know what you guys are talking about. I was about 500 ft from a tornado once. It was INCREDIBLY loud.
Oh, wait. I see what you mean now :).

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