People have asked me what I mean when I say “Forensic Meteorology.” I usually tell them to think about the television show CSI, but for weather. It may not be that dramatic, but it certainly involves piecing together lots of historical weather information to reconstruct what happened at a particular scene. Weather may not be the only factor, but it can certainly play a big role. Cases can be as simple as a slip and fall, but also very complex, like the 1985 airplane crash at the Dallas-Fort Worth airport. There is an excellent book called “Weather in the Courtroom” if anyone is interested in hearing about cases that have actually happened.
With this in mind, I am starting a new segment titled “Forensic Weather Files,” where I take a look back at certain events where the atmosphere may have played a role. Using the best available data, we will try to reconstruct what happened at a particular time in a particular place.
The first event we will cover is recent in many people’s minds, as it made national news a few months ago. On July 19th, 2018, a duck boat at Table Rock Lake (near Branson Missouri) sank with 31 people on board, killing 17. This was a tragic event, and could have been avoided if people listened to the weather report. One of the quotes in the aftermath was that the storm “came out of nowhere.” This is frustrating for a meteorologist, because that usually isn’t the case. In fact, the National Weather Service issued a warning 30 minutes prior to the event happening. Using data archived at NOAAs National Centers for Environmental Information, we can get a good sense as to what happened.
The accident occurred just before 7pm Central Daylight Time, as a mesoscale convective system (MCS) was moving ESE through the southern part of Missouri. The NEXRAD WSR-88D radar in Springfield, Missouri (about 50 miles north of the incident) was able to capture the system rolling through the area.
There are a couple interesting features to notice on this animation.
Red indicates the highest returns of reflectivity, which means the heaviest amount of rainfall, and sometimes hail, occur in this area.
Just ahead of the storm is a light blue line running through the area, this is also known as a gust front, or outflow boundary. As rain begins to fall in an area, the atmosphere begins to cool, and strong sinking motions can occur. These motions spread out when they hit the surface, and sometimes can move faster than the actual storm. This is what we are seeing above, and it should be noted outflow boundaries can have exceptionally high wind gusts.
The system also has a bow like feature. This is known as a bow echo, which can produce strong straight line winds, and sometimes even tornadoes.
About thirty minutes prior to the accident, the National Weather Service in Springfield, Missouri issued a Severe Thunderstorm Warning for the area, including Table Rock Lake.
Given there was a system on its way, and it was warned by the weather service, it’s hard to believe this came “without warning.”
But okay, what were the wind speeds? The NWS warning above indicated 60 mph wind speeds, and the Radar’s velocity signature (not shown here) indicated about the same values. There are two airports nearby, Branson Airport (KBBG), east of Table Rock Lake, and Branson West Municipal (KFWB), which is north of the lake. Here is what was reported around the time of the incident:
KFWB, 6:55pm, Winds from the North, Northwest at 27 kts (31.1mph, gusting to 45 kts (51.8mph)
KBBG, 7:10pm, Winds from the North, Northwest at 30 kts (34.5mph, gusting to 45 kts (51.8mph)
A question that usually comes up is “okay, but you don’t have a weather station plotted right at the incident, how can you be so sure?” Well given that size of the storm (indicated by the radar animation) is quite large, there is some confidence the wind speeds at the accident were about the same, if not higher, than the nearby airports reporting wind.
So, did the weather affect the sinking? This was not an extensive analysis, and there are many other factors to consider, such as the weight of the boat, the position it was in (relative to the wind), and the wave heights in the area, but I am confident weather certainly played a role in the tragic outcome.
Got an interesting case you want me to look at? Let me know!