Posted: Jan 2, 2013 10:54 AM by Meteorologist Matt Elwell
Updated: Jan 2, 2013 10:58 AM
With 2012 officially in the books, the Storm Prediction Center (SPC) out of Norman, Oklahoma has released some interesting statistics regarding the severe weather season from 2012 and previous years. There were a few things that stood out to me. While Texas holds the top spot for average number of tornadoes per year, Montana averages 9 tornadoes per year between 1981 and 2010. There is no surprise in that number. The Treasure State lacks the abundance of heat and moisture that you see in Tornado Alley to get massive severe weather outbreaks. Most of the state's tornadoes occur in the Eastern Plains of Montana where heat and humidity is more prevalent.
In the meteorology world, we often look at the number of tornado and severe thunderstorm watches as an indication of how active any given year is. More active years are going to get more attention from the SPC in the form of number of watches issued. This past year was relatively quiet when compared how active the past two or three years have been.
Fewer tornado watches were issued by the SPC than in 2011 or 2010, although it looks like the number of severe thunderstorm watches are up slightly as a whole. That could be due to a number of factors, but one sticks out more than the obvious ‘it was a quieter year'. A lot of attention has given to the number of ‘false alarms' in the past few years. The complaint has been that there have been a high number of tornado watches issued with few tornadoes or tornado warning being issued by the NWS.
Though this seems like a good problem, the argument is that people will begin to ignore a tornado watch. The Joplin tornado is a good example of this. A tornado watch was issued well in advance of the devastating EF-5 tornado, but many of the residents ignored, or at least dismissed the watch because it had become commonplace. The result was that a major tornado struck a heavily populated area and killed over 160 people on that fateful Sunday. Even before that event, the SPC and National Weather Service (NWS) were working to find ways to give better and more reliable lead-time for tornadoes and severe thunderstorm threats. This is a work in progress, but we could certainly argue that those efforts are a reason that the number of tornado watches appear to be down slightly.
Tornado watches were virtually non-existent in 2012 in Eastern Montana with 2 tornado watches issued in North Central Montana this past year. Severe thunderstorm watches were issued between 1-6 times across Montana in 2012 with the lowest totals coming in the eastern part of the state. The average number of severe thunderstorm watches actually went down this past year across most of the state when compared to the historical averages. There were 2-3 more tornado watches issued this past year along the high line than average.
These numbers have no bearing on how this year unfolds with regard to this year's severe weather season, but does give us good insight on the past season, and should remind us to take severe weather seriously.