That Thin Line on Radar is Important
by Daphne Thompson, on Jul 23, 2018 2:23:30 PM
Many people look at radar images and associate bad weather with the bright colors. Most of the time this would be the correct thing to do. However, sometimes it is the thin line ahead of the reds and yellows that is the most critical feature.
A gust front is an outflow boundary of fast-moving cold air rushing ahead of a thunderstorm or line of storms. Visually, they are easy to see during daytime conditions. If you don't know what you are looking at, they can be quite scary.
When looking at them on radar, a gust front can be hard to pick out to an untrained eye. Let's look back at imagery from August 13, 2011.
The above radar loop was captured on the date of the Indiana State Fair stage collapse. While officials at the fair claimed to be watching radar data at the time, they also stated that the storm got to them faster than expected. Did it? No. What happened was that they were looking at all those reds and not that very thin line in front. When the gust front came through, the stage could not take the wind and collapsed onto workers and guests. Seven people lost their lives. Multiple other failures were noted in the investigation including no clear line of who made the final call to evacuate or call off the show.
Unfortunately, this is not the first, nor the last, time that someone in charge of an outdoor event will make a bad call due to not having a clear understanding of weather and radar data. It happened again, with devastating effects, just last week.
On the evening of July 19, 2018, that misunderstood thin line on radar led to 17 fatalities when a duck boat near Branson, Missouri sank in rough water. A detailed investigation will eventually show what steps could have prevented this tragedy, but having a trained meteorologist definitely could have helped. Below is RadarScope data from the time of the event with reflectivity on the left and velocity on the right. When viewing reflectivity data, it is easy to miss that thin blue line and focus just on the yellows and oranges. When looking at the velocity data, you can easily see that the winds are out in front of the strongest storms. They hit Table Rock Lake just before 7 pm, more than 10 minutes ahead of when the rain started.
"It hit without warning," "it came out of nowhere," "it moved faster than expected,"; these phrases are repeated over and over whenever there is a well-warned weather disaster, and meteorologists can be heard for miles grinding their teeth. Here's the thing, the majority of the time that is not the case. There are plenty of signs and information out there, and it's just that the general public is not paying attention. Even worse is when someone in charge of other people's lives is the one who isn't paying attention or doesn't understand what the data means. The last thing you want is to make national news because your company is attached to preventable fatalities caused by severe storm conditions.