Weather Ready Nation: Counties Warned for Tornadoes by CWAs
In the wake of last night’s post, several questions were raised regarding the time periods of the two images. The biggest concern was that you can’t compare a 22-year average and a 3-year average, as the 3-year average is more easily biased by one or two high years than the 22-year average. Tonight I’ve added a plot that shows the number of counties under a tornado warning by National Weather Service County Warning Areas (CWAs) broken down by year.
Starting with 1986 and advancing toward 2010, one can easily see that the number of counties warned by CWA has increased substantially, with most of the increase occurring in last few years. Although this isn’t the same as the number of tornado warnings (because a single tornado warning could affect multiple counties), it is still an important number. This is because it represents the number of times NOAA Weather Radios would have sounded in each CWA. Why is that? This is because the NOAA Weather Radios, as they currently stand, cannot activate based on the storm-based warning. They are activated based on the county-level warning. Thus, two small storm-based warnings issued for the same county would require two activations of the NOAA Weather Radio for that county, even if the warnings were issued only minutes apart. Thus, for a large portion of the population, the county-level warning is what they would receive.
Tomorrow I’ll post similar maps but instead of counting the number of counties warned, I’ll count the number of tornado warnings.
Weather Ready Nation: Tornado Warning Frequency
Today kicked off the first day of the Weather Ready Nation: A Vital Conversation. (OU is recording and posting the presentations on the web.) Dr. Harold Brooks of the National Severe Storms Laboratory really got things going with a presentation on our known challenges. One of his main take-away points was that the number of tornado warnings issued has dramatically increased in the recent era. To illustrate this point, I provided two county-level heat maps (below). The top figure is the average number of tornado warnings per county per year from 1986-2007. The bottom figure is the same figure except for 2008-2010. As you can see, the average number of tornado warnings per county per year has increased almost uniformly across the county, although the increase is much larger in some areas and almost non-existent in others. Whether or not this is an improvement in National Weather Service “service” is one of the topics open for discussion in the following days.
I’m sure I’ll create more figures in the coming days.
About Patrick
Patrick Marsh is a Ph.D. student at the University of Oklahoma's School of Meteorology. He earned a Bachelors of Science in Mathematics and Physics (cum laude) from the University of Arkansas in 2005 and a Masters of Science in Meteorology in 2007. In addition to working on his doctorate, Patrick serves as the National Severe Storms Laboratory Liaison to the Hazardous Weather Testbed where his research interests lie in working with operational forecasters, data mining, data visualization, and all things high-impact weather. For more about Patrick's work, check out his complete CV!
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