Discussion: The Use of SPC Severe T-Storm Outlooks

Weather Blog

Peoria, Ill. (WMBD) – If you’ve lived in an area prone to severe weather, chances are you’ve seen an SPC outlook on the internet or in our weather forecast in the days leading up to a severe weather event, but do you really understand them?

It has been a topic of conversation in the weather community ever since the Storm Prediction Center (SPC) changed the number of risk categories from 4 to 5 in October of 2014. The change featured new terminology and split the Slight Risk category into two separate categories, Slight and Enhanced-Slight (commonly referred to as just “Enhanced”). Recent studies show that when you ask members of the general public to rank the risk categories (Marginal, Slight, Enhanced, Moderate & High) in order from lowest to highest, they typically mix them up. A recent article from Matthew Cappucci in the Washington Post brought this discussion into the public sphere and showed the results of one study that explored the public perception of the outlook risk categories.

These risk categories were not necessarily designed for public consumption, but more for emergency managers, community leaders and weather forecasters to identify areas of greatest concern. In fact, it gets even more confusing when you dive into the probability guidance that drives these outlooks, something I won’t get into in this article.

Within the weather community these solutions range from changing the colors of the categories to changing the terminology to not showing them at all. Since a lot of people are familiar with the current outlook structure I feel making a big change, particularly on just a local level, will lead to even more confusion. One solution we’ve started to implement here at WMBD is referring to each category with a number, where 1 is the lowest risk category and 5 is the highest. SPC and the NWS have started You can see how the numbers match up with the terminology below.

1 = Marginal
2 = Slight
3 = Enhanced
4 = Moderate
5 = High

This simple process of adding numbers to the categories, and possibly using the numbers only, is a great way to clarify the threat level. Most people know that a category 4 hurricane is worse than a category 3, but based on the latest studies, they don’t know that a moderate severe weather risk is worse than an enhanced risk.

We haven’t dropped the risk category terminology all together, our legends still use the SPC terminology. However instead of saying “We are in a slight risk for severe weather”, we now say “We are in slight risk for severe weather, which is a level 2 threat” and then usually display which threats are the most likely.

Before we make any significant changes to how we relay this information, I wanted to bring the conversation down to our local level. How can we at WMBD help convey the risk to you? What changes to the current outlook structure can we make help the public better understand the threats? Let us know what you think by commenting in this story’s comment section on Facebook!

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