04.14.10
Where Have All The Tornadoes Gone?
Mid-April in Tornado Alley. Only 93 tornado reports so far.
Over the last 30 years, there were on average 191 tornadoes between January 1 and April 15.
Over the last 10 years, there were on average 237 tornadoes.
Over the last 5 years, there were on average 338 tornadoes.
Tornado reports have, on average, gone up over recent years, but that is due in large part to increased tornado awareness, increased storm chasers and spotters, and increased tornado detection through Doppler radar.
But that’s not the point.
The point is that this year is below average. Take a look at the plot below, from the Storm Prediction Center. This graph shows the trend in local storm reports (LSR) of tornadoes in the U.S. Values may be a little higher than the actual tornado count (some tornadoes may have been reported more than once). The last five years are shown, as well as the current year up through April 12.
Now look at the graph below (click to enlarge), also from the Storm Prediction Center. This plot shows annual tornado trends; if you’re curious as to how exactly the trends were calculated, see the website on the bottom of the figure. Basically, the red line is the maximum tornado count in a single year and the pink line is the minimum tornado count in a single year. The other lines show tornado trends in quartiles. Currently, 2010 is in the all-time lowest 25th percentile, near the minimum. That’s how slow this year is in terms of storms and tornadoes.
One thing to note, however, is that in 2004, there was an all-time record of over 1800 tornadoes in the U.S. From January 1 to April 15 of 2004, only 91 tornadoes were reported. As of today, April 14, 2010, 93 tornadoes have been reported this year.
Currently the weather pattern over much of the U.S. is more summer-like than spring-like, with few good troughs digging into the central or southern Plains…however, all this just goes to show that storm chasers shouldn’t be too worried about this season yet (and sane citizens of the Plains shouldn’t get too excited yet)…
Green Sky Chaser » Tornado Season So Far… said,
May 22, 2010 at 3:31 pm
[…] over a month ago, I posted on the unusual lack of tornadoes through mid-April. As expected, however, shortly after that post, there was an explosion in this year’s […]